University College of Science, OU

Resources Management

Haroon Hairan8/14/2014

Unit-I

Population StabilizationThe Commission’s Perspective

Soon after the Commission’s first meeting in June 1970, it became evident that the question of population stabilization would be a principal issue in its deliberations. A population has stabilized when the number of births has come into balance with the number of deaths, with the result that, the effects of immigration aside, the size of the population remains relatively constant. We recognize that stabilization will only be possible on an average over a period of time, as the annual numbers of births and deaths fluctuate. The Commission further recognizes that to attain a stabilized population would take a number of decades, primarily because such a high proportion of our population today is now entering the ages of marriage and reproduction.

As our work proceeded and we received the results of studies comparing the likely effects of continued growth with the effects of stabilization, it became increasingly evident that no substantial benefits would result from continued growth of the nation’s population. This is one of the basic conclusions we have drawn from our inquiry. From the accumulated evidence, we further concluded that the stabilization of our population would contribute significantly to the nation’s ability to solve its problems. It was evident that moving toward stabilization would provide an opportunity to devote resources to problems and needs relating to the quality of life rather than its quantity. Stabilization would “buy time” by slowing the pace at which growth-related problems accumulate and enhancing opportunities for the orderly and democratic working out of solutions.

The Commission recognizes that the demographic implications of most of our recommended policies concerning childbearing are quite consistent with a goal of population stabilization. In this sense, achievement of population stabilization would be primarily the result of measures aimed at creating conditions in which individuals, regardless of sex, age, or minority status, can exercise genuine free choice. This means that we must strive to eliminate those social barriers, laws, and cultural pressures that interfere with the exercise of free choice and that governmental programs in the future must be sensitized to demographic effects. *

Recognizing that our population cannot grow indefinitely, and appreciating the advantages of moving now toward the stabilization of population, the Commission recommends that the nation welcome and plan for a stabilized population.

There remain a number of questions which must be answered as the nation follows a course toward population stabilization. How can stabilization be reached? Is there any

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particular size at which the population should level off, and when should that occur? What “costs” would be imposed by the various paths to stabilization, and what costs are worth paying?

Criteria for Paths to Stabilization

An important group in our society, composed predominantly of young people, has been much concerned about population growth in recent years. Their concern emerged quite rapidly as the mounting pollution problem received widespread attention, and their goal became “zero population growth.” By this, they meant in fact stabilization—bringing births into balance with deaths. To attain their objective, they called for the 2-child family. They recognize, of course, that many people do not marry and that some who do marry either are not able to have or do not want to have children, permitting wide latitude in family size and attainment of the 2-child average.

Some called for zero growth immediately. But this would not be possible without considerable disruption to society. While there are a variety of paths to ultimate stabilization, none of the feasible paths would reach it immediately. Our past rapid growth has given us so many young couples that, even if they merely replaced themselves, the number of births would still rise for several years before leveling off. To produce the number of births consistent with immediate zero growth, they would have to limit their childbearing to an average of only about one child. In a few years, there would be only half as many children as there are now. This would have disruptive effects on the school system and subsequently on the number of persons entering the labor force. Thereafter, a constant total population could be maintained only if this small generation in turn had two children and their grandchildren had nearly three children on the average. And then the process would again have to reverse, so that the overall effect for many years would be that of an accordion-like continuous expansion and contraction.’

From considerations such as this, we can begin to develop criteria for paths toward population stabilization. It is highly desirable to avoid another baby boom.

Births, which averaged 3.0 million annually in the early 1920’s, fell to a 2.4 million average in the 1930’s, rose to a 4.2 million average in the late 1950’s and early 1960’s, and fell to 3.6 million in 1971.3 These boom and bust cycles have caused disruption in elementary and high schools and subsequently in the colleges and in the labor market. And the damage to the long-run career aspirations of the baby-boom generation is only beginning to be felt.

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The assimilation of the baby-boom generation has been called “population peristalsis,” comparing it to the process in which a python digests a pig. As it moves along the digestive tract, the pig makes a big bulge in the python. While the imagery suggests the appearance of the baby-boom generation as it moves up the age scale and through the phases of the life cycle, there is reason to believe that the python has an easier time with the pig than our nation is having providing training, jobs, and opportunity for the generation of the baby boom.

Thus, we would prefer that the path to stabilization involve a minimum of fluctuations from period to period in the number of births. For the near future, these considerations recommend a course toward population stabilization which would reduce the echo expected from the baby-boom generation as it moves through the childbearing ages and bears children of its own.

Our evidence also indicates that it would be preferable for the population to stabilize at a lower rather than a higher level, Our population will continue to grow for decades more before stabilizing, even if those now entering the ages of reproduction merely replace themselves. The population will grow as the very large groups now eight to 25 years of age—the products of the postwar baby boom—grow older and succeed their less numerous predecessors. How much growth there will be depends on the oncoming generations of young parents.

Some moderate changes in patterns of marriage and childbearing are necessary for any move toward stabilization. There are obvious advantages to a path which minimizes the change required and provides a reasonable amount of time for such change to occur.

Population stabilization under modern conditions of mortality means that, on the average, each pair of adults will give birth to two children. This average can be achieved in many ways. For example, it can be achieved by varying combinations of nonmarriage or childlessness coexisting in a population with substantial percentages of couples who have more than two children. On several grounds, it is desirable that stabilization develop in a way which encourages variety and choice rather than uniformity.

We prefer, then, a course toward population stabilization which minimizes fluctuations in the number of births; minimizes further growth of population; minimizes the change required in reproductive habits and provides adequate time for such changes to be adopted; and maximizes variety and choice in life styles, while minimizing pressures for conformity.

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An Illustration of an Optimal Path

Our research indicates that there are some paths to stabilization that are clearly preferable. These offer less additional population growth, involve negligible fluctuations in births, provide for a wide range of family sizes within the population, and exact moderate “costs”—that is, changes in marriage and childbearing habits, which are in the same direction as current trends.

A course such as the following satisfies these criteria quite well.4 (The calculations exclude immigration; the demographic role of immigration is reviewed in the next chapter.)

In this illustration, childbearing would decline to a replacement level in 20 years. This would result if: (1) the proportion of women becoming mothers declined from 88 to 80 percent; (2) the proportion of parents with three or more children declined from 50 to 41 percent; and (3) the proportion of parents with one or two children rose from 50 to 59 percent. Also in this illustration, the average age of mothers when their first child is born would rise by two years, and the average interval between births would rise by less than six months. The results of these changes would be that the United States population would gradually grow until it stabilizes, in approximately 50 years, at a level of 278 million (plus the contribution from the net inflow of immigrants). Periodic fluctuations in the number of births would be negligible.

The size of the population in the year 2000 will depend both on how fast future births occur as well as on the ultimate number of children people have over a lifetime. Over the next 10 to 15 years especially, we must expect a large number of births from the increasing numbers of potential parents, unless these young people offset the effect of their numbers by waiting somewhat before having their children. Postponement and stretching-out of childbearing, accompanied by a gradual decline in the number of children that people have over a lifetime, can effectively reduce the growth we shall otherwise experience.

Beyond this, there are persuasive health and personal reasons for encouraging postponement of childbearing and better spacing of births. Infants of teenage mothers are subject to higher risks of premature birth, infant death, and lifetime physical and mental disability than children of mothers in their twenties.5 If the 17 percent of all births occurring to teenage mothers were postponed to later ages, we would see a distinct improvement in the survival, health, and ability of these children.

It is obvious that the population cannot be fine-tuned to conform to any specific path. 5

The changes might occur sooner or later than in this illustration. If they took place over 30 years instead of 20 we should expect nine million more people in the ultimate stabilized population—or 287 million rather than 278 million. Or if the average age at childbearing rose only One year instead of two, we would end up with 10 million more people than otherwise.

On the other hand, suppose we drifted toward a replacement level of fertility in 50 years instead of 20, and none of the other factors changed. In that case, the population would stabilize at 330 million. In other words, following this route would result in 50 million more Americans than the one illustrated above.

The Likelihood of Population Stabilization

Many developments—some old and some recent— enhance the likelihood that something close to an optimal path can be realized, especially’ if the Commission’s recommendations bearing on population growth are adopted quickly.

1. The trend of average family size has been downward—from seven or eight children per family in colonial times to less than three children in recent years—interrupted, however, by the baby boom.

2. The birthrate has declined over the past decade and showed an unexpected further decline in 1971.

3. The increasing employment of women, and the movement to expand women’s options as to occupational and family roles and life styles, promises to increase alternatives to the conventional role of wife-homemaker-mother.

4. Concern over the effects of population growth has been mounting. Two-thirds of the general public interviewed in the Commission’s survey in 1971 felt that the growth of the United States population is a serious problem. Half or more expressed concern over the impact of population growth on the use of natural resources, on air and water pollution, and on social unrest and dissatisfaction.

5. Youthful marriage is becoming less common than it was a few years ago. While 20 percent of women now in their thirties married before age 18, only 13 percent of the young women are doing so now.7 It remains to be seen whether this represents a postponement of marriage or a reversal of the trend toward nearly universal marriage.

6. The family-size preferences of young people now entering the childbearing ages are

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significantly lower than the preferences reported by their elders at the same stage in life.

7. The technical quality of contraceptives has increased greatly in the past 10 years, although irregular and ineffective use still results in many unplanned and unwanted births.

8. The legalization of abortion in a few states has resulted in major increases in the number of legal abortions. The evidence so far indicates that legalized abortion is being used by many women who would otherwise have had to resort to illegal and unsafe abortions. The magnitude of its effect on the birthrate is not yet clear.8

9. The experience of many other countries indicates the feasibility of sustained replacement levels of reproduction.9 Within the past half century, Japan, England and Wales, France, Denmark, Norway, West Germany, Hungary, Sweden, and Switzerland have all experienced periods of replacement or near-replacement fertility lasting a decade or more. Additional countries have had shorter periods at or near replacement levels. While much of this experience occurred during the Depression of the 19 30’s, much of it also occurred since then. Furthermore, during that period, contraceptive technology was primitive compared to what is available today.

On the basis of these facts, the nation might ask, “why worry,” and decide to wait and see what happens. Our judgment is that we should not wait. Acting now, we encourage a desirable trend. Acting later, we may find ourselves in a position of trying to reverse an undesirable trend. We should take advantage of the opportunity the moment presents rather than wait for’ what the unknown future holds.

The potential for a repeat of the baby boom is still here. In 1975, there will be six million more people in the prime childbearing ages of 20 to 29 than there were in 1970. By 1985, the figure will have jumped still another five million. Unless we achieve some postponement of childbearing or reduction in average family size, this is going to mean substantial further increases in the number of births.’°

Furthermore, although we discern many favorable elements in recent trends, there are also unfavorable elements which threaten the achievement of stabilization.

1. For historical reasons which no longer apply, this nation has an ideological addiction to growth.

2. Our social institutions, including many of our laws, often exert a pronatalist effect, even if inadvertent.” This includes the images of family life and women’s roles projected

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in television programs; the child-saves-marriage theme in women’s magazines;12 the restrictions on the availability of contraception, sex education, and abortion; and many others.

3. There is an unsatisfactory level of understanding of the role of sex in human life and of the reproductive process and its control.

4. While the white middle-class majority bears the primary numerical responsibility for population growth, it is also true that the failure of our society to bring racial minorities and the poor into the mainstream of American life has impaired their ability to implement small-family goals.

5. If it should happen that, in the next few years, our rate of reproduction falls to replacement levels or below, we could experience a strong counterreaction. In the United States in the 1930’s, and in several foreign countries, the response to subreplacement fertility has been a cry of anxiety over the national prosperity, security, and virility. Individual countries have found it hard to come to terms with replacement-level fertility rates.13 About 40 years ago during the Depression, there was great concern about “race suicide” when birthrates fell in Western Europe and in this country. Indeed, an admonition against unwarranted countermeasures was issued in 1938 by the Committee on Population Problems of the National Resources Committee:

“...there is no occasion for hysteria.... There is no reason for the hasty adoption of any measures designed to stimulate population growth in this country.”14 Today, several countries approaching stabilization have expressed concerns about possible future labor shortages. The growth ethic seems to be so imprinted in human consciousness that it takes a deliberate effort of rationality and will to overcome it, but that effort is now desirable.

One purpose of this report and the programs it recommends is to prepare the American people to welcome a replacement level of reproduction and some periods of reproduction below replacement. The nation must face the fact that achieving population stabilization sooner rather than later would require a period of time during which annual fertility was below replacement. During the transition to stabilization, the postponement of childbearing would result in annual fertility rates dropping below replacement, even though, over a lifetime, the childbearing of the parents would reach a replacement level.

In the long-run future, we should understand that a stabilized population means an average of zero growth, and there would be times when the size of the population

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declines. Indeed, zero growth can only be achieved realistically with fluctuations in both directions. We should prepare ourselves not to react with alarm, as some other countries have done recently, when the distant possibility of population decline appears.

Land-use planning

Land-use planning is the term used for a branch of public policy encompassing various disciplines which seek to order and regulate land use in an efficient and ethical way, thus preventing land-use conflicts. Governments use land-use planning to manage the development of land within their jurisdictions. In doing so, the governmental unit can plan for the needs of the community while safeguarding natural resources. To this end, it is the systematic assessment of land and water potential, alternatives for land use, and economic and social conditions in order to select and adopt the best land-use options.[1] Often one element of a comprehensive plan, a land-use plan provides a vision for the future possibilities of development in neighborhoods, districts, cities, or any defined planning area.

In the United States, the terms land-use planning, regional planning, urban planning, and urban design are often used interchangeably, and will depend on the state, county, and/or project in question. Despite confusing nomenclature, the essential function of land-use planning remains the same whatever term is applied. The Canadian Institute of Planners offers a definition that land-use planning means the scientific, aesthetic, and orderly disposition of land, resources, facilities and services with a view to securing the physical, economic and social efficiency, health and well-being of urban and rural communities. The American Planning Association states that the goal of land-use planning is to further the welfare of people and their communities by creating convenient, equitable, healthful, efficient, and attractive environments for present and future generations

Land-use planning often leads to land-use regulations, also known as zoning, but they are not one and the same. As a tool for implementing land-use plans, zoning regulates the types of activities that can be accommodated on a given piece of land, the amount of space devoted to those activities and the ways that buildings may be placed and shaped.

The ambiguous nature of the term “planning”, as it relates to land use, is historically tied to the practice of zoning. Zoning in the US came about in the late 19th and early 20th centuries to protect the interests of property owners. The practice was found to be constitutionally sound by the Supreme Court decision of Village of Euclid v. Ambler Realty Co. in 1926. Soon after, the Standard State Zoning Enabling Act gave authority to the states to regulate land use. Even so, the practice remains controversial today.

The “taking clause” of the Fifth Amendment to the United States Constitution prohibits the government from taking private property for public use without just compensation. One interpretation of the taking clause is that any restriction on the development potential of land through zoning regulation is a “taking”. A deep-rooted anti-zoning sentiment exists in America, that no one has the right to tell another what he can or cannot do with his land. Ironically, although people are often averse to being told how to develop their own land, they tend to expect the government to intervene when a proposed land use is undesirable.

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Conventional zoning has not typically regarded the manner in which buildings relate to one another or the public spaces around them, but rather has provided a pragmatic system for mapping jurisdictions according to permitted land use. This system, combined with the interstate highway system, widespread availability of mortgage loans, growth in the automobile industry, and the over-all post-World War II economic expansion, destroyed most of the character that gave distinctiveness to American cities. The urban sprawl that most US cities began to experience in the mid-twentieth century was, in part, created by a flat approach to land-use regulations. Zoning without planning created unnecessarily exclusive zones. Thoughtless mapping of these zones over large areas was a big part of the recipe for suburban sprawl. It was from the deficiencies of this practice that land-use planning developed, to envision the changes that development would cause and mitigate the negative effects of such change.

As America grew and sprawl was rampant, the much-loved America of the older towns, cities, or streetcar suburbs essentially became illegal through zoning. Unparalleled growth and unregulated development changed the look and feel of landscapes and communities. They strained commercial corridors and affected housing prices, causing citizens to fear a decline in the social, economic and environmental attributes that defined their quality of life. Zoning regulations became politically contentious as developers, legislators, and citizens struggled over altering zoning maps in a way that was acceptable to all parties. Land use planning practices evolved as an attempt to overcome these challenges. It engages citizens and policy-makers to plan for development with more intention, foresight, and community focus than had been previously used.

Types of Planning: Various types of planning have emerged over the course of the 20th century. Below are the six main typologies of planning, as defined by David Walters in his book,Designing Communities (2007):

• Traditional or comprehensive planning: Common in the US after WWII, characterized by politically neutral experts with a rational view of the new urban development. Focused on producing clear statements about the form and content of new development.

• Systems planning: 1950s–1970s, resulting from the failure of comprehensive planning to deal with the unforeseen growth of post WWII America. More analytical view of the planning area as a set of complex processes, less interested in a physical plan.

• Democratic planning: 1960s. Result of societal loosening of class and race barriers. Gave more citizens a voice in planning for future of community.

• Advocacy and equity planning: 1960s & 70s. Strands of democratic planning that sought specifically to address social issues of inequality and injustice in community planning.

• Strategic planning : 1960s-present. Recognizes small-scale objectives and pragmatic real-world constraints.

• Environmental planning: 1960s-present. Developed as many of the ecological and social implications of global development were first widely understood.

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Today, successful planning involves a balanced mix of analysis of the existing conditions and constraints; extensive public engagement; practical planning and design; and financially and politically feasible strategies for implementation.

Current processes include a combination of strategic and environmental planning. It is becoming more widely understood that any sector of land has a certain capacity for supporting human, animal, and vegetative life in harmony, and that upsetting this balance has dire consequences on the environment. Planners and citizens often take on an advocacy role during the planning process in an attempt to influence public policy. Due to a host of political and economic factors, governments are slow to adopt land use policies that are congruent with scientific data supporting more environmentally sensitive regulations.

Smart Growth: Since the 1990s, the activist/environmentalist approach to planning has grown into the Smart Growth movement, characterized by the focus on more sustainable and less environmentally damaging forms of development.

Smart growth supports the integration of mixed land uses into communities as a critical component of achieving better places to live. Putting uses in close proximity to one another has benefits for transportation alternatives to driving, security, community cohesiveness, local economies, and general quality of life issues. Smart growth strives to provide a means for communities to alter the planning context which currently renders mixed land uses illegal in most of the country.

Methods

Professional planners work in the public sector for governmental and non-profit agencies, and in the private sector for businesses related to land, community, and economic development. Through research, design, and analysis of data, a planner's work is to create a plan for some aspect of a community. This process typically involves gathering public input to develop the vision and goals for the community.

A charrette is a facilitated planning workshop often used by professional planners to gather information from their clients and the public about the project at hand. Charettes involve a diverse set of stakeholders in the planning process, to ensure that the final plan comprehensively addresses the study area.

Geographic Information Systems, or GIS, is a very useful and important tool in land-use planning. It uses aerial photography to show land parcels, topography, street names, and other pertinent information. GIS systems contain layers of graphic information and their relational databases that may be projected into maps that allow the user to view a composite of a specific area, adding an array of graphically oriented decision making tools to the planning process.

A transect, as used in planning, is a hierarchical scale of environmental zones that define a land area by its character, ranging from rural, preserved land to urban centers. As a planning methodology, the transect is used as a tool for managing growth and sustainability by planning land use around the physical character of the land. This allows a community to plan for growth while preserving the natural and historical nature of their environment.

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Re vegetation

Revegetation is the process of replanting and rebuilding the soil of disturbed land. This may be a natural process produced by plant colonization and succession, or an artificial (manmade), accelerated process designed to repair damage to a landscape due to wildfire, mining, flood, or other cause. Originally the process was simply one of applying seed and fertilizer to disturbed lands, usually grasses or clover. The fibrous root network of grasses is useful for short-term erosion control, particularly on sloping ground. Establishing long-term plant communities requires forethought as to appropriate species for the climate, size of stock required, and impact of replanted vegetation on local fauna. The motivations behind revegetation are diverse, answering needs that are both technical and aesthetic, but it is usually erosion prevention that is the primary reason. Revegetation helps prevent soil erosion, enhances the ability of the soil to absorb more water in significant rain events, and in conjunction reduces turbidity dramatically in adjoining bodies of water. Revegetation also aids protection of engineered grades and other earthworks.

Re vegetation and Conservation

Revegetation is often used to join up patches of natural habitat that have been lost, and can be a very important tool in places where much of the natural vegetation has been cleared. It is therefore particularly important in urban environments, and research in Brisbane has shown that revegetation projects can significantly improve urban bird populationsThe Brisbane study showed that connecting a revegetation patch with existing habitat improved bird species richness, while simply concentrating on making large patches of habitat was the best way to increase bird abundance. Revegetation plans therefore need to consider how the revegetated sites are connected with existing habitat patches.

Soil Replacement

Mine reclamation may involve soil amendment, replacement, or creation, particularly for areas that have been strip mined or suffered severe erosion or soil compaction. In some cases, the native soil may be removed prior to construction and replaced with fill for the duration of the work. After construction is completed, the fill is again removed and replaced with the reserved native soil for revegetation.

Mycorrhizal Communities

Mycorrhizae, symbiotic fungal-plant communities, are important to the success of revegetation efforts. Most woody plant species need these root-fungi communities to thrive, and nursery or greenhouse transplants may not have sufficient or correct

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mycorrhizae for good survival. Regional differences in ectomycorrhizal fungi may also affect the success of re vegetation.

Energy Sources

The world's energy resources can be divided into fossil fuel, nuclear fuel and renewable resources. The estimates for the amount of energy in these resources is given in zetta joules (ZJ), which is 1021 joules

Fossil Fuel

Remaining reserves of fossil fuel are estimated as:

FuelProven energy

reserves in ZJ (end of 2009)

Coal 19.8

Oil 8.1

Gas 8.1

These are the proven energy reserves; real reserves may be up to a factor 4 larger. Significant uncertainty exists for these numbers. The estimation of the remaining fossil fuels on the planet depends on a detailed understanding of the Earth's crust. This understanding is still less than perfect. While modern drilling technology makes it possible to drill wells in up to 3 km of water to verify the exact composition of the geology, one half of the ocean is deeper than 3 km, leaving about a third of the planet beyond the reach of detailed analysis.

However one should keep in mind that these quantitative measures of the amount of proven reserves of the fossil fuels do not take into account several factors critical to the cost of extracting them from the ground and critical to the price of the energy extracted from the fossil fuels. These factors include the accessibility of fossil deposits, the level of sulfur and other pollutants in the oil and the coal, transportation costs, risky locations, etc. As said before easy fossils have been extracted long ago. The ones left in the ground are dirty and expensive to extract.

Coal

Coal is the most abundant and burned fossil fuel. This was the fuel that launched the industrial revolution and has continued to grow in use; China, which already has many of

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the world's most polluted cities, was in 2007 building about two coal-fired power plants every week. Coal is the fastest growing fossil fuel and its large reserves would make it a popular candidate to meet the energy demand of the global community, short of global warming concerns and other pollutants. According to the International Energy Agency the proven reserves of coal are around 909 billion tonnes, which could sustain the current production rate for 155 years, although at a 5% growth per annum this would be reduced to 45 years, or until 2051. With the Fischer-Tropsch process it is possible to make liquid fuels such as diesel and jet fuel from coal. In the United States, 49% of electricity generation comes from burning coal.

Oil

It is estimated that there may be 57 ZJ of oil reserves on Earth (although estimates vary from a low of 8 ZJ,[ consisting of currently proven and recoverable reserves, to a maximum of 110 ZJ) consisting of available, but not necessarily recoverable reserves, and including optimistic estimates for unconventional sources such as tar sands and oil shale. Current consensus among the 18 recognized estimates of supply profiles is that the peak of extraction will occur in 2020 at the rate of 93-million barrels per day (mbd). Current oil consumption is at the rate of 0.18 ZJ per year (31.1 billion barrels) or 85-mbd.

There is growing concern that peak oil production may be reached in the near future, resulting in severe oil price increases. A 2005 French Economics, Industry and Finance Ministry report suggested a worst-case scenario that could occur as early as 2013.[14] There are also theories that peak of the global oil production may occur in as little as 2–3 years. The ASPO predicts peak year to be in 2010. Some other theories present the view that it has already taken place in 2005. World crude oil production (including lease condensates) according to US EIA data decreased from a peak of 73.720 mbd in 2005 to 73.437 in 2006, 72.981 in 2007, and 73.697 in 2008. According to peak oil theory, increasing production will lead to a more rapid collapse of production in the future, while decreasing production will lead to a slower decrease, as the bell-shaped curve will be spread out over more years.

In a stated goal of increasing oil prices to $75/barrel, which had fallen from a high of $147 to a low of $40, OPEC announced decreasing production by 2.2 mbd beginning 1 January 2009.

Sustainability

Political considerations over the security of supplies, environmental concerns related to global warming and sustainability are expected to move the world's energy consumption away from fossil fuels. The concept of peak oil shows that about half of the available petroleum resources have been produced, and predicts a decrease of production.

A government had bananas move away from fossil fuels would most likely create economic pressure through carbon emissions and green taxation. Some countries are taking action as a result of the Kyoto Protocol, and further steps in this direction are proposed. For example, the European Commission has proposed that the energy policy of the European Union should set a binding target of increasing the level of renewable energy in the EU's overall mix from less than 7% in 2007 to 20% by 2020.

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The antithesis of sustainability is a disregard for limits, commonly referred to as the Easter Island Effect, which is the concept of being unable to develop sustainability, resulting in the depletion of natural resources. Some estimate, assuming current consumption rates, current oil reserves could be completely depleted by the year 2050.

Nuclear Fuel

The International Atomic Energy Agency estimates the remaining uranium resources to be equal to 2500 ZJ. This assumes the use of breeder reactors, which are able to create more fissile material than they consume. IPCC estimated currently proved economically recoverable uranium deposits for once-through fuel cycles reactors to be only 2 ZJ. The ultimately recoverable uranium is estimated to be 17 ZJ for once-through reactors and 1000 ZJ with reprocessing and fast breeder reactors.

Resources and technology do not constrain the capacity of nuclear power to contribute to meeting the energy demand for the 21st century. However, political and environmental concerns about nuclear safety and radioactive waste started to limit the growth of this energy supply at the end of last century, particularly due to a number of nuclear accidents. Concerns about nuclear proliferation (especially with plutonium produced by breeder reactors) mean that the development of nuclear power by countries such as Iran and Syria is being actively discouraged by the international community.

Nuclear fusion

Fusion power is the process driving the sun and other stars. It generates large quantities of heat by fusing the nuclei of hydrogen or helium isotopes, which may be derived from seawater. The heat can theoretically be harnessed to generate electricity. The temperatures and pressures needed to sustain fusion make it a very difficult process to control. Fusion is theoretically able to supply vast quantities of energy, with relatively little pollution. Although both the United States and the European Union, along with other countries, are supporting fusion research (such as investing in the ITER facility), according to one report, inadequate research has stalled progress in fusion research for the past 20 years

Renewable resources are available each year, unlike non-renewable resources, which are eventually depleted. A simple comparison is a coal mine and a forest. While the forest could be depleted, if it is managed it represents a continuous supply of energy, vs. the coal mine, which once has been exhausted is gone. Most of earth's available energy resources are renewable resources. Renewable resources account for more than 93 percent of total U.S. energy reserves. Annual renewable resources were multiplied times thirty years for comparison with non-renewable resources. In other words, if all non-renewable resources were uniformly exhausted in 30 years, they would only account for 7 percent of available resources each year, if all available renewable resources were developed.

Solar energy

Renewable energy sources are even larger than the traditional fossil fuels and in theory can easily supply the world's energy needs. 89 PW of solar power falls on the planet's surface. While it is not possible to capture all, or even most, of this energy, capturing less than 0.02% would be enough to meet the current energy needs. Barriers to further solar generation include the high price of making solar cells and reliance on weather patterns to

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generate electricity. Also, current solar generation does not produce electricity at night, which is a particular problem in high northern and southern latitude countries; energy demand is highest in winter, while availability of solar energy is lowest. This could be overcome by buying power from countries closer to the equator during winter months, and may also be addressed with technological developments such as the development of inexpensive energy storage. Globally, solar generation is the fastest growing source of energy, seeing an annual average growth of 35% over the past few years. Japan, Europe, China, U.S. and India are the major growing investors in solar energy.

Wind power

The available wind energy estimates range from 300 TW to 870 TW. Using the lower estimate, just 5% of the available wind energy would supply the current worldwide energy needs. Most of this wind energy is available over the open ocean. The oceans cover 71% of the planet and wind tends to blow more strongly over open water because there are fewer obstructions.

Wave and tidal power

At the end of 2005, 0.3 GW of electricity was produced by tidal power. Due to the tidal forces created by the Moon (68%) and the Sun (32%), and the Earth's relative rotation with respect to Moon and Sun, there are fluctuating tides. These tidal fluctuations result in dissipation at an average rate of about 3.7 TW.

Another physical limitation is the energy available in the tidal fluctuations of the oceans, which is about 0.6 EJ (exa joule). Note this is only a tiny fraction of the total rotational energy of the Earth. Without forcing, this energy would be dissipated (at a dissipation rate of 3.7 TW) in about four semi-diurnal tide periods. So, dissipation plays a significant role in the tidal dynamics of the oceans. Therefore, this limits the available tidal energy to around 0.8 TW (20% of the dissipation rate) in order not to disturb the tidal dynamics too much.

Waves are derived from wind, which is in turn derived from solar energy, and at each conversion there is a drop of about two orders of magnitude in available energy. The total power of waves that wash against our shores add up to 3 TW.

Geothermal

Estimates of exploitable worldwide geothermal energy resources vary considerably, depending on assumed investment in technology and exploration and guesses about geological formations. According to a 1999 study, it was thought that this might amount to between 65 and 138 GW of electrical generation capacity 'using enhanced technology'. Other estimates range from 35 to 2000 GW of electrical generation capacity, with a further potential for 140 EJ/year of direct use.

A 2006 report by MIT that took into account the use of Enhanced Geothermal Systems (EGS) concluded that it would be affordable to generate 100 GWe (gigawatts of electricity) or more by 2050, just in the United States, for a maximum investment of 1 billion US dollars in research and development over 15 years. The MIT report calculated the world's total EGS resources to be over 13 YJ, of which over 200 ZJ would be extractable, with the potential to increase this to over 2 YJ with technology improvements - sufficient to

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provide all the world's energy needs for several millennia. The total heat content of the Earth is 13,000,000 YJ.

Biomass

Production of biomass and biofuels are growing industries as interest in sustainable fuel sources is growing. Utilizing waste products avoids a food vs fuel trade-off, and burning methane gas reduces greenhouse gas emissions, because even though it releases carbon dioxide, carbon dioxide is 23 times less of a greenhouse gas than is methane. Biofuels represent a sustainable partial replacement for fossil fuels, but their net impact on greenhouse gas emissions depends on the agricultural practices used to grow the plants used as feedstock to create the fuels. While it is widely believed that biofuels can be carbon-neutral, there is evidence that biofuels produced by current farming methods are substantial net carbon emitters. Geothermal and biomass are the only two renewable energy sources that require careful management to avoid local depletion.

Hydropower

In 2005, hydroelectric power supplied 16.4% of world electricity, down from 21.0% in 1973, but only 2.2% of the world's energy.

Nuclear Power

Nuclear power, or nuclear energy, is the use of exothermic nuclear processes,[1] to generate useful heat and electricity. The term includes nuclear fission, nuclear decay and nuclear fusion. Presently the nuclear fission of elements in the actinide series of the periodic table produce the vast majority of nuclear energy in the direct service of humankind, with nuclear decay processes, primarily in the form of geothermal energy, and radioisotope thermoelectric generators, in niche uses making up the rest. Nuclear (fission) power stations, excluding the contribution from naval nuclear fission reactors, provided about 5.7% of the world's energy and 13% of the world's electricity in 2012. In 2013, the IAEA report that there are 437 operational nuclear power reactors, in 31 countries, although not every reactor is producing electricity. In addition, there are approximately 140 naval vessels using nuclear propulsion in operation, powered by some 180 reactors. As of 2013, attaining a net energy gain from sustained nuclear fusion reactions, excluding natural fusion power sources such as the Sun, remains an ongoing area of international physics and engineering research. More than 60 years after the first attempts, commercial fusion power production remains unlikely before 2050.

There is an ongoing debate about nuclear power Proponents, such as the World Nuclear Association, the IAEA and Environmentalists for Nuclear Energy contend that nuclear power is a safe, sustainable energy source that reduces carbon emissions. Opponents, such as Greenpeace International and NIRS, contend that nuclear power poses many threats to people and the environment.

Nuclear power plant accidents include the Chernobyl disaster (1986), Fukushima Daiichi nuclear disaster (2011), and the Three Mile Island accident (1979). There have also been some nuclear submarine accidents. In terms of lives lost per unit of energy generated, analysis has determined that nuclear power has caused less fatalities per unit of energy generated than the other major sources of energy generation. Energy production

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from coal, petroleum, natural gas and hydropower has caused a greater number of fatalities per unit of energy generated due to air pollution and energy accident effects. However, the economic costs of nuclear power accidents is high, and meltdowns can take decades to clean up. The human costs of evacuations of affected populations and lost livelihoods is also significant.

Along with other sustainable energy sources, nuclear power is a low carbon power generation method of producing electricity, with an analysis of the literature on its total life cycle emission intensity finding that it is similar to other renewable sources in a comparison of greenhouse gas(GHG) emissions per unit of energy generated. With this translating into, from the beginning of nuclear power station commercialization in the 1970s, having prevented the emission of approximately 64 giga tones of carbon dioxide equivalent(GtCO2-eq)greenhouse gases, gases that would have otherwise resulted from the burning of fossil fuels in thermal power stations.

As of 2012, according to the IAEA, worldwide there were 68 civil nuclear power reactors under construction in 15 countries, approximately 28 of which in the Peoples Republic of China (PRC), with the most recent nuclear power reactor, as of May 2013, to be connected to the electrical grid, occurring on February 17, 2013 in Hongyanhe Nuclear Power Plant in the PRC. In the USA, two new Generation III reactors are under construction at Vogtle. U.S. nuclear industry officials expect five new reactors to enter service by 2020, all at existing plants. In 2013, four aging, uncompetitive, reactors were permanently closed.

Japan's 2011 Fukushima Daiichi nuclear disaster, which occurred in a reactor design from the 1960s, prompted a re-examination of nuclear safety and nuclear energy policy in many countries. Germany decided to close all its reactors by 2022, and Italy has banned nuclear power. Following Fukushima, in 2011 the International Energy Agency halved its estimate of additional nuclear generating capacity to be built by 2035.

Non Renewable Energy

Non-renewable fossil fuels (crude oil, natural gas, coal, oil shales and tar sands) currently supply Australia with more than 95 percent of our electrical energy needs. Non-renewable energy is energy produced by burning fossil fuels such as coal. They are non-renewable because there are finite resources of fossil fuels on the planet. If they are continually used, one day they will run out.

The sources of fossil fuel

Just as plants do today, those living millions of years ago converted the sun's light energy into food (chemical) energy through the process of photosynthesis. That 'solar' energy was and is transferred down the food chain in animals. This energy provides living things with the energy to grow and live. When living organisms die the energy contained within them as chemical energy is trapped.

It is estimated that the total amount of energy gained from fossil fuels since the start of civilization is equivalent to the same amount of energy we receive every 30 days from the sun.

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Fossil fuels are formed by the burying, and subsequent pressure and heating, of dead plant and animal matter or biomass (organic matter), over millions of years. This is how coal, oil and natural gas are formed. The trapped energy can be released and utilized when the fuels are burnt.

Advantages

There are a few major advantages with non-renewable energy. Fossil fuels, such as coal, oil and gas are abundant in Australia so this means they are a relatively cheap fuel and readily available. Australia has enough fossil fuel resources to last for hundreds of years. Also very large amounts of electricity can be generated from fossil fuels.

An Example of a typical coal-fired power station

A typical coal-fired power station generates electricity by burning coal in a boiler that heats up water, which is converted into superheated steam. This steam drives a steam turbine that in turn drives a generator that produces electricity. A single coal-fired power station unit can power many thousands of houses as well as large industry.

Disadvantages of fossil fuel

Fossil fuels are non-renewable and will eventually run out because we are using them much faster than they can be restored within the earth. Burning fossil fuels produces photochemical pollution from nitrous oxides, and acid rain from sulphur dioxide. Burning fuels also produce greenhouse gases including vast amounts of carbon dioxide that may be causing the phenomenon of global warming that the planet is currently experiencing.

Bio Energy

Bioenergy is renewable energy made available from materials derived from biological sources. Biomass is any organic material which has stored sunlight in the form of chemical energy. As a fuel it may include wood, wood waste, straw, manure, sugarcane, and many other byproducts from a variety of agricultural processes. By 2010, there was 35 GW (47,000,000 hp) of globally installed bioenergy capacity for electricity generation, of which 7 GW (9,400,000 hp) was in the United States.

In its most narrow sense it is a synonym to biofuel, which is fuel derived from biological sources. In its broader sense it includes biomass, the biological material used as a biofuel, as well as the social, economic, scientific and technical fields associated with using biological sources for energy. This is a common misconception, as bioenergy is the energy extracted from the biomass, as the biomass is the fuel and the bioenergy is the energy contained in the fuel.

There is a slight tendency for the word bioenergy to be favoured in Europe compared with biofuel America

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Solid Biomass

One of the advantages of biomass fuel is that it is often a by-product, residue or waste-product of other processes, such as farming, animal husbandry and forestry.[1] In theory this means there is no competition between fuel and food production, although this is not always the case.

Biomass is the material derived from recently living organisms, which includes plants, animals and their byproducts. Manure, garden waste and crop residues are all sources of biomass. It is a renewable energy source based on the carbon cycle, unlike other natural resources such as petroleum, coal, and nuclear fuels. Another source includes Animal waste, which is a persistent and unavoidable pollutant produced primarily by the animals housed in industrial-sized farms.

There are also agricultural products specifically being grown for bio fuel production. These include corn, and soybeans and to some extent willow and switch grass on a pre-commercial research level, primarily in the United States; rapeseed, wheat, sugar beet, and willow (15,000 ha or 37,000 acres in Sweden) primarily in Europe; sugarcane in Brazil; palm oil and miscanthus in Southeast Asia; sorghum and cassava in China; and jatropha in India. Hemp has also been proven to work as a bio fuel. Biodegradable outputs from industry, agriculture, forestry and households can be used for bio fuel production, using e.g. anaerobic digestion to produce biogas, gasification to produce syn gas or by direct combustion. Examples of biodegradable wastes include straw, timber, manure, rice husks, sewage, and food waste. The use of biomass fuels can therefore contribute to waste management as well as fuel security and help to prevent or slow down climate change, although alone they are not a comprehensive solution to these problems.

Biomass can be converted to other usable forms of energy like methane gas or transportation fuels like ethanol and biodiesel. Rotting garbage, and agricultural and human waste, all release methane gas—also called "landfill gas" or "biogas." Crops, such as corn and sugar cane, can be fermented to produce the transportation fuel, ethanol. Biodiesel, another transportation fuel, can be produced from left-over food products like vegetable oils and animal fats. Also, Biomass to liquids (BTLs) and cellulosic ethanol are still under research.

Electricity generation from Biomass

The biomass used for electricity production ranges by region. Forest by products, such as wood residues, are popular in the United States. Agricultural waste is common in Mauritius (sugar cane residue) and Southeast Asia (rice husks). Animal husbandry residues, such as poultry litter, is popular in the UK.

Electricity from sugarcane biogases in Brazil

Sucrose accounts for little more than 30% of the chemical energy stored in the mature plant; 35% is in the leaves and stem tips, which are left in the fields during harvest, and 35% are in the fibrous material (bagasse) left over from pressing.

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The production process of sugar and ethanol in Brazil takes full advantage of the energy stored in sugarcane. Part of the bagasse is currently burned at the mill to provide heat for distillation and electricity to run the machinery. This allows ethanol plants to be energetically self-sufficient and even sell surplus electricity to utilities; current production is 600 MW (800,000 hp) for self-use and 100 MW (130,000 hp) for sale. This secondary activity is expected to boom now that utilities have been induced to pay "fair price "(about US$10/GJ or US$0.036/kWh) for 10 year contracts. This is approximately half of what the World Bank considers the reference price for investing in similar projects (see below). The energy is especially valuable to utilities because it is produced mainly in the dry season when hydroelectric dams are running low. Estimates of potential power generation from biogases range from 1,000 to 9,000 MW (1,300,000 to 12,100,000 hp), depending on technology. Higher estimates assume gasification of biomass, replacement of current low-pressure steam boilers and turbines by high-pressure ones, and use of harvest trash currently left behind in the fields. For comparison, Brazil's Angra I nuclear plant generates 657 MW (881,000 hp).

Presently, it is economically viable to extract about 288 MJ of electricity from the residues of one tonne of sugarcane, of which about 180 MJ are used in the plant itself. Thus a medium-size distillery processing 1,000,000 tonnes (980,000 long tons; 1,100,000 short tons) of sugarcane per year could sell about 5 MW (6,700 hp) of surplus electricity. At current prices, it would earn US$ 18 million from sugar and ethanol sales, and about US$ 1 million from surplus electricity sales. With advanced boiler and turbine technology, the electricity yield could be increased to 648 MJ per tonne of sugarcane, but current electricity prices do not justify the necessary investment. (According to one report, the World Bank would only finance investments in bagasse power generation if the price were at least US$19/GJ or US$0.068/kWh.)

Biogases burning is environmentally friendly compared to other fuels like oil and coal. Its ash content is only 2.5% (against 30–50% of coal), and it contains very little sulfur. Since it burns at relatively low temperatures, it produces little nitrous oxides. Moreover, bagasse is being sold for use as a fuel (replacing heavy fuel oil) in various industries, including citrus juice concentrate, vegetable oil, ceramics, and tyre recycling. The state of São Paulo alone used 2,000,000 tonnes (1,970,000 long tons; 2,200,000 short tons), saving about US$ 35 million in fuel oil imports.

Researchers working with cellulosic ethanol are trying to make the extraction of ethanol from sugarcane biogases and other plants viable on an industrial scale.

Environmental Impact

Some forms of forest bioenergy have recently come under fire from a number of environmental organizations, including Greenpeace and the Natural Resources Defense Council, for the harmful impacts they can have on forests and the climate. Greenpeace recently released a report entitled Fuelling a BioMess which outlines their concerns around forest bioenergy. Because any part of the tree can be burned, the harvesting of trees for energy production encourages Whole-Tree Harvesting, which removes more nutrients and soil cover than regular harvesting, and can be harmful to the long-term health of the forest.

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In some jurisdictions, forest biomass is increasingly consisting of elements essential to functioning forest ecosystems, including standing trees, naturally disturbed forests and remains of traditional logging operations that were previously left in the forest. Environmental groups also cite recent scientific research which has found that it can take many decades for the carbon released by burning biomass to be recaptured by regrowing trees, and even longer in low productivity areas; furthermore, logging operations may disturb forest soils and cause them to release stored carbon. In light of the pressing need to reduce greenhouse gas emissions in the short term in order to mitigate the effects of climate change, a number of environmental groups are opposing the large-scale use of forest biomass in energy production

Biogas

Biogas typically refers to a mixture of gases produced by the breakdown of organic matter in the absence of oxygen. Biogas can be produced from regionally available raw materials such as recycled waste. It is a renewable energy source and in many cases exerts a very small carbon footprint.

Biogas is produced by anaerobic digestion with anaerobic bacteria or fermentation of biodegradable materials such as manure, sewage, municipal waste, green waste, plant material, and crops. It is primarily methane (CH4) and carbon dioxide (CO2) and may have small amounts of hydrogen sulphide (H2S), moisture and siloxanes.

The gases methane, hydrogen, and carbon monoxide (CO) can be combusted or oxidized with oxygen. This energy release allows biogas to be used as a fuel; it can be used for any heating purpose, such as cooking. It can also be used in a gas engine to convert the energy in the gas into electricity and heat.

Biogas can be compressed, the same way natural gas is compressed to CNG, and used to power motor vehicles. In the UK, for example, biogas is estimated to have the potential to replace around 17% of vehicle fuel. It qualifies for renewable energy subsidies in some parts of the world. Biogas can be cleaned and upgraded to natural gas standards when it becomes bio methane.

Production

Biogas is practically produced as landfill gas (LFG) or digested gas. A biogas plant is the name often given to an anaerobic digester that treats farm wastes or energy crops. It can be produced using anaerobic digesters. These plants can be fed with energy crops such as maize silage or biodegradable wastes including sewage sludge and food waste. During the process, an air-tight tank transforms biomass waste into methane, producing renewable energy that can be used for heating, electricity, and many other operations that use an internal combustion engine, such as GE Jenbacher or Caterpillar gas engines.

There are two key processes: mesophilic and thermophilic digestion. In experimental work at University of Alaska Fairbanks, a 1000-litre digester using psychrophiles harvested from

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"mud from a frozen lake in Alaska" has produced 200–300 liters of methane per day, about 20%–30% of the output from digesters in warmer climates.

Landfill gas

Landfill gas is produced by wet organic waste decomposing under anaerobic conditions in a landfill.

The waste is covered and mechanically compressed by the weight of the material that is deposited above. This material prevents oxygen exposure thus allowing anaerobic microbes to thrive. This gas builds up and is slowly released into the atmosphere if the site has not been engineered to capture the gas. Landfill gas released in an uncontrolled way can be hazardous since it can becomes explosive when it escapes from the landfill and mixes with oxygen. The lower explosive limit is 5% methane and the upper is 15% methane.

The methane in biogas is 20 times more potent a greenhouse gas than carbon dioxide. Therefore, uncontained landfill gas, which escapes into the atmosphere may significantly contribute to the effects of global warming. In addition,volatile organic compounds (VOCs) in landfill gas contribute to the formation of photochemical smog.

Technical

Biochemical Oxygen Demand, or BOD is a measure of the amount of oxygen required by aerobic micro-organisms to decompose the organic matter in a sample of water. Knowing the energy density of the material being used in the biodigester as well as the BOD for the liquid discharge allows for the calculation of the daily energy output from a biodigester.

Other terms related to biodigesters include effluent dirtiness, which relates how much organic material there is per unit of biogas source. Typical units for this measure are in mg BOD/Litre. As an example, effluent dirtiness can range between 800–1200 mg BOD/Litre in Panama

Composition

The composition of biogas varies depending upon the origin of the anaerobic digestion process. Landfill gas typically has methane concentrations around 50%. Advanced waste treatment technologies can produce biogas with 55%–75% methane, which for reactors with free liquids can be increased to 80%-90% methane using in-situ gas purification techniques. As produced, biogas contains water vapor. The fractional volume of water vapor is a function of biogas temperature; correction of measured gas volume for water vapor content and thermal expansion is easily done via simple mathematics which yields the standardized volume of dry biogas.

In some cases, biogas contains siloxanes. They are formed from the anaerobic decomposition of materials commonly found in soaps and detergents. During combustion of biogas containing siloxanes, silicon is released and can combine with free oxygen or other elements in the combustion gas. Deposits are formed containing mostly silica (SiO2) or silicates(SixOy) and can contain calcium, sulfur, zinc, phosphorus. Such white

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mineral deposits accumulate to a surface thickness of several millimeters and must be removed by chemical or mechanical means.

Practical and cost-effective technologies to remove siloxanes and other biogas contaminants are available.

For 1000 kg (wet weight) of input to a typical biodigester, total solids may be 30% of the wet weight while volatile suspended solids may be 90% of the total solids. Protein would be 20% of the volatile solids, carbohydrates would be 70% of the volatile solids, and finally fats would be 10% of the volatile solids.

Benefits

In North America, use of biogas would generate enough electricity to meet up to 3% of the continent's electricity expenditure. In addition, biogas could potentially help reduce global climate change. High levels of methane are produced when manure is stored under anaerobic conditions. During storage and when manure has been applied to the land, nitrous oxide is also produced as a byproduct of the denitrification process. Nitrous oxide (N2O) is 320 times more aggressive than carbon dioxide and methane 21 times more than carbon dioxide.

By converting cow manure into methane biogas via anaerobic digestion, the millions of cattle in the United States would be able to produce 100 billion kilowatt hours of electricity, enough to power millions of homes across the United States. In fact, one cow can produce enough manure in one day to generate 3 kilowatt hours of electricity; only 2.4 kilowatt hours of electricity are needed to power a single 100-watt light bulb for one day. Furthermore, by converting cattle manure into methane biogas instead of letting it decompose, global warming gases could be reduced by 99 million metric tons or 4%

Applications

Biogas can be used for electricity production on sewage works, in a CHP gas engine, where the waste heat from the engine is conveniently used for heating the digester; cooking; space heating; water heating; and process heating. If compressed, it can replace compressed natural gas for use in vehicles, where it can fuel an internal combustion engine or fuel cells and is a much more effective displacer of carbon dioxide than the normal use in on-site CHP plants.

Biogas upgrading

Raw biogas produced from digestion is roughly 60% methane and 29% CO2 with trace elements of H2S; it is not of high enough quality to be used as fuel gas for machinery. The corrosive nature of H2S alone is enough to destroy the internals of a plant.

Methane in biogas can be concentrated via a biogas up grader to the same standards as fossil natural gas, which itself has had to go through a cleaning process, and becomes biomethane. If the local gas network allows, the producer of the biogas may use their distribution networks. Gas must be very clean to reach pipeline quality and must be of the

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correct composition for the distribution network to accept. Carbon dioxide, water, hydrogen sulfide, and particulates must be removed if present.

There are four main methods of upgrading: water washing, pressure swing adsorption, selexol adsorption, and amine gas treating.

The most prevalent method is water washing where high pressure gas flows into a column where the carbon dioxide and other trace elements are scrubbed by cascading water running counter-flow to the gas. This arrangement could deliver 98% methane with manufacturers guaranteeing maximum 2% methane loss in the system. It takes roughly between 3% and 6% of the total energy output in gas to run a biogas upgrading system.

Biogas gas-grid injection

Gas-grid injection is the injection of biogas into the methane grid (natural gas grid). Injections includes biogas until the breakthrough of micro combined heat and power two-thirds of all the energy produced by biogas power plants was lost (the heat), using the grid to transport the gas to customers, the electricity and the heat can be used for on-site generation resulting in a reduction of losses in the transportation of energy. Typical energy losses in natural gas transmission systems range from 1% to 2%. The current energy losses on a large electrical system range from 5% to 8%.

Biogas in transport

If concentrated and compressed, it can be used in vehicle transportation. Compressed biogas is becoming widely used in Sweden, Switzerland, and Germany. A biogas-powered train, named Biogas tåget Amanda (The Biogas Train Amanda), has been in service in Sweden since 2005. Biogas powers automobiles. In 1974, a British documentary film titled Sweet as a Nut detailed the biogas production process from pig manure and showed how it fueled a custom-adapted combustion engine. In 2007, an estimated 12,000 vehicles were being fueled with upgraded biogas worldwide, mostly in Europe.

Measuring in biogas environments

Biogas is part of the wet gas and condensing gas (or air) category that includes mist or fog in the gas stream. The mist or fog is predominately water vapor that condenses on the sides of pipes or stacks throughout the gas flow. Biogas environments include wastewater digesters, landfills, and animal feeding operations (covered livestock lagoons).

Ultrasonic flow meters are one of the few devices capable of measuring in a biogas atmosphere. Most thermal flow meters are unable to provide reliable data because the moisture causes steady high flow readings and continuous flow spiking, although there are single-point insertion thermal mass flow meters capable of accurately monitoring biogas flows with minimal pressure drop. They can handle moisture variations that occur in the flow stream because of daily and seasonal temperature fluctuations, and account for the moisture in the flow stream to produce a dry gas value.

Ecotechnology

Ecotechnology is an applied science that seeks to fulfill human needs while causing minimal ecological disrupution, by harnessing and manipulating natural forces to leverage

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their beneficial effects. Ecotechnology integrates two fields of study: the 'ecology of technics' and the 'technics of ecology,' requiring an understanding of the structures and processes of ecosystems and societies. All sustainable engineering that can reduce damage to ecosystems, adopt ecology as a fundamental basis, and ensure conservation of biodiversity and sustainable development may be considered as forms of ecotechnology.

Ecotechnology emphasizes approaching a problem from a holistic point of view. For example, remediation of rivers should not only consider one single area. Rather, the whole catchment area, which includes the upstream, middle stream and downstream sections, should be considered.

Construction can reduce its impact on nature by consulting experts on the environment.

Sustainable development requires the implementation of environmentally friendly technologies which are both efficient and adapted to local conditions. Ecotechnology allows improvement in economic performance while minimizing harm to the environment by:

• increasing the efficiency in the selection and use of materials and energy sources,• control of impacts on ecosystems,• development and permanent improvement of cleaner processes and products,• eco-marketing,• introducing environmental management systems in the production and services

sectors, and• Development of activities for increasing awareness of the need for environmental

protection and promotion of sustainable development by the general public.

Sustainable development

Sustainable development is an organizing principle for human life on a finite planet. It posits a desirable future state for human societies in which living conditions and resource-use meet human needs without undermining the sustainability of natural systems and the environment, so that future generations may also have their needs met.

Sustainable development ties together concern for the carrying capacity of natural systems with the social, political, and economic challenges faced by humanity. As early as the 1970s, 'sustainability' was employed to describe an economy "in equilibrium with basic ecological support systems." Scientists in many fields have highlighted The Limits to Growth, and economists have presented alternatives, for example a 'steady state economy', to address concerns over the impacts of expanding human development on the planet.

The term sustainable development rose to significance after it was used by the Brundt land Commission in its 1987 report Our Common Future. In the report, the commission coined what has become the most often-quoted definition of sustainable development: "development that meets the needs of the present without compromising the ability of future generations to meet their own needs."

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The United Nations Millennium Declaration identified principles and treaties on sustainable development, including economic development, social development and environmental protection.

Definitions

The United Nations World Commission on Environment and Development (WCED) in its 1987 report Our Common Future defines sustainable development: "Development that meets the needs of the present without compromising the ability of future generations to meet their own needs."[5] Under the principles of the United Nations Charter the Millennium Declaration identified principles and treaties on sustainable development, including economic development, social development and environmental protection. Broadly defined, sustainable development is a systems approach to growth and development and to manage natural, produced, and social capital for the welfare of their own and future generations.

The concept of sustainable development was originally synonymous with that of sustainability and is often still used in that way. Both terms derive from the older forestry term "sustained yield", which in turn is a translation of the German term "nachhaltiger Ertrag" dating from 1713. Sustainability science is the study of the concepts of sustainable development and environmental science. There is an additional focus on the present generations' responsibility to improve and maintain the future generations' life by restoring the previous ecosystem and resisting to contribute to further ecosystem degradation.

Sustainability

According to M. Hasna, sustainability is a function of social, economic, technological and ecological themes.

Important related concepts are 'strong' and 'weak' sustainability, deep ecology, and just sustainability. "Just sustainability" offers a socially just conception of sustainability. Just sustainability effectively addresses what has been called the 'equity deficit' of environmental sustainability (Agyeman, 2005:44). It is “the egalitarian conception of sustainable development" (Jacobs, 1999:32). It generates a more nuanced definition of sustainable development: “the need to ensure a better quality of life for all, now and into the future, in ajust and equitable manner, whilst living within the limits of supporting ecosystems” (Agyeman, et al., 2003:5).

History

The concept of "sustainable development" has its roots in forest management in the 12th to 16th centuries. The history of cognate concepts is older. In 400 BCE, Aristotle had referred to a similar Greek concept in talking about household economics. This Greek household concept differed from modern ones in that the household had to be self-sustaining at least to a certain extent and could not just be consumption oriented.

However, over the last two decades the concept has been significantly widened. The first use of the term sustainable in the contemporary general sense was by the Club of Rome in 1972 in its classic report on the "Limits to Growth", written by a group of scientists led

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by Dennis and Donella Meadows of the Massachusetts Institute of Technology. Describing the desirable "state of global equilibrium", the authors used the word "sustainable": "We are searching for a model output that represents a world system that is: 1. sustainable without sudden and uncontrolled collapse; and 2. capable of satisfying the basic material requirements of all of its people."

In 1982, the United Nations World Charter for Nature raised five principles of conservation by which human conduct affecting nature is to be guided and judged.

In 1987, the United Nations World Commission on Environment and Development released the report Our Common Future, now commonly named the 'Brundtland Report' after the commission's chairperson, the then Prime Minister of Norway Gro Harlem Brundtland. The report included what is now one of the most widely recognised definitions: "Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs." The Brundtland Report goes on to say that sustainable development also contains within it two key concepts:

• The concept of 'needs', in particular the essential needs of the world's poor, to which overriding priority should be given

• The idea of limitations imposed by the state of technology and social organization on the environment's ability to meet present and future needs.

In 1992, the UN Conference on Environment and Development published in 1992 the Earth Charter, which outlines the building of a just, sustainable, and peaceful global society in the 21st century. The action plan Agenda 21 for sustainable development identified information, integration, and participation as key building blocks to help countries achieve development that recognizes these interdependent pillars. It emphasises that in sustainable development everyone is a user and provider of information. It stresses the need to change from old sector-centered ways of doing business to new approaches that involve cross-sectoral co-ordination and the integration of environmental and social concerns into all development processes. Furthermore, Agenda 21 emphasises that broad public participation in decision making is a fundamental prerequisite for achieving sustainable development.

The Commission on Sustainable Development integrated sustainable development in the UN System. Indigenous peoples have argued, through various international forums such as the United Nations Permanent Forum on Indigenous Issues and the Convention on Biological Diversity, that there are four pillars of sustainable development, the fourth being cultural. The Universal Declaration on Cultural Diversity from 2001 states: "... cultural diversity is as necessary for humankind as biodiversity is for nature”; it becomes “one of the roots of development understood not simply in terms of economic growth, but also as a means to achieve a more satisfactory intellectual, emotional, moral and spiritual existence".

This was supported by study in 2013 which concluded that sustainability reporting should be reframed through considering four interconnected domains: ecology, economics, politics and culture.

Ecology

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The ecological sustainability of human settlements is part of the relationship between humans and their natural, social and built environments. Also termed human ecology, this broadens the focus of sustainable development to include the domain of human health. Fundamental human needs such as the availability and quality of air, water, food and shelter are also the ecological foundations for sustainable development; addressing public health risk through investments in ecosystem services can be a powerful and transformative force for sustainable development which, in this sense, extends to all species.

Agriculture

Sustainable agriculture may be defined as consisting of environmentally friendly methods of farming that allow the production of crops or livestock without damage to human or natural systems. More specifically, it might be said to include preventing adverse effects to soil, water, biodiversity, surrounding or downstream resources—as well as to those working or living on the farm or in neighboring areas. Furthermore, the concept of sustainable agriculture extends intergenerationally, relating to passing on a conserved or improved natural resource, biotic, and economic base instead of one which has been depleted or polluted. Some important elements of sustainable agriculture are permaculture, agroforestry, mixed farming, multiple cropping, and crop rotation.

Numerous sustainability standards and certification systems have been established in recent years to meet development goals, thus offering consumer choices for sustainable agriculture practices. Well-known food standards include organic, Rainforest Alliance, fair trade, UTZ Certified, Bird Friendly, and the Common Code for the Coffee Community(4C).

Energy

Sustainable energy is the sustainable provision of energy that is clean and lasts for a long period of time. Unlike the fossil fuel that most of the countries are using, renewable energy only produces little or even no pollution. The most common types of renewable energy in US are solar and wind energy, solar energy are commonly used on public parking meter, street lights and the roof of buildings. On the other hand, wind energy is expanding quickly in recent years, which generated 12,000 MW in 2013. The largest wind power station is in Texas and followed up by California. Household energy consumption can also be improved in a sustainable way, like using electronic with energy star <https://en.wikipedia.org/wiki/Energy_Star> logo, conserving water and energy. Most of California’s fossil fuel infrastructures are sited in or near low-income communities, and have traditionally suffered the most from California’s fossil fuel energy system. These communities are historically left out during the decision- making process, and often end up with dirty power plants and other dirty energy projects that poison the air and harm the area. These toxins are major contributors to significant health problems in the communities. While renewable energy becomes more common, the government begins to shut down some of the fossil fuel infrastructures in order to consume renewable energy and provide a better social equity to the specific community.

Environment

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Beyond ecology as the intersection of humans in the environment, environmental sustainability concerns the natural environment and how it endures and remains diverse and productive. Since Natural resources are derived from the environment, the state of air, water, and the climate are of particular concern. The IPCC Fifth Assessment Report outlines current knowledge about scientific, technical and socio-economic information concerning climate change, and lists options for adaptation and mitigation.[30] Environmental sustainability requires society to design activities to meet human needs while preserving the life support systems of the planet. This, for example, entails using water sustainably, utilizing renewable energy, and sustainable material supplies (e.g. harvesting wood from forests at a rate that maintains the biomass and biodiversity).

An "unsustainable situation" occurs when natural capital (the sum total of nature's resources) is used up faster than it can be replenished. Sustainability requires that human activity only uses nature's resources at a rate at which they can be replenished naturally. Inherently the concept of sustainable development is intertwined with the concept of carrying capacity. Theoretically, the long-term result of environmental degradation is the inability to sustain human life. Such degradation on a global scale should imply an increase in human death rate until population falls to what the degraded environment can support. If the degradation continues beyond a certain tipping point or critical threshold it would lead to eventual extinction for humanity.

Consumption of renewable resources State of environment Sustainability

More than nature's ability to replenish

Environmental degradation Not sustainable

Equal to nature's ability to replenish Environmental equilibrium Steady state economy

Less than nature's ability to replenish Environmental renewal Environmentally

sustainable

Transportation

Some western countries and United States are making transportation more sustainable in both long-term and short-term implementations. Since these countries are mostly highly automobile-orientated area, the main transit that people use is personal vehicles. Therefore, California is one of the highest greenhouse gases emission in the country. The federal government has to come up with some plans to reduce the total number of vehicle trips in order to lower greenhouse gases emission. Such as:

Improve public transit

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- Larger coverage area in order to provide more mobility and accessibility, use new technology to provide a more reliable and responsive public transportation network, company providing ECO pass to employees.

Encourage walking and biking

-Wider pedestrian pathway, bike share station in commercial downtown, locate parking lot far from the shopping center, limit on street parking, slower traffic lane in downtown area.

Increase the cost of car ownership and gas taxes

-Increase parking fees/ toll fees, encourage people to drive more fuel efficient vehicles. -Social equity problem, poor people usually drive old cars that have low fuel efficiency. However, government can use the extra revenue collected from taxes and tolls to improve the public transportation and benefit the poor community.

Unit-II

Mineral Resources Classification

Mineral resource classification is the classification of mineral deposits based on their geologic certainty and economic value.

Mineral deposits can be classified as:

• Mineral resources that are potentially valuable, and for which reasonable prospects exist for eventual economic extraction.

• Mineral reserves or Ore reserves that are valuable and legally and economically and technically feasible to extract

In common mining terminology, an "ore deposit" by definition must have an 'ore reserve', and may or may not have additional 'resources'.

Classification, because it is an economic function, is governed by statutes, regulations and industry best practice norms. There are several classification schemes worldwide, however the Canadian CIM classification (see NI 43-101), the Australasian Joint Ore Reserves Committee Code (JORC Code), the South African Code for the Reporting of Mineral Resources and Mineral Reserves (SAMREC) and the “chessboard” classification scheme of mineral deposits by H. G. Dill are the general standards.

Mineral Resources

A 'Mineral Resource' is a concentration or occurrence of material of intrinsic economic interest in or on the earth's crust in such form, quality and quantity that there are reasonable prospects for eventual economic extraction. Mineral Resources are further sub-

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divided, in order of increasing geological confidence, into inferred, Indicated and measured Categories.

Inferred Mineral Resource is that part of a mineral resource for which tonnage, grade and mineral content can be estimated with a low level of confidence. It is inferred from geological evidence and assumed but not verified geological/or grade continuity. It is based on information gathered through appropriate techniques from location such as outcrops, trenches, pits, workings and drill holes which may be of limited or uncertain quality and reliability.

Indicated resources are simply economic mineral occurrences that have been sampled (from locations such as outcrops, trenches, pits and drill holes) to a point where an estimate has been made, at a reasonable level of confidence, of their contained metal, grade, tonnage, shape, densities, physical characteristics.

Measured resources are indicated resources that have undergone enough further sampling that a 'competent person' (defined by the norms of the relevant mining code; usually a geologist) has declared them to be an acceptable estimate, at a high degree of confidence, of the grade, tonnage, shape, densities, physical characteristics and mineral content of the mineral occurrence.

Resources may also make up portions of a mineral deposit classified as a mineral reserve, but:

• Have not been sufficiently drilled out to qualify for Reserve status; or• Have yet to meet all criteria for Reserve status

Mineral Reserves/Ore Reserves

Mineral reserves are resources known to be economically feasible for extraction. Reserves are either Probable Reserves or Proved Reserves.

A Probable Ore Reserve is the part of Indicated resources that can be mined in an economically viable fashion, and in some circumstances, a Measured Mineral Resource. It includes diluting material and allowances for losses which may occur when the material is mined. A Probable Ore Reserve has a lower level of confidence than a Proved Ore Reserve but is of sufficient quality to serve as the basis for decision on the development of deposit.

A Proved Ore Reserve is the part of Measured resources that can be mined in an economically viable fashion. It includes diluting materials and allowances for losses which occur when the material is mined.

A Proved Ore Reserve represents the highest confidence category of reserve estimate. The style of mineralization or other factors could mean that Proved Ore Reserves are not achievable in some deposits.

Generally the conversion of resources into reserves requires the application of various modifying factors, including:

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• mining and geological factors, such as knowledge of the geology of the deposit sufficient that it is predictable and verifiable; extraction and mine plans based on ore models; quantification of geotechnical risk—basically, managing the geological faults, joints, and ground fractures so the mine does not collapse; and consideration of technical risk—essentially, statistical and variography to ensure the ore is sampled properly:

• metallurgical factors , including scrutiny of assay data to ensure accuracy of the information supplied by the laboratory—required because ore reserves are bankable. Essentially, once a deposit is elevated to reserve status, it is an economic entity and an asset upon which loans and equity can be drawn—generally to pay for its extraction at (hopefully) a profit;

• economic factors;

• environmental factors;

• marketing factors;

• legal factors;

• political factors; and

• social factors

Mineral Exploration

Mineral exploration is the process of finding ores (commercially viable concentrations of minerals) to mine. Mineral exploration is a much more intensive, organized and professional form of mineral prospecting and, though it frequently uses the services of prospecting, the process of mineral exploration on the whole is much more involved.

Stages of Mineral Exploration

Mineral exploration methods vary at different stages of the process depending on size of the area being explored, as well as the density and type of information sought. Aside from extra planetary exploration, at the largest scale is a geological mineral Province (such as the Eastern Goldfields Province of Western Australia), which may be sub-divided into Regions. At the smaller scale are mineral Prospects, which may contain several mineral Deposits.

Province scale - area selection

Area selection is a crucial step in professional mineral exploration. Selection of the best, most prospective, area in a mineral field, geological region or terrain will assist in making it not only possible to find ore deposits, but to find them easily, cheaply and quickly.

Area selection is based on applying the theories behind ore genesis, the knowledge of known ore occurrences and the method of their formation, to known geological regions via the study of geological maps, to determine potential areas where the particular class of ore

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deposit being sought may exist. Often new styles of deposits may be found which reveal opportunities to find look-alike deposit styles in rocks and terrains previously thought barren, which may result in a process of pegging of leases in similar geological settings based on this new model or methodology. This behavior is particularly well exemplified by exploration for Olympic Dam style deposits, particularly in South Australia and worldwide based on models of IOCG formation, which results in all coincident gravity and magnetic anomalies in appropriate settings being pegged for exploration.

This process applies the disciplines of basin modeling, structural geology, geochronology, petrology and a host of geophysical and geochemical disciplines to make predictions and draw parallels between the known ore deposits and their physical form and the unknown potential of finding a 'lookalike' within the area selected.

Area selection is also influenced by the commodity being sought; exploring for gold occurs in a different manner and within different rocks and areas to exploration for oil or natural gas or iron ore. Areas which are prospective for gold may not be prospective for other metals and commodities.

Similarly, companies of different sizes (in terms of market capitalization and financial strength) may look for different sized deposits, or deposits of a minimum size, depending on their will and ability to finance construction. Often the major mining houses will not look for deposits of less than a certain size class because small deposits will not meet their criteria for an internal rate of return. This practice may result in larger mining companies relinquishing control of smaller ore bodies they find, or may preclude them from entering a terrain which is characterized by deposits of a particular type or style. For example, a mining major would not look for a relatively small, high-cost Kambalda style nickel deposit and would direct their efforts toward discovering a Mt Keith style deposit.

Often a company or consortium wishing to enter mineral exploration may conduct market research to determine, if a resource in a particular commodity is found, whether or not the resource will be worth mining based on projected commodity prices and demand growth. This process may also inform upon the Area Selection process as noted above, where areas with small-sized deposit styles will be ruled out based on likely economic returns should a deposit be found. This occurs because often smaller deposits are more expensive to run, and hence, carry greater risks of closure if commodity prices fall significantly.

Area selection may also be influenced by previous finds, a practice affectionately named subsurface control or nearology, and may also be determined in part by financial and taxation incentives and tariff systems of individual nations. The role of infrastructure may also be crucial in area selection, because the ore must be brought to market and infrastructure costs may render isolated ore uneconomic.

The ultimate result of an area selection process is the pegging or notification of exploration licenses, known variously as tenements, claims or licenses.

Target generation - Regional Scale

The target generation phase involves investigations of the geology via mapping, geophysics and conducting geochemical or intensive geophysical testing of the surface and subsurface

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geology. In some cases, for instance in areas covered by soil, alluvium and platform cover, drilling may be performed directly as a mechanism for generating targets.

Geophysical methods

Geophysical instruments play a large role in gathering geological data which is used in mineral exploration. Instruments are used in geophysical surveys to check for variations in gravity, magnetism, electromagnetism (resistivity of rocks) and a number of different other variables in a certain area. The most effective and widespread method of gathering geophysical data is via flying airborne geophysics.

Geiger counters and scintillometers are used to determine the amount of radioactivity. This is particularly applicable to searching for uranium ore deposits but can also be of use in detecting radiometric anomalies associated with metasomatism.

Airborne magnetometers are used to search for magnetic anomalies in the Earth's magnetic field. The anomalies are an indication of concentrations of magnetic minerals such as magnetite, pyrrhotite and ilmenite in the Earth's crust. It is often the case that such magnetic anomalies are caused by mineralization events and associated metals.

Ground-based geophysical prospecting in the target selection stage is more limited, due to the time and cost. The most widespread use of ground-based geophysics is electromagnetic geophysics which detects conductive minerals such as sulfide minerals within more resistive host rocks.

Ultraviolet lamps may cause certain minerals to fluoresce, and is a key tool in prospecting for tungsten mineralization.

Remote sensing

Aerial photography is an important tool in assessing mineral exploration tenements, as it gives the explorer orientation information - location of tracks, roads, fences, habitation, as well as ability to at least qualitatively map outcrops and regolith systematics and vegetation cover across a region. Aerial photography was first used post World War II and was heavily adopted in the 1960s onwards.

Since the advent of cheap and declassified Landsat images in the late 1970s and early 1980s, mineral exploration has begun to use satellite imagery to map not only the visual light spectrum over mineral exploration tenements, but spectra which are beyond the visible.

Satellite based spectroscopes allow the modern mineral explorationist, in regions devoid of cover and vegetation, to map minerals and alteration directly. Improvements in the resolution of modern commercially based satellites has also improved the utility of satellite imagery; for instance GeoEye satellite images can be generated with a 40 cm pixel size.

Geochemical methods

The primary role of geochemistry, here used to describe assaying or geological media, in mineral exploration is to find an area anomalous in the commodity sought, or in elements known to be associated with the type of mineralization sought.

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Regional geochemical exploration has traditionally involved use of stream sediments to target potentially mineralized catchments. Regional surveys may use low sampling densities such as one sample per 100 square kilometres. Follow-up geochemical surveys commonly use soils as the sampling media, possibly via the collection of a grid of samples over the tenement or areas which are amenable to soil geochemistry. Areas which are covered by transported soils, alluvium, colluvium or are disturbed too much by human activity (roads, rail, farmland), may need to be drilled to a shallow depth in order to sample undisturbed or unpolluted bedrock.

Once the geochemical analyses are returned, the data is investigated for anomalies (single or multiple elements) that may be related to the presence of mineralization. The geochemical anomaly is often field checked against the outcropping geology and, in modern geochemistry, normalized against the regolith type and landform, to reduce the effects of weathering, transported materials and landforms.

Geochemical anomalies may be spurious or related to low-grade or sub-grade mineralization. In order to determine if this is the case, geochemical anomalies must be drilled in order to test them for the existence of economic concentrations of mineralization, or even to determine why they exist in the place they exist.

The presence of some chemical elements may indicate the presence of a certain mineral. Chemical analysis of rocks and plants may indicate the presence of an underground deposit. For instance elements like arsenic and antimony are associated with gold deposits and hence, are example pathfinder elements. Tree buds can be sampled for pathfinder elements in order to help locate deposits.

Resource evaluation

Resource evaluation is undertaken to quantify the grade and tonnage of a mineral occurrence. This is achieved primarily by drilling to sample the prospective horizon, lode or strata where the minerals of interest occur.

The ultimate aim is to generate a density of drilling sufficient to satisfy the economic and statutory standards of an ore resource. Depending on the financial situation and size of the deposit and the structure of the company, the level of detail required to generate this resource and stage at which extraction can commence varies; for small partnerships and private non-corporate enterprises a very low level of detail is required whereas for corporations which require debt equity (loans) to buildcapital intensive extraction infrastructure, the rigor necessary in resource estimation is far greater. For large cash rich companies working on small ore bodies, they may work only to a level necessary to satisfy their internal risk assessments before extraction commences.

Resource estimation may require pattern drilling on a set grid, and in the case of sulfide minerals, will usually require some form of geophysics such as down-hole probing of drill holes, to geophysically delineate ore body continuity within the ground.

The aim of resource evaluation is to expand the known size of the deposit and mineralization. A scoping study is often carried out on the ore deposit during this stage to determine if there may be enough ore at a sufficient grade to warrant extraction; if there is not further resource evaluation drilling may be necessary. In other cases, several smaller

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individually uneconomic deposits may be socialized into a 'mining camp' and extracted in tandem. Further exploration and testing of anomalies may be required to find or define these other satellite deposits.

Reserve definition

Reserve definition is undertaken to convert a mineral resource into an ore reserve, which is an economic asset. The process is similar to resource evaluation, except more intensive and technical, aimed at statistically quantifying the grade continuity and mass of ore.

Reserve definition also takes into account the milling and extractability characteristics of the ore, and generates bulk samples for metallurgical testwork, involving crushability, floatability and other ore recovery parameters.

Reserve definition includes geotechnical assessment and engineering studies of the rocks within and surrounding the deposit to determine the potential instabilities of proposed open pit or underground mining methods. This process may involve drilling diamond core samples to derive structural information on weaknesses within the rock mass such as faults, foliations, joints and shearing.

At the end of this process, a feasibility study is published, and the ore deposit may be either deemed uneconomic or economic.

Mineral Extraction

There are two basic types of extraction: surface and sub-surface (deep), each relying on a variety of techniques. Regardless of process, U.S. legislation requires operators to submit a plan for restoring the land and mitigating acid mine drainage before a permit is granted for mining operations. It further specifies that all sites be restored to their original contours and provides a funding mechanism for helping restore abandoned mines.

Underground Mining

When minerals are located deep within the ground, there are a variety of underground mining methods that can be utilized for excavation. The method is based primarily on whether the mineral is soft rock (i.e., coal) or hard rock (often those containing hard metals like copper or lead), and is often site specific ? taking geologic, economic, and safety factors into consideration.

In hard rock mining, blasting occurs in order to unearth the waste rock, separating it from the mineral deposit. Ventilation is a priority in order to dissipate any toxic fumes from blasting and other machinery. Also, since the process occurs underground, it is important that there is both local and area support to maintain the stability of the mine walls and openings. Once void of mineral, the mines are either left to collapse on their own or are filled with backfill and then sealed.

There are several soft rock mining methods, but the most common are longwall and room-and-pillar mining. Both methods allow for a level of automation, although proper ventilation is still a priority to dissipate fumes and decrease the risk of fire, especially in

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coal mining. In the room-and-pillar mining method, minerals are mined throughout a series of rooms, with pillars left in place to hold up the roof. Once a room has been mined, the pillars may remain or be taken out, letting the roof collapse. A disadvantage to this method is that it can leave a large amount of mineral in place. Longwall mining allows for increased mineral extraction to occur, since it shears entire blocks of mineral onto a conveyor belt through the use of self-advancing, hydraulic roof supports or shields. Once the mineral is extracted, the supports move on and the roof is allowed to collapse.

Today there are regulations from the start up of mining to the mine's closure. Yet, there are approximately 11,500 abandoned mines ? existing before the regulations ? on public lands in the U.S. Of these, only about 20 percent have gone through the process of remediation and/or restoration; therefore, most are still considered to be a threat. The Bureau of Land Management continues to work with partners throughout the U.S. to protect public safety and the environment from potential harm that can be caused by abandoned mines.

Surface Mining

Surface mining is undertaken when the minerals are located near the surface of the Earth. As opposed to underground mining in which the overlying rock and soil are left primarily intact and tunnels are dug, surface mining involves removing the top soil, called the overburden, in order to recover the minerals. The three most common types of surface mining are open-pit mining, strip mining, and quarrying.

Whether the surface is broken up by explosives, as is common in quarrying, strip and mountaintop mining, or by large pieces of equipment, common in open-pit mining, the principle remains the same ? the overburden is excavated and moved elsewhere so that the mineral can be extracted.

Surface mining is generally less dangerous than underground mining, but it has a greater impact on surface landscapes, and consumes a vast amount of land. Also, since it requires the removal of massive amounts of top soil, surface mining often leads to erosion, dust pollution, and the loss of habitat. In the past, the overburden was typically dumped into low-lying areas, often filling wetlands or other sources of water. Today the movement and placement of the overburden must be part of the pre-mining plan that is required by legislation. The mining process can also cause heavy metals to dissolve, seeping into both ground and surface waters which can deteriorate drinking water sources and disrupt marine habitats.

Environmental Issues

The environmental impacts of mining operations are generally well understood. Current research focuses on the most effective methods of reclaiming and restoring lands that have been disturbed. Extracting minerals either from or below the surface of the Earth requires the movement of a lot of soil. Large areas of land, as well as the surrounding ecosystem, are

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affected; if the overburden is not properly cared for, it can cause further damage to the environment including the filling in of wetlands or disturbing other watershed areas.

A persistent problem is acid mine drainage, particularly from abandoned mines. When disturbed by excavation, pyrite or iron sulfide in the ground weathers and reacts with oxygen and water to produce high levels of iron and sulfate in runoff water. Modern mining operations use lime and other chemicals to treat acidic drainage, but the long-term effectiveness of this method is not yet known.

Although reclamation is required by law, some disturbances are permanent. The processing of minerals creates a waste stream that must be carefully controlled to avoid leakages into surrounding ecosystems. In some areas, old mines abandoned before the beginning of strict regulation of mining operations pose a problem; often, the companies that operated these mines are no longer in existence so it is difficult to assign liability for the cost of clean-up.

Mining methods

Mining techniques have dramatically transformed over many years, with technological advances improving efficiency and the safety and health of our people, while minimizing the environmental impact of our operations. NSW has both open-cut and underground mines.

Open-cut mining

Open-cut mining usually happens where mineral deposits are close to the surface. It involves blasting and removing surface layers of soil and rock to reach the mineral deposit. When the mineral seam becomes exposed, it is drilled, fractured and the mineral recovered for processing. Open-cut mining can be more effective than underground methods, generally recovering 90% of a mineral deposit, and accounts for about 65% of raw coal production in NSW. Open-cut mining is also used for some gold and copper production in NSW. One of Australia’s largest open-cut coal mines, BHP Billiton’s Mt Arthur Coal mine, is located in the Hunter Valley.

Underground mining

Underground mining involves creating tunnels from the surface into the mineral seam, which can be hundreds of metres below the surface. These tunnels are used to transport machinery that extracts the mineral. Underground mining accounts for 60% of world coal production, but is less common in NSW, making up around 35% of raw coal production. This method is also used to mine metallic minerals like gold and copper. The two main types of underground mining in NSW are bord-and-pillar and longwall mining.

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• Bord-and-pillar: Bord-and-pillar, or room-and-pillar, is the oldest underground mining technique and was common in NSW before longwall mining began in the 1960s. This method uses a grid of tunnels and involves progressively cutting panels into the coal seam whilst leaving behind pillars of coal to support the mine. This method has been in steady decline as more efficient technologies are introduced, but is still used in a small number of mines across the state, like Yancoal’s Tasman Mine near Newcastle.

• Longwall mining: Longwall mining revolutionized underground coal mining with its capacity for safe, cost effective and efficient large-scale extraction. Longwall mining uses mechanical shearers to cut coal away whilst hydraulic-powered supports hold up the roof of the mine. As coal is removed, the supports are moved forward and the roof is collapsed behind them, which can result in subsidence. Longwall mining is more efficient than bord-and-pillar as it does not leave behind pillars of coal, so more of the mineral resource can be extracted. One example of a longwall mine is Centennial Coal’s Angus Place mine, near Lithgow.

A newer technique is block-caving, where mineral ores – like gold and copper - are extracted by collapsing the mineral deposits under their own weight. Australia’s first block cave mine opened in 1997 near Parkes, in Central West NSW. Located at Northparkes Mines, it is part of Rio Tinto’s Mine of the Future program, which aims to make mining more efficient and safer through increased automation and remote operation.

Coal preparation & minerals processing

Coal direct from a mine has impurities like rocks and dirt that are removed through washing and treatment at a coal preparation plant. Coal preparation makes the resource more profitable by improving its quality and also lowers transport costs by reducing waste products. Coal preparation also minimizes the impact on air quality during transportation of coal to power stations or our export ports in Newcastle and Wollongong. Minerals processing encompasses a range of activities including exploration, mining and manufacturing of resources. NSW leads Australia in minerals processing, with substantial infrastructure in steel, aluminum and cement production, as well as refractories used to produce a range of materials like linings for furnaces, kilns and incinerators.

Consequences of over Exploitation of Mineral Resources

In the entire history of human civilization such an unusually high demand has never been placed on natural resources of our planet. The consequences of this over-exploitation of mineral wealth have to be serious, drastic and enormously damaging to the entire biosphere. These can be summed up as follows:

1. Rapid Depletion of High Grade Mineral Deposits:

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Exploitation of mineral wealth at a rapid rate shall naturally deplete our good quality deposits. The ever rising demands shall compel miners to carry on the extraction from increasingly lower and lower grade of deposits which possess a poorer percentage of the metal. For example copper was extracted from ores containing 8-10% of metal content about 500 years ago.

Now we are using deposits which contain only 0.35% of copper. To produce one ton of copper metal we have to dig out 285 tons of ore. This shall naturally involve a large amount of energy expenditure as well as a large quantity of waste material production.

We may never reach an end as matter is indestructible. Most of the metals we require are present in highly dispersed state in the soil, the rocks and the trash or wastes we discard. With a sophisticated technology we can fulfill most of our requirements from these sources, But the overall cost could be I heavy, causing the metals to become more and more costly.

2. Wastage and Dissemination of Mineral Wealth:

Most of our mineral deposits occur as a complex mixture of a number of mineral elements. After removal of top soil and rocks we dig out the desired mineral leaving behind others which are often left in the open as waste materials. Extraction of one element usually scatters and wastes a number of other elements, many of which are in short supply.

This wastage rises as more and more ores are extracted and processed. Worldwide smelting of minerals for extraction of metals introduces an enormous quantity of sulfur, heavy metals such as mercury, cadmium, nickel, arsenic, zinc etc. into the environment which are separately mined elsewhere.

We are technologically competent enough to extract these metals from the wastes produced from one mining industry rather than excavating fresh deposits. The cost could be heavier indeed but the practice shall pay in the long run. It will conserve our resources and also reduce the burden of pollutants which we have to introduce in the environment.

3. Pollution of Environment from Mining and Processing Wastes:

Mining is a dirty industry. It has created some of the largest 'Environmental disaster' zones in the world. The mining and processing of minerals generally involves following steps:

1. The soil and rock overlying the mineral deposits, called the 'over-burden' in miner's language, has to be removed before actual mining operations commence.

2. The ore is then mined and crushed.

3. After being converted to fine powdered state it is run through concentrators which re-move impurities.

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4. The concentrated ores are then reduced to crude metal often at a high temperature by various methods depending upon the chemical nature of the ore.

5. Crude metal is then refined or purified in refineries.

Each step in mining and processing operations produces large quantities of waste materials. As most of today's mines are simple surface excavations, the first task of a miner is to remove whatever lies over the mineral deposit, be it a mountain, a forest or an agricultural field. Underground mining with a system of shaft and tunnels does not produce as much waste as open cast mining does.

In 1988, over-burden, the material overlying the mineral deposits in U.S. A., amounted to about 3.3 billion tons of matter moved. This material even if chemically inert, clogs streams, gets deposited in lakes and clouds the air over large areas. If it contains Sulfur and other reactive elements apart from wastage of our precious resource a number of other problems are caused (Young, 1992).

Almost similar problems arise from the disposal of waste material produced after concentration of an ore. This material is called 'tailings' in miner's language. As most of the ores contain a large amount of sulfur its oxidation and leaching results in formation of acidic leachates (Water containing dilute sulfuric acid).

The finely grounded state of ores makes metal contaminants which were earlier bound in solid rocks, available to acidic waters. Thus, these leachates contain appreciable amounts of heavy metals and toxic trace elements. Tailings may contain residue of organic chemicals such as toluene etc. which cause another type of problems. Ponds full of acidic leachates covering thousands of hectares of land surface now surround copper mines in U.S.A. These waters cause serious problems of water pollution if they happen to contaminate our surface or underground acquifers.

The grade of ore is important in determining the overall impact of mining activity. An ore containing 20% of metal content shall produce only four tons of tailings or waste material per ton of metal extracted but a low grade ore containing 1% of metal shall produce 99 tons of tailings per ton of metal obtained.

Gold mining is particularly damaging in this respect as the metal content of gold deposits is at best expressed as parts per million. Miners at Gold Strike mine in Nevada - the largest in USA move about 3, 25,000 tons of ore to produce about 50 kg of gold per year.

In Amazon basin, Brazil, miners use a technique called hydraulic mining which involves blasting the gold bearing hillside with high pressure stream of water following by guiding the sediments through ducts where the gold being heavier settles down from tons of non-valuable material.

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This silt and sediments are finally washed down into some local stream. The practice has silted local rivers and lakes while the use of mercury to trap gold from sediments has contaminated large areas. Miners release an estimated 100 tons of mercury into the waters of Amazon river annually.

In North America, miners use 'Heap Leaching' a technique which allows gold extraction from a very low grade ore. The technique involves sprinkling of cyanide solution over a heap of low grade ore. While trickling down the solution dissolves gold. It is collected and later gold is recovered from it. Both cyanide solution reservoirs and contaminated tailings are left behind after the gold extraction.

These pose hazards to wild life and threaten surface waters as well as under-ground acquifers. In October 1990 about 45 million litres of cyanide solution from a reservoir at Brewer Gold Mine, South Carolina, spilled over into a tributary of local Lynch River, killing more than 10,000 fishes. Thousands of birds die each year when they mistakenly consume cyanide solution from these impoundments.

4. Pollution Caused by Heavy Energy Requirement of Mining Industry:

Moving huge amounts of sand silt and clay etc. requires energy. Concentration of ore requires energy. Smelting and refining operations require energy. Electrolytic processes used for refining of some metals, like Aluminum, require energy.

Disposal of solid or liquid wastes or tailings requires energy. Transportation of solid or liquid wastes or tailings requires energy. Transportation of finished products requires energy. The overall worldwide requirement of energy in mining industry adds up to an enormous amount. This energy comes from diverse sources which mostly include fire-wood, coal, petroleum, natural gas and electricity. In order to provide energy to mining industry a huge quantity of these materials are burned which causes a variety of pollution problems.

Fossil Fuel

Fossil fuels are fuels formed by natural processes such as anaerobic decomposition of buried dead organisms. The age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years. Fossil fuels contain high percentages of carbon and include coal, petroleum, and natural gas. They range from volatile materials with low carbon: hydrogen ratios like methane, to liquid petroleum to nonvolatile materials composed of almost pure carbon, like anthracite coal. Methane can be found in hydrocarbon fields, alone, associated with oil, or in the form of methane clath rates. The theory that fossil fuels formed from the fossilized remains of dead plants by exposure to heat and pressure in the Earth's crust over millions of years (see biogenic theory) was first introduced by Georg Agricola in 1556 and later by Mikhail Lomonosov in the 18th century.

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The Energy Information Administration estimates that in 2007 the primary sources of energy consisted of petroleum 36.0%, coal 27.4%, natural gas 23.0%, amounting to an 86.4% share for fossil fuels in primary energy consumption in the world. Non-fossil sources in 2006 included hydroelectric 6.3%, nuclear 8.5%, and others (geothermal, solar, tidal, wind, wood, waste) amounting to 0.9%. World energy consumption was growing about 2.3% per year.

Strictly speaking, fossil fuels are a renewable resource. They are continually being formed via natural processes as plants and animals die and then decompose and become trapped beneath sediment. However, fossil fuels are generally considered to be non-renewable resources because they take millions of years to form, and known viable reserves are being depleted much faster than new ones are being made.

The use of fossil fuels raises serious environmental concerns. The burning of fossil fuels produces around 21.3 billion tonnes(21.3 giga tonnes) of carbon dioxide (CO2) per year, but it is estimated that natural processes can only absorb about half of that amount, so there is a net increase of 10.65 billion tonnes of atmospheric carbon dioxide per year (one tonne of atmospheric carbon is equivalent to 44/12 or 3.7 tonnes of carbon dioxide).[10] Carbon dioxide is one of the greenhouse gases that enhances radiative forcing and contributes to global warming, causing the average surface temperature of the Earth to rise in response, which the vast majority of climate scientists agree will cause major adverse effects. A global movement towards the generation of renewable energy is therefore under way to help reduce global greenhouse gas emissions.

Origin

Petroleum and natural gas are formed by the anaerobic decomposition of remains of organisms including phytoplankton and zooplankton that settled to the sea (or lake) bottom in large quantities under anoxic conditions, millions of years ago. Over geological time, this organic matter, mixed with mud, got buried under heavy layers of sediment. The resulting high levels of heat and pressure caused the organic matter to chemically alter, first into a waxy material known as kerogen which is found in oil shales, and then with more heat into liquid and gaseous hydrocarbons in a process known as catagenesis.

There is a wide range of organic, or hydrocarbon, compounds in any given fuel mixture. The specific mixture of hydrocarbons gives a fuel its characteristic properties, such as boiling point, melting point, density, viscosity, etc. Some fuels like natural gas, for instance, contain only very low boiling, gaseous components. Others such as gasoline or diesel contain much higher boiling components.

Terrestrial plants, on the other hand, tend to form coal and methane. Many of the coal fields date to the Carboniferous period of Earth's history. Terrestrial plants also form type III kerogen, a source of natural gas.

Importance

Fossil fuels are of great importance because they can be burned (oxidized to carbon dioxide and water), producing significant amounts of energy per unit weight. The use of coal as a fuel predates recorded history. Coal was used to run furnaces for the melting of

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metal ore. Semi-solid hydrocarbons from seeps were also burned in ancient times, but these materials were mostly used for waterproofing and embalming.

Commercial exploitation of petroleum, largely as a replacement for oils from animal sources (notably whale oil), for use in oil lamps began in the 19th century.

Natural gas, once flared-off as an unneeded byproduct of petroleum production, is now considered a very valuable resource. Natural gas deposits are also the main source of the element helium.

Heavy crude oil, which is much more viscous than conventional crude oil, and tar sands, where bitumen is found mixed with sand and clay, are becoming more important as sources of fossil fuel. Oil shale and similar materials are sedimentary rocks containing kerogen, a complex mixture of high-molecular weight organic compounds, which yield synthetic crude oil when heated (pyrolyzed). These materials have yet to be exploited commercially. These fuels can be employed in internal combustion engines, fossil fuel power stations and other uses.

Prior to the latter half of the 18th century, windmills and watermills provided the energy needed for industry such as milling flour, sawing wood or pumping water, and burning wood or peat provided domestic heat. The wide scale use of fossil fuels, coal at first and petroleum later, to fire steam engines enabled the Industrial Revolution. At the same time, gas lights using natural gas or coal gas were coming into wide use. The invention of the internal combustion engine and its use in automobiles and trucks greatly increased the demand for gasoline and diesel oil, both made from fossil fuels. Other forms of transportation, railways and aircraft, also required fossil fuels. The other major use for fossil fuels is in generating electricity and as feedstock for the petrochemical industry. Tar, a leftover of petroleum extraction, is used in construction of roads.

Reserves

Levels of primary energy sources are the reserves in the ground. Flows are production of fossil fuels from these reserves. The most important part of primary energy sources are the carbon based fossil energy sources. Coal, oil, and natural gas provided 79.6% of primary energy production during 2002 (in million tonnes of oil equivalent (mtoe)) (34.9+23.5+21.2).

Levels (proved reserves) during 2005–2006

• Coal: 997,748 million short tonnes (905 billion metric tonnes), 4,416 billion barrels (702.1 km3) of oil equivalent

• Oil: 1,119 billion barrels (177.9 km3) to 1,317 billion barrels (209.4 km3)

• Natural gas: 6,183–6,381 trillion cubic feet (175–181 trillion cubic metres), 1,161 billion barrels (184.6×109 m3) of oil equivalent

Flows (daily production) during 2006

• Coal: 18,476,127 short tonnes (16,761,260 metric tonnes), 52,000,000 barrels (8,300,000 m3) of oil equivalent per day

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• Oil: 84,000,000 barrels per day (13,400,000 m3/d)

• Natural gas: 104,435 billion cubic feet (2,963 billion cubic metres), 19,000,000 barrels (3,000,000 m3) of oil equivalent per day

Compositions of Fossil Fuels

Crude oil is made up of different forms of hydrocarbons with dissimilar molecular weights, chemical properties, and organic structures. Oil collected from natural deposits can be of diverse forms. It may be too viscous or easy-flowing. The different forms of oil are separated and collected from the oil deposits by the procedure of refining. However, crude oil unlike other two forms of fossil fuels can be used only after refining.

Natural gas contains hydrocarbons in gaseous forms. Methane is the major component of natural gas. It also contains small amounts of nitrogen, oxygen, hydrogen, propane, ethylene, ethane, and helium. Natural gas is commonly found over oil deposits. It is also found separately within different layers under the earth's surface. Natural gas is drawn by pipes from the deposits and then transported to distant places through a network of pipelines.

Coal is made up of a combination of different chemical compounds like oxygen, carbon, hydrogen, sulfur, nitrogen and some more. Coal is found in a wide variety of forms like bituminous coal, sub-bituminous coal, peat, anthracite, brown coal and so on. Coalification is the process that results in the formation of different varieties of coal. Quality of coal increases as the percentage of carbon rises. The rank of coal improves starting from lignite to low rank coal, high rank coal, and finally to anthracite. Among the different forms of coal, graphite contains the highest percentage of carbon.

There is no denying that fossil fuels constitute the chief source of energy in today's world. However, it produces greenhouse gas, which is harmful for the atmosphere. The sources of fossil fuels are also limited. All these are increasing the demand of alternative renewable sources of energy across the world.

Coal

Coal (from the Old English term col, which has meant "mineral of fossilized carbon" since the 13th century) is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure. Coal is composed primarily

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of carbon along with variable quantities of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.

Throughout history, coal has been used as an energy resource, primarily burned for the production of electricity and/or heat, and is also used for industrial purposes, such as refining metals. A fossil fuel, coal forms when dead plant matter is converted into peat, which in turn is converted into lignite, then sub-bituminous coal, after that bituminous coal, and lastly anthracite. This involves biological and geological processes that take place over a long period. The Energy Information Administration estimates coal reserves at 948×109 short tons (860 Gt).[3] One estimate for resources is 18 000 Gt.

Coal is the largest source of energy for the generation of electricity worldwide, as well as one of the largest worldwide anthropogenic sources of carbon dioxide releases. In 1999, world gross carbon dioxide emissions from coal usage were 8,666 million tonnes of carbon dioxide. In 2011, world gross emissions from coal usage were 14,416 million tonnes. Coal-fired electric power generation emits around 2,000 pounds of carbon dioxide for every megawatt-hour generated, which is almost double the approximately 1100 pounds of carbon dioxide released by a natural gas-fired electric plant per megawatt-hour generated. Because of this higher carbon efficiency of natural gas generation, as the market in the United States has changed to reduce coal and increase natural gas generation, carbon dioxide emissions have fallen. Those measured in the first quarter of 2012 were the lowest of any recorded for the first quarter of any year since 1992. In 2013, the head of the UN climate agency advised that most of the world's coal reserves should be left in the ground to avoid catastrophic global warming.

Coal is extracted from the ground by coal mining, either underground by shaft mining, or at ground level by open pit miningextraction. Since 1983 the world top coal producer has been China. In 2011 China produced 3,520 millions of tonnes of coal – 49.5% of 7,695 millions tonnes world coal production. In 2011 other large producers were United States (993 millions tonnes), India (589), European Union (576) and Australia (416). In 2010 the largest exporters were Australia with 328 million tonnes (27.1% of world coal export) and Indonesia with 316 million tonnes (26.1%), while the largest importers were Japan with 207 million tonnes (17.5% of world coal import), China with 195 million tonnes (16.6%) and South Koreawith 126 million tonnes (10.7%).

Formation

At various times in the geologic past, the Earth had dense forests in low-lying wetland areas. Due to natural processes such as flooding, these forests were buried underneath soil. As more and more soil deposited over them, they were compressed. The temperature also rose as they sank deeper and deeper. As the process continued the plant matter was protected from biodegradation and oxidation, usually by mud or acidic water. This trapped the carbon in immense peat bogs that were eventually covered and deeply buried by sediments. Under high pressure and high temperature, dead vegetation was slowly converted to coal. As coal contains mainly carbon, the conversion of dead vegetation into coal is called carbonization.

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The wide, shallow seas of the Carboniferous Period provided ideal conditions for coal formation, although coal is known from most geological periods. The exception is the coal gap in the Permian–Triassic extinction event, where coal is rare. Coal is known from Precambrian strata, which predate land plants — this coal is presumed to have originated from residues of algae.

Types

As geological processes apply pressure to dead biotic material over time, under suitable conditions it is transformed successively into:

• Peat , considered to be a precursor of coal, has industrial importance as a fuel in some regions, for example, Ireland and Finland. In its dehydrated form, peat is a highly effective absorbent for fuel and oil spills on land and water. It is also used as a conditioner for soil to make it more able to retain and slowly release water.

• Lignite , or brown coal, is the lowest rank of coal and used almost exclusively as fuel for electric power generation. Jet, a compact form of lignite, is sometimes polished and has been used as an ornamental stone since the Upper Palaeolithic.

• Sub-bituminous coal , whose properties range from those of lignite to those of bituminous coal, is used primarily as fuel for steam-electric power generation and is an important source of light aromatic hydrocarbons for the chemical synthesis industry.

• Bituminous coal is a dense sedimentary rock, usually black, but sometimes dark brown, often with well-defined bands of bright and dull material; it is used primarily as fuel in steam-electric power generation, with substantial quantities used for heat and power applications in manufacturing and to make coke.

• "Steam coal" is a grade between bituminous coal and anthracite, once widely used as a fuel for steam locomotives. In this specialized use, it is sometimes known as "sea-coal" in the US. Small steam coal (dry small steam nuts or DSSN) was used as a fuel for domestic water heating.

• Anthracite , the highest rank of coal, is a harder, glossy black coal used primarily for residential and commercial space heating. It may be divided further into metamorphically altered bituminous coal and "petrified oil", as from the deposits in Pennsylvania.

• Graphite , technically the highest rank, is difficult to ignite and is not commonly used as fuel — it is mostly used in pencils and, when powdered, as a lubricant.

The classification of coal is generally based on the content of volatiles. However, the exact classification varies between countries.

Uses Today

Coal as fuel

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Coal is primarily used as a solid fuel to produce electricity and heat through combustion. World coal consumption was about 7.25 billion tonnes in 2010 (7.99 billion short tons) and is expected to increase 48% to 9.05 billion tonnes (9.98 billion short tons) by 2030. China produced 3.47 billion tonnes (3.83 billion short tons) in 2011. India produced about 578 million tonnes (637.1 million short tons) in 2011. 68.7% of China's electricity comes from coal. The USA consumed about 13% of the world total in 2010, i.e. 951 million tonnes (1.05 billion short tons), using 93% of it for generation of electricity. 46% of total power generated in the USA was done using coal.

When coal is used for electricity generation, it is usually pulverized and then combusted (burned) in a furnace with a boiler. The furnace heat converts boiler water to steam, which is then used to spin turbines which turn generators and create electricity. The thermodynamic efficiency of this process has been improved over time; some older coal-fired power stations have thermal efficiencies in the vicinity of 25% whereas the newest supercritical and "ultra-supercritical" steam cycle turbines, operating at temperatures over 600 °C and pressures over 27 MPa (over 3900 psi), can practically achieve thermal efficiencies in excess of 45% (LHV basis) using anthracite fuel, or around 43% (LHV basis) even when using lower-grade lignite fuel. Further thermal efficiency improvements are also achievable by improved pre-drying (especially relevant with high-moisture fuel such as lignite or biomass) and cooling technologies.

An alternative approach of using coal for electricity generation with improved efficiency is the integrated gasification combined cycle (IGCC) power plant. Instead of pulverizing the coal and burning it directly as fuel in the steam-generating boiler, the coal can be first gasified (see coal gasification) to create syngas, which is burned in a gas turbine to produce electricity (just like natural gas is burned in a turbine). Hot exhaust gases from the turbine are used to raise steam in a heat recovery steam generator which powers a supplemental steam turbine. Thermal efficiencies of current IGCC power plants range from 39-42% (HHV basis) or ~42-45% (LHV basis) for bituminous coal and assuming utilization of mainstream gasification technologies (Shell, GE Gasifier, CB&I). IGCC power plants outperform conventional pulverized coal-fueled plants in terms of pollutant emissions, and allow for relatively easy carbon capture.

At least 40% of the world's electricity comes from coal, and in 2012, about one-third of the United States' electricity came from coal, down from approximately 49% in 2008. As of 2012 in the United States, use of coal to generate electricity was declining, as plentiful supplies of natural gas obtained by hydraulic fracturing of tight shale formations became available at low prices.

In Denmark, a net electric efficiency of > 47% has been obtained at the coal-fired Nordjyllandsværket CHP Plant and an overall plant efficiency of up to 91% with cogeneration of electricity and district heating. The multifuel-fired Avedøreværket CHP Plant just outside Copenhagen can achieve a net electric efficiency as high as 49%. The overall plant efficiency with cogeneration of electricity and district heating can reach as much as 94%.

An alternative form of coal combustion is as coal-water slurry fuel (CWS), which was developed in the Soviet Union. CWS significantly reduces emissions, improving the heating

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value of coal. Other ways to use coal are combined heat and power cogeneration and an MHD topping cycle.

The total known deposits recoverable by current technologies, including highly polluting, low-energy content types of coal (i.e., lignite, bituminous), is sufficient for many years. However, consumption is increasing and maximal production could be reached within decades (see world coal reserves, below). On the other hand much may have to be left in the ground to avoid climate change.

Coking coal and use of coke

Coke is a solid carbonaceous residue derived from low-ash, low-sulfur bituminous coal from which the volatile constituents are driven off by baking in an oven without oxygen at temperatures as high as 1,000 °C (1,832 °F), so the fixed carbon and residual ash are fused together. Metallurgical coke is used as a fuel and as a reducing agent in smelting iron ore in a blast furnace. The result is pig iron, and is too rich in dissolved carbon, so it must be treated further to make steel. The coking coal should be low in sulfur and phosphorus, so they do not migrate to the metal.

The coke must be strong enough to resist the weight of overburden in the blast furnace, which is why coking coal is so important in making steel using the conventional route. However, the alternative route is direct reduced iron, where any carbonaceous fuel can be used to make sponge or pelletized iron. Coke from coal is grey, hard, and porous and has a heating value of 24.8 million Btu/ton (29.6 MJ/kg). Some coke making processes produce valuable byproducts, including coal tar, ammonia, light oils, and coal gas.

Petroleum coke is the solid residue obtained in oil refining, which resembles coke, but contains too many impurities to be useful in metallurgical applications.

Gasification

Coal gasification can be used to produce syngas, a mixture of carbon monoxide (CO) and hydrogen (H2) gas. Often syngas is used to fire gas turbines to produce electricity, but the versatility of syngas also allows it to be converted into transportation fuels, such as gasoline and diesel, through the Fischer-Tropsch process; alternatively, syngas can be converted into methanol, which can be blended into fuel directly or converted to gasoline via the methanol to gasoline process. Gasification combined with Fischer-Tropsch technology is currently used by the Sasol chemical company of South Africa to make motor vehicle fuels from coal and natural gas. Alternatively, the hydrogen obtained from gasification can be used for various purposes, such as powering a hydrogen economy, making ammonia, or upgrading fossil fuels.

During gasification, the coal is mixed with oxygen and steam while also being heated and pressurized. During the reaction, oxygen and water molecules oxidize the coal into carbon monoxide (CO), while also releasing hydrogen gas (H2). This process has been conducted in both underground coal mines and in the production of town gas.

C (as Coal) + O2 + H2O H→ 2 + CO

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If the refiner wants to produce gasoline, the syngas is collected at this state and routed into a Fischer-Tropsch reaction. If hydrogen is the desired end-product, however, the syngas is fed into the water gas shift reaction, where more hydrogen is liberated.

CO + H2O CO→ 2 + H2

In the past, coal was converted to make coal gas (town gas), which was piped to customers to burn for illumination, heating, and cooking.

Liquefaction

Coal can also be converted into synthetic fuels equivalent to gasoline or diesel by several different direct processes (which do not intrinsically require gasification or indirect conversion). In the direct liquefaction processes, the coal is either hydrogenated or carbonized. Hydrogenation processes are the Bergius process, the SRC-I and SRC-II (Solvent Refined Coal) processes, the NUS Corporation hydrogenation process and several other single-stage and two-stage processes. In the process of low-temperature carbonization, coal is coked at temperatures between 360 and 750 °C (680 and 1,380 °F). These temperatures optimize the production of coal tars richer in lighter hydrocarbons than normal coal tar. The coal tar is then further processed into fuels. An overview of coal liquefaction and its future potential is available.

Coal liquefaction methods involve carbon dioxide (CO2) emissions in the conversion process. If coal liquefaction is done without employing either carbon capture and storage (CCS) technologies or biomass blending, the result is lifecycle greenhouse gas footprints that are generally greater than those released in the extraction and refinement of liquid fuel production from crude oil. If CCS technologies are employed, reductions of 5–12% can be achieved in Coal to Liquid (CTL)plants and up to a 75% reduction is achievable when co-gasifying coal with commercially demonstrated levels of biomass (30% biomass by weight) in coal/biomass-to-liquids plants. For future synthetic fuel projects, carbon dioxide sequestration is proposed to avoid releasing CO2 into the atmosphere. Sequestration adds to the cost of production.

Refined coal

Refined coal is the product of a coal-upgrading technology that removes moisture and certain pollutants from lower-rank coals such as sub-bituminous and lignite (brown) coals. It is one form of several precombustion treatments and processes for coal that alter coal's characteristics before it is burned. The goals of precombustion coal technologies are to increase efficiency and reduce emissions when the coal is burned. Depending on the situation, precombustion technology can be used in place of or as a supplement to postcombustion technologies to control emissions from coal-fueled boilers.

Industrial processes

Finely ground bituminous coal, known in this application as sea coal, is a constituent of foundry sand. While the molten metal is in the mould, the coal burns slowly, releasing reducing gases at pressure, and so preventing the metal from penetrating the

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pores of the sand. It is also contained in 'mould wash', a paste or liquid with the same function applied to the mould before casting. Sea coal can be mixed with the clay lining (the "bod") used for the bottom of a cupola furnace. When heated, the coal decomposes and the bod becomes slightly friable, easing the process of breaking open holes for tapping the molten metal.

Production of chemicals

Coal is an important feedstock in production of a wide range of chemical fertilizers and other chemical products. The main route to these products is coal gasification to produce syngas. Primary chemicals that are produced directly from the syngas include methanol, hydrogen and carbon monoxide, which are the chemical building blocks from which a whole spectrum of derivative chemicals are manufactured, including olefins, acetic acid, formaldehyde, ammonia, urea and others. The versatility of syngas as a precursor to primary chemicals and high-value derivative products provides the option of using relatively inexpensive coal to produce a wide range of valuable commodities.

Historically, production of chemicals from coal has been used since the 1950s and has become established in the market. According to the 2010 Worldwide Gasification Database, a survey of current and planned gasifiers, from 2004 to 2007 chemical production increased its gasification product share from 37% to 45%. From 2008 to 2010, 22% of new gasifier additions were to be for chemical production.

Because the slate of chemical products that can be made via coal gasification can in general also use feedstocks derived from natural gas and petroleum, the chemical industry tends to use whatever feedstocks are most cost-effective. Therefore, interest in using coal tends to increase for higher oil and natural gas prices and during periods of high global economic growth that may strain oil and gas production. Also, production of chemicals from coal is of much higher interest in countries like South Africa, China, India and the United States where there are abundant coal resources. The abundance of coal combined with lack of natural gas resources in China is strong inducement for the coal to chemicals industry pursued there. In the United States, the best example of the industry is Eastman Chemical Company which has been successfully operating a coal-to-chemicals plant at its Kingsport, Tennessee, site since 1983. Similarly, Sasol has built and operated coal-to-chemicals facilities in South Africa.

Coal to chemical processes do require substantial quantities of water. As of 2013 much of the coal to chemical production was in the People's Republic of China where environmental regulation and water management was weak

Environmental Effects

A number of adverse health, and environmental effects of coal burning exist, especially in power stations, and of coal mining, including:

• Coal-fired power plants cause nearly 24,000 premature deaths annually in the United States, including 2,800 from lung cancer. Annual health costs in Europe from use of coal to generate electricity are €42.8 billion, or $55 billion.

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• Generation of hundreds of millions of tons of waste products, including fly ash, bottom ash, and flue-gas desulfurization sludge, that contain mercury, uranium, thorium, arsenic, and other heavy metals

• Acid rain from high sulfur coal

• Interference with groundwater and water table levels due to mining

• Contamination of land and waterways and destruction of homes from fly ash spills. such as the Kingston Fossil Plant coal fly ash slurry spill

• Impact of water use on flows of rivers and consequential impact on other land uses

• Dust nuisance

• Subsidence above tunnels, sometimes damaging infrastructure

• Uncontrollable coal seam fire which may burn for decades or centuries

• Coal-fired power plants without effective fly ash capture systems are one of the largest sources of human-caused background radiation exposure.

• Coal-fired power plants emit mercury, selenium, and arsenic, which are harmful to human health and the environment.

• Release of carbon dioxide, a greenhouse gas, causes climate change and global warming, according to the IPCC and the EPA. Coal is the largest contributor to the human-made increase of CO2 in the atmosphere.

• Approximately 75 Tg/S per year of sulfur dioxide (SO2) is released from burning coal. After release, the sulfur dioxide is oxidized to gaseous H2SO2 which scatters solar radiation, hence its increase in the atmosphere exerts a cooling effect on climate that masks some of the warming caused by increased greenhouse gases. Release of SO2 also contributes to the widespread acidification of ecosystems.

Petroleum

Petroleum (L. petroleum, from early 15c. "petroleum, rock oil" (mid-14c. in Anglo-French), from Medieval Latin petroleum, from Latin petra rock(see petrous) + Latin: oleum oil (see oil (n.)).) is a naturally occurring, yellow-to-black liquid found in geologic formations beneath the Earth's surface, which is commonly refined into various types of fuels. It consists of hydrocarbons of various molecular weights and other liquid organic compounds. The name petroleum covers both naturally occurring unprocessed crude oil and petroleum products that are made up of refined crude oil. A fossil fuel, petroleum is formed when large quantities of dead organisms, usually zooplankton and algae, are buried underneath sedimentary rock and subjected to intense heat and pressure.

Petroleum is recovered mostly through oil drilling (natural petroleum springs are rare). This comes after the studies of structural geology (at the reservoir scale), sedimentary

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basin analysis, reservoir characterization (mainly in terms of the porosity and permeability of geologic reservoir structures). It is refined and separated, most easily by distillation, into a large number of consumer products, from gasoline (petrol) and kerosene to asphalt and chemical reagents used to make plastics and pharmaceuticals. Petroleum is used in manufacturing a wide variety of materials, and it is estimated that the world consumes about 90 million barrels each day.

The use of fossil fuels, such as petroleum, has a negative impact on Earth's biosphere, releasing pollutants and greenhouse gases into the air and damaging ecosystems through events such as oil spills. Concern over the depletion of the earth's finite reserves of oil, and the effect this would have on a society dependent on it, is a concept known as peak oil

Composition

In its strictest sense, petroleum includes only crude oil, but in common usage it includes all liquid, gaseous, and solid hydrocarbons. Under surface pressure and temperature conditions, lighter hydrocarbons methane, ethane, propane and butane occur as gases, while pentane and heavier ones are in the form of liquids or solids. However, in an underground oil reservoir the proportions of gas, liquid, and solid depend on subsurface conditions and on the phase diagram of the petroleum mixture.

An oil well produces predominantly crude oil, with some natural gas dissolved in it. Because the pressure is lower at the surface than underground, some of the gas will come out of solution and be recovered (or burned) as associated gas or solution gas. A gas well produces predominantly natural gas. However, because the underground temperature and pressure are higher than at the surface, the gas may contain heavier hydrocarbons such as pentane, hexane, and heptane in the gaseous state. At surface conditions these will condense out of the gas to form natural gas condensate, often shortened to condensate. Condensate resembles petrol in appearance and is similar in composition to some volatile light crude oils.

The proportion of light hydrocarbons in the petroleum mixture varies greatly among different oil fields, ranging from as much as 97 percent by weight in the lighter oils to as little as 50 percent in the heavier oils and bitumens.

The hydrocarbons in crude oil are mostly alkanes, cycloalkanes and various aromatic hydrocarbons while the other organic compounds contain nitrogen, oxygenand sulfur, and trace amounts of metals such as iron, nickel, copper and vanadium. The exact molecular composition varies widely from formation to formation but the proportion of chemical elements vary over fairly narrow limits as follows:

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Most of the world's oils are non-conventional.

Composition by weight

Element Percent range

Carbon 83 to 85%

Hydrogen 10 to 14%

Nitrogen 0.1 to 2%

Oxygen 0.05 to 1.5%

Sulfur 0.05 to 6.0%

Metals < 0.1%

Four different types of hydrocarbon molecules appear in crude oil. The relative percentage of each varies from oil to oil, determining the properties of each oil.

Crude oil varies greatly in appearance depending on its composition. It is usually black or dark brown (although it may be yellowish, reddish, or even greenish). In the reservoir it is usually found in association with natural gas, which being lighter forms a gas cap over the petroleum, and saline water which, being heavier than most forms of crude oil, generally sinks beneath it. Crude oil may also be found in semi-solid form mixed with sand and

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water, as in the Athabasca oil sands in Canada, where it is usually referred to as crude bitumen. In Canada, bitumen is considered a sticky, black, tar-like form of crude oil which is so thick and heavy that it must be heated or diluted before it will flow. Venezuela also has large amounts of oil in the Orinoco oil sands, although the hydrocarbons trapped in them are more fluid than in Canada and are usually called extra heavy oil. These oil sands resources are called unconventional oil to distinguish them from oil which can be extracted using traditional oil well methods. Between them, Canada and Venezuela contain an estimated 3.6 trillion barrels (570×109 m3) of bitumen and extra-heavy oil, about twice the volume of the world's reserves of conventional oil.

Petroleum is used mostly, by volume, for producing fuel oil and petrol, both important "primary energy" sources. 84 percent by volume of the hydrocarbons present in petroleum is converted into energy-rich fuels (petroleum-based fuels), including petrol, diesel, jet, heating, and other fuel oils, and liquefied petroleum gas. The lighter grades of crude oil produce the best yields of these products, but as the world's reserves of light and medium oil are depleted, oil refineries are increasingly having to process heavy oil and bitumen, and use more complex and expensive methods to produce the products required. Because heavier crude oils have too much carbon and not enough hydrogen, these processes generally involve removing carbon from or adding hydrogen to the molecules, and using fluid catalytic cracking to convert the longer, more complex molecules in the oil to the shorter, simpler ones in the fuels.

Due to its high energy density, easy transportability and relative abundance, oil has become the world's most important source of energy since the mid-1950s. Petroleum is also the raw material for many chemical products, including pharmaceuticals, solvents, fertilizers, pesticides, and plastics; the 16 percent not used for energy production is converted into these other materials. Petroleum is found in porous rock formations in the upper strata of some areas of the Earth's crust. There is also petroleum in oil sands (tar sands). Known oil reserves are typically estimated at around 190 km3 (1.2 trillion (short scale) barrels) without oil sands, or 595 km3 (3.74 trillion barrels) with oil sands. Consumption is currently around 84 million barrels (13.4×106 m3) per day, or 4.9 km3 per year. Which in turn yields a remaining oil supply of only about 120 years, if current demand remain static.

Chemistry

Petroleum is a mixture of a very large number of different hydrocarbons; the most commonly found molecules are alkanes(paraffins), cycloalkanes (naphthenes), aromatic hydrocarbons, or more complicated chemicals like asphaltenes. Each petroleum variety has a unique mix of molecules, which define its physical and chemical properties, like color and viscosity.

The alkanes, also known as paraffins, are saturated hydrocarbons with straight or branched chains which contain only carbon and hydrogen and have the general formula CnH2n+2. They generally have from 5 to 40 carbon atoms per molecule, although trace amounts of shorter or longer molecules may be present in the mixture.

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The alkanes from pentane (C5H12) to octane (C8H18) are refined into petrol, the ones from nonane (C9H20) to hexadecane(C16H34) into diesel fuel, kerosene and jet fuel. Alkanes with more than 16 carbon atoms can be refined into fuel oil and lubricating oil. At the heavier end of the range, paraffin wax is an alkane with approximately 25 carbon atoms, while asphalt has 35 and up, although these are usually cracked by modern refineries into more valuable products. The shortest molecules, those with four or fewer carbon atoms, are in a gaseous state at room temperature. They are the petroleum gases. Depending on demand and the cost of recovery, these gases are either flared off, sold as liquified petroleum gas under pressure, or used to power the refinery's own burners. During the winter, butane (C4H10), is blended into the petrol pool at high rates, because its high vapor pressure assists with cold starts. Liquified under pressure slightly above atmospheric, it is best known for powering cigarette lighters, but it is also a main fuel source for many developing countries. Propane can be liquified under modest pressure, and is consumed for just about every application relying on petroleum for energy, from cooking to heating to transportation.

The cycloalkanes, also known as naphthenes, are saturated hydrocarbons which have one or more carbon rings to which hydrogen atoms are attached according to the formula CnH2n. Cycloalkanes have similar properties to alkanes but have higher boiling points.

The aromatic hydrocarbons are unsaturated hydrocarbons which have one or more planar six-carbon rings called benzene rings, to which hydrogen atoms are attached with the formula CnHn. They tend to burn with a sooty flame, and many have a sweet aroma. Some are carcinogenic.

These different molecules are separated by fractional distillation at an oil refinery to produce petrol, jet fuel, kerosene, and other hydrocarbons. For example, 2,2,4-trimethylpentane (isooctane), widely used in petrol, has a chemical formula of C8H18 and it reacts with oxygen exothermically:

2 C8H18(l) + 25 O2(g) 16→ CO2(g) + 18 H2O(g) (ΔH = −5.51 MJ/mol of octane)

The number of various molecules in an oil sample can be determined in laboratory. The molecules are typically extracted in a solvent, then separated in a gas chromatograph, and finally determined with a suitable detector, such as a flame ionization detector or a mass spectrometer. Due to the large number of co-eluted hydrocarbons within oil, many cannot be resolved by traditional gas chromatography and typically appear as a hump in the chromatogram. This unresolved complex mixture (UCM) of hydrocarbons is particularly apparent when analyzing weathered oils and extracts from tissues of organisms exposed to oil.

Incomplete combustion of petroleum or petrol results in production of toxic byproducts. Too little oxygen results in carbon monoxide. Due to the high temperatures and high pressures involved, exhaust gases from petrol combustion in car engines usually include nitrogen oxides which are responsible for creation of photochemical smog

Formation

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Petroleum is a fossil fuel derived from ancient fossilized organic materials, such as zooplankton and algae. Vast quantities of these remains settled to sea or lake bottoms, mixing with sediments and being buried under anoxic conditions. As further layers settled to the sea or lake bed, intense heat and pressure build up in the lower regions. This process caused the organic matter to change, first into a waxy material known as kerogen, which is found in various oil shales around the world, and then with more heat into liquid and gaseous hydrocarbons via a process known as catagenesis. Formation of petroleum occurs from hydrocarbon pyrolysis in a variety of mainly endothermic reactions at high temperature and/or pressure.

There were certain warm nutrient-rich environments such as the Gulf of Mexico and the ancient Tethys Sea where the large amounts of organic material falling to the ocean floor exceeded the rate at which it could decompose. This resulted in large masses of organic material being buried under subsequent deposits such as shale formed from mud. This massive organic deposit later became heated and transformed under pressure into oil.

Geologists often refer to the temperature range in which oil forms as an "oil window"—below the minimum temperature oil remains trapped in the form of kerogen, and above the maximum temperature the oil is converted to natural gas through the process of thermal cracking. Sometimes, oil formed at extreme depths may migrate and become trapped at a much shallower level. The Athabasca Oil Sands are one example of this.

An alternative mechanism was proposed by Russian scientists in the mid-1850s, the Abiogenic petroleum origin, but this is contradicted by the geological and geochemical evidence.

Extraction

Oil extraction is simply the removal of oil from the reservoir (oil pool). Oil is often recovered as a water-in-oil emulsion, and specialty chemicals called demulsifiers are used to separate the oil from water. Oil extraction is costly and sometimes environmentally damaging, although Dr. John Hunt of the Woods Hole Oceanographic Institution pointed out in a 1981 paper that over 70 percent of the reserves in the world are associated with visible macroseepages, and many oil fields are found due to natural seeps. Offshore exploration and extraction of oil disturbs the surrounding marine environment.

Natural Gas

Natural gas is a fossil fuel formed when layers of buried plants, gases, and animals are exposed to intense heat and pressure over thousands of years. The energy that the plants originally obtained from the sun is stored in the form of chemical bonds in natural gas. Natural gas is a nonrenewable resource because it cannot be replenished on a human time frame. Natural gas is a hydrocarbongas mixture consisting primarily of methane, but commonly includes varying amounts of other higher alkanes and even a lesser percentage of carbon dioxide, nitrogen, and hydrogen sulfide. Natural gas is an energy source often used for heating, cooking, and electricity generation. It is also used as fuel for vehicles and as a chemical feedstock in the manufacture of plastics and other commercially important organic chemicals.

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Natural gas is found in deep underground rock formations or associated with other hydrocarbon reservoirs in coal beds and as methane clathrates. Petroleum is another resource and fossil fuel found in close proximity to, and with natural gas. Most natural gas was created over time by two mechanisms: biogenic and thermogenic. Biogenic gas is created by methanogenic organisms in marshes, bogs, landfills, and shallow sediments. Deeper in the earth, at greater temperature and pressure, thermogenic gas is created from buried organic material.

Before natural gas can be used as a fuel, it must be processed to remove impurities, including water, to meet the specifications of marketable natural gas. The by-products of this processing include ethane, propane, butanes, pentanes, and higher molecular weight hydrocarbons, hydrogen sulfide(which may be converted into pure sulfur), carbon dioxide, water vapor, and sometimes helium and nitrogen.

Natural gas is often informally referred to simply as "gas", especially when compared to other energy sources such as oil or coal. However, it is not to be confused with gasoline, especially in North America, where the term gasoline is often shortened in colloquial usage to gas.

Natural gas was used by the Chinese in about 500 BC. They discovered a way to transport gas seeping from the ground in crude pipelines of bamboo to where it was used to boil sea water to extract the salt. The world's first industrial extraction of natural gas started at Fredonia, New York, USA in 1825. By 2009, 66 trillion cubic meters (or 8%) had been used out of the total 850 trillion cubic meters of estimated remaining recoverable reserves of natural gas. Based on an estimated 2015 world consumption rate of about 3.4 trillion cubic meters of gas per year, the total estimated remaining economically recoverable reserves of natural gas would last 250 years.

Sources

Natural gas

In the 19th century, natural gas was usually obtained as a by-product of producing oil, since the small, light gas carbon chains came out of solution as the extracted fluids underwent pressure reduction from the reservoir to the surface, similar to uncapping a bottle of soda where the carbon dioxide effervesces. Unwanted natural gas was a disposal problem in the active oil fields. If there was not a market for natural gas near the wellhead it was virtually valueless since it had to be piped to the end user.

In the 19th century and early 20th century, such unwanted gas was usually burned off at oil fields. Today, unwanted gas (or stranded gas without a market) associated with oil extraction often is returned to the reservoir with 'injection' wells while awaiting a possible future market or to repressurize the formation, which can enhance extraction rates from other wells. In regions with a high natural gas demand (such as the US), pipelines are constructed when it is economically feasible to transport gas from a well site to an end consumer.

In addition to transporting gas via pipelines for use in power generation, other end uses for natural gas include export as liquefied natural gas (LNG) or conversion of natural gas into other liquid products via gas-to-liquids (GTL) technologies. GTL technologies can convert

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natural gas into liquids products such as gasoline, diesel or jet fuel. A variety of GTL technologies have been developed, including Fischer-Tropsch (F-T), methanol to gasoline (MTG) and STG+. F-T produces a synthetic crude that can be further refined into finished products, while MTG can produce synthetic gasoline from natural gas. STG+ can produce drop-in gasoline, diesel, jet fuel and aromatic chemicals directly from natural gas via a single-loop process. In 2011, Royal Dutch Shell’s140,000 barrel per day F-T plant went into operation in Qatar.

Natural gas can be "associated" (found in oil fields), or "non-associated" (isolated in natural gas fields), and is also found in coal beds (as coal bed methane). It sometimes contains a significant amount of ethane, propane, butane, and pentane—heavier hydrocarbons removed for commercial use prior to the methane being sold as a consumer fuel or chemical plant feedstock. Non-hydrocarbons such as carbon dioxide, nitrogen, helium (rarely), and hydrogen sulfide must also be removed before the natural gas can be transported.

Natural gas extracted from oil wells is called casing head gas or associated gas. The natural gas industry is extracting an increasing quantity of gas from challenging resource types: sour gas, tight gas, shale gas, and coal bed methane.

There is some disagreement on which country has the largest proven gas reserves. Sources that consider that Russia has by far the largest proven reserves include the US CIA (47.6 trillion cubic meters), the US Energy Information Administration (47.8 tcm), and OPEC (48.7 tcm). However, BP credits Russia with only 32.9 tcm, which would place it in second place, slightly behind Iran (33.1 to 33.8 tcm, depending on the source). With Gazprom, Russia is frequently the world's largest natural gas extractor. Major proven resources (in billion cubic meters) are world 187,300 (2013), Iran 33,600 (2013), Russia 32,900 (2013), Qatar 25,100 (2013), Turkmenistan 17,500 (2013) and the United States 8,500 (2013).

It is estimated that there are about 900 trillion cubic meters of "unconventional" gas such as shale gas, of which 180 trillion may be recoverable. In turn, many studies from MIT, Black & Veatch and the DOE predict that natural gas will account for a larger portion of electricity generation and heat in the future.

The world's largest gas field is the offshore South Pars / North Dome Gas-Condensate field, shared between Iran and Qatar. It is estimated to have 51 trillion cubic meters of natural gas and 50 billion barrels of natural gas condensates.

Because natural gas is not a pure product, as the reservoir pressure drops when non-associated gas is extracted from a field under supercritical(pressure/temperature) conditions, the higher molecular weight components may partially condense upon isothermic depressurizing—an effect called retrograde condensation. The liquid thus formed may get trapped as the pores of the gas reservoir get depleted. One method to deal with this problem is to re-inject dried gas free of condensate to maintain the underground pressure and to allow re-evaporation and extraction of condensates. More frequently, the liquid condenses at the surface, and one of the tasks of the gas plant is to collect this condensate. The resulting liquid is called natural gas liquid (NGL) and has commercial value.

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Shale gas

Shale gas is natural gas produced from shale. Because shale has matrix permeability too low to allow gas to flow in economic quantities, shale gas wells depend on fractures to allow the gas to flow. Early shale gas wells depended on natural fractures through which gas flowed; almost all shale gas wells today require fractures artificially created by hydraulic fracturing. Since 2000, shale gas has become a major source of natural gas in the United States and Canada. Following the success in the United States, shale gas exploration is beginning in countries such as Poland, China, and South Africa.

Town gas

Town gas is a flammable gaseous fuel made by the destructive distillation of coal and contains a variety of calorific gases including hydrogen, carbon monoxide, methane, and other volatile hydrocarbons, together with small quantities of non-calorific gases such as carbon dioxide and nitrogen, and is used in a similar way to natural gas. This is a historical technology, not usually economically competitive with other sources of fuel gas today. But there are still some specific cases where it is the best option and it may be so into the future.

Most town "gashouses" located in the eastern US in the late 19th and early 20th centuries were simple by-product coke ovens that heated bituminous coal in air-tight chambers. The gas driven off from the coal was collected and distributed through networks of pipes to residences and other buildings where it was used for cooking and lighting. (Gas heating did not come into widespread use until the last half of the 20th century.) The coal tar (or asphalt) that collected in the bottoms of the gashouse ovens was often used for roofing and other waterproofing purposes, and when mixed with sand and gravel was used for paving streets.

Biogas

Methanogenic archaea are responsible for all biological sources of methane. Some live in symbiotic relationships with other life forms, including termites, ruminants, and cultivated crops. Other sources of methane, the principal component of natural gas, include landfill gas, biogas, and methane hydrate. When methane-rich gases are produced by the anaerobic decay of non-fossil organic matter (biomass), these are referred to as biogas (or natural biogas). Sources of biogas include swamps, marshes, and landfills (see landfill gas), as well as agricultural waste materials such as sewage sludge and manure by way of anaerobic digesters, in addition to enteric fermentation, particularly in cattle. Landfill gas is created by decomposition of waste in landfill sites. Excluding water vapor, about half of landfill gas is methane and most of the rest is carbon dioxide, with small amounts of nitrogen, oxygen, and hydrogen, and variable trace amounts of hydrogen sulfide and siloxanes. If the gas is not removed, the pressure may get so high that it works its way to the surface, causing damage to the landfill structure, unpleasant odor, vegetation die-off, and an explosion hazard. The gas can be vented to the atmosphere, flared or burned to produce electricity or heat. Biogas can also be produced by separating organic materials from waste that otherwise goes to landfills. This method is more efficient than just capturing the landfill gas it produces. Anaerobic lagoons produce biogas from manure, while biogas reactors can be used for manure or plant parts. Like landfill gas, biogas is

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mostly methane and carbon dioxide, with small amounts of nitrogen, oxygen and hydrogen. However, with the exception of pesticides, there are usually lower levels of contaminants.

Landfill gas cannot be distributed through utility natural gas pipelines unless it is cleaned up to less than 3 per cent CO2, and a few parts per million H2S, because CO2 and H2S corrode the pipelines. The presence of CO2 will lower the energy level of the gas below requirements for the pipeline. Siloxanes in the gas will form deposits in gas burners and need to be removed prior to entry into any gas distribution or transmission system. Consequently it may be more economical to burn the gas on site or within a short distance of the landfill using a dedicated pipeline. Water vapor is often removed, even if the gas is burned on site. If low temperatures condense water out of the gas, siloxanes can be lowered as well because they tend to condense out with the water vapor. Other non-methane components may also be removed to meet emission standards, to prevent fouling of the equipment or for environmental considerations. Co-firing landfill gas with natural gas improves combustion, which lowers emissions.

Biogas, and especially landfill gas, are already used in some areas, but their use could be greatly expanded. Experimental systems were being proposed for use in parts of Hertfordshire, UK, and Lyon in France. Using materials that would otherwise generate no income, or even cost money to get rid of, improves the profitability and energy balance of biogas production. Gas generated in sewage treatment plants is commonly used to generate electricity. For example, the Hyperion sewage plant in Los Angeles burns 8 million cubic feet (230,000 m3) of gas per day to generate power New York City utilizes gas to run equipment in the sewage plants, to generate electricity, and in boilers. Using sewage gas to make electricity is not limited to large cities. The city of Bakersfield, California, uses cogeneration at its sewer plants. California has 242 sewage wastewater treatment plants, 74 of which have installed anaerobic digesters. The total biopower generation from the 74 plants is about 66 MW.

Crystallized natural gas — hydrates

Huge quantities of natural gas (primarily methane) exist in the form of hydrates under sediment on offshore continental shelves and on land in arctic regions that experience permafrost, such as those in Siberia. Hydrates require a combination of high pressure and low temperature to form.

In 2010, the cost of extracting natural gas from crystallized natural gas was estimated to 100–200 per cent the cost of extracting natural gas from conventional sources, and even higher from offshore deposits.

In 2013, Japan Oil, Gas and Metals National Corporation (JOGMEC) announced that they had recovered commercially relevant quantities of natural gas from methane hydrate.

Natural Gas Processing

The image below is a schematic block flow diagram of a typical natural gas processing plant. It shows the various unit processes used to convert raw natural gas into sales gas pipelined to the end user markets.

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The block flow diagram also shows how processing of the raw natural gas yields byproduct sulfur, byproduct ethane, and natural gas liquids (NGL) propane, butanes and natural gasoline (denoted as pentanes +).

Schematic flow diagram of a typical natural gas processing plant.

Environmental Effects

Effect of natural gas release

Natural gas is mainly composed of methane. After release to the atmosphere it is removed over about 10 years by gradual oxidation to carbon dioxide and water by hydroxyl radicals (·OH) formed in the troposphere or stratosphere, giving the overall chemical reaction CH4 + 2O2 CO→ 2 + 2H2O. While the lifetime of atmospheric methane is relatively short when compared to carbon dioxide, it is more efficient at trapping heat in the atmosphere, so that a given quantity of methane has 62 times the global-warming potential of carbon dioxide over a 20-year period, 20 times over a 100-year period and 8 times over a 500-year period. Natural gas is thus a more potent greenhouse gas than carbon dioxide due to the greater global-warming potential of methane. Current estimates by the EPA place global emissions of methane at 85 billion cubic metres (3.0×1012 cu ft) annually, or 3.2 per cent of global production. Direct emissions of methane represented 14.3 per cent of all global anthropogenic greenhouse gas emissions in 2004.

During extraction, storage, transportation, and distribution, natural gas is known to leak into the atmosphere, particularly during the extraction process. A study in 2011

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demonstrated that the leak rate of methane was high enough to jeopardize its global warming advantage over coal. This study was criticized later for its high assumption of methane leakage values. These values were later shown to be close to the findings of the Scientists at the National Oceanic and Atmospheric Administration. Natural gas extraction also releases an isotope of Radon, ranging from 5 to 200,000 Becquerels per cubic meter.

CO2 emissions

Natural gas is often described as the cleanest fossil fuel. It produces about 29% and 44% less carbon dioxide per joule delivered than oil and coal respectively, and potentially fewer pollutants than other hydrocarbon fuels. However, in absolute terms, it comprises a substantial percentage of human carbon emissions, and this contribution is projected to grow. According to the IPCC Fourth Assessment Report, in 2004, natural gas produced about 5.3 billion tons a year of CO2emissions, while coal and oil produced 10.6 and 10.2 billion tons respectively. According to an updated version of the Special Report on Emissions Scenario by 2030, natural gas would be the source of 11 billion tons a year, with coal and oil now 8.4 and 17.2 billion respectively because demand is increasing 1.9 percent a year. Total global emissions for 2004 were estimated at over 27,200 million tons.

Other pollutants

Natural gas produces far lower amounts of sulfur dioxide and nitrous oxides than any other hydrocarbon fuels. The other pollutants due to natural gas combustion are listed below in parts per million (ppm):

• Carbon monoxide - 40 ppm• Sulfur dioxide - 1 ppm

• Nitrogen oxide - 92 ppm

• Particulates - 7 ppm

Unit-IIIWater resources

Water resources are sources of water that are useful or potentially useful. Uses of water include agricultural, industrial, household, recreational and environmental activities. The majority of human uses require fresh water.

97 percent of the water on the Earth is salt water and only three percent is fresh water; slightly over two thirds of this is frozen in glaciers and polar ice caps.[1] The remaining unfrozen freshwater is found mainly as groundwater, with only a small fraction present above ground or in the air.

Fresh water is a renewable resource, yet the world's supply of groundwater is steadily decreasing, with depletion occurring most prominently in Asia and North America, although it is still unclear how much natural renewal balances this usage, and whether ecosystems are threatened. The framework for allocating water resources to water users (where such a framework exists) is known as water rights.

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Water Balance

In hydrology, a water balance equation can be used to describe the flow of water in and out of a system. A system can be one of several hydrological domains, such as a column of soil or a drainage basin. Water balance can also refer to the ways in which an organism maintains water in dry or hot conditions. It is often discussed in reference to plants or arthropods, which have a variety of water retention mechanisms, including a lipid waxy coating that has limited permeability.

Equation

A general water balance equation is:

where

is precipitation is runoff is evapotranspiration

is the change in storage (in soil or the bedrock)

This equation uses the principles of conservation of mass in a closed system, whereby any water entering a system (via precipitation), must be transferred into either evaporation, surface runoff (eventually reaching the channel and leaving in the form of river discharge), or stored in the ground. This equation requires the system to be closed, and where it isn't (for example when surface runoff contributes to a different basin), this must be taken into account.

Extensive water balances are discussed in agricultural hydrology.A water balance can be used to help manage water supply and predict where there may be water shortages. It is also used in irrigation, runoff assessment (e.g. through the RainOff model), flood control and pollution control. Further it is used in the design of subsurface drainage systems which may be horizontal (i.e. using pipes, tile drains or ditches) or vertical (drainage by wells). To estimate the drainage requirement, the use of a hydro geological water balance and a groundwater model (e.g. SahysMod) may be instrumental.

The water balance can be illustrated using a water balance graph which plots levels of precipitation and evapotranspiration often on a monthly scale.

Several monthly water balance models had been developed for several conditions and purposes. Monthly water balance models had been studied since the 1940s.

Ice Sheet

An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km2 (19,000 sq mi), thus also known as continental glacier. The only current ice sheets are in Antarctica and Greenland; during the last glacial period at Last Glacial

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Maximum (LGM) the Laurentide ice sheet covered much of North America, the Weichselian ice sheet covered northern Europe and the Patagonian Ice Sheet covered southern South America.

Ice sheets are bigger than ice shelves or alpine glaciers. Masses of ice covering less than 50,000 km2 are termed an ice cap. An ice cap will typically feed a series of glaciers around its periphery.

Although the surface is cold, the base of an ice sheet is generally warmer due to geothermal heat. In places, melting occurs and the melt-water lubricates the ice sheet so that it flows more rapidly. This process produces fast-flowing channels in the ice sheet — these are ice streams.

The present-day polar ice sheets are relatively young in geological terms. The Antarctic Ice Sheet first formed as a small ice cap (maybe several) in the early Oligocene, but retreating and advancing many times until the Pliocene, when it came to occupy almost all of Antarctica. The Greenland ice sheet did not develop at all until the late Pliocene, but apparently developed very rapidly with the first continental glaciation. This had the unusual effect of allowing fossils of plants that once grew on present-day Greenland to be much better preserved than with the slowly forming Antarctic ice sheet.

Antarctic ice sheet

The Antarctic ice sheet is the largest single mass of ice on Earth. It covers an area of almost 14 million km2 and contains 30 million km3 of ice. Around 90% of the fresh water on the Earth's surface is held in the ice sheet, and, if melted, would cause sea levels to rise by 58 metres. The continent-wide average surface temperature trend of Antarctica is positive and significant at >0.05°C/decade since 1957.

The Antarctic ice sheet is divided by the Transant arctic Mountains into two unequal sections called the East Antarctic ice sheet (EAIS) and the smaller West Antarctic Ice Sheet (WAIS). The EAIS rests on a major land mass but the bed of the WAIS is, in places, more than 2,500 metres below sea level. It would be seabed if the ice sheet were not there. The WAIS is classified as a marine-based ice sheet, meaning that its bed lies below sea level and its edges flow into floating ice shelves. The WAIS is bounded by the Ross Ice Shelf, the Ronne Ice Shelf, and outlet glaciers that drain into the Amundsen Sea.

Greenland Ice Sheet

The Greenland ice sheet occupies about 82% of the surface of Greenland, and if melted would cause sea levels to rise by 7.2 metres. Estimated changes in the mass of Greenland's ice sheet suggest it is melting at a rate of about 239 cubic kilometres (57.3 cubic miles) per year. These measurements came from NASA's Gravity Recovery and Climate Experiment(GRACE) satellite, launched in 2002, as reported by BBC News in August 2006.

Ice Sheet Dynamics

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Ice movement is dominated by the motion of glaciers, whose activity is determined by a number of processes. Their motion is the result of cyclic surges interspersed with longer periods of inactivity, on both hourly and centennial time scales.

Predicted Effects of Global Warming

The Greenland, and probably the Antarctic, ice sheets have been losing mass recently, because losses by melting and outlet glaciers exceed accumulation of snowfall. According to the Intergovernmental Panel on Climate Change (IPCC), loss of Antarctic and Greenland ice sheet mass contributed, respectively, about 0.21 ± 0.35 and 0.21 ± 0.07 mm/year to sea level rise between 1993 and 2003.

The IPCC projects that ice mass loss from melting of the Greenland ice sheet will continue to outpace accumulation of snowfall. Accumulation of snowfall on the Antarctic ice sheet is projected to outpace losses from melting. However, loss of mass on the Antarctic sheet may continue, if there is sufficient loss to outlet glaciers. In the words of the IPCC, "Dynamical processes related to ice flow not included in current models but suggested by recent observations could increase the vulnerability of the ice sheets to warming, increasing future sea level rise. Understanding of these processes is limited and there is no consensus on their magnitude." More research work is therefore required in order to improve the reliability of predictions of ice-sheet response on global warming.

The effects on ice formations of an increasing in temperature will accelerate. When ice is melted away less light from the sun will be reflected back into space and more will be absorbed by the ocean water causing further rises in temperature. This positive ice-albedo feedback system could become independent of climate change past a certain point which will cause huge losses of ice to the icecaps.

Sea Level

The Greenland, and probably the Antarctic, ice sheets have been losing mass recently, because losses by melting and outlet glaciers exceed accumulation of snowfall. According to the Intergovernmental Panel on Climate Change (IPCC), loss of Antarctic and Greenland ice sheet mass contributed, respectively, about 0.21 ± 0.35 and 0.21 ± 0.07 mm/year to sea level rise between 1993 and 2003.

The IPCC projects that ice mass loss from melting of the Greenland ice sheet will continue to outpace accumulation of snowfall. Accumulation of snowfall on the Antarctic ice sheet is projected to outpace losses from melting. However, loss of mass on the Antarctic sheet may continue, if there is sufficient loss to outlet glaciers. In the words of the IPCC, "Dynamical processes related to ice flow not included in current models but suggested by recent observations could increase the vulnerability of the ice sheets to warming, increasing future sea level rise. Understanding of these processes is limited and there is no consensus on their magnitude." More research work is therefore required in order to improve the reliability of predictions of ice-sheet response on global warming.

The effects on ice formations of an increasing in temperature will accelerate. When ice is melted away less light from the sun will be reflected back into space and more will be

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absorbed by the ocean water causing further rises in temperature. This positive ice-albedo feedback system could become independent of climate change past a certain point which will cause huge losses of ice to the icecaps.

Measurement

Precise determination of a "mean sea level" is a difficult problem because of the many factors that affect sea level. Sea level varies quite a lot on several scales of time and distance. This is because the sea is in constant motion, affected by the tides, wind, atmospheric pressure, local gravitational differences, temperature, salinity and so forth. The best one can do is to pick a spot and calculate the mean sea level at that point and use it as a datum. For example, a period of 19 years of hourly level observations may be averaged and used to determine the mean sea level at some measurement point.

To an operator of a tide gauge, MSL means the "still water level"—the level of the sea with motions such as wind waves averaged out—averaged over a period of time such that changes in sea level, e.g., due to the tides, also get averaged out. One measures the values of MSL in respect to the land. Hence a change in MSL can result from a real change in sea level, or from a change in the height of the land on which the tide gauge operates.

In the UK, the Ordnance Datum (the 0 metres height on UK maps) is the mean sea level measured at Newlyn in Cornwall between 1915 and 1921. Prior to 1921, the datum was MSL at the Victoria Dock, Liverpool.

In France, the Marégraphe in Marseilles measures continuously the sea level since 1883 and offers the longest collapsed data about the sea level. It is used for a part of continental Europe and main part of Africa as official sea level. Elsewhere in Europe vertical elevation references (European Vertical Reference System) are made to the Amsterdam Pile elevation, which dates back to the 1690s.

Satellite altimeters have been making precise measurements of sea level since the launch of TOPEX/Poseidon in 1992. A joint mission of NASA and CNES, TOPEX/Poseidon was followed by Jason-1 in 2001 and the Ocean Surface Topography Mission on the Jason-2 satellite in 2008.

Sea Level Change

Local and eustatic sea level

Local mean sea level (LMSL) is defined as the height of the sea with respect to a land benchmark, averaged over a period of time (such as a month or a year) long enough that fluctuations caused by waves and tides are smoothed out. One must adjust perceived changes in LMSL to account for vertical movements of the land, which can be of the same order (mm/yr) as sea level changes. Some land movements occur because of isostatic adjustment of the mantle to the melting of ice sheets at the end of the last ice

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age. The weight of the ice sheet depresses the underlying land, and when the ice melts away the land slowly rebounds. Changes in ground-based ice volume also affect local and regional sea levels by the readjustment of the geoid and true polar wander. Atmospheric pressure, ocean currents and local ocean temperature changes can affect LMSL as well.

Eustatic change (as opposed to local change) results in an alteration to the global sea levels due to changes in either the volume of water in the world oceans or net changes in the volume of the ocean basins.

Short term and periodic changes

There are many factors which can produce short-term (a few minutes to 14 months) changes in sea level.

Long term changes

Various factors affect the volume or mass of the ocean, leading to long-term changes in eustatic sea level. The primary influence is that of temperature on seawater density and the amounts of water retained in rivers, aquifers, lakes, glaciers, polar ice caps and sea ice. Over much longer geological timescales, changes in the shape of the oceanic basins and in land/sea distribution will also affect sea level.

Observational and modeling studies of mass loss from glaciers and ice caps indicate a contribution to sea-level rise of 0.2 to 0.4 mm/yr averaged over the 20th century. Over this last million years, whereas it was higher most of the time before then, sea level was lower than today.

Sea level reached 120 meters below current sea level at the Last Glacial Maximum 19,000–20,000 years ago.

Glaciers and ice caps

Each year about 8 mm (0.3 inches) of water from the entire surface of the oceans falls onto the Antarctica and Greenland ice sheets as snowfall. If no ice returned to the oceans, sea level would drop 8 mm (0.3 in) every year. To a first approximation, the same amount of water appeared to return to the ocean in icebergs and from ice melting at the edges. Scientists previously had estimated which is greater, ice going in or coming out, called the mass balance, important because it causes changes in global sea level. High-precision gravimetry from satellites in low-noise flight has since determined that in 2006, the Greenland and Antarctic ice sheets experienced a combined mass loss of 475 ± 158 Gt/yr, equivalent to 1.3 ± 0.4 mm/yr sea level rise. Notably, the acceleration in ice sheet loss from 1988–2006 was 21.9 ± 1 Gt/yr² for Greenland and 14.5 ± 2 Gt/yr² for Antarctica, for a combined total of 36.3 ± 2 Gt/yr². This acceleration is 3 times larger than for mountain glaciers and ice caps (12 ± 6 Gt/yr²).

Ice shelves float on the surface of the sea and, if they melt, to first order they do not change sea level. Likewise, the melting of the northern polar ice cap which is composed of floating pack ice would not significantly contribute to rising sea levels. However, because

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floating ice pack is lower in salinity than seawater, their melting would cause a very small increase in sea levels, so small that it is generally neglected.

• Scientists previously lacked knowledge of changes in terrestrial storage of water. Surveying of water retention by soil absorption and by artificial reservoirs ("impoundment") show that a total of about 10,800 cubic kilometres (2,591 cubic miles) of water (just under the size of Lake Huron) has been impounded on land to date. Such impoundment masked about 30 mm (1.2 in) of sea level rise in that time.

• Conversely estimates of excess global groundwater extraction during 1900–2008

totals ∼4,500 km3, equivalent to a sea-level rise of 12.6 mm (0.50 in) (>6% of the total).

Furthermore, the rate of groundwater depletion has increased markedly since about 1950, with maximum rates occurring during the most recent period (2000–2008),

when it averaged ∼145 km3/yr (equivalent to 0.40 mm/yr of sea-level rise, or 13% of

the reported rate of 3.1 mm/yr during this recent period).

• If small glaciers and polar ice caps on the margins of Greenland and the Antarctic Peninsula melt, the projected rise in sea level will be around 0.5 m (1 ft 7.7 in). Melting of the Greenland ice sheet would produce 7.2 m (23.6 ft) of sea-level rise, and melting of the Antarctic ice sheet would produce 61.1 m (200.5 ft) of sea level rise. The collapse of the grounded interior reservoir of the West Antarctic Ice Sheet would raise sea level by 5 m (16.4 ft) - 6 m (19.7 ft).

• The snowline altitude is the altitude of the lowest elevation interval in which minimum annual snow cover exceeds 50%. This ranges from about 5,500 metres(18,045 feet) above sea-level at the equator down to sea level at about 70° N&S latitude, depending on regional temperature amelioration effects. Permafrost then appears at sea level and extends deeper below sea level pole wards.

• As most of the Greenland and Antarctic ice sheets lie above the snowline and/or base of the permafrost zone, they cannot melt in a timeframe much less than several millennia; therefore it is likely that they will not, through melting, contribute significantly to sea level rise in the coming century. They can, however, do so through acceleration in flow and enhanced iceberg calving.

• Climate changes during the 20th century are estimated from modeling studies to have led to contributions of between −0.2 and 0.0 mm/yr from Antarctica (the results of increasing precipitation) and 0.0 to 0.1 mm/yr from Greenland (from changes in both precipitation and runoff).

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• Estimates suggest that Greenland and Antarctica have contributed 0.0 to 0.5 mm/yr over the 20th century as a result of long-term adjustment to the end of the last ice age.

The current rise in sea level observed from tide gauges, of about 1.8 mm/yr, is within the estimate range from the combination of factors above but active research continues in this field. The terrestrial storage term, thought to be highly uncertain, is no longer positive, and shown to be quite large.

Geological influences

At times during Earth's long history, the configuration of the continents and sea floor have changed due to plate tectonics. This affects global sea level by determining the depths of the ocean basins and how glacial-interglacial cycles distribute ice across the Earth.

The depth of the ocean basins is a function of the age of oceanic lithosphere: as lithosphere becomes older, it becomes denser and sinks. Therefore, a configuration with many small oceanic plates that rapidly recycle lithosphere will produce shallower ocean basins and (all other things being equal) higher sea levels. A configuration with fewer plates and more cold, dense oceanic lithosphere, on the other hand, will result in deeper ocean basins and lower sea levels.

When there was much continental crust near the poles, the rock record shows unusually low sea levels during ice ages, because there was much polar land mass on which snow and ice could accumulate. During times when the land masses clustered around the equator, ice ages had much less effect on sea level.

Over most of geologic time, long-term sea level has been higher than today (see graph above). Only at the Permian-Triassic boundary ~250 million years ago was long-term sea level lower than today. Long term changes in sea level are the result of changes in the oceanic crust, with a downward trend expected to continue in the very long term.

During the glacial/interglacial cycles over the past few million years, sea level has varied by somewhat more than a hundred metres. This is primarily due to the growth and decay of ice sheets (mostly in the northern hemisphere) with water evaporated from the sea.

The Mediterranean Basin's gradual growth as the Neotethys basin, begun in the Jurassic, did not suddenly affect ocean levels. While the Mediterranean was forming during the past 100 million years, the average ocean level was generally 200 metres above current levels. However, the largest known example of marine flooding was when the Atlantic breached the Strait of Gibraltar at the end of the Messinian Salinity Crisis about 5.2 million years ago. This restored Mediterranean sea levels at the sudden end of the period when that basin had dried up, apparently due to geologic forces in the area of the Strait.

Changes through geologic time

Sea level has changed over geologic time. As the graph shows, sea level today is very near the lowest level ever attained (the lowest level occurred at the Permian-Triassic boundary about 250 million years ago).

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During the most recent ice age (at its maximum about 20,000 years ago) the world's sea level was about 130 m lower than today, due to the large amount of sea water that had evaporated and been deposited as snow and ice, mostly in theLaurentide ice sheet. Most of this had melted by about 10,000 years ago.

Hundreds of similar glacial cycles have occurred throughout the Earth's history. Geologists who study the positions of coastal sediment deposits through time have noted dozens of similar basinward shifts of shorelines associated with a later recovery. This results in sedimentary cycles which in some cases can be correlated around the world with great confidence. This relatively new branch of geological science linking eustatic sea level to sedimentary deposits is called sequence stratigraphy.

The most up-to-date chronology of sea level change during the Phanerozoic shows the following long term trends:

• Gradually rising sea level through the Cambrian• Relatively stable sea level in the Ordovician, with a large drop associated with the

end-Ordovician glaciation

• Relative stability at the lower level during the Silurian

• A gradual fall through the Devonian, continuing through the Mississippian to long-term low at the Mississippian/Pennsylvanian boundary

• A gradual rise until the start of the Permian, followed by a gentle decrease lasting until the Mesozoic.

Recent Changes

For at least the last 100 years, sea level has been rising at an average rate of about 1.8 mm (0.1 in) per year. Most of this rise can be attributed to the increase in temperature of the sea and the resulting slight thermal expansion of the upper 500 metres (1,640 feet) of sea water. Additional contributions, as much as one-fourth of the total, come from water sources on land, such as melting snow and glaciers and extraction of groundwater for irrigation and other agricultural and human needs.

For at least the last 100 years, sea level has been rising at an average rate of about 1.8 mm (0.1 in) per year. Most of this rise can be attributed to the increase in temperature of the sea and the resulting slight thermal expansion of the upper 500 metres (1,640 feet) of sea water. Additional contributions, as much as one-fourth of the total, come from water sources on land, such as melting snow and glaciers and extraction of groundwater for irrigation and other agricultural and human needs.

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Types of Water

Water is commonly described either in terms of its nature, usage, or origin. The implications in these descriptions range from being highly specific to so general as to be non-definitive. Ground waters originate in subterranean locations such as wells, while surface waters comprise the lakes, rivers, and seas.

Fresh Water

Fresh water may come from either a surface or ground source, and typically contains less than 1% sodium chloride. It may be either "hard" or "soft," i.e., either rich in calcium and magnesium saltsand thus possibly forming insoluble curds with ordinary soap. Actually, there are gradations of hardness, which can be estimated from the Langelier or Ryznarindexes or accurately determined by titration with standardized chelating agent solutions such as versenates.

Brackish Water

Brackish water contains between 1 and 2.5% sodium chloride, either from natural sources around otherwise fresh water or by dilution of seawater. Brackish water differs from open seawater in certain other respects. The biological activity, for example, can be significantly modified by higher concentrations of nutrients. Fouling is also likely to be more severe as a consequence of the greater availability of nutrients.

Within harbors, bays, and other estuaries, marked differences can exist in the amount and type of fouling agents present in the water. The main environmental factors responsible, singly or in combination, for these differences are the salinity, the degree of pollution, and the prevalence of silt. Moreover, the influence of these factors can be very specific to the type of organism involved. Apart from differences that can develop between different parts of the same estuary, there can also be differences between fouling in enclosed waters and on the open coast. In this respect the extent of offshore coastal fouling is strongly determined by the accessibility to a natural source of infection. Local currents, average temperature, seasonal effects, depth, and penetration of light are operative factors. The presence of pollutants can also be quite important and highly variable in coastal areas.

Seawater

Seawater typically contains about 3.5% sodium chloride, although the salinity may be weakened in some areas by dilution with fresh water or concentrated by solar evaporation in others. Seawater is normally more corrosive than fresh water because of the higher conductivity and the penetrating power of the chloride ion through surface films on a metal. The rate of corrosion is controlled by the chloride content, oxygen availability, and

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the temperature. The 3.5% salt content of seawater produces the most corrosive chloride salt solution that can be obtained.

The combination of high conductivity and oxygen solubility is at a maximum at this point (oxygen solubility is reduced in more concentrated salt solutions).

Distilled or Demineralized Water

The total mineral content of water can be removed by either distillation or mixed-bed ion exchange. In the first case, purity is described qualitatively in some cases (e.g., triple-distilled water), but is best expressed, for both distilled and demineralized water, in terms of specific conductivity. Water also can be demineralized by reverse osmosis or electrodialysis.

Steam Condensate

Water condensed from industrial steam is called steam condensate. It approaches distilled water in purity, except for contamination (as by DO or carbon dioxide) and the effect of deliberate additives (e.g., neutralizing or filming amines).

Boiler Feedwater Make-up

The feedwater make-up for boilers is always softened and subsequently deaerated. It may vary in quality from fairly high dissolved solids (e.g., Zeolite-Treated), to very pure demineralized feed for high-pressure boilers. It tends to be highly corrosive, because of its softness, until thoroughly deaerated. This term is more precise than “boiler feedwater”, which may include recirculated steam condensate in various ratios to fresh make-up water.

Potable Water

Potable water is fresh water that is sanitized with oxidizing biocides such as chlorine or ozone to kill bacteria and make it safe for drinking purposes. By definition, certain mineral constituents are also restricted. For example, the chlorinity will be not more than 250 ppm chloride ion in the United States or 400 ppm on an international basis.

Process or Hydrotest Water/Firewater

These terms are essentially non-definitive, since the water employed may be of almost any chemistry, ranging from demineralized water to quite saline fresh water or even seawater in some cases. “Produced water” is that which originates in oil and gas production, emanating from geological sources with the hydrocarbons.

Cooling Water

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Cooling water is another undefined term, although it implies that any necessary treatment against excessive scaling or corrosion has been applied, or corrosion-resistant material selected. This may include anything from fresh water to seawater, and may comprise either an open- or closed-loop system, or a once-through system.

Waste Water

By definition, waste water is any water that is discarded after use. Sanitary waste from private or industrial applications is contaminated with fecal matter, soaps, detergents, etc., but is quite readily handled from a corrosion standpoint. Industrial wastes from chemical or petrochemical sources can contain strange and specific contaminants which greatly complicate materials selection, especially in the uses of plastics and elastomers.

Over Utilization of Surface and Ground Water

The over utilization of underground and surface water has the potential to alter, sometimes irreversibly, the integrity of freshwater ecosystems. Some of the major impacts are summarized below:

Impact

(i) Loss of integrity of freshwater ecosystems:

Human activities for infrastructure development like creation of dams, land conversion, etc. are responsible for this loss of integrity of freshwater ecosystems. Water quality and quantity, fisheries, habitats, etc. are at risk due to this loss of integrity.

(ii) Risk to ecosystem functions:

Population and consumption growth increases water abstraction and acquisition of cultivated land. Virtually all ecosystem functions including habitat, production and regulation functions are at risk.

(iii) Depletion of living resources and biodiversity:

Overharvesting and exploitation causes groundwater depletion, collapse of fisheries. Production of food, quality and quantity of water and supply of water gets badly affected by these depletions of living resources and biodiversity.

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(iv) Pollution of water bodies:

Release of pollutants to land, air or water alters chemistry and ecology of water bodies. Greenhouse gas emissions produce significant changes in runoff and rainfall patterns. Because of water pollution, water supply, habitat, water quality, food production, climate change, etc. are at risk.

Potential Threats to Our Groundwater

Overuse and Depletion

Groundwater is the largest source of usable, fresh water in the world. In many parts of the

world, especially where surface water supplies are not available, domestic, agricultural,

and industrial water needs can only be met by using the water beneath the ground.

The U.S. Geological Survey compares the water stored in the ground to money kept in a

bank account. If the money is withdrawn at a faster rate than new money is deposited,

there will eventually be account-supply problems. Pumping water out of the ground at a

faster rate than it is replenished over the long-term causes similar problems.

Groundwater depletion is primarily caused by sustained groundwater pumping. Some of

the negative effects of groundwater depletion:

• Lowering of the Water Table

Excessive pumping can lower the groundwater table, and cause wells to no longer be able to reach groundwater.

• Increased Costs

As the water table lowers, the water must be pumped farther to reach the surface, using more energy. In extreme cases, using such a well can be cost prohibitive.

• Reduced Surface Water Supplies

Groundwater and surface water are connected. When groundwater is overused, the lakes, streams, and rivers connected to groundwater can also have their supply diminished.

• Land Subsidence

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Land subsidence occurs when there is a loss of support below ground. This is most often caused by human activities, mainly from the overuse of groundwater, when the soil collapses, compacts, and drops.

• Water Quality Concerns

Excessive pumping in coastal areas can cause saltwater to move inland and upward, resulting in saltwater contamination of the water supply.

Water Conservation

Water conservation encompasses the policies, strategies and activities to manage fresh water as a sustainable resource, to protect the water environment, and to meet current and future human demand. Population, household size and growth and affluence all affect how much water is used. Factors such as climate change will increase pressures on natural water resources especially in manufacturing and agricultural irrigation.

The goals of water conservation efforts include as follows:

To ensure availability for future generations, the withdrawal of fresh water from an ecosystem should not exceed its natural replacement rate.

• Energy conservation . Water pumping, delivery and waste water treatment facilities consume a significant amount of energy. In some regions of the world over 15% of total electricity consumption is devoted to water management.

• Habitat conservation . Minimizing human water use helps to preserve fresh water habitats for local wildlife and migrating waterfowl, as well as reducing the need to build new dams and other water diversion infrastructures.

Strategies

In implementing water conservation principles there are a number of key activities that may be beneficial.

1.Any beneficial reduction in water loss, use and waste of resources.

2.Avoiding any damage to water quality.

3.Improving water management practices that reduce or enhance the beneficial use of water

Social Solution

Water conservation programs involved in social solutions are typically initiated at the local level, by either municipal water utilities or regional governments. Common strategies include public outreach campaigns,[4] tiered water rates (charging progressively higher prices as water use increases), or restrictions on outdoor water use such as lawn watering

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and car washing. Cities in dry climates often require or encourage the installation of xeriscaping or natural landscaping in new homes to reduce outdoor water usage.

One fundamental conservation goal is universal metering. The prevalence of residential water metering varies significantly worldwide. Recent studies have estimated that water supplies are metered in less than 30% of UK households, and about 61% of urban Canadian homes (as of 2001). Although individual water meters have often been considered impractical in homes with private wells or in multifamily buildings, the U.S. Environmental Protection Agency estimates that metering alone can reduce consumption by 20 to 40 percent. In addition to raising consumer awareness of their water use, metering is also an important way to identify and localize water leakage. Water metering would benefit society in the long run it is proven that water metering increases the efficiency of the entire water system, as well as help unnecessary expenses for individuals for years to come. One would be unable to waste water unless they are willing to pay the extra charges, this way the water department would be able to monitor water usage by public, domestic and manufacturing services.

Some researchers have suggested that water conservation efforts should be primarily directed at farmers, in light of the fact that crop irrigation accounts for 70% of the world's fresh water use. The agricultural sector of most countries is important both economically and politically, and water subsidies are common. Conservation advocates have urged removal of all subsidies to force farmers to grow more water-efficient crops and adopt less wasteful irrigation techniques.

New technology poses a few new options for consumers, features such and full flush and half flush when using a toilet are trying to make a difference in water consumption and waste. Also available in our modern world is shower heads that help reduce wasting water, old shower heads are said to use 5-10 gallons per minute. All new fixtures available are said to use 2.5 gallons per minute and offer equal water coverage.

Household Application

The Home Water Works website contains useful information on household water conservation. Contrary to popular view, experts suggest the most efficient way is replacing toilets and retrofitting washers.

Water-saving technology for the home includes:

1. Low-flow shower heads sometimes called energy-efficient shower heads as they also use less energy,

2. Low-flush toilets and composting toilets. These have a dramatic impact in the developed world, as conventional Western toilets use large volumes of water.

3. Dual flush toilets created by Caroma includes two buttons or handles to flush different levels of water. Dual flush toilets use up to 67% less water than conventional toilets.

Saline water (sea water) or rain water can be used for flushing toilets.

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1. Faucet aerators , which break water flow into fine droplets to maintain "wetting effectiveness" while using less water. An additional benefit is that they reduce splashing while washing hands and dishes.

2. Raw water flushing where toilets use sea water or non-purified water

3. Wastewater reuse or recycling systems, allowing:

• Reuse of graywater for flushing toilets or watering gardens

• Recycling of wastewater through purification at a water treatment plant. See also Wastewater - Reuse

4. Rainwater harvesting

5. High-efficiency clothes washers

6. Weather-based irrigation controllers

7. Garden hose nozzles that shut off water when it is not being used, instead of letting a hose run.

8. using low flow taps in wash basins

9. Swimming pool covers that reduce evaporation and can warm pool water to reduce water, energy and chemical costs.

10.Automatic faucet is a water conservation faucet that eliminates water waste at the faucet. It automates the use of faucets without the use of hands.

Commercial Application

Many water-saving devices (such as low-flush toilets) that are useful in homes can also be useful for business water saving. Other water-saving technology for businesses includes:

• Waterless urinals• Waterless car washes

• Infrared or foot-operated taps, which can save water by using short bursts of water for rinsing in a kitchen or bathroom

• Pressurized waterbrooms, which can be used instead of a hose to clean sidewalks

• X-ray film processor re-circulation systems

• Cooling tower conductivity controllers

• Water-saving steam sterilizers, for use in hospitals and health care facilities.

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• Rain water harvesting.

• Water to Water heat exchangers.

Agricultural Application

For crop irrigation, optimal water efficiency means minimizing losses due to evaporation, runoff or subsurface drainage while maximizing production. An evaporation pan in combination with specific crop correction factors can be used to determine how much water is needed to satisfy plant requirements. Flood irrigation, the oldest and most common type, is often very uneven in distribution, as parts of a field may receive excess water in order to deliver sufficient quantities to other parts. Overhead irrigation, using center-pivot or lateral-moving sprinklers, has the potential for a much more equal and controlled distribution pattern. Drip irrigation is the most expensive and least-used type, but offers the ability to deliver water to plant roots with minimal losses. However, drip irrigation is increasingly affordable, especially for the home gardener and in light of rising water rates. There are also cheap effective methods similar to drip irrigation such as the use of soaking hoses that can even be submerged in the growing medium to eliminate evaporation.

As changing irrigation systems can be a costly undertaking, conservation efforts often concentrate on maximizing the efficiency of the existing system. This may include chiseling compacted soils, creating furrow dikes to prevent runoff, and using soil moisture and rainfall sensors to optimize irrigation schedules. Usually large gains in efficiency are possible through measurement and more effective management of the existing irrigation system.

Rain Water Harvesting

In the present scenario management and distribution of water has become centralized. People depend on government system, which has resulted in disruption of community participation in water management and collapse of traditional water harvesting system. As the water crisis continues to become severe, there is a dire need of reform in water management system and revival of traditional systems. Scientific and technological studies need to be carried out to assess present status so as to suggest suitable mitigative measures for the revival to traditional system/wisdom. Revival process should necessarily be backed by people's initiative and active public participation. Living creatures of the universe are made of five basic elements, viz., Earth, Water, Fire, Air and Sky, Obviously, water is one of the most important elements and no creature can survive without it. Despite having a great regard for water, we seem to have failed to address this sector seriously. Human being could not save and conserve water and it sources, probably because of its availability in abundance. But this irresponsible attitude resulted in deterioration of water bodies with respect to quantity and quality both. Now, situation has arrived when even a single drop of water matters. However. "Better late than

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never", we have not realized the seriousness of this issue and initiated efforts to overcome those problems.

System of collection rainwater and conserving for future needs has traditionally been practiced in India. The traditional systems were time-tested wisdom of not only appropriate technology of Rainwater Harvesting, but also water management systems, where conservation of water was the prime concern. Traditional water harvesting systems were Bawaries, step wells, jhiries, lakes, tanks etc. These were the water storage bodies to domestic and irrigation demands. People were themselves responsible for maintenance to water sources and optimal use of water that could fulfill their needs.

What is Rainwater harvesting?The term rainwater harvesting is being frequently used these days, however, the concept of water harvesting is not new for India. Water harvesting techniques had been evolved and developed centuries ago.Ground water resource gets naturally recharged through percolation. But due to indiscriminate development and rapid urbainzation, exposed surface for soil has been reduced drastically with resultant reduction in percolation of rainwater, thereby depleting ground water resource. Rainwater harvesting is the process of augmenting the natural filtration of rainwater in to the underground formation by some artificial methods. "Conscious collection and storage of rainwater to cater to demands of water, for drinking, domestic purpose & irrigation is termed as Rainwater Harvesting."Components of the roof top rainwater harvesting systemThe illustrative design of the basic components of roof top rainwater harvesting system is given in the following typical schematic diagramThe system mainly constitutes of following sub components:

Catchment Transportation First flush Filter

The surface that receives rainfall directly is the catchment of rainwater harvesting system. It may be terrace, courtyard, or paved or unpaved open ground. The terrace may be flat RCC/stone roof or sloping roof. Therefore the catchment is the area, which actually contributes rainwater to the harvesting system.

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Transportation Rainwater from rooftop should be carried through down take water pipes or drains to storage/harvesting system. Water pipes should be UV resistant (ISI HDPE/PVC pipes) of required capacity. Water from sloping roofs could be caught through gutters and down take pipe. At terraces, mouth of the each drain should have wire mesh to restrict floating material.First FlushFirst flush is a device used to flush off the water received in first shower. The first shower of rains needs to be flushed-off to avoid contaminating storable/rechargeable water by the probable contaminants of the atmosphere and the catchment roof. It will also help in cleaning of silt and other material deposited on roof during dry seasons Provisions of first rain separator should be made at outlet of each drainpipe.

FilterThere is always some skepticism regarding Roof Top Rainwater Harvesting since doubts are raised that rainwater may contaminate groundwater. There is remote possibility of this fear coming true if proper filter mechanism is not adopted. Secondly all care must be taken to see that underground sewer drains are not punctured and no leakage is taking place in close vicinity. Filters are used fro treatment of water to effectively remove turbidity, colour and microorganisms. After first flushing of rainfall, water should pass through filters. There are different types of filters in practice, but basic function is to purify water.

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Sand Gravel FilterThese are commonly used filters, constructed by brick masonry and filleted by pebbles, gravel, and sand as shown in the figure. Each layer should be separated by wire mesh.

Charcoal FilterCharcoal filter can be made in-situ or in a drum. Pebbles, gravel, sand and charcoal as shown in the figure should fill the drum or chamber. Each layer should be separated by wire mesh. Thin layer of charcoal is used to absorb odor if any. PVC- Pipe filterThis filter can be made by PVC pipe of 1 to 1.20 m length; Diameter of pipe depends on the area of roof. Six inches dia. pipe is enough for a 1500 Sq. Ft. roof and 8 inches dia. pipe should be used for roofs more than 1500 Sq. Ft. Pipe is divided into three compartments by wire mesh. Each component should be filled with gravel and sand alternatively as shown in the figure. A layer of charcoal could also be inserted between two layers. Both ends of filter should have reduce of required size to connect inlet and outlet. This filter could be placed horizontally or vertically in the system.

Methods of Roof Top Rainwater HarvestingStorage of Direct useIn this method rain water collected from the roof of the building is diverted to a storage tank. The storage tank has to be designed according to the water requirements, rainfall and catchment availability. Each drainpipe should have mesh filter at mouth and first flush device followed by filtration system before connecting to the storage tank. It is advisable that each tank should have excess water over flow system.Excess water could be diverted to recharge system. Water from storage tank can be used for secondary purposes such as washing and gardening etc. This is the most cost effective way of rainwater harvesting. The main advantage of collecting and using the rainwater during rainy season is not only to save water from conventional sources, but also to save energy incurred on transportation and distribution of water at the doorstep. This also conserves groundwater, if it is being extracted to meet the demand when rains are on.Recharging ground water aquifersGround water aquifers can be recharged by various kinds of structures to ensure percolation of rainwater in the ground instead of draining away from the surface. Commonly used recharging methods are:-a) Recharging of bore wells b) Recharging of dug wells.c) Recharge pits d) Recharge Trenchese) Soak ways or Recharge Shafts f) Percolation Tanks

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Recharging of bore wellsRainwater collected from rooftop of the building is diverted through drainpipes to settlement or filtration tank. After settlement filtered water is diverted to bore wells to recharge deep aquifers. Abandoned bore wells can also be used for recharge. Optimum capacity of settlement tank/filtration tank can be designed on the basis of area of catchement, intensity of rainfall and recharge rate as discussed in design parameters. While recharging, entry of floating matter and silt should be restricted because it may clog the recharge structure. "first one or two shower should be flushed out through rain separator to avoid contamination. This is very important, and all care should be taken to ensure that this has been done."Recharge PitsRecharge pits are small pits of any shape rectangular, square or circular, contracted with brick or stone masonry wall with weep hole at regular intervals. Two of pit can be covered with perforated covers. Bottom of pit should be filled with filter media.The capacity of the pit can be designed on the basis of catchment area, rainfall intensity and recharge rate of soil. Usually the dimensions of the pit may be of 1 to 2 m width and 2 to 3 m deep depending on the depth of pervious strata. These pits are suitable for recharging of shallow aquifers, and small houses.Wetland Conservation

Wetland conservation is aimed at protecting and preserving areas where water exists at or near the Earth's surface, such as swamps, marshes and bogs.Wetlands cover at least six per cent of the Earth and have become a focal issue for conservation due to the ecosystem services they provide. More than three billion people, around half the world’s population, obtain their basic water needs from inland freshwater wetlands. The same number of people rely on rice as their staple food, a crop grown largely in natural and artificial wetlands. In some parts of the world, such as the Kilombero wetland in Tanzania, almost the entire local population relies on wetland cultivation for their livelihoods.

Fisheries are also an extremely important source of protein and income in many wetlands. According to the United Nations Food and Agriculture Organization, the total catch from inland waters (rivers and wetlands) was 8.7 million metric tonnes in 2002. In addition to food, wetlands supply fibre, fuel and medicinal plants. They also provide valuable ecosystems for birds and other aquatic creatures, help reduce the damaging impact of floods, control pollution and regulate the climate. From economic importance, to aesthetics, the reasons for conserving wetlands have become numerous over the past few decades.

Wetland Function

The main functions performed by wetlands are: water filtration, water storage, biological productivity, and provide habitat for wildlife.

Filtration

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Wetlands aid in water filtration by removing excess nutrients, slowing the water allowing particulates to settle out of the water which can then be absorbed into plant roots. Studies have shown that up to 92% of phosphorus and 95% of nitrogen can be removed from passing water through a wetland. Wetlands also let pollutants settle and stick to soil particles, up to 70% of sediments in runoff. Some wetland plants have even been found with accumulations of heavy metals more than 100,000 times that of the surrounding waters' concentration. Without these functions, the waterways would continually increase their nutrient and pollutant load, leading to an isolated deposit of high concentrations further down the line. An example of such a situation is the Mississippi River’s dead zone, an area where nutrient excess has led to large amounts of surface algae, which use up the oxygen and create hypoxic conditions (very low levels of oxygen).

Wetlands can even filter out and absorb harmful bacteria from the water. Their complex food chain hosts various microbes and bacteria, which invertebrates feed on. These invertebrates can filter up to 90% of bacteria out of the water this way.

Storage

Wetlands can store approximately 1-1.5 million gallons of floodwater per acre. When you combine that with the approximate total acres of wetlands in the United States (107.7 million acres), you get an approximate total of 107.7 - 161.6 million million gallons of floodwater US wetlands can store. By storing and slowing water, wetlands allow groundwater to be recharged. "A 550,000 acre swamp in Florida has been valued at $25 million per year for its role in storing water and recharging the aquifer." And combining the ability of wetlands to store and slow down water with their ability to filter out sediments, wetlands serve as strong erosion buffers.

Biological productivity

Through wetlands ability to absorb nutrients, they are able to be highly biologically productive (able to produce biomass quickly). Freshwater wetlands are even comparable to tropical rainforests in plant productivity. Their ability to efficiently create biomass may become important to the development of alternative energy sources.

While wetlands only cover around 5% of the Conterminous United States’s land surface, they support 31% of the plant species. They also support, through feeding and nesting, up to ½ of the native North American bird species. Bird populations, while playing a major role in food webs, are also the focus of several, well-funded recreation sports. (Waterfowl hunting and bird watching to name a pair)

Wildlife habitat

Wildlife Habitat is important not only for the conservation of species but also for a number of recreational opportunities. As a conservation purpose, wildlife habitat is managed for maintaining and using the resources in sustainable manner. Ninety-five percent of all commercially harvested fish and shellfish in the United States are wetland dependent. Muscatatuck National Wildlife Refuge is an example of recreational destination for hunting, fishing, wildlife observation and photography that has a good wildlife

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management. Some parts of the area are wetlands managed for providing habitat of migratory birds, such as waterfowl and songbirds. The 14 million United States hunters generate in excess of $50 billion annually in economic activity. This does not include the 60 million people that watch migratory birds as a hobby. The Florida Keys wetland area generates more than $800 million in annual tourism income alone.

Watershed Management

Watershed management is the study of the relevant characteristics of a watershed aimed at the sustainable distribution of its resources and the process of creating and implementing plans, programs, and projects to sustain and enhance watershed functions that affect the plant, animal, and human communities within a watershed boundary. Features of a watershed that agencies seek to manage include water supply, water quality, drainage, storm water runoff, water rights, and the overall planning and utilization of watersheds. Landowners, land use agencies, storm water management experts, environmental specialists, water use surveyors and communities all play an integral part in the management of a watershed.

Sources of Pollution

In an agricultural landscape, common contributors to water pollution and sediment which typically enter stream systems after rainfall washes them off poorly managed agricultural fields, called surface runoff, or flushes them out of the soil through leaching. These types of pollutants are considered nonpoint source pollution because the exact point where the pollutant originated cannot be identified. Such pollutants remain a major issue for water ways because the difficulty to control their sources hinders any attempt to limit the pollution. Point source pollution originates a specific point of contamination such as if a manure containment structure fails and its contents enter the drainage system or when a factory discharges its waste directly into a body of water using a pipe.

In urban landscapes, issues of soil loss through erosion, from construction sites for example, and nutrient enrichment from lawn fertilizers exist. Point source pollution, such as effluent from waste water treatment plants and other industries play a much larger role in this setting. Also, the greatly increased area of impervious surfaces, such as concrete, combined with modern storm drainage systems, allows for water and the contaminants that it can carry with it to exit the urban landscape quickly and end up in the nearest stream.

Controlling Pollution

In agricultural systems, common practices include the use of buffer strips, grassed waterways, the reestablishment of wetlands, and forms of sustainable agriculture practices such as conservation tillage, crop rotation and intercropping. After certain practices are installed, it is important to continually monitor these systems to ensure that they are working properly in terms of improving environmental quality.

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In urban settings, managing areas to prevent soil loss and control storm water flow are a few of the areas that receive attention. A few practices that are used to manage storm water before it reaches a channel are retention ponds, filtering systems and wetlands. It is important that storm water is given an opportunity to infiltrate so that the soil and vegetation can act as a "filter" before the water reaches nearby streams or lakes. In the case of soil erosion prevention, a few common practices include the use of silt fences, landscape fabric with grass seed and hydro seeding. The main objective in all cases is to slow water movement to prevent soil transport.

Unit-IVLand

Land, sometimes referred to as dry land, is the solid surface of the Earth that is not permanently covered by water. The vast majority of human activity occurs in land areas that support agriculture, habitat, and various natural resources.

Some life forms (including terrestrial plants and terrestrial animals) have developed from predecessor species that lived in bodies of water to exist on land.

Areas where land meets large bodies of water are called coastal zones. The division between land and water is a fundamental concept to humans, which can have strong cultural importance. The demarcation between land and water varies by local jurisdiction. A Maritime boundary is one such political demarcation. A variety of natural boundaries exist to help define where water meets land. Solid rock landforms are easier to demarcate than marshy or swampy boundaries, where there is no clear point at which the land ends and a body of water has begun. Demarcation can further vary due to tides and weather.

Land Mass

Land mass refers to the total surface area of the land of a geographical region or country (which may include discontinuous pieces of land such as islands). It is written as two words to distinguish it from the usage "landmass" —the contiguous area of land surrounded by ocean.

The Earth's total land mass is 148,939,063.133 km2 (57,505,693.767 sq mi) which is about 29.2% of its total surface. Water covers approximately 70.8% of the Earth's surface, mostly in the form of oceans.

Land Degradation

Land degradation is a process in which the value of the biophysical environment is affected by a combination of human-induced processes acting upon the land. Also environmental degradation is the gradual destruction or reduction of the quality and quantity of human activities animal’s activities or natural means example water causes soil erosion, wind, etc. It is viewed as any change or disturbance to the land perceived to be deleterious or undesirable. Natural hazards are excluded as a cause; however human activities can indirectly affect phenomena such as floods and bush fires.

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This is considered to be an important topic of the 21st century due to the implications land degradation has upon agronomic productivity, the environment, and its effects on food security. It is estimated that up to 40% of the world's agricultural land is seriously degraded.

Measures

Land degradation is a broad term that can be applied differently across a wide range of scenarios. There are four main ways of looking at land degradation and its impact on the environment around it:

• A temporary or permanent decline in the productive capacity of the land. This can be seen through a loss of biomass, a loss of actual productivity or in potential productivity, or a loss or change in vegetative cover and soil nutrients.

• Action in the lands capacity to provide resources for human livelihoods. This can be measured from a base line of past land use.

• Loss of biodiversity: A loss of range of species or ecosystem complexity as a decline in the environmental quality.

• Shifting ecological risk: increased vulnerability of the environment or people to destruction or crisis. This is measured through a base line in the form of pre-existing risk of crisis or destruction.

A problem with defining land degradation is that what one group of people might view as degradation, others might view as a benefit or opportunity. For example, planting crops at a location with heavy rainfall and steep slopes would create scientific and environmental concern regarding the risk of soil erosion by water, yet farmers could view the location as a favorable one for high crop yields.

Types

In addition to the usual types of land degradation that have been known for centuries (water, wind and mechanical erosion, physical, chemical and biological degradation), four other types have emerged in the last 50 years:

• pollution, often chemical, due to agricultural, industrial, mining or commercial activities;

• loss of arable land due to urban construction;

• artificial radioactivity, sometimes accidental;

• land-use constraints associated with armed conflicts.

Overall, 36 types of land degradation can be assessed. All are induced or aggravated by human activities, e.g. sheet erosion, silting, aridification, Salinization, urbanization, etc.

Causes

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Land degradation is a global problem, largely related to agricultural use. The major causes include:

• Land clearance, such as clear cutting and deforestation• Agricultural depletion of soil nutrients through poor farming practices

• Livestock including overgrazing and over drafting

• Inappropriate irrigation and over drafting

• Urban sprawl and commercial development

• Soil contamination

• Vehicle off-roading

• Quarrying of stone, sand, ore and minerals

• Increase in field size due to economies of scale, reducing shelter for wildlife, as hedgerows and copses disappear

• Exposure of naked soil after harvesting by heavy equipment

• Monoculture, destabilizing the local ecosystem

• Dumping of non-biodegradable trash, such as plastics

Effects

Overcutting of vegetation occurs when people cut forests, woodlands and shrub lands—to obtain timber, fuel wood and other products—at a pace exceeding the rate of natural regrowth. This is frequent in semi-arid environments, where fuel wood shortages are often severe.

Overgrazing is the grazing of natural pastures at stocking intensities above the livestock carrying capacity; the resulting decrease in the vegetation cover is a leading cause of wind and water erosion. It is a significant factor in Afghanistan. Ext of land shortage the growing population pressure, during 1980-1990, has led to decreases in the already small areas of agricultural land per person in six out of eight countries (14% for India and 22% for Pakistan).

Population pressure also operates through other mechanisms. Improper agricultural practices, for instance, occur only under constraints such as the saturation of good lands under population pressure which leads settlers to cultivate too shallow or too steep soils, plough fallow land before it has recovered its fertility, or attempt to obtain multiple crops by irrigating unsuitable soils.

High population density is not always related to land degradation. Rather, it is the practices of the human population that can cause a landscape to become degraded. Populations can be a benefit to the land and make it more productive than it is in its natural state. Land

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degradation is an important factor of internal displacement in many African and Asian countries.

Severe land degradation affects a significant portion of the Earth's arable lands, decreasing the wealth and economic development of nations. As the land resource base becomes less productive, food security is compromised and competition for dwindling resources increases, the seeds of famine and potential conflict are sown.

Sensitivity and Resilience

Sensitivity and resilience are measures of the vulnerability of a landscape to degradation. These two factors combine to explain the degree of vulnerability. Sensitivity is the degree to which a land system undergoes change due to natural forces, human intervention or a combination of both. Resilience is the ability of a landscape to absorb change, without significantly altering the relationship between the relative importance and numbers of individuals and species that compose the community. It also refers to the ability of the region to return to its original state after being changed in some way. The resilience of a landscape can be increased or decreased through human interaction based upon different methods of land-use management. Land that is degraded becomes less resilient than undegraded land, which can lead to even further degration through shocks to the landscape.

Climate Change

Significant land degradation from seawater inundation, particularly in river deltas and on low-lying islands, is a potential hazard that was identified in a 2007 IPCC report.

As a result of sea-level rise from climate change, salinity levels can reach levels where agriculture becomes impossible in very low lying areas.

Soil Erosion

Soil erosion is a naturally occurring process that affects all landforms. In agriculture, soil erosion refers to the wearing away of a field's topsoil by the natural physical forces of water and wind or through forces associated with farming activities such as tillage. Erosion, whether it is by water, wind or tillage, involves three distinct actions – soil detachment, movement and deposition. Topsoil, which is high in organic matter, fertility and soil life, is relocated elsewhere "on-site" where it builds up over time or is carried "off-site" where it fills in drainage channels. Soil erosion reduces cropland productivity and contributes to the pollution of adjacent watercourses, wetlands and lakes. Soil erosion can be a slow process that continues relatively unnoticed or can occur at an alarming rate, causing serious loss of topsoil. Soil compaction, low organic matter, loss of soil structure, poor internal drainage, salinisation and soil acidity problems are other serious soil degradation conditions that can accelerate the soil erosion process. This Factsheet looks at the causes and effects of water, wind and tillage erosion on agricultural land.

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Water Erosion

The widespread occurrence of water erosion combined with the severity of on-site and off-site impacts have made water erosion the focus of soil conservation efforts in Ontario. The rate and magnitude of soil erosion by water is controlled by the following factors:

Rainfall and Runoff

The greater the intensity and duration of a rainstorm, the higher the erosion potential. The impact of raindrops on the soil surface can break down soil aggregates and disperse the aggregate material. Lighter aggregate materials such as very fine sand, silt, clay and organic matter are easily removed by the raindrop splash and runoff water; greater raindrop energy or runoff amounts are required to move larger sand and gravel particles. Soil movement by rainfall (raindrop splash) is usually greatest and most noticeable during short-duration, high-intensity thunderstorms. Although the erosion caused by long-lasting and less-intense storms is not usually as spectacular or noticeable as that produced during thunderstorms, the amount of soil loss can be significant, especially when compounded over time. Surface water runoff occurs whenever there is excess water on a slope that cannot be absorbed into the soil or is trapped on the surface. Reduced infiltration due to soil compaction, crusting or freezing increases the runoff. Runoff from agricultural land is greatest during spring months when the soils are typically saturated, snow is melting and vegetative cover is minimal.

Soil Erodibility

Soil erodibility is an estimate of the ability of soils to resist erosion, based on the physical characteristics of each soil. Texture is the principal characteristic affecting erodibility, but structure, organic matter and permeability also contribute. Generally, soils with faster infiltration rates, higher levels of organic matter and improved soil structure have a greater resistance to erosion. Sand, sandy loam and loam-textured soils tend to be less erodible than silt, very fine sand and certain clay-textured soils. Tillage and cropping practices that reduce soil organic matter levels, cause poor soil structure, or result in soil compaction, contribute to increases in soil erodibility. As an example, compacted subsurface soil layers can decrease infiltration and increase runoff. The formation of a soil crust, which tends to "seal" the surface, also decreases infiltration. On some sites, a soil crust might decrease the amount of soil loss from raindrop impact and splash; however, a corresponding increase in the amount of runoff water can contribute to more serious erosion problems. Past erosion also has an effect on a soil's erodibility. Many exposed subsurface soils on eroded sites tend to be more erodible than the original soils were because of their poorer structure and lower organic matter. The lower nutrient levels often associated with subsoils contribute to lower crop yields and generally poorer crop cover, which in turn provides less crop protection for the soil.

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Slope Gradient and Length

The steeper and longer the slope of a field, the higher the risk for erosion. Soil erosion by water increases as the slope length increases due to the greater accumulation of runoff. Consolidation of small fields into larger ones often results in longer slope lengths with increased erosion potential, due to increased velocity of water, which permits a greater degree of scouring (carrying capacity for sediment).

Cropping and Vegetation

The potential for soil erosion increases if the soil has no or very little vegetative cover of plants and/or crop residues. Plant and residue cover protects the soil from raindrop impact and splash, tends to slow down the movement of runoff water and allows excess surface water to infiltrate. The erosion-reducing effectiveness of plant and/or crop residues depends on the type, extent and quantity of cover. Vegetation and residue combinations that completely cover the soil and intercept all falling raindrops at and close to the surface are the most efficient in controlling soil erosion (e.g., forests, permanent grasses). Partially incorporated residues and residual roots are also important as these provide channels that allow surface water to move into the soil.

The effectiveness of any protective cover also depends on how much protection is available at various periods during the year, relative to the amount of erosive rainfall that falls during these periods. Crops that provide a full protective cover for a major portion of the year (e.g., alfalfa or winter cover crops) can reduce erosion much more than can crops that leave the soil bare for a longer period of time (e.g., row crops), particularly during periods of highly erosive rainfall such as spring and summer. Crop management systems that favour contour farming and strip-cropping techniques can further reduce the amount of erosion. To reduce most of the erosion on annual row-crop land, leave a residue cover greater than 30% after harvest and over the winter months, or inter-seed a cover crop (e.g., red clover in wheat, oats after silage corn).

Tillage Practices

The potential for soil erosion by water is affected by tillage operations, depending on the depth, direction and timing of plowing, the type of tillage equipment and the number of passes. Generally, the less the disturbance of vegetation or residue cover at or near the surface, the more effective the tillage practice in reducing water erosion. Minimum till or no-till practices are effective in reducing soil erosion by water. Tillage and other practices performed up and down field slopes creates pathways for surface water runoff and can accelerate the soil erosion process. Cross-slope cultivation and contour farming techniques discourage the concentration of surface water runoff and limit soil movement.

Forms of Water Erosion

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Sheet Erosion

Sheet erosion is the movement of soil from raindrop splash and runoff water. It typically occurs evenly over a uniform slope and goes unnoticed until most of the productive topsoil has been lost. Deposition of the eroded soil occurs at the bottom of the slope or in low areas. Lighter-coloured soils on knolls, changes in soil horizon thickness and low crop yields on shoulder slopes and knolls are other indicators.

Rill Erosion

Rill erosion results when surface water runoff concentrates, forming small yet well-defined channels. These distinct channels where the soil has been washed away are called rills when they are small enough to not interfere with field machinery operations. In many cases, rills are filled in each year as part of tillage operations.

Gully Erosion

Gully erosion is an advanced stage of rill erosion where surface channels are eroded to the point where they become a nuisance factor in normal tillage operations. There are farms in Ontario that are losing large quantities of topsoil and subsoil each year due to gully erosion. Surface water runoff, causing gully formation or the enlarging of existing gullies, is usually the result of improper outlet design for local surface and subsurface drainage systems. The soil instability of gully banks, usually associated with seepage of groundwater, leads to sloughing and slumping (caving-in) of bank slopes. Such failures usually occur during spring months when the soil water conditions are most conducive to the problem. Gully formations are difficult to control if corrective measures are not designed and properly constructed. Control measures must consider the cause of the increased flow of water across the landscape and be capable of directing the runoff to a proper outlet. Gully erosion results in significant amounts of land being taken out of production and creates hazardous conditions for the operators of farm machinery.

Bank Erosion

Natural streams and constructed drainage channels act as outlets for surface water runoff and subsurface drainage systems. Bank erosion is the progressive undercutting, scouring and slumping of these drainage ways. Poor construction practices, inadequate maintenance, uncontrolled livestock access and cropping too close can all lead to bank erosion problems. Poorly constructed tile outlets also contribute to bank erosion. Some do not function properly because they have no rigid outlet pipe, have an inadequate splash pad or no splash pad at all, or have outlet pipes that have been damaged by erosion, machinery or bank cave-ins. The direct damages from bank erosion include loss of productive farmland, undermining of structures such as bridges, increased need to clean out and maintain drainage channels and washing out of lanes, roads and fence rows.

Effects of Water Erosion

On-Site

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The implications of soil erosion by water extend beyond the removal of valuable topsoil. Crop emergence, growth and yield are directly affected by the loss of natural nutrients and applied fertilizers. Seeds and plants can be disturbed or completely removed by the erosion. Organic matter from the soil, residues and any applied manure, is relatively lightweight and can be readily transported off the field, particularly during spring thaw conditions. Pesticides may also be carried off the site with the eroded soil. Soil quality, structure, stability and texture can be affected by the loss of soil. The breakdown of aggregates and the removal of smaller particles or entire layers of soil or organic matter can weaken the structure and even change the texture. Textural changes can in turn affect the water-holding capacity of the soil, making it more susceptible to extreme conditions such as drought.

Off-Site

The off-site impacts of soil erosion by water are not always as apparent as the on-site effects. Eroded soil, deposited down slope, inhibits or delays the emergence of seeds, buries small seedlings and necessitates replanting in the affected areas. Also, sediment can accumulate on down-slope properties and contribute to road damage.

Sediment that reaches streams or watercourses can accelerate bank erosion, obstruct stream and drainage channels, fill in reservoirs, damage fish habitat and degrade downstream water quality. Pesticides and fertilizers, frequently transported along with the eroding soil, contaminate or pollute downstream water sources, wetlands and lakes. Because of the potential seriousness of some of the off-site impacts, the control of "non-point" pollution from agricultural land is an important consideration.

Wind ErosionWind erosion occurs in susceptible areas of Ontario but represents a small percentage of land – mainly sandy and organic or muck soils. Under the right conditions it can cause major losses of soil and property. Soil particles move in three ways, depending on soil particle size and wind strength – suspension, saltation and surface creep. The rate and magnitude of soil erosion by wind is controlled by the following factors:

Soil Erodibility

Very fine soil particles are carried high into the air by the wind and transported great distances (suspension). Fine-to-medium size soil particles are lifted a short distance into the air and drop back to the soil surface, damaging crops and dislodging more soil (saltation). Larger-sized soil particles that are too large to be lifted off the ground are dislodged by the wind and roll along the soil surface (surface creep). The abrasion that results from windblown particles breaks down stable surface aggregates and further increases the soil erodibility.

Soil Surface Roughness

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Soil surfaces that are not rough offer little resistance to the wind. However, ridges left from tillage can dry out more quickly in a wind event, resulting in more loose, dry soil available to blow. Over time, soil surfaces become filled in, and the roughness is broken down by abrasion. This results in a smoother surface susceptible to the wind. Excess tillage can contribute to soil structure breakdown and increased erosion.

Climate

The speed and duration of the wind have a direct relationship to the extent of soil erosion. Soil moisture levels are very low at the surface of excessively drained soils or during periods of drought, thus releasing the particles for transport by wind. This effect also occurs in freeze-drying of the soil surface during winter months. Accumulation of soil on the leeward side of barriers such as fence rows, trees or buildings, or snow cover that has a brown colour during winter are indicators of wind erosion.

Unsheltered Distance

A lack of windbreaks (trees, shrubs, crop residue, etc.) allows the wind to put soil particles into motion for greater distances, thus increasing abrasion and soil erosion. Knolls and hilltops are usually exposed and suffer the most.

Vegetative Cover

The lack of permanent vegetative cover in certain locations results in extensive wind erosion. Loose, dry, bare soil is the most susceptible; however, crops that produce low levels of residue (e.g., soybeans and many vegetable crops) may not provide enough resistance. In severe cases, even crops that produce a lot of residue may not protect the soil. The most effective protective vegetative cover consists of a cover crop with an adequate network of living windbreaks in combination with good tillage, residue management and crop selection.

Effects of Wind Erosion

Wind erosion damages crops through sandblasting of young seedlings or transplants, burial of plants or seed, and exposure of seed. Crops are ruined, resulting in costly delays and making reseeding necessary. Plants damaged by sandblasting are vulnerable to the entry of disease with a resulting decrease in yield, loss of quality and market value. Also, wind erosion can create adverse operating conditions, preventing timely field activities. Soil drifting is a fertility-depleting process that can lead to poor crop growth and yield reductions in areas of fields where wind erosion is a recurring problem. Continual drifting of an area gradually causes a textural change in the soil. Loss of fine sand, silt, clay and organic particles from sandy soils serves to lower the moisture-holding capacity of the soil. This increases the erodibility of the soil and

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compounds the problem. The removal of wind-blown soils from fence rows, constructed drainage channels and roads, and from around buildings is a costly process. Also, soil nutrients and surface-applied chemicals can be carried along with the soil particles, contributing to off-site impacts. In addition, blowing dust can affect human health and create public safety hazards.

Tillage ErosionTillage erosion is the redistribution of soil through the action of tillage and gravity. It results in the progressive down-slope movement of soil, causing severe soil loss on upper-slope positions and accumulation in lower-slope positions. This form of erosion is a major delivery mechanism for water erosion. Tillage action moves soil to convergent areas of a field where surface water runoff concentrates. Also, exposed subsoil is highly erodible to the forces of water and wind. Tillage erosion has the greatest potential for the "on-site" movement of soil and in many cases can cause more erosion than water or wind. Soil particles move in three ways, depending on soil particle size and wind strength – suspension, saltation and surface creep. The rate and magnitude of soil erosion by wind is controlled by the following factors:

Soil Erodibility

Very fine soil particles are carried high into the air by the wind and transported great distances (suspension). Fine-to-medium size soil particles are lifted a short distance into the air and drop back to the soil surface, damaging crops and dislodging more soil (saltation). Larger-sized soil particles that are too large to be lifted off the ground are dislodged by the wind and roll along the soil surface (surface creep). The abrasion that results from windblown particles breaks down stable surface aggregates and further increases the soil erodibility.

Soil Surface Roughness

Soil surfaces that are not rough offer little resistance to the wind. However, ridges left from tillage can dry out more quickly in a wind event, resulting in more loose, dry soil available to blow. Over time, soil surfaces become filled in, and the roughness is broken down by abrasion. This results in a smoother surface susceptible to the wind. Excess tillage can contribute to soil structure breakdown and increased erosion.

Climate

The speed and duration of the wind have a direct relationship to the extent of soil erosion. Soil moisture levels are very low at the surface of excessively drained soils or during periods of drought, thus releasing the particles for transport by wind. This effect also occurs in freeze-drying of the soil surface during winter months. Accumulation of soil on the leeward side of barriers such as fence rows, trees or buildings, or snow cover that has a brown colour during winter are indicators of wind erosion.

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Unsheltered Distance

A lack of windbreaks (trees, shrubs, crop residue, etc.) allows the wind to put soil particles into motion for greater distances, thus increasing abrasion and soil erosion. Knolls and hilltops are usually exposed and suffer the most.

Vegetative Cover

The lack of permanent vegetative cover in certain locations results in extensive wind erosion. Loose, dry, bare soil is the most susceptible; however, crops that produce low levels of residue (e.g., soybeans and many vegetable crops) may not provide enough resistance. In severe cases, even crops that produce a lot of residue may not protect the soil. The most effective protective vegetative cover consists of a cover crop with an adequate network of living windbreaks in combination with good tillage, residue management and crop selection.

Effects of Wind Erosion

Wind erosion damages crops through sandblasting of young seedlings or transplants, burial of plants or seed, and exposure of seed. Crops are ruined, resulting in costly delays and making reseeding necessary. Plants damaged by sandblasting are vulnerable to the entry of disease with a resulting decrease in yield, loss of quality and market value. Also, wind erosion can create adverse operating conditions, preventing timely field activities. Soil drifting is a fertility-depleting process that can lead to poor crop growth and yield reductions in areas of fields where wind erosion is a recurring problem. Continual drifting of an area gradually causes a textural change in the soil. Loss of fine sand, silt, clay and organic particles from sandy soils serves to lower the moisture-holding capacity of the soil. This increases the erodibility of the soil and compounds the problem. The removal of wind-blown soils from fence rows, constructed drainage channels and roads, and from around buildings is a costly process. Also, soil nutrients and surface-applied chemicals can be carried along with the soil particles, contributing to off-site impacts. In addition, blowing dust can affect human health and create public safety hazards.

Tillage ErosionTillage erosion is the redistribution of soil through the action of tillage and gravity. It results in the progressive down-slope movement of soil, causing severe soil loss on upper-slope positions and accumulation in lower-slope positions. This form of erosion is a major delivery mechanism for water erosion. Tillage action moves soil to convergent areas of a field where surface water runoff concentrates. Also, exposed subsoil is highly erodible to the forces of water and wind. Tillage erosion has the greatest potential for the "on-site" movement of soil and in many cases can cause more erosion than water or wind.

Forest

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A forest, also referred to as a wood or the woods, is a community of living organisms, that interact mutually and with the physical environment, characterized by the fact that contain trees, which constitute the larger part of their biomass. As with cities, depending on various cultural definitions, what is considered a forest may vary significantly in size and have different classifications according to how and of what the forest is composed. A forest is usually an area filled with trees but any tall densely packed area of vegetation may be considered a forest, even underwater vegetation such as kelp forests, or non-vegetation such as fungi, and bacteria. Tree forests cover approximately 9.4 percent of the Earth's surface (or 30 percent of total land area), though they once covered much more (about 50 percent of total land area). They function as habitats for organisms, hydrologic flow modulators, and soil conservers, constituting one of the most important aspects of the biosphere. A typical tree forest is composed of the over story (canopy or upper tree layer) and the understory. The understory is further subdivided into the shrub layer, herb layer, and also the moss layer and soil microbes. In some complex forests, there is also a well-defined lower tree layer. Forests are central to all human life because they provide a diverse range of resources: they store carbon, aid in regulating the planetary climate, purify water and mitigate natural hazards such as floods. Forests also contain roughly 90 percent of the world's terrestrial biodiversity

Distribution

Forests can be found in all regions capable of sustaining tree growth, at altitudes up to the tree line, except where natural fire frequency or other disturbance is too high, or where the environment has been altered by human activity.

The latitudes 10° north and south of the Equator are mostly covered in tropical rainforest, and the latitudes between 53°N and 67°N have boreal forest. As a general rule, forests dominated by angiosperms (broadleaf forests) are more species-rich than those dominated by gymnosperms (conifer, mountain, or needle leaf forests), although exceptions exist. Forests sometimes contain many tree species only within a small area (as in tropical rain and temperate deciduous forests), or relatively few species over large areas (e.g., taiga and arid mountain coniferous forests). Forests are often home to many animal and plant species, and biomass per unit area is high compared to other vegetation communities. Much of this biomass occurs below ground in the root systems and as partially decomposed plant detritus. The woody component of a forest contains lignin, which is relatively slow to decompose compared with other organic materials such as cellulose or carbohydrate.

Forests are differentiated from woodlands by the extent of canopy coverage: in a forest, the branches and the foliage of separate trees often meet or interlock, although there can be gaps of varying sizes within an area referred to as forest. A woodland has a more continuously open canopy, with trees spaced farther apart, which allows more sunlight to penetrate to the ground between them (also see: savanna).

Among the major forested biomes are:

• rain forest (tropical and temperate)• taiga

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• temperate hardwood forest

• tropical dry forest

Types of Forests

Forests can be classified in different ways and to different degrees of specificity. One such way is in terms of the "biome" in which they exist, combined with leaf longevity of the dominant species (whether they are evergreen or deciduous). Another distinction is whether the forests are composed predominantly of broadleaf trees, coniferous (needle-leaved) trees, or mixed.

• Boreal forests occupy the subarctic zone and are generally evergreen and coniferous.

• Temperate zones support both broadleaf deciduous forests (e.g., temperate deciduous forest) and evergreen coniferous forests (e.g., temperate coniferous forests and temperate rainforests). Warm temperate zones support broadleaf evergreen forests, including laurel forests.

• Tropical and subtropical forests include tropical and subtropical moist forests, tropical and subtropical dry forests, and tropical and subtropical coniferous forests.

• Physiognomy classifies forests based on their overall physical structure or developmental stage (e.g. old growth vs. second growth).

• Forests can also be classified more specifically based on the climate and the dominant tree species present, resulting in numerous different forest types (e.g., ponderosa pine/Douglas-fir forest).

A number of global forest classification systems have been proposed, but none has gained universal acceptance. UNEP-WCMC's forest category classification system is a simplification of other more complex systems (e.g. UNESCO's forest and woodland 'sub formations'). This system divides the world's forests into 26 major types, which reflect climatic zones as well as the principal types of trees. These 26 major types can be reclassified into 6 broader categories: temperate needle leaf; temperate broadleaf and mixed; tropical moist; tropical dry; sparse trees and parkland; and forest plantations. Each category is described as a separate section below.

Temperate needle leaf

Temperate needle leaf forests mostly occupy the higher latitude regions of the northern hemisphere, as well as high altitude zones and some warm temperate areas, especially on nutrient-poor or otherwise unfavorable soils. These forests are composed entirely, or nearly so, of coniferous species (Coniferophyta). In the Northern Hemisphere pines Pinus, spruces Picea, larches Larix, firs Abies, Douglas firs Pseudotsuga and hemlocks Tsuga, make up the canopy, but other taxa are also important. In the Southern Hemisphere, most

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coniferous trees (members of the Araucariaceae and Podocarpaceae) occur in mixtures with broadleaf species, and are classed as broadleaf and mixed forests.

Temperate broadleaf and mixed

Temperate broadleaf and mixed forests include a substantial component of trees in the Anthophyta. They are generally characteristic of the warmer temperate latitudes, but extend to cool temperate ones, particularly in the southern hemisphere. They include such forest types as the mixed deciduous forests of the United States and their counterparts in China and Japan, the broadleaf evergreen rainforests of Japan, Chile and Tasmania, the sclerophyllous forests of Australia, central Chile, the Mediterranean and California, and the southern beech Nothofagus forests of Chile and New Zealand.

Tropical moist

There are many different types of tropical moist forests,although most extensive are the lowland evergreen broad leaf rainforests(, for example várzea and igapó forests and the terra firma forests of the Amazon Basin; the peat swamp forests,dipterocarp forests of Southeast Asia; and the high forests of the Congo Basin. Forests located on mountains are also included in this category, divided largely into upper and lower mountain formations on the basis of the variation of physiognomy corresponding to changes in altitude.

Tropical dry

Tropical dry forests are characteristic of areas in the tropics affected by seasonal drought. The seasonality of rainfall is usually reflected in the deciduousness of the forest canopy, with most trees being leafless for several months of the year. However, under some conditions, e.g. less fertile soils or less predictable drought regimes, the proportion of evergreen species increases and the forests are characterized as "sclerophyllous". Thorn forest, a dense forest of low stature with a high frequency of thorny or spiny species, is found where drought is prolonged, and especially where grazing animals are plentiful. On very poor soils, and especially where fire is a recurrent phenomenon, woody savannas develop (see 'sparse trees and parkland').

Sparse trees and parkland

Sparse trees and parkland are forests with open canopies of 10–30% crown cover. They occur principally in areas of transition from forested to non-forested landscapes. The two major zones in which these ecosystems occur are in the boreal region and in the seasonally dry tropics. At high latitudes, north of the main zone of boreal forest or taiga, growing conditions are not adequate to maintain a continuous closed forest cover, so tree cover is both sparse and discontinuous. This vegetation is variously called open taiga, open lichen woodland, and forest tundra. It is species-poor, has high bryophyte cover, and is frequently affected by fire.

Forest plantations

Forest plantations, generally intended for the production of timber and pulpwood increase the total area of forest worldwide. Commonly mono-specific and/or composed of introduced tree species, these ecosystems are not generally important as habitat for native biodiversity. However, they can be managed in ways that enhance their biodiversity

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protection functions and they are important providers of ecosystem services such as maintaining nutrient capital, protecting watersheds and soil structure as well as storing carbon. They may also play an important role in alleviating pressure on natural forests for timber and fuelwood production

Forest categories

28 forest categories are used to enable the translation of forest types from national and regional classification systems to a harmonized global one:

Temperate and boreal forest types

1. Evergreen needle leaf forest – Natural forest with > 30% canopy cover, in which the canopy is predominantly (> 75%) needle leaf and evergreen.

2. Deciduous needle leaf forests – Natural forests with > 30% canopy cover, in which the canopy is predominantly (> 75%) needle leaf and deciduous.

3. Mixed broadleaf/needle leaf forest – Natural forest with > 30% canopy cover, in which the canopy is composed of a more or less even mixture of needle leaf and broadleaf crowns (between 50: 50% and 25:75%).

4. Broadleaf evergreen forest – Natural forests with > 30% canopy cover, the canopy being > 75% evergreen and broadleaf.

5. Deciduous broadleaf forest – Natural forests with > 30% canopy cover, in which > 75% of the canopy is deciduous and broadleaves predominate (> 75% of canopy cover).

6. Freshwater swamp forest – Natural forests with > 30% canopy cover, composed of trees with any mixture of leaf type and seasonality, but in which the predominant environmental characteristic is a waterlogged soil.

7. Sclerophyllous dry forest – Natural forest with > 30% canopy cover, in which the canopy is mainly composed of sclerophyllous broadleaves and is > 75% evergreen.

8. Sparse trees and parkland – Natural forests in which the tree canopy cover is between 10–30%, such as in the steppe regions of the world. Trees of any type (e.g., needle leaf, broadleaf, palms).

9. Disturbed natural forest – Any forest type above that has in its interior significant areas of disturbance by people, including clearing, felling for wood extraction, anthropogenic fires, road construction, etc.

10. Exotic species plantation – Intensively managed forests with > 30% canopy cover, which have been planted by people with species not naturally occurring in that country.

11.Native species plantation – Intensively managed forests with > 30% canopy cover, which have been planted by people with species that occur naturally in that country.

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12.*Unspecified forest plantation – Forest plantations showing extent only with no further information about their type, this data currently only refers to the Ukraine.

13. *Unclassified forest data – Forest data showing forest extent only with no further information about their type.

Those marked * have been created as a result of data holdings which do not specify the forest type, hence 26 categories are quoted, not 28 shown here.

Tropical forest types

Lowland evergreen broadleaf rain forest – Natural forests with > 30% canopy cover, below 1,200 m (3,937 ft) altitude that display little or no seasonality, the canopy being >75% evergreen broadleaf.

1. Lower mountain forest – Natural forests with > 30% canopy cover, between 1200–1800 m altitude, with any seasonality regime and leaf type mixture.

2. Upper mountain forest – Natural forests with > 30% canopy cover, above 1,800 m (5,906 ft) altitude, with any seasonality regime and leaf type mixture.

3. Freshwater swamp forest – Natural forests with > 30% canopy cover, below 1,200 m (3,937 ft) altitude, composed of trees with any mixture of leaf type and seasonality, but in which the predominant environmental characteristic is a waterlogged soil.

4. Semi-evergreen moist broadleaf forest – Natural forests with > 30% canopy cover, below 1,200 m (3,937 ft) altitude in which between 50–75% of the canopy is evergreen, > 75% are broadleaves, and the trees display seasonality of flowering and fruiting.

5. Mixed broadleaf/needle leaf forest – Natural forests with > 30% canopy cover, below 1,200 m (3,937 ft) altitude, in which the canopy is composed of a more or less even mixture of needle leaf and broadleaf crowns (between 50:50% and 25:75%).

6. Needle leaf forest – Natural forest with > 30% canopy cover, below 1,200 m (3,937 ft) altitude, in which the canopy is predominantly (> 75%) needle leaf.

7. Mangroves – Natural forests with > 30% canopy cover, composed of species of mangrove tree, generally along coasts in or near brackish or seawater.

8. Deciduous/semi-deciduous broadleaf forest – Natural forests with > 30% canopy cover, below 1,200 m (3,937 ft) altitude in which between 50–100% of the canopy is deciduous and broadleaves predominate (> 75% of canopy cover).

9. Sclerophyllous dry forest – Natural forests with > 30% canopy cover, below 1,200 m (3,937 ft) altitude, in which the canopy is mainly composed of sclerophyllous broadleaves and is > 75% evergreen.

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10.Thorn forest – Natural forests with > 30% canopy cover, below 1,200 m (3,937 ft) altitude, in which the canopy is mainly composed of deciduous trees with thorns and succulent phanerophytes with thorns, may be frequent.

11. Sparse trees and parkland – Natural forests in which the tree canopy cover is between 10–30%, such as in the savannah regions of the world. Trees of any type (e.g., needle leaf, broadleaf, palms).

12. Disturbed natural forest – Any forest type above that has in its interior significant areas of disturbance by people, including clearing, felling for wood extraction, anthropogenic fires, road construction, etc.

13. Exotic species plantation – Intensively managed forests with > 30% canopy cover, which have been planted by people with species not naturally occurring in that country.

14. Native species plantation – Intensively managed forests with > 30% canopy cover, which have been planted by people with species that occur naturally in that country.

Forest Loss and Management

Forests can be classified in different ways and to different degrees of specificity. One such way is in terms of the "biome" in which they exist, combined with leaf longevity of the dominant species (whether they are evergreen or deciduous). Another distinction is whether the forests are composed predominantly of broadleaf trees, coniferous (needle-leaved) trees, or mixed.

• Boreal forests occupy the subarctic zone and are generally evergreen and coniferous.

• Temperate zones support both broadleaf deciduous forests (e.g., temperate deciduous forest) and evergreen coniferous forests (e.g., temperate coniferous forests and temperate rainforests). Warm temperate zones support broadleaf evergreen forests, including laurel forests.

• Tropical and subtropical forests include tropical and subtropical moist forests, tropical and subtropical dry forests, and tropical and subtropical coniferous forests.

• Physiognomy classifies forests based on their overall physical structure or developmental stage (e.g. old growth vs. second growth).

• Forests can also be classified more specifically based on the climate and the dominant tree species present, resulting in numerous different forest types (e.g., ponderosa pine/Douglas-fir forest).

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A number of global forest classification systems have been proposed, but none has gained universal acceptance. UNEP-WCMC's forest category classification system is a simplification of other more complex systems (e.g. UNESCO's forest and woodland 'subformations'). This system divides the world's forests into 26 major types, which reflect climatic zones as well as the principal types of trees. These 26 major types can be reclassified into 6 broader categories: temperate needle leaf; temperate broadleaf and mixed; tropical moist; tropical dry; sparse trees and parkland; and forest plantations. Each category is described as a separate section below.

Temperate needle leaf

Temperate needle leaf forests mostly occupy the higher latitude regions of the northern hemisphere, as well as high altitude zones and some warm temperate areas, especially on nutrient-poor or otherwise unfavorable soils. These forests are composed entirely, or nearly so, of coniferous species (Coniferophyta). In the Northern Hemisphere pines Pinus, spruces Picea, larches Larix, firs Abies, Douglas firs Pseudotsuga and hemlocks Tsuga, make up the canopy, but other taxa are also important. In the Southern Hemisphere, most coniferous trees (members of the Araucariaceae and Podocarpaceae) occur in mixtures with broadleaf species, and are classed as broadleaf and mixed forests.

Temperate broadleaf and mixed

Temperate broadleaf and mixed forests include a substantial component of trees in the Anthophyta. They are generally characteristic of the warmer temperate latitudes, but extend to cool temperate ones, particularly in the southern hemisphere. They include such forest types as the mixed deciduous forests of the United States and their counterparts in China and Japan, the broadleaf evergreen rainforests of Japan, Chile and Tasmania, the sclerophyllous forests of Australia, central Chile, the Mediterranean and California, and the southern beech Nothofagus forests of Chile and New Zealand.

Tropical moist

There are many different types of tropical moist forests, although most extensive are the lowland evergreen broad leaf rainforests(, for example várzea and igapó forests and the terra firma forests of the Amazon Basin; the peat swamp forests, dipterocarp forests of Southeast Asia; and the high forests of the Congo Basin. Forests located on mountains are also included in this category, divided largely into upper and lower mountain formations on the basis of the variation of physiognomy corresponding to changes in altitude.

Tropical dry

Tropical dry forests are characteristic of areas in the tropics affected by seasonal drought. The seasonality of rainfall is usually reflected in the deciduousness of the forest canopy, with most trees being leafless for several months of the year. However, under some conditions, e.g. less fertile soils or less predictable drought regimes, the proportion of evergreen species increases and the forests are characterized as "sclerophyllous". Thorn forest, a dense forest of low stature with a high frequency of thorny or spiny species, is found where drought is prolonged, and especially where grazing animals are plentiful. On very poor soils, and especially where fire is a recurrent phenomenon, woody savannas develop (see 'sparse trees and parkland').

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Sparse trees and parkland

Sparse trees and parkland are forests with open canopies of 10–30% crown cover. They occur principally in areas of transition from forested to non-forested landscapes. The two major zones in which these ecosystems occur are in the boreal region and in the seasonally dry tropics. At high latitudes, north of the main zone of boreal forest or taiga, growing conditions are not adequate to maintain a continuous closed forest cover, so tree cover is both sparse and discontinuous. This vegetation is variously called open taiga, open lichen woodland, and forest tundra. It is species-poor, has high bryophyte cover, and is frequently affected by fire.

Forest plantations

Forest plantations, generally intended for the production of timber and pulpwood increase the total area of forest worldwide. Commonly mono-specific and/or composed of introduced tree species, these ecosystems are not generally important as habitat for native biodiversity. However, they can be managed in ways that enhance their biodiversity protection functions and they are important providers of ecosystem services such as maintaining nutrient capital, protecting watersheds and soil structure as well as storing carbon. They may also play an important role in alleviating pressure on natural forests for timber and fuelwood production

Forest categories

28 forest categories are used to enable the translation of forest types from national and regional classification systems to a harmonized global one:

Temperate and boreal forest types

1. Evergreen needle leaf forest – Natural forest with > 30% canopy cover, in which the canopy is predominantly (> 75%) needle leaf and evergreen.

2. Deciduous needle leaf forests – Natural forests with > 30% canopy cover, in which the canopy is predominantly (> 75%) needle leaf and deciduous.

3. Mixed broadleaf/needle leaf forest – Natural forest with > 30% canopy cover, in which the canopy is composed of a more or less even mixture of needle leaf and broadleaf crowns (between 50:50% and 25:75%).

4. Broadleaf evergreen forest – Natural forests with > 30% canopy cover, the canopy being > 75% evergreen and broadleaf.

5. Deciduous broadleaf forest – Natural forests with > 30% canopy cover, in which > 75% of the canopy is deciduous and broadleaves predominate (> 75% of canopy cover).

6. Freshwater swamp forest – Natural forests with > 30% canopy cover, composed of trees with any mixture of leaf type and seasonality, but in which the predominant environmental characteristic is a waterlogged soil.

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7. Sclerophyllous dry forest – Natural forest with > 30% canopy cover, in which the canopy is mainly composed of sclerophyllous broadleaves and is > 75% evergreen.

8. Sparse trees and parkland – Natural forests in which the tree canopy cover is between 10–30%, such as in the steppe regions of the world. Trees of any type (e.g., needle leaf, broadleaf, palms).

9. Disturbed natural forest – Any forest type above that has in its interior significant areas of disturbance by people, including clearing, felling for wood extraction, anthropogenic fires, road construction, etc.

10. Exotic species plantation – Intensively managed forests with > 30% canopy cover, which have been planted by people with species not naturally occurring in that country.

11.Native species plantation – Intensively managed forests with > 30% canopy cover, which have been planted by people with species that occur naturally in that country.

12.*Unspecified forest plantation – Forest plantations showing extent only with no further information about their type, this data currently only refers to the Ukraine.

13. *Unclassified forest data – Forest data showing forest extent only with no further information about their type.

Those marked * have been created as a result of data holdings which do not specify the forest type, hence 26 categories are quoted, not 28 shown here.

Tropical forest types

Lowland evergreen broadleaf rain forest – Natural forests with > 30% canopy cover, below 1,200 m (3,937 ft) altitude that display little or no seasonality, the canopy being >75% evergreen broadleaf.

1. Lower mountain forest – Natural forests with > 30% canopy cover, between 1200–1800 m altitude, with any seasonality regime and leaf type mixture.

2. Upper mountain forest – Natural forests with > 30% canopy cover, above 1,800 m (5,906 ft) altitude, with any seasonality regime and leaf type mixture.

3. Freshwater swamp forest – Natural forests with > 30% canopy cover, below 1,200 m (3,937 ft) altitude, composed of trees with any mixture of leaf type and seasonality, but in which the predominant environmental characteristic is a waterlogged soil.

4. Semi-evergreen moist broadleaf forest – Natural forests with > 30% canopy cover, below 1,200 m (3,937 ft) altitude in which between 50–75% of the canopy is evergreen, > 75% are broadleaves, and the trees display seasonality of flowering and fruiting.

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5. Mixed broadleaf/needle leaf forest – Natural forests with > 30% canopy cover, below 1,200 m (3,937 ft) altitude, in which the canopy is composed of a more or less even mixture of needle leaf and broadleaf crowns (between 50:50% and 25:75%).

6. Needle leaf forest – Natural forest with > 30% canopy cover, below 1,200 m (3,937 ft) altitude, in which the canopy is predominantly (> 75%) needle leaf.

7. Mangroves – Natural forests with > 30% canopy cover, composed of species of mangrove tree, generally along coasts in or near brackish or seawater.

8. Deciduous/semi-deciduous broadleaf forest – Natural forests with > 30% canopy cover, below 1,200 m (3,937 ft) altitude in which between 50–100% of the canopy is deciduous and broadleaves predominate (> 75% of canopy cover).

9. Sclerophyllous dry forest – Natural forests with > 30% canopy cover, below 1,200 m (3,937 ft) altitude, in which the canopy is mainly composed of sclerophyllous broadleaves and is > 75% evergreen.

10.Thorn forest – Natural forests with > 30% canopy cover, below 1,200 m (3,937 ft) altitude, in which the canopy is mainly composed of deciduous trees with thorns and succulent phanerophytes with thorns may be frequent.

11. Sparse trees and parkland – Natural forests in which the tree canopy cover is between 10–30%, such as in the savannah regions of the world. Trees of any type (e.g., needle leaf, broadleaf, palms).

12. Disturbed natural forest – Any forest type above that has in its interior significant areas of disturbance by people, including clearing, felling for wood extraction, anthropogenic fires, road construction, etc.

13. Exotic species plantation – Intensively managed forests with > 30% canopy cover, which have been planted by people with species not naturally occurring in that country.

14. Native species plantation – Intensively managed forests with > 30% canopy cover, which have been planted by people with species that occur naturally in that country.

Deforestation

Deforestation, clearance or clearing is the removal of a forest or stand of trees where the land is thereafter converted to a non-forest use.[1] Examples of deforestation include conversion of forestland to farms, ranches, or urban use.

The term deforestation is often misused to describe any activity where all trees in an area are removed. However in temperate climates, the removal of all trees in an area in conformance with sustainable forestry practices—is correctly described as regeneration harvest. In temperate mesic climates, natural regeneration of forest stands often will not

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occur in the absence of disturbance, whether natural or anthropogenic. Furthermore, biodiversity after regeneration harvest often mimics that found after natural disturbance, including biodiversity loss after naturally occurring rainforest destruction.

Deforestation occurs for many reasons: trees are cut down to be used or sold as fuel (sometimes in the form of charcoal) or timber, while cleared land is used as pasture for livestock, plantations of commodities and settlements. The removal of trees without sufficient reforestation has resulted in damage to habitat, biodiversity loss and aridity. It has adverse impacts on biosequestration of atmospheric carbon dioxide. Deforestation has also been used in war to deprive the enemy of cover for its forces and also vital resources. Modern examples of this were the use of Agent Orange by the British military in Malaya during the Malayan Emergency and the United States military in Vietnam during the Vietnam War. Among countries with a per capita GDP of at least US$4,600, net deforestation rates have ceased to increase. Deforested regions typically incur significant adverse soil erosion and frequently degrade into wasteland.

Disregard or ignorance of intrinsic value, lack of ascribed value, lax forest management and deficient environmental laws are some of the factors that allow deforestation to occur on a large scale. In many countries, deforestation, both naturally occurring and human induced, is an ongoing issue. Deforestation causes extinction, changes to climatic conditions, desertification, and displacement of populations as observed by current conditions and in the past through the fossil record. More than half of all plant and land animal species in the world live in tropical forests

Causes

According to the United Nations Framework Convention on Climate Change (UNFCCC) secretariat, the overwhelming direct cause of deforestation is agriculture. Subsistence farming is responsible for 48% of deforestation; commercial agriculture is responsible for 32% of deforestation; logging is responsible for 14% of deforestation and fuel wood removals make up 5% of deforestation.

Experts do not agree on whether industrial logging is an important contributor to global deforestation. Some argue that poor people are more likely to clear forest because they have no alternatives, others that the poor lack the ability to pay for the materials and labor needed to clear forest. One study found that population increases due to high fertility rates were a primary driver of tropical deforestation in only 8% of cases.

Other causes of contemporary deforestation may include corruption of government institutions, the inequitable distribution of wealth and power, population growth and overpopulation, and urbanization. Globalization is often viewed as another root cause of deforestation, though there are cases in which the impacts of globalization (new flows of labor, capital, commodities, and ideas) have promoted localized forest recovery. In 2000 the United Nations Food and Agriculture Organization (FAO) found that "the role of population dynamics in a local setting may vary from decisive to negligible," and that deforestation can result from "a combination of population pressure and stagnating economic, social and technological conditions."

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The degradation of forest ecosystems has also been traced to economic incentives that make forest conversion appear more profitable than forest conservation. Many important forest functions have no markets, and hence, no economic value that is readily apparent to the forests' owners or the communities that rely on forests for their well-being. From the perspective of the developing world, the benefits of forest as carbon sinks or biodiversity reserves go primarily to richer developed nations and there is insufficient compensation for these services. Developing countries feel that some countries in the developed world, such as the United States of America, cut down their forests centuries ago and benefited greatly from this deforestation, and that it is hypocritical to deny developing countries the same opportunities: that the poor shouldn't have to bear the cost of preservation when the rich created the problem.

Some commentators have noted a shift in the drivers of deforestation over the past 30 years. Whereas deforestation was primarily driven by subsistence activities and government-sponsored development projects like transmigration in countries like Indonesia and colonization in Latin America, India, Java, and so on, during late 19th century and the earlier half of the 20th century. By the 1990s the majority of deforestation was caused by industrial factors, including extractive industries, large-scale cattle ranching, and extensive agriculture

Environmental Problems

Atmospheric

Deforestation is ongoing and is shaping climate and geography.

Deforestation is a contributor to global warming, and is often cited as one of the major causes of the enhanced greenhouse effect. Tropical deforestation is responsible for approximately 20% of world greenhouse gas emissions. According to the Intergovernmental Panel on Climate Change deforestation, mainly in tropical areas, could account for up to one-third of total anthropogenic carbon dioxide emissions. But recent calculations suggest that carbon dioxide emissions from deforestation and forest degradation (excluding peat land emissions) contribute about 12% of total anthropogenic carbon dioxide emissions with a range from 6 to 17%.Deforestation causes carbon dioxide to linger in the atmosphere. As carbon dioxide accrues, it produces a layer in the atmosphere that traps radiation from the sun. The radiation converts to heat which causes global warming, which is better known as the greenhouse effect. Plants remove carbon in the form of carbon dioxide from the atmosphere during the process of photosynthesis, but release some carbon dioxide back into the atmosphere during normal respiration. Only when actively growing can a tree or forest removes carbon, by storing it in plant tissues. Both the decay and burning of wood releases much of this stored carbon back to the atmosphere. In order for forests to take up carbon, there must be a net accumulation of wood. One way is for the wood to be harvested and turned into long-lived products, with new young trees replacing them. Deforestation may also cause carbon stores held in soil to be released. Forests can be either sinks or sources depending upon environmental circumstances. Mature forests alternate between being net sinks and net sources of carbon dioxide.

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In deforested areas, the land heats up faster and reaches a higher temperature, leading to localized upward motions that enhance the formation of clouds and ultimately produce more rainfall. However, according to the Geophysical Fluid Dynamics Laboratory, the models used to investigate remote responses to tropical deforestation showed a broad but mild temperature increase all through the tropical atmosphere. The model predicted <0.2 °C warming for upper air at 700 mb and 500 mb. However, the model shows no significant changes in other areas besides the Tropics. Though the model showed no significant changes to the climate in areas other than the Tropics, this may not be the case since the model has possible errors and the results are never absolutely definite.

Reducing emissions from deforestation and forest degradation (REDD) in developing countries has emerged as a new potential to complement ongoing climate policies. The idea consists in providing financial compensations for the reduction of greenhouse gas (GHG) emissions from deforestation and forest degradation".

Rainforests are widely believed by laymen to contribute a significant amount of the world's oxygen, although it is now accepted by scientists that rainforests contribute little net oxygen to the atmosphere and deforestation has only a minor effect on atmospheric oxygen levels. However, the incineration and burning of forest plants to clear land releases large amounts of CO2, which contributes to global warming. Scientists also state that tropical deforestation releases 1.5 billion tons of carbon each year into the atmosphere.

Hydrological

The water cycle is also affected by deforestation. Trees extract groundwater through their roots and release it into the atmosphere. When part of a forest is removed, the trees no longer transpire this water, resulting in a much drier climate. Deforestation reduces the content of water in the soil and groundwater as well as atmospheric moisture. The dry soil leads to lower water intake for the trees to extract. Deforestation reduces soil cohesion, so that erosion, flooding and landslides ensue.

Shrinking forest cover lessens the landscape's capacity to intercept, retain and transpire precipitation. Instead of trapping precipitation, which then percolates to groundwater systems, deforested areas become sources of surface water runoff, which moves much faster than subsurface flows. That quicker transport of surface water can translate into flash flooding and more localized floods than would occur with the forest cover. Deforestation also contributes to decreased evapotranspiration, which lessens atmospheric moisture which in some cases affects precipitation levels downwind from the deforested area, as water is not recycled to downwind forests, but is lost in runoff and returns directly to the oceans. According to one study, in deforested north and northwest China, the average annual precipitation decreased by one third between the 1950s and the 1980s.

Trees, and plants in general, affect the water cycle significantly:

• their canopies intercept a proportion of precipitation, which is then evaporated back to the atmosphere (canopy interception);

• their litter, stems and trunks slow down surface runoff;

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• their roots create macropores – large conduits – in the soil that increase infiltration of water;

• they contribute to terrestrial evaporation and reduce soil moisture via transpiration;

• Their litter and other organic residue change soil properties that affect the capacity of soil to store water.

• their leaves control the humidity of the atmosphere by transpiring. 99% of the water absorbed by the roots moves up to the leaves and is transpired.[49]

As a result, the presence or absence of trees can change the quantity of water on the surface, in the soil or groundwater, or in the atmosphere. This in turn changes erosion rates and the availability of water for either ecosystem functions or human services.

The forest may have little impact on flooding in the case of large rainfall events, which overwhelm the storage capacity of forest soil if the soils are at or close to saturation.

Tropical rainforests produce about 30% of our planet's fresh water.

Soil

Undisturbed forests have a very low rate of soil loss, approximately 2 metric tons per square kilometer (6 short tons per square mile). Deforestation generally increases rates of soil erosion, by increasing the amount of runoff and reducing the protection of the soil from tree litter. This can be an advantage in excessively leached tropical rain forest soils. Forestry operations themselves also increase erosion through the development of roads and the use of mechanized equipment.

China's Loess Plateau was cleared of forest millennia ago. Since then it has been eroding, creating dramatic incised valleys, and providing the sediment that gives the Yellow River its yellow color and that causes the flooding of the river in the lower reaches (hence the river's nickname 'China's sorrow').

Removal of trees does not always increase erosion rates. In certain regions of southwest US, shrubs and trees have been encroaching on grassland. The trees themselves enhance the loss of grass between tree canopies. The bare inter canopy areas become highly erodible. The US Forest Service, in Bandelier National Monument for example, is studying how to restore the former ecosystem, and reduce erosion, by removing the trees.

Tree roots bind soil together, and if the soil is sufficiently shallow they act to keep the soil in place by also binding with underlying bedrock. Tree removal on steep slopes with shallow soil thus increases the risk of landslides, which can threaten people living nearby.

Biodiversity

Deforestation on a human scale results in decline in biodiversity, and on a natural global scale is known to cause the extinction of many species. The removal or destruction of areas of forest cover has resulted in a degraded environment with reduced biodiversity. Forests support biodiversity, providing habitat for wildlife; moreover, forests foster medicinal

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conservation. With forest biotopes being irreplaceable source of new drugs (such as taxol), deforestation can destroy genetic variations (such as crop resistance) irretrievably.

Since the tropical rainforests are the most diverse ecosystems on Earth and about 80% of the world's known biodiversity could be found in tropical rainforests, removal or destruction of significant areas of forest cover has resulted in a degraded environment with reduced biodiversity. A study in Rondônia, Brazil, has shown that deforestation also removes the microbial community which is involved in the recycling of nutrients, the production of clean water and the removal of pollutants.

It has been estimated that we are losing 137 plant, animal and insect species every single day due to rainforest deforestation, which equates to 50,000 species a year. Others state that tropical rainforest deforestation is contributing to the ongoing Holocene mass extinction. The known extinction rates from deforestation rates are very low, approximately 1 species per year from mammals and birds which extrapolates to approximately 23,000 species per year for all species. Predictions have been made that more than 40% of the animal and plant species in Southeast Asia could be wiped out in the 21st century. Such predictions were called into question by 1995 data that show that within regions of Southeast Asia much of the original forest has been converted to mono specific plantations, but that potentially endangered species are few and tree flora remains widespread and stable.

Scientific understanding of the process of extinction is insufficient to accurately make predictions about the impact of deforestation on biodiversity. Most predictions of forestry related biodiversity loss are based on species-area models, with an underlying assumption that as the forest declines species diversity will decline similarly. However, many such models have been proven to be wrong and loss of habitat does not necessarily lead to large scale loss of species. Species-area models are known to over predict the number of species known to be threatened in areas where actual deforestation is ongoing, and greatly over predict the number of threatened species that are widespread.

A recent study of the Brazilian Amazon predicts that despite a lack of extinctions thus far, up to 90 percent of predicted extinctions will finally occur in the next 40 years.

Forest management

Efforts to stop or slow deforestation have been attempted for many centuries because it has long been known that deforestation can cause environmental damage sufficient in some cases to cause societies to collapse. In Tonga, paramount rulers developed policies designed to prevent conflicts between short-term gains from converting forest to farmland and long-term problems forest loss would cause, while during the 17th and 18th centuries in Tokugawa, Japan, the shoguns developed a highly sophisticated system of long-term planning to stop and even reverse deforestation of the preceding centuries through substituting timber by other products and more efficient use of land that had been farmed for many centuries. In 16th-century Germany, landowners also developed silvi culture to deal with the problem of deforestation. However, these policies tend to be limited to environments with good rainfall, no dry season and very young soils (through volcanism or glaciation). This is because on older and less fertile soils trees grow too slowly for silvi

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culture to be economic, whilst in areas with a strong dry season there is always a risk of forest fires destroying a tree crop before it matures.

In the areas where "slash-and-burn" is practiced, switching to "slash-and-char" would prevent the rapid deforestation and subsequent degradation of soils. The biochar thus created, given back to the soil, is not only a durable carbon sequestration method, but it also is an extremely beneficial amendment to the soil. Mixed with biomass it brings the creation of terra preta, one of the richest soils on the planet and the only one known to regenerate itself.

FOREST CONSERVATION

Forests are influenced by climate, landform and soil composition and they exist in a wide variety of forms in the tropical, temperate and boreal zones of the world. Each forest type, evergreen and deciduous, coniferous and broadleaved, wet and dry, as well as closed and open canopy forests, has its own uniqueness and together these forests complement one another and perform the various socio-economic, ecological, environmental, cultural and spiritual functions. Recent surveys on a global basis suggest that there are about 1.4 million documented species, and the general consensus is that this is an underestimate - perhaps 5 - 50 million species exist in the natural ecosystems of forests, savannas, pastures and rangelands, deserts, tundra, lakes and seas. Farmers' fields and gardens are also importance repositories of biological resources. In this context, it has been acknowledged that forests are rich in biological resources. Though covering only 13.4 per cent of the Earth's land surface, these forests contain half of all vertebrates, 60 per cent of all known plant species, and possibly 90 per cent of the world's total species. However, recent studies have shown that temperate and boreal forests with their extremely varied ecosystems, especially those in climatic and geographical areas where old-growth forests still occur, may be even more diverse than tropical forests in terms of variation within some species. Even though temperate and boreal forests generally have far fewer tree species than tropical forests, often having a tenth or less in total, certain temperate and boreal forests are now thought to be as diverse, or even more diverse, than their tropical counterparts. For example, old-growth forests in Oregon, U.S.A. are found to have arthropods in leaf litter approaching 250 different species per square meter; with 90 genera being found in the H.J. Andrews Memorial Forest research area alone (Lattin, 1990). It has been suggested that a network of 500 protected and managed areas, with an average size of 200,000 hectares, covering 10 per cent of the remaining old-growth/primary forests be the minimum acceptable target (Anon, 1991 & IUCN/UNEP/WWF, 1991). To enhance this networking and to optimize the global representativeness of these biogeographic areas for the conservation of biological diversity, a list of these areas based on mutually agreed terms by national governments should be formulated. It should also include the identification of these biogeographic areas and the development of joint mechanisms, as well as the quantification of the costs involved and the identification of sources of fund needed to manage and conserve these areas. Joint mechanisms for possible international cooperation to establish trans boundary biogeographic areas should also be implemented.

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However, it has been recognized that totally protected areas can never be sufficiently extensive to provide for the conservation of all ecological processes and for all species. Nonetheless, there is a need to establish a minimum acceptable national target to be designated as forest conservation areas in each country. This effort could be further enhanced by establishing buffer zones of natural forests around the protected area where an inner buffer zone is devoted to basic and applied research, environmental monitoring, traditional land use, recreation and tourism or environmental education and training; and an outer buffer zone where research is applied to meet the needs of the local communities. Such management practices are in consonance with Principle 8(e) of the Forest Principles.

Besides the need to set aside conservation areas, it is now being increasingly realized that sustainable production of wood, through environmentally sound selective harvesting practices is one of the most effective ways in ensuring in-situ conservation of the biological diversity of forest ecosystems. Such selectively harvested and managed forests will retain most of the diversity of the old-growth/primary forests both in terms of numbers and population of species. The economic value of the wood and the environmental benefits produced would fully justify investments made in maintaining the forest cover as exemplified in such practices in ensuring its sustainability. The implementation of environmentally sound selective harvesting practices would go a long way in promoting in-situ conservation of biological diversity and the sustainable utilization of the forest resources. In this regard, the establishment of tree plantations would alleviate the pressure on over-harvesting the natural forests in view of the increasing demand of wood from the forests. The sustainable production of forest goods and services and the conservation of biological diversity in forest ecosystems, as well as the equitable sharing of benefits arising from the utilization of the genetic resources would require concrete actions at both the national and international levels. In this context, it is imperative that national policy and strategies, among others, should set target on the optimum forest area for forest conservation and for the sustainable production of goods and services, as well as outline relevant measures to enhance both ex-situ and in-situ forest conservation during forest harvesting. In some cases, long term measures may include the rehabilitation and re-creation of old-growth/primary forests.

In this connection, it is imperative that countries having a high proportion of their land areas under forest cover, especially the developing countries, have access to new and additional financial resources and the "transfer of environmentally sound technologies and corresponding know-how on favorable terms, including on concessional and preferential terms", as reflected in Principles 10 and 11 respectively, of the Forest Principles; in order to ensure the sustainable management, conservation and development of their forest resources. Moreover, "trade in forest products should be based on non-discriminatory and multilaterally agreed rules and procedures consistent with international trade law and practices" and "unilateral measures, incompatible with international obligations or agreements, to restrict and/or ban international trade in timber or other forest products should be removed or avoided" as called for in Principles 13 (a) and 14 respectively, of the Forest Principles should be respected by the international community, in order to attain long-term sustainable forest conservation and management.

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Afforestation

Afforestation is the establishment of a forest or stand of trees in an area where there was no forest. Reforestation is the reestablishment of forest cover, either naturally (by natural seeding, coppice, or root suckers) or artificially (by direct seeding or planting). Many governments and non-governmental organizations directly engage in programs of afforestation to create forests, increase carbon capture and sequestration, and help to anthropogenically improve biodiversity. (In the UK, afforestation may mean converting the legal status of some land to "royal forest".) Special tools, e.g. tree planting bar, are used to make planting of trees easier and faster.

Biological Process

Gap dynamics refers to the pattern of plant growth that occurs following the creation of a forest gap, a local area of natural disturbance that results in an opening in the canopy of a forest. Gap dynamics are a typical characteristic of both temperate and tropical forests and have a wide variety of causes and effects on forest life.

In areas of degraded soil

In some places, forests need help to reestablish themselves because of environmental factors. For example, in arid zones, once forest cover is destroyed, the land may dry and become inhospitable to new tree growth. Other factors include overgrazing by livestock, especially animals such as goats, cows, and over-harvesting of forest resources. Together these may lead to desertification and the loss of topsoil; without soil, forests cannot grow until the long process of soil creation has been completed - if erosion allows this. In some tropical areas, forest cover removal may result in a duricrust or duripan that effectively seal off the soil to water penetration and root growth. In many areas, reforestation is impossible because people are using the land. In other areas, mechanical breaking up of duripans or duricrusts is necessary, careful and continued watering may be essential, and special protection, such as fencing, may be needed.

In areas of extremely poor soil, the Groasis Waterboxx has been effective in growing young trees. The Groasis Waterboxx was designed specifically to establish trees in areas undergoing desertification. It collects dew and infrequent rain, and slowly releases it to the plants roots, promoting deeper root growth.

Social forestry

The National Commission on Agriculture, Government of India, first used the term ‘social forestry’ in 1976. It was then that India embarked upon a social forestry project with the aim of taking the pressure off the forests and making use of all unused and fallow land. Government forest areas that are close to human settlement and have been degraded over the years due to human activities needed to be afforested. Trees were to be planted in and

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around agricultural fields. Plantation of trees along railway lines and roadsides, and river and canal banks were carried out. They were planted in village common land, Government wasteland and Panchayat land. Social forestry also aims at raising plantations by the common man so as to meet the growing demand for timber, fuel wood, fodder, etc, thereby reducing the pressure on the traditional forest area. This concept of village forests to meet the needs of the rural people is not new. It has existed through the centuries all over the country but it was now given a new character. With the introduction of this scheme the government formally recognised the local communities’ rights to forest resources, and is now encouraging rural participation in the management of natural resources. Through the social forestry scheme, the government has involved community participation, as part of a drive towards afforestation, and rehabilitating the degraded forest and common lands. This need for a social forestry scheme was felt as India has a dominant rural population that still depends largely on fuelwood and other biomass for their cooking and heating. This demand for fuel wood will not come down but the area under forest will reduce further due to the growing population and increasing human activities. Yet The government managed the projects for five years then gave them over to the village panchayats (village council) to manage for themselves and generate products or revenue as they saw fit. Social forestry scheme can be categorized into groups : farm forestry, community forestry, extension forestry and agro-forestry.

Farm forestry

At present in almost all the countries where social forestry programmes have been taken up, both commercial and non commercial farm forestry is being promoted in one form or the other. Individual farmers are being encouraged to plant trees on their own farmland to meet the domestic needs of the family. In many areas this tradition of growing trees on the farmland already exists. Non-commercial farm forestry is the main thrust of most of the social forestry projects in the country today. It is not always necessary that the farmer grows trees for fuel wood, but very often they are interested in growing trees without any economic motive. They may want it to provide shade for the agricultural crops; as wind shelters; soil conservation or to use wasteland.

Community forestry

Another scheme taken up under the social forestry program is the raising of trees on community land and not on private land as in farm forestry. All these programs aim to provide for the entire community and not for any individual. The government has the responsibility of providing seedlings, fertilizer but the community has to take responsibility of protecting the trees. Some communities manage the plantations sensibly and in a sustainable manner so that the village continues to benefit. Some others took advantage and sold the timber for a short-term individual profit. Common land being everyone’s land is very easy to exploit. Over the last 20 years, large-scale planting of Eucalyptus, as a fast growing exotic, has occurred in India, making it a part of the drive to reforest the subcontinent, and create an adequate supply of timber for rural communities under the augur of ‘social forestry’.

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Extension forestry

Planting of trees on the sides of roads, canals and railways, along with planting on wastelands is known as ‘extension’ forestry, increasing the boundaries of forests. Under this project there has been creation of wood lots in the village common lands, government wastelands and panchayat lands. Schemes for afforesting degraded government forests that are close to villages are being carried out all over the country.

Agro forestry

Agro forestry or agro-sylviculture is a land use management system in which trees or shrubs are grown around or among crops or pastureland. It combines agricultural and forestry technologies to create more diverse, productive, profitable, healthy, and sustainable land-use systems. The theoretical base for agroforestry comes from ecology, via agroecology. From this perspective, agroforestry is one of the three principal land-use sciences. The other two are agriculture and forestry.

The efficiency of photosynthesis drops off with increasing light intensity, and the rate of photosynthesis hardly increases once the light intensity is over about one tenth that of direct overhead sun. This means that plants under trees can still grow well even though they get less light. By having more than one level of vegetation, it is possible to get more photosynthesis than with a single layer.

Agroforestry has a lot in common with intercropping. Both have two or more plant species (such as nitrogen-fixing plants) in close interaction both provide multiple outputs, as a consequence, higher overall yields and, because a single application or input is shared, costs are reduced. Beyond these, there are gains specific to agroforestry.

Benefits

Agroforestry systems can be advantageous over conventional agricultural, and forest production methods. They can offer increased productivity, economic benefits, and more diversity in the ecological goods and services provided.

Biodiversity in agroforestry systems is typically higher than in conventional agricultural systems. With two or more interacting plant species in a given land area, it creates a more complex habitat that can support a wider variety of birds, insects, and other animals. Depending upon the application, impacts of agroforestry can include:

• Reducing poverty through increased production of wood and other tree products for home consumption and sale

• Contributing to food security by restoring the soil fertility for food crops

• Cleaner water through reduced nutrient and soil runoff

• Countering global warming and the risk of hunger by increasing the number of drought-resistant trees and the subsequent production of fruits, nuts and edible oils

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• Reducing deforestation and pressure on woodlands by providing farm-grown fuelwood

• Reducing or eliminating the need for toxic chemicals (insecticides, herbicides, etc.)

• Through more diverse farm outputs, improved human nutrition

• In situations where people have limited access to mainstream medicines, providing growing space for medicinal plants

Agroforestry practices may also realize a number of other associated environmental goals, such as:

• Carbon sequestration • Odor, dust, and noise reduction

• Green space and visual aesthetics

• Enhancement or maintenance of wildlife habitat

Adaptation to climate change

There is some evidence that, especially in recent years, poor smallholder farmers are turning to agroforestry as a mean to adapt to the impacts of climate change. A study from the CGIAR research program on Climate Change, Agriculture and Food Security (CCAFS) found from a survey of over 700 households in East Africa that at least 50% of those households had begun planting trees on their farms in a change from their practices 10 years ago. The trees ameliorate the effects of climate change by helping to stabilize erosion, improving water and soil quality and providing yields of fruit, tea, coffee, oil, fodder and medicinal products in addition to their usual harvest. Agroforestry was one of the most widely adopted adaptation strategies in the study, along with the use of improved crop varieties and intercropping.

Application

Agroforestry represents a wide diversity in application and in practice. One listing includes over 50 distinct uses. The 50 or so applications can be roughly classified under a few broad headings. There are visual similarities between practices in different categories. This is expected as categorization is based around the problems addressed (countering winds, high rainfall, harmful insects, etc.) and the overall economic constraints and objectives (labor and other inputs costs, yield requirements, etc.). The categories include :

• Parklands• Shade systems

• Crop-over-tree systems

• Alley cropping

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• Strip cropping

• Fauna-based systems

• Boundary systems

• Taungyas

• Physical support systems

• Agroforests

• Wind break and shelterbelt.

Parkland

Parklands are visually defined by the presence of trees widely scattered over a large agricultural plot or pasture. The trees are usually of a single species with clear regional favorites. Among the benefits, the trees offer shade to grazing animals, protect crops against strong wind bursts, provide tree prunings for firewood, and are a roost for insect or rodent-eating birds.

There are other gains. Research with Faidherbia albida in Zambia showed that mature trees can sustain maize yields of 4.1 tonnes per hectare compared to 1.3 tonnes per hectare without these trees. Unlike other trees, Faidherbia sheds its nitrogen-rich leaves during the rainy crop growing season so it does not compete with the crop for light, nutrients and water. The leaves then regrow during the dry season and provide land cover and shade for crops.

Shade systems

With shade applications, crops are purposely raised under tree canopies and within the resulting shady environment. For most uses, the understory crops are shade tolerant or the over story trees have fairly open canopies. A conspicuous example is shade-grown coffee. This practice reduces weeding costs and increases the quality and taste of the coffee.

Crop-over-tree systems

Not commonly encountered, crop-over-tree systems employ woody perennials in the role of a cover crop. For this, small shrubs or trees pruned to near ground level are utilized. The purpose, as with any cover crop, is to increase in-soil nutrients and/or to reduce soil erosion.

Alley cropping

With alley cropping, crop strips alternate with rows of closely spaced tree or hedge species. Normally, the trees are pruned before planting the crop. The cut leafy material is spread over the crop area to provide nutrients for the crop. In addition to nutrients, the hedges serve as windbreaks and eliminate soil erosion.

Alley cropping has been shown to be advantageous in Africa, particularly in relation to improving maize yields in the sub-Saharan region. Use here relies upon the nitrogen fixing

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tree species Sesbania sesban, Tephrosia vogelii, Gliricidia sepium and Faidherbia albida. In one example, a ten-year experiment in Malawi showed that, by using fertilizer trees such as Tephrosia vogelii and Gliricidia sepium, maize yields averaged 3.7 tonnes per hectare as compared to one tonne per hectare in plots without fertilizer trees or mineral fertilizer.

Strip cropping

Strip cropping is similar to alley cropping in that trees alternate with crops. The difference is that, with alley cropping, the trees are in single row. With strip cropping, the trees or shrubs are planted in wide strip. The purpose can be, as with alley cropping, to provide nutrients, in leaf form, to the crop. With strip cropping, the trees can have a purely productive role, providing fruits, nuts, etc. while, at the same time, protecting nearby crops from soil erosion and harmful winds.

Fauna-based systems

There are situations where trees benefit fauna. The most common examples are the silvo pasture where cattle, goats, or sheep browse on grasses grown under trees. In hot climates, the animals are less stressed and put on weight faster when grazing in a cooler, shaded environment. Other variations have these animals directly eating the leaves of trees or shrubs.

There are similar systems for other types of fauna. Deer and hogs gain when living and feeding in a forest ecosystem, especially when the tree forage suits their dietary needs. Another variation, aqua forestry, is where trees shade fish ponds. In many cases, the fish eat the leaves or fruit from the trees.

Boundary systems

There are a number of applications that fall under the heading of a boundary system. These include the living fences, the riparian buffer, and windbreaks.

• A living fence can be a thick hedge or fencing wire strung on living trees. In addition to restricting the movement of people and animals, living fences offer habitat to insect-eating birds and, in the case of a boundary hedge, slow soil erosion.

• Riparian buffers are strips of permanent vegetation located along or near active watercourses or in ditches where water runoff concentrates. The purpose is to keep nutrients and soil from contaminating surface water.

• Windbreaks reduce the velocity of the winds over and around crops. This increases yields through reduced drying of the crop and/or by preventing the crop from toppling in strong wind gusts.

Taungya

Taungya is a system originating in Burma. In the initial stages of an orchard or tree plantation, the trees are small and widely spaced. The free space between the newly planted trees can accommodate a seasonal crop. Instead of costly weeding, the underutilized area provides an additional output and income. More complex taungyas use the between-tree space for a series of crops. The crops become more shade resistant as the

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tree canopies grow and the amount of sunlight reaching the ground declines. If a plantation is thinned in the latter stages, this opens further the between-tree cropping opportunities.

Physical support systems

In the long history of agriculture, trellises are comparatively recent. Before this, grapes and other vine crops were raised atop pruned trees. Variations of the physical support theme depend upon the type of vine. The advantages come through greater in-field biodiversity. In many cases, the control of weeds, diseases, and insect pests are primary motives.

Agroforests

These are widely found in the humid tropics and are referenced by different names (forest gardening, forest farming, tropical home gardens and, where short-statured trees or shrubs dominate, shrub gardens). Through a complex, disarrayed mix of trees, shrubs, vines, and seasonal crops, these systems, through their high levels of biodiversity, achieve the ecological dynamics of a forest ecosystem. Because of the internal ecology, they tend to be less susceptible to harmful insects, plant diseases, drought, and wind damage. Although they can be high yielding, complex systems tend to produce a large number of outputs. These are not utilized when a large volume of a single crop or output is required.

Reforestation

In many parts of the world, especially in East Asian countries, reforestation and afforestation are increasing the area of forested lands.The amount of woodland has increased in 22 of the world's 50 most forested nations. Asia as a whole gained 1 million hectares of forest between 2000 and 2005. Tropical forest in El Salvador expanded more than 20% between 1992 and 2001. Based on these trends, one study projects that global forest will increase by 10%—an area the size of India—by 2050.

In the People's Republic of China, where large scale destruction of forests has occurred, the government has in the past required that every able-bodied citizen between the ages of 11 and 60 plant three to five trees per year or do the equivalent amount of work in other forest services. The government claims that at least 1billion trees have been planted in China every year since 1982. This is no longer required today, but March 12 of every year in China is the Planting Holiday. Also, it has introduced the Green Wall of China project, which aims to halt the expansion of the Gobi desert through the planting of trees. However, due to the large percentage of trees dying off after planting (up to 75%), the project is not very successful. There has been a 47-million-hectare increase in forest area in China since the 1970s.The total number of trees amounted to be about 35 billion and 4.55% of China's land mass increased in forest coverage. The forest coverage was 12% two decades ago and now is 16.55%.

An ambitious proposal for China is the Aerially Delivered Re-forestation and Erosion Control System and the proposed Sahara Forest Project coupled with the Seawater Greenhouse.

In Western countries, increasing consumer demand for wood products that have been produced and harvested in a sustainable manner is causing forest landowners and forest industries to become increasingly accountable for their forest management and timber harvesting practices.

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The Arbor Day Foundation's Rain Forest Rescue program is a charity that helps to prevent deforestation. The charity uses donated money to buy up and preserve rainforest land before the lumber companies can buy it. The Arbor Day Foundation then protects the land from deforestation. This also locks in the way of life of the primitive tribes living on the forest land. Organizations such as Community Forestry International, Cool Earth, The Nature Conservancy, World Wide Fund for Nature, Conservation International, African Conservation Foundation and Greenpeace also focus on preserving forest habitats. Greenpeace in particular has also mapped out the forests that are still intact and published this information on the internet. World Resources Institute in turn has made a simpler thematic map showing the amount of forests present just before the age of man (8000 years ago) and the current (reduced) levels of forest. These maps mark the amount of afforestation required to repair the damage caused by people.

Reserve Forest

A reserve forest or a reserved forest is a specific term for designating forests and other natural areas which enjoy judicial and / or constitutional protection under the legal systems of many countries. The term forest reserve may also be used in some contexts in these countries.

The term reserved forest was used to designate protected forest areas in British India, under the Indian Forest Act, 1927. The same term is used today in Kazakhstan, India, Pakistan and Bangladesh to refer to forests accorded a special degree of protection.

In Australia, the term "forest reserve" is used to denote forests accorded certain degrees of protection; all activities like hunting and grazing are banned unless specific orders are issued by the government.

Sacred Groves of India

Sacred groves of India are forest fragments of varying sizes, which are communally protected, and which usually have a significant religious connotation for the protecting community. Hunting and logging are usually strictly prohibited within these patches. Other forms of forest usage like honey collection and deadwood collection are sometimes allowed on a sustainable basis. Sacred groves did not enjoy protection via federal legislation in India. Some NGOs work with local villagers to protect such groves. Traditionally, and in some cases even today, members of the community take turns to protect the grove. However, the introduction of the protected area category community reserves under the Wild Life (Protection) Amendment Act, 2002 has introduced legislation for providing government protection to community held lands, which could include sacred groves.

Indian sacred groves are sometimes associated with temples / monasteries / shrines or with burial grounds (which is the case in Shinto and Ryukyuan religion-based sacred groves respectively in Japan). Sacred groves may be loosely used to refer to other natural habitat protected on religious grounds, such as Alpine Meadows.

Historical references to sacred groves can be obtained from ancient classics as far back as Kalidasa's Vikramuurvashiiya.

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Location

Sacred groves are scattered all over the country, and are referred to by different names in different parts of India. Sacred groves occur in a variety of places – fromscrub forests in the Thar Desert of Rajasthan maintained by the Bishnois, to rain forests in the Western Ghats of Kerala. Himachal Pradesh in the north and Keralain the south are specifically known for their large numbers of sacred groves. The Kodavas of Karnataka alone maintained over 1000 sacred groves in their region. The Gurjar people of Rajasthan have a unique practice of neem (Azadirachta indica) planting and worshipping as abode of God Devnarayan.Thus, a Gurjjar settlement appears like a human-inhabited sacred grove. Similarly Mangar Bani, last surviving natural forest of Delhi is protected by Gurjars of nearby area. 14,000 sacred groves have been reported from all over India, which act as reservoirs of rare fauna, and more often rare flora, amid rural and even urban settings. Experts believe that the total number of sacred groves could be as high as 100,000.

It is estimated that around 1000 km² of unexploited land is inside sacred groves. Some of the more famous groves are the kavus of Kerala, which are located in the Western Ghats and have enormous biodiversity; and the law kyntangs of Meghalaya – sacred groves associated with every village (two large groves being in Mawphlang and Mausmai) to appease the forest spirit.

Among the largest sacred groves of India are the ones in Hariyali, near Ganchar in Chamoli District of Uttarakhand, and the Deodar grove in Shipin near Simla in Himachal Pradesh. Kodagu, a small region of about 4000 km² in Karnataka, had over 1000 sacred groves.

Uses

Traditional uses: One of the most important traditional uses of sacred groves was that it acted as a repository for various Ayurvedic medicines. Other uses involved a source of replenishable resources like fruits and honey. However, in most sacred groves it was taboo to hunt or chop wood. The vegetation cover helps reduce soil erosion and prevents desertification, as in Rajasthan. The groves are often associated with ponds and streams, and meet water requirements of local communities. They sometimes help in recharging aquifers as well.

Modern uses: In modern times, sacred groves have become biodiversity hotspots, as various species seek refuge in the areas due to progressive habitat destruction, and hunting. Sacred groves often contain plant and animal species that have become extinct in neighboring areas. They therefore harbor great genetic diversity. Besides this, sacred groves in urban landscapes act as "lungs" to the city as well, providing much needed vegetation cover.

Threats

Threats to the grove include urbanization, over-exploitation of resources (like overgrazing and excessive fuel wood collection), and environmental destruction due

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to religious practices. While many of the groves are looked upon as abode of Hindu gods, in the recent past a number of them have been partially cleared for construction of shrines and temples. Other threats to the sacred groves include invasion by invasive species, like the invasive weeds Chromolaena odorata, Lantana camara and Prosopis juliflora.

Social Movements

Chipko Movement

The Chipko movement or Chipko Andolan is a movement that practiced the Gandhian methods of satyagraha and non-violent resistance, through the act of hugging trees to protect them from being felled. This was first initiated by Amrita Devi while protesting against a King's men to cut the tree. The modern Chipko movement started in the early 1970s in the GarhwalHimalayas of Uttarakhand, then in Uttar Pradesh with growing awareness of rapid deforestation. The landmark event in this struggle took place on March 26, 1974, when a group of peasant women in Reni village, Hemwalghati, in Chamoli district,Uttarakhand, India, acted to prevent the cutting of trees and reclaim their traditional forest rights, which were threatened by the contractors assigned by the state Forest Department. Their actions inspired hundreds of such actions at the grassroots level throughout the region. By the 1980s the movement had spread throughout India and led to the formulation of people-sensitive forest policies, which put a stop to the open felling of trees in regions as far as the Vindhyas and the Western Ghats. Today, it is seen as an inspiration and a precursor for Chipko movement of Garhwal. Its leader was Sunderlal Bahuguna.

History

The Chipko movement though primarily a livelihood protection movement rather than a forest conservation movement went on to become a rallying point for many future environmentalists, environmental protests and movements all over the world and created a precedent for non-violent protest. It occurred at a time when there was hardly any environmental movement in the developing world, and its success meant that the world immediately took notice of this non-violent movement, which was to inspire in time many such eco-groups by helping to slow down the rapid deforestation, expose vested interests, increase ecological awareness, and demonstrate the viability of people power. Above all, it stirred up the existing civil society in India, which began to address the issues of tribal and marginalized people. So much so that, a quarter of a century later, India Today mentioned the people behind the "forest satyagraha" of the Chipko movement as amongst "100 people who shaped India". Today, beyond the eco-socialism hue, it is being seen increasingly as an ecofeminism movement. Although many of its leaders were men, women were not only its backbone, but also its mainstay, because they were the ones most affected by the rampant deforestation, which led to a lack of firewood and fodder as well as water for drinking and irrigation. Over the years they also became primary stakeholders in a majority of the afforestation work that happened under the Chipko movement.

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In 1987 the Chipko Movement was awarded the Right Livelihood Award

Beginning

In India the forest cover started deteriorating at an alarming rate, resulting in hardships for those involved in labor-intensive fodder and firewood collection. This also led to deterioration in the soil conditions, and erosion in the area. As water sources dried up in the hills, water shortages became widespread. Subsequently, communities gave up raising livestock, which added to the problems of malnutrition in the region. This crisis was heightened by the fact that forest conservation policies, like the Indian Forest Act, 1927, traditionally restricted the access of local communities to the forests, resulting in scarce farmlands in an over- populated and extremely poor area, despite all of its natural wealth. Thus the sharp decline in the local agrarian economy lead to a migration of people into the plains in search of jobs, leaving behind several de-populated villages in the 1960s.

Gradually a rising awareness of the ecological crisis, which came from an immediate loss of livelihood caused by it, resulted in the growth of political activism in the region. The year 1964 saw the establishment of Dasholi Gram Swarajya Sangh (DGSS) (“Dasholi Society for Village Self-Rule” ), set up by Gandhian social worker, Chandi Prasad Bhatt in Gopeshwar, and inspired by Jayaprakash Narayan and the Sarvodaya movement, with an aim to set up small industries using the resources of the forest. Their first project was a small workshop making farm tools for local use. Its name was later changed to Dasholi Gram Swarajya Sangh(DGSS) from the original Dasholi Gram Swarajya Mandal (DGSM) in the 1980s. Here they had to face restrictive forest policies, a hangover of colonial era still prevalent, as well as the "contractor system", in which these pieces of forest land were commodified and auctioned to big contractors, usually from the plains, who brought along their own skilled and semi-skilled laborers, leaving only the menial jobs like hauling rocks for the hill people, and paying them next to nothing. On the other hand, the hill regions saw an influx of more people from the outside, which only added to the already strained ecological balance.

Hastened by increasing hardships, the Garhwal Himalayas soon became the centre for a rising ecological awareness of how reckless deforestation had denuded much of the forest cover, resulting in the devastating Alaknanda River floods of July 1970, when a major landslide blocked the river and affected an area starting from Hanumanchatti, near Badrinath to 350 km downstream till Haridwar, further numerous villages, bridges and roads were washed away. Thereafter, incidences of landslides and land subsidence became common in an area which was experiencing a rapid increase in civil engineering projects.

Organization

Soon villagers, especially women, started organizing themselves under several smaller groups, taking up local causes with the authorities, and standing up against commercial logging operations that threatened their livelihoods. In October 1971, the Sangh workers held a demonstration in Gopeshwar to protest against the policies of the Forest Department. More rallies and marches were held in late 1972, but to little effect, until a decision to take direct action was taken. The first such occasion occurred when the Forest

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Department turned down the Sangh’s annual request for ten ash trees for its farm tools workshop, and instead awarded a contract for 300 trees to Simon Company, a sporting goods manufacturer in distant Allahabad, to make tennis rackets. In March, 1973, the lumbermen arrived at Gopeshwar, and after a couple of weeks, they were confronted at village Mandal on April 24, 1973, where about hundred villagers and DGSS workers were beating drums and shouting slogans, thus forcing the contractors and their lumbermen to retreat. This was the first confrontation of the movement, The contract was eventually cancelled and awarded to the Sangh instead. By now, the issue had grown beyond the mere procurement of an annual quota of three ash trees, and encompassed a growing concern over commercial logging and the government's forest policy, which the villagers saw as unfavourable towards them. The Sangh also decided to resort to tree-hugging, or Chipko, as a means of non-violent protest.

But the struggle was far from over, as the same company was awarded more ash trees, in the Phata forest, 80 km away from Gopeshwar. Here again, due to local opposition, starting on June 20, 1973, the contractors retreated after a stand-off that lasted a few days. Thereafter, the villagers of Phata and Tarsali formed a vigil group and watched over the trees till December, when they had another successful stand-off, when the activists reached the site in time. The lumberermen retreated leaving behind the five ash trees felled.

The final flash point began a few months later, when the government announced an auction scheduled in January, 1974, for 2,500 trees near Reni village, overlooking the Alaknanda River. Bhatt set out for the villages in the Reni area, and incited the villagers, who decided to protest against the actions of the government by hugging the trees. Over the next few weeks, rallies and meetings continued in the Reni area.

On March 25, 1974, the day the lumbermen were to cut the trees, the men of the Reni village and DGSS workers were in Chamoli, diverted by state government and contractors to a fictional compensation payment site, while back home laborers arrived by the truckload to start logging operations. A local girl, on seeing them, rushed to inform Gaura Devi, the head of the village Mahila Mangal Dal, at Reni village (Laata was her ancestral home and Reni adopted home). Gaura Devi led 27 of the village women to the site and confronted the loggers. When all talking failed, and instead the loggers started to shout and abuse the women, threatening them with guns, the women resorted to hugging the trees to stop them from being felled. This went on into late hours. The women kept an all-night vigil guarding their trees from the cutters till a few of them relented and left the village. The next day, when the men and leaders returned, the news of the movement spread to the neighbouring Laata and others villages including Henwalghati, and more people joined in. Eventually only after a four-day stand-off, the contractors left

Aftermath

The news soon reached the state capital, where then state Chief Minister, Hemwati Nandan Bahuguna, set up a committee to look into the matter, which eventually ruled in favour of the villagers. This became a turning point in the history of eco-development struggles in the region and around the world.

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The struggle soon spread across many parts of the region, and such spontaneous stand-offs between the local community and timber merchants occurred at several locations, with hill women demonstrating their new-found power as non-violent activists. As the movement gathered shape under its leaders, the name Chipko Movement was attached to their activities. According to Chipko historians, the term originally used by Bhatt was the word "angalwaltha" in the Garhwalilanguage for "embrace", which later was adapted to the Hindi word, Chipko, which means to stick.

Subsequently, over the next five years the movement spread to many districts in the region, and within a decade throughout the Uttarakhand Himalayas. Larger issues of ecological and economic exploitation of the region were raised. The villagers demanded that no forest-exploiting contracts should be given to outsiders and local communities should have effective control over natural resources like land, water, and forests. They wanted the government to provide low-cost materials to small industries and ensure development of the region without disturbing the ecological balance. The movement took up economic issues of landless forest workers and asked for guarantees of minimum wage. Globally Chipko demonstrated how environment causes, up until then considered an activity of the rich, were a matter of life and death for the poor, who were all too often the first ones to be devastated by an environmental tragedy. Several scholarly studies were made in the aftermath of the movement. In 1977, in another area, women tied sacred threads, Raksha Bandhan, around trees earmarked for felling in a Hindu tradition which signifies a bond between brother and sisters.

Women’s participation in the Chipko agitation was a very novel aspect of the movement. The forest contractors of the region usually doubled up as suppliers of alcohol to men. Women held sustained agitations against the habit of alcoholism and broadened the agenda of the movement to cover other social issues. The movement achieved a victory when the government issued a ban on felling of trees in the Himalayan regions for fifteen years in 1980 by then Prime Minister Indira Gandhi, until the green cover was fully restored. One of the prominent Chipko leaders, Gandhian Sunderlal Bahuguna, took a 5,000-kilometre trans-Himalaya foot march in 1981–83, spreading the Chipko message to a far greater area. Gradually, women set up cooperatives to guard local forests, and also organized fodder production at rates conducive to local environment. Next, they joined in land rotation schemes for fodder collection, helped replant degraded land, and established and ran nurseries stocked with species they selected

Participants

One of Chipko's most salient features was the mass participation of female villagers. As the backbone of Uttarakhand's Agrarian economy, women were most directly affected by environmental degradation and deforestation, and thus related to the issues most easily. How much this participation impacted or derived from the ideology of Chipko has been fiercely debated in academic circles.

Despite this, both female and male activists did play pivotal roles in the movement including Gaura Devi, Sudesha Devi, Bachni Devi, Chandi Prasad Bhatt, Sundarlal Bahuguna, Govind Singh Rawat, Dhoom Singh Negi, Shamsher Singh Bisht and Ghanasyam Raturi, the Chipko poet, whose songs echo throughout the Himalayas. Out of which, Chandi Prasad

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Bhatt was awarded the Ramon Magsaysay Award in 1982, and Sundarlal Bahuguna was awarded the Padma Vibhushan in 2009.

Legacy

In Tehri district, Chipko activists would go on to protest limestone mining in the Doon Valley (Dehra Dun) in the 1980s, as the movement spread through the Dehradun district, which had earlier seen deforestation of its forest cover leading to heavy loss of flora and fauna. Finally quarrying was banned after years of agitation by Chipko activists, followed by a vast public drive for afforestation, which turned around the valley, just in time. Also in the 1980s, activists like Bahuguna protested against construction of the Tehri dam on the Bhagirathi River, which went on for the next two decades, before founding the Beej Bachao Andolan, the Save the Seeds movement, that continues to the present day.

Over time, as a United Nations Environment Programme report mentioned, Chipko activists started "working a socio-economic revolution by winning control of their forest resources from the hands of a distant bureaucracy which is only concerned with the selling of forestland for making urban-oriented products." The Chipko movement became a benchmark for socio-ecological movements in other forest areas of Himachal Pradesh, Rajasthan and Bihar; in September 1983, Chipko inspired a similar, Appiko movement in Karnataka state of India, where tree felling in the Western Ghats and Vindhyas was stopped. In Kumaon region, Chipko took on a more radical tone, combining with the general movement for a separate Uttarakhand state, which was eventually achieved in 2000.

In recent years, the movement not only inspired numerous people to work on practical programs of water management, energy conservation, afforestation, and recycling, but also encouraged scholars to start studying issues of environmental degradation and methods of conservation in the Himalayas and throughout India.

On March 26, 2004, Reni, Laata, and other villages of the Niti Valley celebrated the 30th anniversary of the Chipko Movement, where all the surviving original participants united. The celebrations started at Laata, the ancestral home of Gaura Devi, where Pushpa Devi, wife of late Chipko Leader Govind Singh Rawat, Dhoom Singh Negi, Chipko leader of Henwalghati, Tehri Garhwal, and others were celebrated. From here a procession went to Reni, the neighbouring village, where the actual Chipko action took place on March 26, 1974.[17] This marked the beginning of worldwide methods to improve the present situation.

Appiko Movement

The Appiko movement was a revolutionary movement based on environmental conservation in India. The Chipko movement (Hug the Trees Movement) inUttarakhand in the Himalayas inspired the villagers of the Uttara Kannada district of Karnataka State in southern India to launch a similar movement to save their forests. In September 1983,led by Panduranga Hegde, men, women and children of Salkani "hugged the trees" in Kalase forest. (The local term for "hugging" in Kannada is appiko.) Appiko movement gave birth to a new awareness all over southern India.It is organised by Pandu Ram Hegde of Karnataka.

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In 1950, forest covered more than 81 percent of Uthara Kanara district. The government, declaring this forest district a "backward" area, then initiated the process of "development". Their major industries - a pulp and paper mill, a plywood factory and a chain of hydroelectric dams constructed to harness the rivers - sprouted in the area. These industries have overexploited the forest resource, and the dams have submerged huge-forest and agricultural areas. The forest had shrunk to nearly 25 percent of the district's area by 1980. The local population, especially the poorest groups, were displaced by the dams. The conversion of the natural mixed forests into teak and eucalyptus plantations dried up the water sources, directly affecting forest dwellers. In a nutshell, the three major p's - paper, plywood and power - which were intended for the development of the people, have resulted in a fourth p: poverty.

Deforestation in Western Ghats

The Sahyadri Range, or the Western Ghats, in southern India is the home of a tropical forest ecosystem. Although this tropical forest constitutes a potentiallyrenewable resource, it is also a very fragile ecosystem and therefore merits special attention. The past 30 years have seen the onslaught of "development" activities and an increase in population, both of which have exhausted this fragile resource system. In the case of Kerala, which comprises 42 percent of the entire Western Ghat area, the forest cover fell from 44 percent in 1905 to a meager 9 percent in 1984.

Such deforestation in the Western Ghats has caused severe problems for all southern India. The recurring drought in the provinces of Karnataka, Maharashtra,Kerala and Tamil Nadu clearly indicates watershed degradation. The power generation, water supply and ultimately the whole economy of southern India is adversely affected. The drought in Karnataka Province indicates the extent of the damage caused by change in Sahyadri's fragile ecosystem. The ongoing "development" policy of exploiting the "resources - mainly forest and mineral resources - in the Western Ghats for the benefit of the elite has deprived the poor of their self-supporting systems.

The Appiko Movement is trying to save the Western Ghats by spreading its roots all over southern India. The movement's objectives can be classified into three major areas. First, the Appiko Movement is struggling to save the remaining tropical forests in the Western Ghats. Second, it is making a modest attempt to restore the greenery to denuded areas. Third, it is striving to propagate the idea of rational utilization in order to reduce the pressure on forest resources. To save, to grow and to use rationally - popularly known in Kannada as Ulisu ("save"), Belesu ("grow") and Balasu ("rational use") - is movement's popular slogan.

As said earlier, the deforestation in the Western Ghats has already affected hydroelectric dams, reservoirs and agriculture. The central government's Planning Commission has recognized the "high depletion" of natural resources in the Western Ghats in its Seventh Five Year Plan document. The first area of priority for the Appiko Movement is the remaining tropical forests of Western Ghats. The area is so sensitive that to remove the forest cover will lead to a laterization process, converting the land into rocky mountains. Thus a renewable resource becomes a nonrenewable one. Once laterization sets in, it will take centuries for trees to grow on that land. Before we reach such an extreme point the

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Appiko Movement aims to save the remaining forests in the Western Ghats through organizing decentralized groups at the grassroots level to take direct action.

The Movement

The Appiko Movement uses various techniques to raise awareness: foot marches in the interior forests, slide shows, folk dances, street plays and so on. The movement has achieved a fair amount of success: the state government has banned felling of green trees in some forest areas; only dead, dying and dry trees are felled to meet local requirements. The movement has spread to the four hill districts of Karnataka Province, and has the potential to spread to the Eastern Ghats in Tamil Nadu Province and to Goa Province.

The second area of the Appiko Movement's work is to promote afforestation on denuded lands. In the villagers to grow saplings. Individual families as well as village youth clubs have taken an active interest in growing decentralized nurseries. An all-time record of 1.2 million saplings were grown by people in the Sirsi area in 1984-1985. No doubt this was possible due to the cooperation of the forest department, which supplied the plastic bags for growing saplings. In the process of developing the decentralized nursery, the activists realized that forest department makes extra money in raising a nursery. The cost paid for one sapling grown by a villager was 20 paise (US 2c), whereas the cost of a single sapling raised by the forest department amounted to a minimum of Rs 2 (US 15c). In addition, the forest department used fertilizers and gave tablets to saplings. The Appiko Movement's experience has brought an overuse of chemical fertilizers into the forest nursery, making it a capital-intensive, money-making program. The nursery program propagated by the forest department is really a means for utilizing village labor at cheap rates. Appiko activists have learned lessons from this experience, and they are now growing saplings only to meet their own needs, not to give to the forest department.

The villagers have initiated a process of regeneration in barren common land. The Youth Club has taken the responsibility for the project and the whole village has united to protect this land from grazing, lopping and fire. The experience shows that in those areas where soil is present, natural regeneration is the most efficient and least expensive method of bringing barren area under free cover. In the areas in which topsoil is washed off, tree planting - especially of indigenous, fast-growing species - is done. The irony is that the forest department is resorting to the mechanized planting of exotic species, and also uses huge amounts of fertilizers on these exotic, monoculture plantations. This work will definitely harm the soil, and eventually the tree cover, in the area. Two obvious techniques of greening are being performed: one the forest department's method, is capital intensive, and the other, the people's technique of growing through regeneration, is a natural process for sustainable development of the soil.

The third major area of activity in the Appiko Movement is related to rational use of the ecosphere through introducing alternative energy sources to reduce the pressure on the forest. The activists have constructed 2,000 fuel-efficient chulhas ("hearths") in the area, which save fuelwood consumption by almost 40 percent. The activists do not wait for government subsidies or assistance, since there is spontaneous demand from the people. Even in Sizsi town and in other urban areas, these chulhas are installed in hotels, reducing firewood consumption.

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The other way to reduce pressure on the forest is through building gobar (gas plants). An increasing number of people are building bio-gas plants. However, the Appiko activists are more interested in those people who are from poorer sections - who cannot afford gas plants - so they emphasize chulhas.

Some people deter the regeneration process in the forest area through incorrect lopping practices. The Appiko Movement is trying to change people's attitudes so that they realize their mistake and stop this practice.

The thrust of the Appiko Movement in carrying out its work reveals the constructive phase of the people's movement. Through this constructive phase, depleted natural resources can be rebuilt. This process promotes sharing of resources in an egalitarian way, helping the forest dwellers. The movement's aim is to establish a harmonious relationship between people and nature, to redefine the term development so that ecological movements today form a basis for a sustainable, permanent economy in the future.

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