IJRES 4 (2017) 1-12 ISSN 2059-1977

In situ and ex situ conservation: Complementary approaches for maintaining biodiversity

Haileab Zegeye

Department of Biology, Faculty of Natural and Computational Sciences, Debre Tabor University, P. O. Box 272, Debre Tabor, Ethiopia. E-mail: haileabzegeye@fastmail.fm; haileabzt@yahoo.com.

Article History ABSTRACT Received 30 October, 2016 Received in revised form 09 December, 2016 Accepted 12 December, 2016 Keywords: Biodiversity, Conservation, Sustainable use, Threats. Article Type: Review

This review highlights the threats to biodiversity and the conservation methods from a global perspective. Biodiversity includes a number of different levels of variation in the natural world. It can be measured at various levels. The most commonly used measures of biological diversity are genetic diversity, species diversity and ecosystem diversity. At spatial scales, biodiversity can be measured as alpha diversity, beta diversity, gamma diversity and delta diversity. Biodiversity also includes cultural diversity (biocultural diversity). Biodiversity has environmental, cultural, social, economic, medicinal, scientific, educational and aesthetic values. However, biodiversity is being lost at an alarming rate due to natural and more importantly anthropogenic factors. The threats to biodiversity are agricultural expansion, overexploitation, urbanization and industrialization, pollution, fire incidence, exotic species, genetically modified organisms (GMOs) and global climate change, which are all driven by human population growth. The conservation of biodiversity is achieved by two approaches – in situ and ex situ. In order to ensure the maintenance of biodiversity, there is a need to employ complementary in situ and ex situ conservation. There is also a need to prioritize ecosystems, species and populations for conservation actions. Moreover, promotion of indigenous resource management systems and practices, involvement of local people in conservation planning and endeavours, development of appropriate benefit-sharing mechanisms, awareness creation, promotion of the involvement of all relevant stakeholders and provision of adequate human, financial and physical resources for conservation efforts are important measures that should be taken in order to ensure the conservation, management and sustainable use of biodiversity. Above all, biodiversity conservation requires a multidisciplinary approach, and needs to be a continuous endeavour.

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INTRODUCTION The Earth holds a vast diversity of living organisms (plants, animals, microorganisms) and an immense variety of ecosystems. Biological diversity or biodiversity is the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems (CBD, 1992). Biodiversity includes a number of different levels of variation in the

natural world. The most commonly used measures of biological diversity are genetic diversity, species diversity and ecosystem diversity. These three main components of biodiversity are inextricably interlinked.

Genetic diversity is the variation in the genetic makeup of organisms (nucleotides, genes, chromosomes). It refers to the genetic variability between species and within species (that is, the genetic variation between individuals within populations and between populations

within species). In a broader sense, genetic diversity exists at various taxonomic levels such as subspecies, species, genera, families, orders, phyla, kingdoms and domains. Species diversity is the diversity of species in a given area. Species diversity contains two quite distinct concepts – richness and evenness (Krebs, 1989; Begon et al., 1996; Barnes et al., 1998). Species richness refers to the number of species in a given area. It is the most fundamental component and commonly used measure of biological diversity. Species evenness or equitability is the relative abundance of species in an area. Relative abundance can be measured by number of individuals, cover, biomass, productivity, or any measure that quantifies the importance of the species. Ecosystem diversity is the diversity of ecosystems in an area. It refers to the variety of terrestrial and aquatic ecosystems.

Biodiversity is dynamic; it varies in space and time. At spatial scales, biodiversity can be measured as alpha diversity, beta diversity, gamma diversity and delta diversity (Bisby, 1995; Rosenzweig, 1995; Ricklefs and Miller, 2000; Lomolino et al., 2006). Alpha diversity (local diversity) is the diversity of species at local spatial scales. It refers to the number of species in a single site or habitat (WCMC, 1992; Rosenzweig, 1995; Ricklefs and Miller, 2000), or the number of species occurring within an area of a given size (Bisby, 1995). It is a measure of within-area diversity. Beta diversity, also known as species turnover or differentiation diversity, is the degree of change in species composition across a region or landscape along major environmental gradients such as latitudinal, altitudinal and ecological gradients (WCMC, 1992; Bisby, 1995). It is a measure of the difference in diversity from one habitat or area to the next. Beta diversity is a measure of between-area diversity. Gamma diversity (regional diversity) is the species diversity at regional spatial scales. It is the total number of species in all habitats within a region (Rosenzweig, 1995; Ricklefs and Miller, 2000). Like alpha diversity, gamma diversity is also a measure of within-area diversity. However, it most often refers to overall diversity within a large region (Bisby, 1995). Delta diversity is the degree of change in species composition between large geographical areas (Lomolino et al., 2006). Like beta diversity, delta diversity is between-area diversity.

Biodiversity also includes the human dimension and this aspect of biodiversity is referred to as cultural diversity (Heywood and Baste, 1995), or more recently biocultural diversity (Loh and Harmon, 2014). Most biodiversity and landscapes are the products of nature and culture. There are innumerable interactions between humans and biodiversity. Indeed, humans interact with all levels of biodiversity. The different cultural dimensions in various parts of the world have played a major role in the conservation, management and sustainable use of biodiversity.

Biodiversity is unevenly distributed on Earth. In fact,

Int. J. Res. Environ. Stud. 2 this is associated with the uneven distribution of environmental factors, human population and disturbance regimes. As a result, some areas are rich in biodiversity while others are poor. Those areas with spectacularly high species diversity and endemism have been regarded as biodiversity hotspots (Myers et al., 2000; Gaston, 2010; Laurance, 2010). Myers et al. (2000) identified 25 biodiversity hotspots worldwide, which they proposed for conservation priorities. These have been revisited, and today there are 34 biodiversity hotspots in the world.

Biodiversity has environmental, cultural, social, economic, medicinal, scientific, educational and aesthetic values. Ecosystems provide diverse goods and services: repository of genetic resources; soil formation and fertility; erosion control; nutrient cycling; hydrological cycle regulation; drought and flood mitigation; watershed protection; carbon sequestration; climate regulation; siltation prevention; pollination and seed dispersal; pest and disease control; pollution control; products (food, medicines, fodder, wood, fibers, etc.); and recreation (Troy and Bagstad, 2009; Gaston, 2010; Sekercioglu, 2010; FAO, 2014). As such, biodiversity has fundamental importance in maintaining environmental stability and improving human wellbeing. THREATS TO BIODIVERSITY The world human population is increasing at a faster rate. The world population reached about 7.4 billion by 2015, and is projected to reach about 11.2 billion by 2100 (Ortiz-Ospina and Roser, 2016). More people means more resources are depleted, more land is developed, and more pollution is created. The demand for resources rises with increasing human population. Human population growth causes changes in land and water use patterns, which directly or indirectly affect biodiversity. Habitat destruction and overexploitation of resources are associated with increase in human population, and constitute a major threat to biodiversity (Mooney et al., 1995a). Overexploitation causes loss of populations, species and ecosystems. Human population growth and the increasing consumption of natural resources are the main forces driving the global transformation of the biosphere (Heywood and Baste, 1995). Human use of resources has led to simplification of ecological systems and reduction in biodiversity. The highest rate of human population growth on Earth prevails in Sub-Saharan Africa, and the region is plagued by overexploitation of natural resources (Ricklefs and Miller, 2000).

Globally, humans (Homo sapiens) are the dominant species influencing biodiversity. The influence of humans on the Earth’s biological systems is increasing exponentially (Heywood and Baste, 1995). The world’s terrestrial and aquatic ecosystems have been so

Zegeye 3 significantly modified by human activities. The increased human interference has resulted in destruction of the environment and, consequently, disruption of evolu-tionary and ecological processes. Tropical regions, which harbor the greatest species diversity and are the richest centres of endemism and thereby possess many biodiversity hotspots, are manifesting the highest rates of habitat loss (Laurance, 2010; Sodhi and Ehrlich, 2010). Tropical forests are disappearing at up to 130,000 km

2

per year (Laurance, 2010). The Atlantic forests of Brazil and rainforests of West Africa, both of which are examples of biodiversity hotspots, have been severely reduced and degraded. The most rapid decline in biodiversity is now happening in the tropics, the part of the world with the greatest diversity (Loh and Harmon, 2014).

As a result of heedless human actions, biodiversity is being lost at an alarming rate (Heywood and Baste, 1995; Jeffries, 1997; Engels and Engelmann, 2002). There is a rapidly accelerating loss of populations, species and ecosystems. The vast majority of populations and species of plants and animals are in decline, and many are already extinct. For instance, of the known 400,000 or so higher plant species, 148,000 (37 %) are threatened (Pimm and Jenkins, 2010). Escalating human population growth and consumption of resources have precipitated an extinction crisis – the “six mass extinction,” which is comparable to past extinction events such as the Cretaceous-Tertiary mass extinction 65 million years ago that wiped out all the dinosaurs (Sodhi and Ehrlich, 2010). They pointed out that unlike the previous extinction events, which were attributed to natural catastrophes including volcanic eruptions, meteorite impact and global cooling, the current mass extinction is exclusively humanity’s fault. Recent and current rates of extinction are 100 times faster than the background rate, while future rates may be 1,000 times faster (Pimm and Jenkins, 2010).

The Earth has been taking care of us while most of us admit that we have not been too kind to our planet recently. Human damage to the Earth is wide in scope. The threats to biodiversity (that is, drivers of biodiversity loss) are agricultural expansion, overexploitation, urbanization and industrialization, pollution, fire incidence, exotic species, GMOs and global climate change.

Agricultural expansion Globally, agriculture is the biggest cause of habitat destruction (Barlow and Tzotzos, 1995; Laurance, 2010). The soil on farmlands has been eroded away or paved over, and farmers increasingly are forced to turn to marginal lands to grow more food. There is agricultural expansion into ecologically fragile areas. Agricultural

expansion (farmland expansion, overgrazing) has resulted in the conversion of forests, woodlands, savannahs, grasslands and wetlands into farming and grazing lands. The increased demand for agricultural lands has caused habitat loss and fragmentation, and consequently reduction in biodiversity. Overgrazing has resulted in severe degradation of rangelands and bush encroachment (Mooney et al., 1995a). Therefore, it is important to take measures that reduce agricultural expansion into natural ecosystems. Overexploitation Biodiversity is under heavy threat from anthropogenic overexploitation. In an increasingly human-dominated world, where most of us seem oblivious to the liquidation of Earth’s natural resource capital, exploitation of biological populations has become one of the most important threats to the persistence of global biodiversity (Peres, 2010). Humans assess the surface of the Earth and even probe into the inner strata to remove resources for use, which is unsustainable. The economies of both developing and developed nations still depend heavily on primary extractive industries, such as logging, hunting and fishing. Human exploitation of biological commodities involves resource extraction from the land, freshwater bodies or oceans, so that wild plants, animals or their products are used for a wide variety of purposes ranging from food to medicines, fuel, shelter, fiber, construction materials, household and garden items, pets and cosmetics. Overexploitation occurs when the harvest rate of any given population exceeds its natural replacement rate, either through reproduction alone in closed populations or through both reproduction and immigration from other populations.

Many species are relatively insensitive to harvesting, remaining abundant under relatively high rates of offtake, whereas others can be driven to local extinction by even the lightest levels of offtake (Peres, 2010). A number of species are threatened by unsustainable logging in forest regions, overhunting of wildlife in many terrestrial ecosystems, overfishing in aquatic ecosystems, or many other forms of unsustainable extraction. Humans are depleting the Earth’s biodiversity at a faster rate than before and thereby depriving future generations. Urbanization and industrialization Urbanization, industrial development and road construc-tion affect biodiversity. The loss of habitat due to development of infrastructure causes reduction in biodiversity. Urbanization results in loss of natural vegetation and thereby decline in wildlife. An important consequence of urbanization is the increased demand on

food production to feed the urban population. Further more, urban areas are the major sources of pollutants (McNeely et al., 1995). Pollution Discharge of domestic and industrial wastes and unwise use of agricultural chemicals (fertilizers, insecticides, pesticides, herbicides) have caused pollution of air, water and soil. As a result of discharge of wastes from heavily populated and industrialized areas, the nutrient content of marine and other aquatic ecosystems has increased significantly (Mooney et al., 1995a). The increased nutrient load has caused changes in their physical, chemical and biological properties. Pollution reduces or eliminates populations of sensitive species (Kaya and Raynal, 2001). The negative impacts of pollution on biotas can be considerable (McNeely et al., 1995). Wildfires Fire is both an ecological and anthropogenic factor. Fire has both positive and negative impacts on the environment. Many species in fire-prone ecosystems are not only fire-tolerant, but depend on fire to complete their life cycles and to retain a competitive edge in their environment. The benefits of fire to the species include increased resource availability associated with the destruction of both living and dead biomass, nutrient-rich ash, high light conditions, and seed germination. For instance, the seeds of Acacia species and other legumes are stimulated to germinate by fire. On the other hand, there are fire-sensitive species and ecosystems. Fire has caused great devastation of ecosystems in various parts of the world, for example, Australia. In recent years, climate change has increased the risk of fire. The effects of fire on biodiversity have been highlighted by Bowman and Murphy (2010). Exotic species Exotic species are species that are introduced to an area outside their normal range through intentional or unintentional human assistance (Hawksworth and Kalin-Arroyo, 1995). Exotic species are also known as alien species, introduced species and non-native species. Most exotic species are harmless or beneficial in their new environments. However, some exotic species become invasive and disrupt the functioning of ecosystems. Not all introduced species become invasive, however (Simberloff, 2010). Many plant species introduced as ornamentals persist in gardens with human assistance but cannot establish in less modified habitats.

Int. J. Res. Environ. Stud. 4 Here it is important to note that native species can also become invasive.

Exotic species disrupt evolutionary and ecological processes. They often have major impacts on native species and ecosystems, and may be considered ecological disasters (McNeely et al., 1995; Mooney et al., 1995b). Exotic species compete aggressively for local resources and affect the growth and reproduction of native species.

Ecosystems with relatively low species richness such as island and temperate ecosystems are vulnerable to introduced species. Introduced species can be disastrous to island flora and fauna. Hawaiian Islands have lost more than half of their original endemic species due to introduced plants and animals (IUCN/UNEP, 1986). For the Hawaiian Islands, almost 50% of the plant species, 40% of birds, most freshwater fishes, and 25% of insects are introduced (Simberloff, 2010). Islands of Africa like Mauritius, Reunion and Rodrigues have suffered from a devastating wave of extinctions in historic times, much of which can be attributed to introduced species (IUCN, 1990).

The introduction of new species into aquatic ecosystems, especially freshwater ecosystems, can produce considerable effects (Mooney et al., 1995b). For example, the introduction of the Nile perch (Lates niloticus) into Lake Victoria has severely affected the Lake’s entire fishery (Ricklefs and Miller, 2000). It was a purposeful introduction for subsistence and sports fishing, and has become a great disaster.

Many exotic species have significant impacts on the environment, economy and human health. Invasive alien species cause myriad sorts of conservation problems. Therefore, there is a need for a careful assessment of past experiences to provide general, scientifically based policies and guidelines about species introductions, taking into account ecological and economic considera-tions. Genetically modified organisms (GMOs) Biotechnology has wide applications in agriculture, health, industry and the environment. Biotechnology provides a variety of applications for understanding of biodiversity. It has also become important for conservation and sustainable use of biodiversity. However, modern biotechnology can affect biodiversity in various ways. GMOs that result from genetic engineering may have adverse impacts on biodiversity and human health (Barlow and Tzotzos, 1995). GMOs affect evolutionary and ecological processes. The splicing of genes into other organisms from unrelated species causes genetic pollution (Barlow and Tzotzos, 1995). Furthermore, the transgene may transfer to other related species, and this can have significant impacts on the

Zegeye 5 genetic makeup of the species (McNeely et al., 1995). GMOs may become weeds, competitors of native species, produce pathogenic or toxic agents, or disrupt energy flow and nutrient cycling. Enhanced ability of GMOs to invade natural habitats may lead to loss of populations and species, thereby reducing biodiversity. Furthermore, the widespread monoculture of genetically improved crops leads to replacement of traditional crop varieties and landraces and presents a potential threat to agrobiodiversity.

Therefore, there is a need for appropriate safeguards to ensure safe applications of biotechnology. The use and release of GMOs require appropriate policy, regulation, management, control and monitoring in order to ensure adequate safety regarding the potential impacts on the environment and human health. It requires risk assessment. Risk reduction is achieved mainly by confinement (Barlow and Tzotzos, 1995). Past experience with GMOs is often a good guide for best management and practice. Global climate change The Earth’s climate is rapidly changing as a result of increases in the concentrations of greenhouse gases (GHGs) in the atmosphere mainly caused by human activities, particularly burning of fossil fuels, agriculture, deforestation and other land use changes (Wigley, 1999; Stern, 2006; IPCC, 2007). Since 1900, the global average surface temperature has risen by 0.76°C (IPCC, 2007; Deeb et al., 2011). The Intergovernmental Panel on Climate Change (IPCC) asserts that continued emissions of GHGs at or above the current rates would cause an increase in the global average surface temperature by 1.8 to 4.0°C by 2100 (IPCC, 2007). On the other hand, precipitation has showed different spatial and temporal patterns (increases or decreases) in different regions of the world.

Global climate change is one of the greatest challenges the world is facing today. Climate change has led to sea level rise (due to melting of ice and glaciers and expansion of sea water resulting from rising temperatures), changes in global precipitation patterns, increased frequency and intensity of extreme weather events (droughts, floods, heat waves, cold snaps, storms/hurricanes, etc.), shifts in the distribution of species and ecosystems, expansion of desertification, increased intensity and frequency of wildfires, decline in or loss of biodiversity, increased environmental pollution, decline in agricultural production and productivity, water scarcity, increased incidence of pests and diseases, and human migration and conflict. There are observed and expected impacts of climate change.

Climate change is quickly emerging as a key issue in the battle to preserve biodiversity. Human-induced

climate change will significantly threaten levels of biodiversity with concerns over the subsequent loss of genetic resources and ecosystem goods and services. It brings complex changes in species composition and interactions, and may result in a significant reduction in biodiversity (Heywood and Baste, 1995; Mooney et al., 1995a; Ricklefs and Miller, 2000). Ecosystems are vulnerable to climate change with the risk of extinction of certain species.

The most recent models based on a temperature rise of 2-3°C over the next 100 years suggest that up to 50% of the 400,000 or so higher plant species will be threatened with extinction (Bramwell, 2007). Prediction models have shown that the humid tropical ecosystems will be under severe threat from climate change. The wet tropical forests of the Amazon Basin will all but disappear with huge losses of biodiversity (Nobre, 2004). The tropical forests of West and Central Africa will be seriously affected and that between 50 and 80% of species will have their range severely reduced, many to the point of extinction (Lovett et al., 2005). The impact of climate change on biodiversity of the tropical rainforests of northern Queensland, Australia is likely to be very serious and could be catastrophic under some scenarios; many species of plants and animals are at highly increased risk of extinction (Krockenberger et al., 2004). All boreal ecosystems are vulnerable to climate change, and boreal forests in particular could decline if climatic conditions become significantly warmer or drier (Laurance, 2010). Climate change models also predict that there will be drastic, rapid and chaotic shifts in the distribution of species and habitats across the globe (Pritchard and Harrop, 2010). For instance, the Quiver tree (Aloe dichotoma) – the iconic desert species – is undergoing population collapse in the northern part of its geographic range, in Namibia, and active expansion in the cooler southern parts, in Namaqualand (Foden, 2002).

Therefore, there is a need to take an urgent action to protect biodiversity from the threats of climate change. Steps to mitigate and adapt to new and often dramatic climatic conditions are being widely debated and encouraged by politicians and the media. Environmen-talism is fashionable but still the value of maintaining biodiversity is not given the attention it deserves. CONSERVATION APPROACHES There are several methods for conservation of biodiversity. The different conservation methods can be broadly divided into two approaches – in situ and ex situ. In situ (on-site) conservation is the conservation of genetic resources within the natural ecosystem in which they occur, while ex situ (off-site) conservation is the conservation of genetic resources outside the natural ecosystem in which they occur. Each of in situ and ex situ

Int. J. Res. Environ. Stud. 6

1

Most effective 2

In situ

Single use wildland

management

____ Scientific reserves/strict nature reserves

Multiple use

wildland

management

____ National parks, natural monuments,

managed nature reserves, protected

landscapes, resource reserves,

anthropological reserves, multiple use

management areas

Areas other than

wildlands

____ Converted land managed for genetic

diversity

Ex situ

Whole organism ____ Botanical gardens, zoos

Organism parts ____ Sperm, egg and embryo banks; organ

banks; seed and pollen banks;

genebanks; tissue culture

Least effective 3

Figure 1. The roles of in situ and ex situ conservation. Source: Whitmore (1990).

conservation can be subdivided as shown in Figure 1.

In situ and ex situ conservation are mutually reinforcing and complementary approaches (Miller et al., 1995; Jeffries, 1997; Wolf, 1999; Wyse Jackson and Sutherland, 2000; Pritchard and Harrop, 2010). In order to ensure the conservation of the widest possible range of biodiversity and minimize the risk of genetic erosion, the various conservation methods should be combined in an integrated approach (that is, integrated biodiversity conservation). Indeed, there is no universal method that can cover all conservation purposes. The development of complementary conservation strategies in which different conservation approaches and methods are being combined helps to achieve the most stable and cost-effective conservation effort for a given genepool under locally prevailing conditions (Wyse Jackson, 1998). Here it is important to note that both in situ and ex situ conservation have merits and demerits. Furthermore, the

costs, risks and research needs of ex situ conservation are significantly higher than that of in situ conservation.

Due to the complexity of biodiversity, rapid loss of biodiversity, and increased realization of the importance of undertaking cost-effective programmes, developing realistic and viable strategies and setting priorities for effective conservation and management of genetic resources will always be necessary (IPGRI, 1993; Miller et al., 1995; Kigomo, 1999; Wolf, 1999; Coates and Atkins, 2001; Engels and Engelmann, 2002). There is a need for identification of action priorities both in geographical space and biological importance (Jarvis et al., 2002). Indeed, the choice of suitable conservation methods depends on the objectives of the envisaged genetic conservation and the ecological requirements of the species in question. Conservation is a dynamic process, and requires continuous evaluation based on emerging issues and newly acquired research findings.

Zegeye 7 In situ conservation In situ conservation maintains species in dynamic relationships with the habitat and allows gene flow and geographical distribution (Edwards and Kelbessa, 1999). Ecosystems, species and populations are dynamic; they are variable in space and time. In situ conservation allows evolutionary and ecological processes to take place and promotes genetic variability and adaptability of species to changing environmental conditions. Therefore, the conservation of biodiversity is best achieved in natural ecosystems (WCMC, 1992; Heywood and Baste, 1995). The in situ conservation approach allows the conservation of a large amount of genetic diversity, species diversity and ecosystem diversity in a very extensive and cost-effective manner (Wolf, 1999). The costs, risks and research needs of in situ conservation are generally low. However, in situ conservation is not feasible in areas with high environmental and human pressures. The reconciliation of the conservation activities with immediate and basic human needs, for example, for agricultural land, is often difficult. Species or populations conserved in situ may be susceptible to calamities or deliberate damages (for example, fire) depending on the level of disturbance. As such, in situ conservation is not feasible for threatened species due to escalating human pressure. Moreover, in situ conservation may be impaired by lack of direct influence due to ownership. In situ conservation methods include the different protected area systems, and on-farm conservation in which cultivated plants and domesticated animals are conserved in the agroecosystems where they have been developed and utilized.

Protected area systems Biodiversity conservation is most often achieved by establishment and management of protected areas. Protected areas are geographically delineated areas that are designated or regulated and managed to achieve specific conservation objectives (Miller et al., 1995). Protected areas should have sufficient size that can allow the maintenance of a given ecosystem or species (IUCN, 1990; Jeffries, 1997; Wolf, 1999). In addition, there is a need to have protected area systems that are representative of major landforms and ecosystems. Protected areas play a great role in the conservation of biodiversity. They have environmental, social, economic, scientific, educational and aesthetic values. There are different forms of protected areas based upon management objectives (for details refer to IUCN, 1992; WCMC, 1992; Hawksworth, 1995; Miller et al., 1995).

The sustainability of in situ conservation in protected areas depends on the long-term protection and effective-ness of management (IUCN, 1990, 1992; Miller et al.,

1995; Jeffries, 1997; Wolf, 1999). It is necessary to provide adequate human and financial resources in order to ensure the effectiveness of protected areas for maintaining biodiversity. In addition, the development and management of protected areas needs the participation of the local people in making decisions and undertaking conservation measures. The conservation of biodiversity in protected areas requires the generation of appropriate incentives from international, regional and national agencies for resource users both in and around the protected areas. It is important to provide incentives of various forms (for example, tax breaks, subsidies) for the local people in order to ensure the sustainability of protected areas. There is a need to have appropriate mechanisms for sharing benefits that are generated from the conservation and sustainable use of biodiversity within protected areas. For instance, in Cameroon and Zimbabwe, the involvement of local people in conservation activities and sharing of benefits derived from the protected areas have been found most effective (Jeffries, 1997). However, in many African countries, protected areas have failed to meet their conservation objectives mainly because of the exclusion of local people from participation and lack of appropriate mechanisms to provide incentives (Jeffries, 1997; Zegeye, 2004).

In many developing countries with rich tropical biodiversity, government agencies responsible for the management of protected areas lack the necessary technical capacity to stem biodiversity loss effectively (Rao and Ginsberg, 2010). Managers of protected areas often have limited access to the vast and dynamic body of knowledge and tools in conservation science. There is an urgent and critical need to transfer the advances in conservation science to individuals and institutions in biodiversity-rich countries. On-farm conservation On-farm conservation is the conservation of crops and their wild relatives, livestock, and the agroecosystems in which they occur. Agroecosystems include homegardens, crop fields, agroforestry systems, fallow fields and grazing lands. Agricultural biodiversity, or agrobiodiver-sity, is that component of biodiversity that contributes to food and agricultural production. In situ conservation on-farm is important for maintenance of agrobiodiversity.

Indigenous resource management systems and agricultural practices play an important role in the maintenance and diversification of domesticated plants and animals (McNeely et al., 1995). Low-input agricultural systems are important sources and custodians of agrobiodiversity. Farmers and pastoralists maintain a tremendous diversity of crop and livestock varieties around the world. Indigenous knowledge, skills and

practices of farmers play an important role in the conservation and management of agricultural bio-diversity. They are better options for building the scientific basis of in situ conservation of agrobiodiversity on-farm (Deribe et al., 2002). For instance, the farmers’ indigenous knowledge and practices in germplasm selection, storage and exchange are major elements in the conservation of agricultural biodiversity through community genebanks.

The expansion of large-scale/modern agricultural systems, in which relatively a few improved varieties have replaced many farmers’ varieties, has caused erosion of agricultural biodiversity. Therefore, there is a need for basing the rural development strategy on traditional farming systems, knowledge and agro-ecological techniques in order to ensure the maintenance and continual use of the diverse genetic resources associated with traditional agricultural systems (Miller et al., 1995). Farmer-based on-farm conservation of agro-biodiversity has been found a more successful approach. Ex situ conservation If in situ conservation is not feasible due to various reasons, threatened species can only be conserved ex situ (Jeffries, 1997; Wolf, 1999). Moreover, ex situ conservation serves as a source of material for research and ecosystem restoration. However, ex situ conser-vation interrupts evolutionary and ecological processes and limits genetic variability and adaptability of species to changing environmental conditions. Furthermore, the costs, risks and research needs of ex situ conservation are significantly higher than that of in situ conservation. Ex situ conservation methods include botanic gardens and arboreta, zoos, field genebanks and genebanks. Botanic gardens Botanic gardens are institutions holding documented collections of living plants for the purposes of scientific research, conservation, display and education (Wyse Jackson, 1999). Botanic gardens have played a vital role in the conservation of the world’s plant diversity. Many of the world’s threatened plant species are represented in their living collections or seedbanks which collectively provide an insurance policy supporting the maintenance of global biodiversity (Waylen, 2006). In fact, botanic gardens have a strong focus on wild species which are endangered in their natural habitat (Heywood, 1999; Wyse Jackson, 1998). In more recent years, some botanic gardens started to accept new responsibilities and were designed to be broadly based botanical resource centres (Wyse Jackson, 1998). They have been and still are ideal institutions for managing wild species

Int. J. Res. Environ. Stud. 8 genebanks with the aim of preserving rare and threatened plants and making the material available for research. In addition, many botanic gardens are involved in the conservation of plants of importance for food and agriculture, as well as those used for many other economic purposes.

Botanic gardens worldwide maintain approximately 80,000 species as living plants (nearly 30% of the known vascular plant species of the world) represented by more than 4 million living accessions (individual plant collections), and keep 250,000 seedbank accessions (Hawksworth, 1995; Wyse Jackson, 1999). Many botanic gardens around the world have developed effective seedbanks for conserving germplasm of wild plant species. Perhaps the most important one to date is the Millennium Seed Bank (MSB) at the Royal Botanic Gardens, Kew, UK, a major investment for the long-term future of plant diversity (Smith et al., 2007). The two principal aims of the project are to: i) collect and conserve the world’s wild seed-bearing flora; and ii) develop bilateral research, training and capacity-building relationships worldwide in order to support and advance the seed conservation effort. The emphasis is on threatened and endemic species. A reserve of germplasm of wild plants will be vital for reintroduction of threatened species and restoration of ecosystems. Germplasm banks will also be a source of plants and genetic diversity for the development of new crops and for the adaptation of old ones, for medicinal plants, and other uses. If, as currently predicted, large numbers of species do become extinct in the wild, then the world’s seedbanks will become the only source to human kind of those species and their germplasm in the future (Bramwell, 2007).

Botanic gardens, in cooperation with other bodies, are increasingly involved in the in situ conservation of plant resources (Hawksworth, 1995; Heywood, 1999; Wyse Jackson and Sutherland, 2000; Bramwell, 2007). They are involved in habitat management and restoration, plant reintroduction, control of invasive species and environ-mental education. For instance, the Central Siberian Botanical Garden, Novosibirsk, Russia is working with the managers of strictly protected scientific reserves to assist in management and restoration of rare and endangered species for their own region. The Gladstone Tondoon Botanic Gardens, Queensland, Australia are collaborating with the Queensland National Park and Wildlife Service to manage and restore degraded areas of the forest. The Aburi Botanical Garden, Aburi, Ghana is involved in complementary activities, such as promotion of some traditional medicinal plant management systems, management of protected areas and habitat restoration. Botanic gardens worldwide are also ideally placed to raise awareness on the values of and threats to forests.

Over 400 botanic gardens worldwide manage areas of natural vegetation or have natural areas within their

Zegeye 9 boundaries (Wyse Jackson and Sutherland, 2000). For example, the Rio de Janeiro Botanical Garden, Brazil has an in situ conservation area of forest which is contiguous with the National Park of Tijuca in the Atlantic Rainforest – one of the world’s biodiversity hotspots (Guedes-Bruni and Pereira, 2008). All the National Botanical Gardens (NBGs) in South Africa conserve an area of natural vegetation (Willis and Morkel, 2008). Botanic gardens can be directed towards promoting integrated biodiversity conservation, combining and utilizing ex situ and in situ techniques (Wyse Jackson and Sutherland, 2000). Therefore, ex situ and in situ conservation are merging in the world’s botanic gardens.

Botanic gardens are living laboratories. They undertake and promote scientific research on plants in particular and biological diversity in general. The research areas include botany, taxonomy/systematics, ecology, horti-culture, plant breeding, evolutionary biology, conservation biology, population genetics, molecular biology, biotechnology, invasive species biology and control, climate change and environmental education. Many botanic gardens maintain extensive collections and undertake research on useful plants of actual or potential value for agriculture, healthcare, horticulture, forestry, habitat management and restoration, amenity and many other purposes. However, most botanic gardens do not have sufficient human, financial and physical resources to be able to achieve much effective conservation and research into biodiversity. Therefore, there is a need to provide the necessary resources so that botanic gardens play important roles in the assessment and conservation of biodiversity. Zoos Zoos have become increasingly important in the conservation of threatened wildlife. They are also important for educational and recreational purposes. However, zoos generally are poorly developed and lack adequate funding. Therefore, there is a need for providing adequate human, financial and physical resources so that zoos can play an important role in the conservation of threatened wild animals. Field genebanks Field genebanks are important for conservation of plant species that do not produce seeds and propagate vegetatively or produce the so-called recalcitrant seeds (seeds which cannot be stored at low temperature). Usually these difficult-to-conserve species can be maintained as living collections in field genebanks. On the other hand, conservation in field genebanks requires sound information on the ecological requirements of the

species in question. It needs area of sufficient size and site conditions similar to that of the original population but with a lower environmental load or pressure (Wolf, 1999). Genebanks Genebanks are important for the conservation of germplasm or genetic material. Germplasms that can be stored in genebanks include seeds, pollen, spores, semen (sperms), eggs, embryos, cells and tissues. More recently, DNA sequences are also being kept in specialized banks (Smith et al., 2007). In any case, representative sampling is necessary. Approximately 6 million accessions of plants are maintained in genebanks worldwide (Engels and Engelmann, 2002; Frison et al., 2002). Germplasm conserved in genebanks serves for research and restoration purposes.

In vitro conservation methods (storage of germplasm in laboratory conditions) such as tissue culture storage (micropropagation, that is, in slow growth condition) and cryopreservation (storage of germplasm in dormant state) are important for preservation of germplasm. Cryopreservation of biological material using liquid nitrogen (-196°C) has a good potential for long-term storage of germplasm (Santos and Stushnoff, 2002). Increasingly, the difficult-to-conserve species are being maintained as in vitro collections.

Based on their storage behaviour, seeds are categorized into three groups – orthodox, intermediate and recalcitrant. Orthodox seeds are seeds which can withstand conventional storage conditions (5% moisture content and -20°C) without viability loss, while recalcitrant seeds are seeds which cannot be stored below 20% moisture content and 0°C (Balcha, 1999; Allem, 2002; Santos and Stushnoff, 2002). Generally, recalcitrant seeds do not show dormancy because they are in continuous growth, that is, there is no resting period. Seeds are generally used for long-term storage of plant germplasm provided they are orthodox seeds (about 90% of plant species). Storage of orthodox seeds is not a high technology procedure. Seeds need to be dried down to 5-7% moisture content and then stored in a cold room, usually at 4°C for short-term storage or -20°C for long-term storage (Smith et al., 2007). The drying stage is particularly critical because if a seed is not dry when frozen, it will be killed.

Many countries lack the resources and technologies to maintain germplasm in genebanks. Therefore, there is a need for regional and international collaboration for sharing of human, financial and physical resources and technology development. The key areas where collaboration in germplasm management should be encouraged are: germplasm collection, documentation, conservation, characterization, evaluation and rege-neration; exchange of germplasm and information;

identification of core collections (representative samples of accessions); and research and training. CONCLUSION AND RECOMMENDATIONS Biodiversity includes a number of different levels of variation in the natural world. It can be measured at various levels. The most commonly used measures of biological diversity are genetic diversity, species diversity and ecosystem diversity. At spatial scales, biodiversity can be measured as alpha diversity, beta diversity, gamma diversity and delta diversity. Biodiversity also includes cultural diversity (biocultural diversity). Bio-diversity has environmental, cultural, social, economic, medicinal, scientific, educational and aesthetic values. However, biodiversity is being lost at an alarming rate due to natural and more importantly anthropogenic factors. The threats to biodiversity are agricultural expansion, overexploitation, urbanization and industria-lization, pollution, fire incidence, exotic species, GMOs and global climate change, which are all driven by human population growth.

The conservation of biodiversity is achieved by two approaches – in situ and ex situ. In order to ensure the maintenance of biodiversity, there is a need to employ complementary in situ and ex situ conservation. There is also a need to prioritize ecosystems, species and populations for conservation actions. Moreover, promo-tion of indigenous resource management systems and practices, involvement of local people in conservation planning and endeavours, development of appropriate benefit-sharing mechanisms, awareness creation, promotion of the involvement of all relevant stakeholders and provision of adequate human, financial and physical resources for conservation efforts are important mea-sures that should be taken in order to ensure the conservation, management and sustainable use of biodiversity. Above all, biodiversity conservation requires a multidisciplinary approach, and needs to be a continuous endeavour.

Therefore, in order to ensure the maintenance of biodiversity, the following recommendations are forwarded:

It is necessary to curb human population growth, which is the major driving force for environmental and socio-economic problems;

There is a need to take urgent actions to protect biodiversity from the threats including climate change;

In order to ensure the maintenance of biodiversity, there is a need to employ complementary in situ and ex situ conservation;

Scientists, policymakers, local communities, academic institutions, conservation organizations, practitioners and all other relevant stakeholders around the world

Int. J. Res. Environ. Stud. 10 need to work closely for conserving biodiversity and improving human wellbeing.

ACKNOWLEDGEMENTS I would like to thank the National Herbarium (ETH) of the Addis Ababa University, Ethiopian Biodiversity Institute (EBI), Ethiopian Institute of Agricultural Research (EIAR) and the National Archives and Library Agency (NALA) of the Ministry of Culture and Tourism (MoCT) for allowing me to use their library. I also thank my relatives, friends and colleagues for their help and encouragement during the writeup of the review. The anonymous reviewers are greatly acknowledged for their valuable comments. REFERENCES Allem A. C. (2002). State of conservation and utilization of wild manihot

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