Plate Tectonics: the Earth’s lithosphere is
divided into plates, most of which are in
constant motion
The movement of the plates is driven by
convection in the mantle
Seafloor spreading creates new crust at ridges
at the bottom of the ocean (mid-Atlantic ridge)
Plate contact includes
Divergent
Convergent
Transform fault
Divergent boundaries create rift valleys (ex:
the Rift Valley in Africa)
Convergent boundaries create
Oceanic to continental creates subduction zones
which push up long, narrow coastal mountain
ranges such as the Andes (Nazca plate into South
American plate)
Continental to continental creates uplift, creating
tall mountain ranges such as the Himalayas (Indian
plate into the Eurasian plate)
Transform boundaries create faults, the
slippage of which produces earthquakes
Rocks come in three “flavors”
Igneous—formed directly from magma
Sedimentary—formed when mud, sand or gravel is
compressed
Metamorphic—formed when igneous or
sedimentary rocks are subjected to high
temperature and pressure
Exposed rock is subjected to weathering and
erosion
Weathering can be
Physical
Chemical
Soil links the abiotic lithosphere to the
biosphere!
Soil has geologic (rock/mineral) components
and organic components
Ecosystem services provided by soil include
Breaking down organic materials and recycling
nutrients
Providing habitat
Filtering water
Plant growth medium
O horizon
Organic detritus like, leaves, pine needles, twigs
and animal bodies in various stages of
decomposition
A horizon
Topsoil
Zone where organic and mineral materials are
mixed together
Plant roots are found here
E horizon
Zone of leaching
Occurs mostly in acidic soils
Fe, Al and organic acids from O and A are leach
through E to the B where they accumulate
B horizon
Subsoil
Mostly minerals with very little organic matter
C horizon
Least weathered zone
Similar in composition to the parent material
Permeability
How quickly soil drains
Sand is most permeable, clay is least permeable
Best agricultural soil is loam (40/40/20)
Soil texture is important to how an ecosystem
responds to pollution
If the soil is sandy, groundwater can be
contaminated by pollution infiltration
Soil degradation can be caused by
Erosion due to topsoil disturbance
Compaction (humans, machines, livestock)
Intensive agriculture (herbicides, pesticides,
fungicides, fertilizers)
Irrigation (salinization)
Mining is the extraction of mineral resources
from the Earth’s crust
Ores are concentrated accumulations of
minerals from which economically valuable
minerals can be extracted
Overburden is the economically undesirable
rock covering ore
Two types of mining
Surface
Subsurface
Surface mining includes
Strip mining—the removal of strips of overburden to expose ore
Once the resource is extracted from the ore, the waste material is called spoils or tailings
Spoils/tailings are returned to the fill in the strips
Open pit mining—a large hole is dug to access the ore
Copper mining is open pit
Mountaintop removal
Miners blowup an entire mountaintop with explosives to expose the ore
ALL forms of surface mining are HIGHLY environmentally destructive!!
Subsurface mining is used to reach ores that are
significantly below the Earth’s surface
Coal, diamonds and gold are mined subsurface
(although coal is also dug in strip mines)
Subsurface mining is genrally less environmentally
destructive than surface mining
General Mining Act of 1872, Surface Mining and
Reclamation Act of 1977, Clean Air Act, Clean Water
Act, the Safe Drinking Water Act and CERCLA
(Superfund) regulate the environmental effects of
mining
STUDY TABLE 8.2 ON PAGE 228 IN FRIEDMAN
AND RELYEA FOR ENVIRONMENTAL EFFECTS
OF MINING
LAND USE
Case Study: Julia Butterfly Hill and Luna
Northern California
Privately held stand of old growth redwood trees
scheduled to be clear-cut
Julia organized a “tree sit”—activists climb trees
scheduled to be cut and stay there as long as
possible to save them from logging and gain time
for legal proceedings
Julia occupied Luna, a 180 ft. redwood for TWO
YEARS without coming down!
Why do we care? Her actions brought worldwide attention to the
destructive practice of clear cutting
The logging company agreed to protect Luna and sell the U.S. government 7,500 acres of old growth forest in the area
The logging company eventually had to file for bankruptcy due to their legal debt from fighting the environmentalists
Some people called Julia a criminal because she did her “tree sit” on private land and blocked a legal activity (just because its legal doesn’t mean its right!)
LAND USE
Humans use land in a variety of ways
Agriculture
Housing
Recreation
Industry
Mining
Waste disposal
All land use has environmental consequences
Tragedy of the Commons
The tendency of a shared, limited resource to become depleted because people act from self-interest for short-term gain
Overfishing and overgrazing are good examples
Can be avoided by practicing maximum sustainable yield (MSY)—the maximum amount that can be harvested without compromising the future availability of a resource
In actuality, MSY is very hard to calculate because of the difficulty in obtaining birth rates, death rates and estimating the carrying capacity of the ecosystem
Rangelands
Dry, open grasslands
Most common land type in the U.S.
Often overgrazed, causing environmental problems
such as
Loss of vegetation
Land erosion and subsidence
Forests
Used for logging
Timber is culled from both private (73%) and U.S.
National Forests (27%)
Timber harvesting includes clear-cutting and
selctive cutting
Clear-cutting: removes all trees in an area
PROS
Easiest, cheapest harvesting method
Land often seeded with comercially valuable seedlings shortly after harvest so all trees are the same age
CONS
Increases wind and water erosion
Causes soil loss and sedimentation of nearby waterways
Denuded soil prone to landslides
Increases direct sunlight to streams, raising water temperatures, which harms aquatic species
Herbicides often used on the land prior to seedling replanting
Same-age/type trees reduces biodiversity
Selective cutting: removes single trees or
relatively small numbers of trees from many in
a forest
PROS
Creates gaps in which seedlings can be planted,
resulting in different age trees
Less loss of biodiversity because trees of different
species/ages remain
CONS
Costs more to plan and implement
Still must build logging roads to haul out cut trees
Heavy logging often replaces forests with tree
plantations—large areas planted with fast-
growing, commercially valuable species
Tree plantations are easily clear-cut and
replanted
Because of the managed cycle of clear-cutting
and replanting, tree plantations never develop
into mature forests
These managed cycles often deplete the land
of nutrients
Using fire to manage forests
Fires free up nutrients tied up in dead biomass
Cleared areas provide space for early successional
species
Suppressing fire is dangerous and leads to an
excess of dead biomass, which can fuel an out-of-
control fire and which can also harbor pests
Prescribed burns reduce the risk of uncontrolled
natural fire and assist with nutrient cycling
National Park System
Based on the “multi-use” principle (just like
rangelands and forests)
First park was Yellowstone in 1872
Began with the “preservation” mindset and has
progressed to the “conservation” mindset
Are often “victims of their own success”…too
many human visitors which reduces biodiversity
and creates waste and pollution
National Wildlife Refuges
The only federal public lands managed for the
primary purpose of protecting wildlife
National Wilderness Areas
Set aside with the intent of preserving large areas
of intact ecosystems
Allow only limited human use
NO logging, road building or mining allowed
Land use for residential areas is increasing rapidly
Urban sprawl is the creation of urbanized areas that spread into rural areas and is characterized by clusters of housing, retail, office building, “big box” stores and miles of large roads (“suburbia”)
People in suburban areas drive TWICE as much as those in urban areas
Suburban homes are larger than urban homes, and take up more land area
Sprawl displaces agricultural land, increasing the distance from farmers to consumers
Feeding the World
Humans were gatherers/hunters until about
10,000 years ago
Agriculture began around 10,000 years ago
and the human population became more
sedentary (agricultural revolution)
Undernutrition
Not consuming enough calories to be healthy
Has increased globally since 1996
Malnutrition
A diet lacking in the proper balance of protein,
carbohydrates, vitamins and minerals
A person can be overweight and malnourished!
Famine
A condition where food insecurity is widespread
and extreme, and many people die in a short period
of time
Anemia
Iron deficiency
Most common nutritional deficiency worldwide
Overnutrition
Eating too many calories and improper foods
Causes people to be overweight
Becoming very common in developed countries—WHO estimates there are over 1 billion overweight people worldwide
Consumption of meat increases with income and consumption has been increasing globally and in the U.S.
The primary reason for undernutrition and malnutrition is POVERTY; poverty and the “wealth gap” between rich and poor is increasing worldwide
Starvation is usually the result of unequal food
distribution, rather than actual food scarcity
With the world population expected to be 9 to
11 billion by 2050, in order to feed everyone,
we’ll need to…
Put more land into agricultural production
Improve crop yields
Reduce meat consumption (sorry, folks!)
Harvest more ocean resources
The Green Revolution began in the 1940’s in
the U.S.
Goal was to increase crop yields through selective
breeding of high-yield seed varieties
Also used wide-scale mechanization, irrigation,
fertilization and chemical pest control
The Green Revolution has allowed us to feed
more people, but has had serious negative
environmental consequences
Mechanization involves economies of scale,
which means that the cost of production falls
as output increases
Profits increase with size, so larger farms
outcompete smaller ones
Also leads to monocropping, because specialized
equipment is needed to plant and harvest each type
of crop
Irrigation allows crops to be grown in dry
areas where they wouldn’t normally be able to
grow and make already productive land VERY
productive. But…
It depletes groundwater and aquifers (Ogallala)
In coastal areas, in can cause saltwater intrusion
into freshwater wells
It can cause soil degradation through
Waterlogging—when soil remains submerged for
extended periods of time, which impairs root growth
Salinization—when small amounts of salts naturally
present in groundwater become concentrated on the soil
surface and impedes plant growth
Agriculture removes nutrients from the soil
which must somehow be replaced
Nutrients can be replaced with fertilizers,
which contain primarily nitrogen and
phosphorus (limiting factors for plant growth)
Two types of fertilizers
Organic: composed of composted plant and animal
waste
Synthetic: produced from combusting natural gas
(fossil fuel based)
Synthetic fertilizer advantages
Easy to apply
Can be customized for the crop
Concentrated, so a little goes a long way
Designed to be applied once per growing season
Disadvantages
Manufacturing uses fossil fuels in an energy-intensive process
Concentration leads to runoff, leading to eutrophication
Do not add organic matter to the soil, so does not feed the microorganisms or increase soil quality
Monocropping: growing large amounts of a
single crop variety, usually genetic clones
Most common agricultural practice in the U.S.
Efficient, if used with mechanization, irrigation
and fertilizer
Can lead to soil erosion from wind
Also prone to pests because the plants are
genetically similar (so pesticides must be used
continuously)
Pesticides are natural or synthetic chemicals
designed to kill or control organisms people
consider pests
Insecticides target insects
Herbicides target “weed” species
Rodenticides target rodents
Can be broad-spectrum (kill many different
types of pests) or selective (focus on a narrow
range of organisms)
Selective pesticides are usually a better choice
environmentally (biodiversity)
Some pesticides (DDT) are persistent—they
remain in the environment for a long time
Persistent pesticides tend to bioaccumulate.
They build up in the fatty tissues of organisms,
so the top-level consumers in an ecosystem
have the highest concentration in their bodies
Non-persistent pesticides are thought to be
safer, but must be repeatedly applied, so their
overall environmental impact may not actually
be lower
Genetically Modified Organisms (GMOs)
offer possibilities
increasing yields for crops and livestock, which
may reduce global hunger
May be bred to be resistant to pests, leading to less
fertilizer costs (and more profit) for the farmer
May be bred to tolerate drought and poor soil
Genes may be added to make the crop more
nutritious (like adding a sweet potato gene to rice
plant to produce vitamin A-enriched rice; vitamin
A deficiency is the #1 cause of childhood
blindness)
…and drawbacks
Are they safe from human consumption? We don’t
know!
GMOs reduce biodiversity (they’re all clones)
when they cross pollinate with native species
GMOs are patented, which means agribusiness
companies, like Monsanto, own the rights to the
seed
Regulation/labeling of GMOs in the U.S. is
currently non-existent, so we don’t know where
they are (probably everywhere!)
Alternatives to conventional agriculture
Shifting agriculture (slash and burn)/subsistence
farming—often leads to desertification (expansion
of desert into already dry areas)
Nomadic grazing
Sustainable agriculture
Intercropping—two or more species of crop are planted
in the same field at the same time
Crop rotation—rotation of crops in the same field
during different seasons (usually with nitrogen heavy
and nitrogen fixing crops)
Agroforestry—intercropping food crops with trees
Contour plowing—plowing parallel to the topography
of the land to reduce erosion and retain moisture
No till or low till agriculture—reduced tillage reduces wind erosion and oxidation of topsoil
Integrated Pest Management (IPM)
The goal is not to eliminates pests completely, but to reduce the economic impact of pests to a reasonable level
Techniques include
Crop rotation
Intercropping
Using pest-resistant crop varieties
Creating habitats for pest predators
Biological pest control (predator introduction or pheromone lures)
Limited use of specific (not broad-spectrum) pesticides
Organic farming: the production of crops without the use of synthetic fertilizers or pesticides
CAFOs: concentrated animal feeding operations
High density confined animals
Animals given antibiotics and nutrient supplements to reduce density-dependent diseases
Routine use of antibiotics is leading to resistant “superbugs” in animals and people
Waste runs off into waterways and causes eutrophication and disease (hog farming and pfiesteria??)
Fish and shellfish can be farmed on CAFOs,
too…Aquaculture
Animals must be provided with food and
antibiotics
Clean water is pumped into one end of the
enclosure and water contaminated with uneaten
food, antibiotic residue, bacteria, viruses and feces
flows out the other end (yummy!)
Diseases from farms can infect non-farmed species
Almost 100% of catfish and trout and over 50% of
shrimp and salmon eaten in the U.S. are farmed