Genesis of EdenGlobal Biodiversity Assessment Part 2
Genetic diversity is being eroded
Many samples of crop varieties and livestock that have been displaced by the world wide spread of new varieties are now conserved ex situ (off site) in seed banks, field gene banks, and through cryopreservation of semen and embryos, or in situ on-farm conservation programmes. For example, plant germplasm collections hold approxi mately 4 million samples, representing at least 10 000 species in total. About 3 million of those accessions relate to only about 100 species. However, losses of genetic resources still continue in ex situ collections, due to lack of resources for appropriate management, such as the need to germinate seeds periodically in order to maintain the viability of the collection, and in some cases whole collections are at risk or have even been lost. There are very few samples of wild species in gene banks. It is important to recognize that ex situ collections no longer continue to evolve in response to new environmental conditions: only wild populations continue to do so, and thus only wild populations can provide a continually evolving suite of genes from which to draw. Loss of cultural information about how to use the varieties in ex situ collections is also quite serious.
Table 3 Number of species considered 'Threatened' by the World Conservation Monitoring Centre (WCMC classifies all species listed as 'Endangered', 'Vulnerable', 'Rare' or 'Indeterminate' as threatened species). (WCMC pers. comm. 1 995.)
| threatened | endangered | vulnerable | rare | indeterminate | total |
| mammals | 177 | 199 | 89 | 68 | 533 |
| birds | 188 | 241 | 257 | 176 | 862 |
| reptiles | 47 | 88 | 79 | 43 | 257 |
| amphibians | 32 | 32 | 55 | 14 | 133 |
| fishes | 158 | 226 | 246 | 304 | 934 |
| invertebrates | 582 | 702 | 422 | 941 | 2647 |
| plants | 3632 | 5687 | 11485 | 5302 | 26106 |
For most wild species, little information is available on the extent of the loss of genetically distinct populations and consequent genetic erosion (Box 8). Each one of these populations may house genes, gene combinations or adaptations which are unique. Species that are already threatened probably suffer from some loss of genet ic diversity because of population loss, while the genetic composition of some wild populations of species has also been altered by genes from introduced species. Reduction in population size normally increases the rate of loss of genetic diversity and can lead to substantial reductions in adaptational fitness, especially in crossbreeding species.
Ecological consequences of reductions in biodiversity
The consequences of different ways of losing biodiversity for the sustainable provi sion of goods and services are described here.
Transformation and fragmentation of communities
Some fragmentation of existing ecological communities is inevitable, except in areas that have been specifically protected. In nearly all cases, the fragmentation reduces the diversity of native species in their natural habitats. The species most likely to be lost are large predators and other species with large body sizes and large area requirements. Also likely to be lost are species less able to disperse and colonize habitat patches. Species likely to survive fragmentation will be those best adapted to patchy and frequently disturbed environments, such as early successional and easily dispersed species. Fragmentation is thus expected to result in ecosystems dominated by opportunistic species, i.e. those characterized by good dispersal and colonizing abilities, rapid growth and short life cycles. Such systems have characteristically higher losses of nutrients, nitrogen and carbon; higher litter quality and therefore faster decomposition rates; simpler spatial structure; and less overall protection from herbivores than the original communities that preceded them.
Box 8 Loss of genetic diversity in salmonids
Loss of genetic diversity at multiple levels in wild species can be exemplified by salmonid fishes. These fishes are typically structured genetically and the occurrence of local adaptations is well documented. In some salmonids, hundreds of local populations have been extirpated or are threatened because of pollution, dam-building and other forms of water use. Loss of genetic diversity within populations has occurred in several species following hatchery programmes which were based on few parental fish. In addition, genetic diversity between populations has been compromised by both the intentional and accidental release of non-native (including cultured) populations into environments inhabited by wild populations of the same species. Thus genetic erosion occurs both within and between several salmonid species and some releases have even led to the introgression of genes from one salmonid species into the gene pool of another.
The transformation, fragmentation and loss of habitats has had many different effects on the provision of ecological goods and services. The massive creation of new agroecosystems has increased food production dramatically. At the same time, it has led to the impoverishment of natural communities and can reduce the ability of ecosystems to maintain productivity in the face of environmental fluctuation. Substantial alteration in soil fertility can be driven by changes in plant species composition and microbial groups required for the cycling of important plant nutrients. The loss of particular plant species and loss of critical communities, such as forested watersheds, can reduce the ability of some ecosystems to control soil erosion and retain water. Conversion from forest or shrubland to grassland dramatically increases stream flow, and if this occurs in the upper reaches of a watershed, it can increase the need for additional water control measures through dams and other measures to combat increased flooding and sedimentation. Increases in the extent and yield of rice agroecosystems have provided food for vast numbers of people, especially in Asia. At the same time, these increases in rice cultivation and numbers of livestock have been major contributors to the increased methane concentrations in the atmosphere, and thus to concerns over greenhouse warming. It is likely, although less certain, that increases in the use of nitrogenous fertilizer in the tropics are also contributing to rising concentrations of nitrous oxide, a very powerful greenhouse gas. Large-scale transformations of habitat can also affect the local climate. Deforestation has also led to major malaria outbreaks in the western Amazon, due to the creation of new habitats for mosquito vectors, and to increased colonization by susceptible human populations. The large-scale transformation of forested ecosystems to pasture, grassland and agriculture has been an important contributor to the increase in atmospheric carbon dioxide over the last several hundred years. The first phase of this transformation occurred in the developed countries of the north, but in recent decades, tropical conversion of forest to grassland has become the main contributor. During the 1980s, conversion of tropical forest contributed approximately 1.6 gigatonnes of carbon per year to the atmosphere, in addition to the 5.5 gigatonnes released by fossil fuel combustion. This was slightly offset by regrowth of temperate and boreal forests, which sequestered about 0.5 gigatonnes per year during the same time period. Improved management of forested ecosystems and reforestation in both temperate and tropical regions can continue to sequester carbon from the atmosphere and move it to longer-lived soil pools, thus reducing the rate at which greenhouse gases are added to the atmosphere. Within reasonable bounds, we cannot consider transformations of ecological communities to have only local effects. In marine systems, changes in geographically distant ecosystems may greatly affect one another through, for example, larval transport or the transport of pollutants by currents. In terrestrial ecosystems, changes in one area may have atmospheric consequences that affect other regions, while loss of habitat may affect species that range widely, thus affecting other distant ecosystems. Fragmentation of temperate forests in North America can, for example, affect the survival of tropical-temperate migratory birds, which are important seed dispersal and biological control agents in neotropical areas. The transformation of forested ecosystems affects atmospheric composition on a global scale.
On a less dramatic scale, changes in forested watersheds can affect water flow and quality far downstream.
Overexploitation of resources
Overexploitation of resources, such as poorly managed cropping and timber harvesting, while providing food and wood also tends to disrupt ecosystem services by decreasing the ability of the ecosystem to retain nutrients, water and topsoil. These effects are due directly to the process of extracting the desired materials, along with the longer-term biogeochemical effects of removing carbon, nitrogen and nutrients. Over the long term, reductions in soil carbon and soil fertility, and increases in overland flow and sedimentation rates are often the result. Increased fertilizer and pesticide subsidies are then often required to maintain adequate agricultural yields, resulting in increased direct costs. The period from 1950 to 1970 saw the collapse of many of the world's largest fisheries for small pelagic species, primarily through overexploitation. All but one (Icelandic spring-spawning herring) have recovered, though to varying degrees and at various rates. More recently, many of the major fisheries in the North Atlantic have collapsed through overfishing.
Box 9 Introductions of genetically modified organisms
Introduced species or varieties, whether developed through traditional breeding methods or through genetic engineering, have the potential to affect both ecological relationships and evolution. Genetic material from introduced plants, animals and microorganisms can be transferred into wild populations of related species through the formation offertile hybrids. The new genetic material can then potentially alter the ecological interactions ofthat wild relative. For example, a disease or frost resistance gene transferred into a wild weedy relative of the crop could extend the range of that wild relative. In aquatic systems, substantial gene flow occurs between hatchery reared fish and wild populations. To date, in agricultural systems, most gene flow has taken place between crops and their weedy relatives. Once a species is released ora new gene is introduced into a population, there is usually no means of undoing that action. Using current methods for modelling eco systems, we cannot reliably predict the outcome ofthe release of new species or new cultivated varieties. Effects of new genes or new species on population dynamics are extremely sensitive to environmental influences and their manifestations are often slow to be recognized.
Invasions and introductions
International travel and trade have provided many opportunities for the deliberate introduction or accidental invasion of species (Box 9). When a species enters an ecosystem in which it previously did not occur, it can adversely disrupt ecosystem processes, or less commonly have positive effects such as biocontrol of pests or pathogens in an agroecosystem. Introductions of agricultural species into new regions, beyond the range of their natural predators and pathogens, have often resulted in increased yields and improved economic returns. However, introductions of exotic species in many freshwater ecosystems for sport or food have led to loss of native species (Fig. 10), and subsequent alterations in many ecosystem processes. Microbial species introductions, particularly of plant pathogens, have had a large effect on ecosystem composition in both natural and managed systems, but these effects do not always have large observable effects on ecosystem processes. For example, the loss of chestnut from the eastern deciduous forests in North America, due to the introduction of chestnut blight from Europe, was both rapid and dramatic, but there have been no discernible consequences for ecosystem functioning, as
Fig. 10 In the flathead lake and its tributaries
in Montana, the food web was dis trupted by the introduction of
the opossum shrimp (Mysis relicts). The natural food chain involved
grizzly bear, bald eagles, and lake trout eating kokanee salmon-I
kokanee eating zooplankton (cladocerans and copepods); and zooplankton
eating phytoplankton (algae). Opossum shrimp, introduced as a
food source for the salmon, ate so much zooplankton that there
was far less food available for the fish. Kokanee salmon numbers
than declined radically, as did the eagle population that relied
on the salmon (source as Fig. 5).
other tree species seem to have fulfilled the chestnut's original functional roles. On the other hand, introductions of pests and pathogens into agricultural systems typically pose great danger of loss of productivity and yield. Introductions of new capabilities, such as nitrogen fixation, into ecosystems whose component species previously did not have this ability, typically have dramatic effects on both composi tion and ecosystem functioning. The introduction of nitrogen-fixing trees into sites in Hawaii has led to a complete restructuring of the plant communities, with conse quent increases in nutrient supply and fire frequency, leading to rapid losses in the populations of the original species. Systems with limited genetic diversity, especially crops, are often the most susceptible to the effects of introductions and invasions, with the introduction of pathogens being of primary concern. Islands and ecosystems with relatively few component species, such as boreal forests, seem to be more susceptible to species introductions than species-rich biomes such as tropical forests, so it would be expected that establishment of intro duced species leading to disruption of ecosystem processes is more likely to occur in the former than in the latter. Freshwater ecosystems in all climatic zones also seem to be especially sensitive to invasions and introductions. In general, areas that have been subjected to disturbance or stress from other environmental factors, such as fire, drought, overgrazing or extensive clearing, can provide open habitat and resources for introduced species to exploit. Whether or not the introduced species will spread depends on the particulars of their biology, and the biology of the native species they encounter. The combination of introduction of non-native species and overexploitation of resources has been especially prevalent in grassland ecosystems. On the one hand this has stimulated ranching activities that have been economically productive. On the other hand, in arid and semi-arid regions, the introduction of cattle, sheep and other non-native grazers, if poorly managed, can result in invasion by new plant communities, soil compaction and desertification. Apart from these generalizations, there is very little ability to predict a priori the effects of accidental or deliberate introductions, suggesting that considerable prudence should be exercised.
Pollution of soil, water and atmosphere
Pollutants stress ecosystems and may reduce populations of sensitive species. For example, acid deposition (sulphate and nitrate) has made thousands of lakes virtually lifeless in Scandanavia and North America and, in combination with other kinds of air pollution (e.g. ozone), has damaged forests throughout Europe. Acidic deposition has also been implicated in other effects, e.g. trace element deficiencies iii the diet of moose, leading to increased mortality, and birds producing eggs with thin and porous shells, resulting in a high incidence of clutch desertion and empty nests. In addition, air pollution has been linked to the impoverishment of grasslands in Poland where plant diversity and growth have been severely reduced and soil fauna decreased. Marine pollution, particularly from non-point sources, has severely affected the Mediterranean and many coral reefs, estuaries and coastal seas through out the world, thus impacting the reproduction of some marine species.
Long-term climate change
In the coming decades anthropogenic climate change, otherwise known as global warming, could adversely affect the world's living organisms, especially when coupled with population growth and accelerating rates of resource use. The Earth's climate is projected to warm by 1-4 'C during the next 100 years, alter precipitation patterns and lead to an increase in sea level of 10-1 20 cm. These projected changes in climate would cause a poleward migration of certain species by hundreds of kilometres and an altitudinal displacement by hundreds of metres. Many species will not be able to redistribute themselves fast enough to keep pace with the projected changes in climate. Considerable alterations in ecosystem structure and function are likely, with some loss of species. Figure I I illustrates some natural and human impediments to the poleward migration for temperate forest species. Flora and fauna in coastal ecosystems and on small islands will be adversely affected by projected increases in sea level. Because carbon dioxide is the dominant greenhouse gas directly affected by human activities its beneficial affects on productivity need to be considered.
Fig. 11 If global climate increases over the next
century as some models suggest, north temperate tree species will
have to disperse 160 640km (From: Intergovernmental Panel on Climate
Change, 1995) northward in order to find sites with a hospitable
climate. Not only will these species encounter natural barriers
such as mountains, oceans, rivers, and unsuitable terrain, but
they face barriers created by people such as agricultural fields,
cities, suburbs, roads and fences (source as Fig. 5).
Loss of ability to resist or recover from disturbance
Reductions in species diversity can lower an ecosystem's ability to resist stress from other environmental factors, and to recover from disturbance. Experimental studies have shown that species-rich temperate grasslands exhibit smaller changes in plant biomass after drought than is the case in less rich areas. The existence of relatively undisturbed communities within a mosaic of different land uses can serve as sources of propagules, seeds and dispersing animals to recolonize areas that have been adversely affected by other stresses. The sensitivity of ecosystems to changes in biodiversity appears to be influ enced in part by the number of species that influence individual ecosystem process es in similar ways. For example, the ecosystem-level consequences of species losses should be greatest for systems that have few species, such as boreal forests, deserts and islands, because there will be few species that can substitute for the missing taxa, and thus the chance of even a single loss adversely affecting an ecosystem process is high. In addition, since each individual species may play many different functional roles, ecosystems with few species may lose important functions by the deletion of even a single species. Conversely, ecosystems with many functionally similar species should be better protected from disruptions, because there are more species available to react to the environmental stress. On short time scales, some degree of substitutability can be documented, as shown by experiments in a grass land system, when dominant species fully compensated for the removal of subordinate species while the subordinate species only partially compensated for the removal of dominant species. The variety of functional roles that individual species play in ecosystems is seldom fully known. Indeed, it is known that some species have functional roles that seem to be far out of proportion to their abundance. There is no a priori means of predicting which species will exhibit this characteristic, leading to inherent limitations in our ability to predict the results of losing particular species. Modern agriculture and plantation forestry are based on the premise that low diversity ecosystems can be highly productive. While this premise is broadly validated in intensively managed ecosystems, the experience of agriculture highlights the critical sensitivity of low-diversity ecosystems to variation in climate as well as outbreaks of pests and pathogens. When changes in ecosystem composition and functioning do occur, they are often gradual. However, some ecosystems exhibit dynamic thresholds in their response to a major stress or disturbance notably islands, takes and agroecosystems. Others, such as boreal, Arctic and alpine systems, seem susceptible to chronic stress. No biome remains unaffected by landscape-scale changes in diver sity, particularly those changes due to anthropogenic alterations. The large-scale conversion of ecosystems within landscapes tends to have long-lasting effects on system processes irrespective of whether the particular ecosystems were originally of high or low diversity. The effects of human-induced change on biodiversity and on the functioning of ecosystems, together with the feedbacks involved, are conceptualized in Fig. 12.
Fig. 12 Conceptual model of the effect of human-induced
changes on biodiversity and on the functioning of ecosystems,
together with the feedbacks involved.
Conservation, sustainable use and equitable sharing of benefits
The objectives of conserving biodiversity, ensuring its sustainable use, and ensuring the equitable sharing of benefits form the foundation of the Convention on Biological Diversity. The mutually reinforcing objectives of the Convention on Biological Diversity i ie three issues of conservation, sustainable use and equitable sharing of benefits from biodiversity are not separable. Effective national action depends on developing aii institutional and legal franiework that integrates the benefits gained from con servation and sustainable use of biodiversity into national decision making. It is important to recognize the social, cultural and economic contexts in which actions are contemplated, including the importance of local knowledge and values. Experience sfiows that the most successful regional and national strategies integrate all these factors (Fig. 1 3). Economic and institutional factors play iitiportant roles in integrating the objectives ofthe Biodiversity Convention. Biodiversitv nianagement calls for greater levels of co-operation and co ordination than are found intraditional sectoral approaches and while certain managenient activities, such as setting up protected ureas or gene banks, niay be targeted explicitly at biodiversity, most effects on bio diversity result from the secondary consequence of activities such as agriculture, forestry, fisheries, water supply, transportation, urban development, energy and so forth. Maiiageiiient ob,jectives must incorporate the concerns and aspirations of the
Levels of Action: Farm, village, forest or Laboratory; Bioregional; National; International
Fig. 13 The three issues of conservation, sustainable use and equitable sharing of benefits froni biodiversity are not separate. Exi)erience shows that the most success fail regional and national strategies recognize the social, cultural and economic contexts of biodiversity, including the importance of local knowledge and values (from WRI/IUCN/tJNI'P, 1992. Global Biodiversity Strategy: Guidelines for Action to Save, Study and Use Earth's Biotic Wealth Sustainably and Equitably. World Resources Institute, Washington DC, IUCN The World Conservation Union, Gland, Switzerland, and the United Nations Environment Programme, Nairobi, Kenya).
many stake-holders, including local communities. Objectives must also be identified at a geographic scale large enough to allow flexibility in implementation in order to adapt to changing conditions, ensure the protection of critical habitat, and maintain the ecosystem processes that provide goods and services. Often, management actions are taken on scales that are too small to have the desired effect, or they fail to incorporate the many small individual resource management decisions, each with minimal impact on its own, but which together have significant impacts on a regional scale. Increasing our understanding of biodiversity's benefits, and the ways in which our perception of these change over time, is a critical task. Experience with mechanisms for benefit sharing is very recent, and not yet well understood. Most experience to date has come from agreements that regulate access to genetic resources by private companies, and from experimenting with different ways of appropriating the benefits to national and local beneficiaries, thus treating international and national aspects simultaneously (Box 10). Another important concern, however, is the degree to which knowledge and understanding of biodiversity is gained and shared. The role of research and monitoring is especially critical, since these activities underlie countries' abilities to take advantage of the cultural and economic opportunities afforded by biodiversity, and to make informed decisions about its ultimate uses. 'Technology can be an important tool for managing biodiversity well. Agricultural technology, for example, has often led to major increases in food pro duction when used appropriately. New technologies, such as low-impact agriculture, have the potential to maintain or even further increase yields, while reducing unintended adverse environmental impacts. The advance of biotechnology (Box I 1) holds promise for increasing the benefits of biodiversity, while at the same time introducing additional concerns over unintended consequences
Equitable sharing of benefits
Poverty and an inequitable distribution of income and assets is both a cause and a consequence of biodiversity loss. The poorest individuals and societies often face the largest relative effects from biodiversity loss, and the lowest incentives to conserve biodiversity. An equitable distribution of income and assets is an important component of a strategy to conserve biodiversity. In particular, an equitable distribution of the benefits of biodiversity conservation is a prerequisite for creating the incentives needed to maintain the Earth's biological wealth. In many cases an equitable sharing of benefits requires local benefit sharing. This is particularly important for conservation projects or for integrated conservation and development projects. Local benefit sharing has the effect of lowering the opportunity cost of forgoing conversion to commercial alternative uses, such as arable agriculture, pasture or industry (Box 12).
Wide-ranging approaches to conservation
Conservation measures require both in situ and ex situ methods (Fig. 14). Effective in situ approaches for the conservation of individual species include legal protection of
Box 10 Economic tools and incentives
Economic and financial policies that could help address local market failures by captur ing for local populations the benefits from goods and services derived from biodiversi ty conservation include:
Lowering forest protection costs. Costs can be reduced by directly involving the local populations in the protection and management of natural ecosystems (as guards, tour guides, collectors of non-timber forest products and scientific samples).
Using water fees as ecosystem conservation Incentives. Local communities derive little benefit from maintaining watersheds, since the principal beneficiaries are located downstream. Water and hydropower pricing that includes a watershed protec tion charge levied upon farmers and urban and industrial users provides a way of com pensating local communities.
Internalizing ecotourism benefits. The portion of ecotourism benefits that flow to the local population can be expanded by engaging local people as guards and tour guides, and by issuing ecotourism franchises to communities and allocating a portion of the ensuing revenues to the development of local employment opportunities.
Reforestation incentives. Land owners who keep their land in forests can receive a tax credit. Since this approach is especially beneficial to large, wealthy owner a system can be devised whereby small-holders can earn tax credits that they can sell to wealthy taxpayers having high taxes to offset.
Differential land use taxes. Categories for classifying land uses can range from environmentally most beneficial (e.g. natural forest) to environmentally most destruc tive (e.g. industrial site). To internalize the environmental cost of habitat conversion, a charge is imposed on land owners when land use is changed from a higher to a lower class.
Environmental performance bands. Environmental bonds shift responsibility for controlling deforestation, monitoring and enforcement to individual producers and consumers who are charged in advance for the potential damage. These bonds can ensure that adequate measures are taken to minimize environmental damage and that funds are available for restoration of environments if compliance is poor.
Forest compacts. Compacts are undertaken by one country with the support of another to engage in policy reforms, conservation, and investment programmes that achieve specified targets of sustainable forest management or preservation in exchange for financial and technology resources. For example, Carbon Offsets agree ments have been established between a power utility company in a developed country and a developing coun" to finance a shift to more sustainable logging practices in exchange for tax credit by the utility for the carbon stored or retained on sites by the funded forestry activity.
Transferable development rights (TORS) and conservation easements. These policy instruments enable a country or private land owner to sell the'right'to convert a natural habitat for a price that fully covers the opportunity cost.
Box 11 Opportunity and concerns raised by biotechnology
Biotechnology can provide important advances in the use of genetic and biological resources for economic gain. It provides a means of using living organisms to produce important chemicals for medicine and industry; it can be harnessed for environmental remediation; and it provides enzymatic reactions used in industrial processes. Biotechnology also provides tools for advancing our understanding of the living world, and thus may aid the assessment and monitoring of biodiversity. lt can contribute greatly to biodiversity conservation in situ and ex 5itu, thereby enhancing our ability to manage biodiversity wisely.
The Convention on Biological Diversity calls for measures to ensure the safe transfer, handling and use of modified organisms resulting from biotechnology. Because of the potential for great benefits from biotechnology, its use is increasing rapidly, and thus questions about its safety have been raised. The direct impacts of biotechnology can be ecological or evolutionary, operating through biological pro cesses, e.g. gene transfer to non-target populations. Many countries have already devised scientific methodologi(.,s for assessing the probability of negative impacts through field and laboratory trials. Although negative impacts cannot be completely ruled out, these methods provide a way of evaluating the risks involved, and therefore should allow maximum benefits to be gained from biotechnology applications.
endangered species, the preparation and implementation of management or recovery plans, and the establishment of protected areas specifically to protect particular species or to protect unique genetic resources such as wild relatives of crop species. Large protected areas have the advantage of protecting large numbers of species at the same time, but can be justified in their own right for their protection of the diver sity of different ecological communities, letting natural processes continue to operate, and thus preserving the natural communities'ability to provide ecosystem services. The proportion of biomes covered by protected areas ranges from less than I % for temperate grasslands and lake ecosystems to nearly I 0% for subtropical alid temperate rain forests and island ecosystems. Table 4 shows the distribution of protected areas by biome type, while Table 5 shows the percentage of African countries' bird species found within protected areas. Countries vary considerably in the proportion and degree to which their land areas are protected. The effectiveness of conservation actions varies dramatically, and the management of protected areas around the world faces serious obstacles. The establishment of areas in which all economic activity is restricted may conflict with the needs of local people, so that park boundaries and regulations are not observed. Many designated protected areas are not effectively managed due to a lack of trained personnel, financial resources or ecological knowledge and as a consequence face serious threats from agricultural expansion, resource extraction, tourism and poaching. Protected areas generally must be seen in the context of overall landscapes and augmented by additional measures, including the preservation of natural corridors
Box 12 Local sharing of the non-use values of biodiversity
Since many of the social values ascribed to biodiversity are'non-market'values, a large discrepancy persists between the private and social values accorded to it. In general, global markets are lacking for many of the values that people place on biodiversity or with the environmental benefits associated with it: for example, carbon storage in forests, or the existence values placed by people in the North on biodiversity of the South. The lack of such global markets means that these values cannot be appropriat ed by the people ofthe South. Furthermore, many existing economic incentives (i.e. subsidies) promote over-harvesting and depletion. For example, some countries con sider land not used for agriculture as 'unproductive'and tax it at higher rates than agri cultural lands. Private and social values can be brought into better alignment by altering the incentive structure to favour conservation and sustainable management. This involves raising the local benefits from diverse ecosystems and lowering the opportunity costs of forgoing the conversion of natural ecosystems to alternatives such as agriculture, pasture or settlement. Local economic benefits from biodiversity can be enhanced by:
More generally, changes in the behaviour and management practices of local people can be encouraged through the use of:
within a matrix of more intensive human uses, and must return some economic benefit to local populations in order to succeed. Fx situ conservation centres arboreta, aquaria, botanic gardens, seed banks, clonal collections, microbial culture collections, field gene banks, forest nurseries, propagation units, tissue and cell cultures, zoological gardens and museums can all help to conserve stocks of both wild and domesticated animals, plants, fungi and microorganisms, but are less able to maintain populations. While ex situ facilities can provide genetic material needed for breeding programmes to improve and maintain domestic plants and animals, serious gaps exist in the coverage of those species that are of known, direct economic importance, par ticularly in the tropics. Exceptions include major crop plants, certain pathogens of humans and crops, and 'model organisms' used in scientific research. Most ex situ
Fig. 14 Conservation measures require both in
situ and ex situ methods (source as Fig. 13).
facilities notably botanic gardens, zoological gardens and aquaria also heighten public awareness of biodiversity and provide material for basic and applied scientific research in such areas as reproductive biology, genetics and systematics. Figure IS shows the inverse relationship between the global distribution of plant species and botanic gardens. All ex situ facilities are potentially vulnerable to pests and diseases, physical damage from fires and floods and economic or policy changes. Reintroduction of species and restoration and rehabilitation of habitats will come to play increasingly important roles in re-establishing biological diversity. They depend on both ex situ and in situ approaches. No menu of methods for sustainable use of biodiversity can ever be completely successful, and we are already faced with the prospect of needing to return ecosystems damaged by unsustainable prac tices to a state where ecological goods and services can be restored to acceptable levels. Methodologies for restoration are showing rapid advances, though technical and ecological challenges still hinder efforts to restore some species, communities and ecosystem services. Setting priorities for restoration and rehabilitation is a major challenge, particularly when these activities may require ongoing subsidies to maintain goods and services at acceptable levels.
Sustainable use of biodiversity
Sustainable use of biodiversity is considered today to be a prerequisite for sustainable social and economic development. Properly done, it ensures the continuing pro
Fig. 15 World distribution of plant species and
botanic gardens (from WWF and IUCN-BGCS,
Botanic Gardens Conservation Strategy. IUCN, Gland).
vision of goods and services from ecosystems and their components. In order to use biodiversity sustainably, it is essential to have a basic understanding of ecosystems, their components, and the social and economic pressures that affect them. Resource management practices that use our knowledge of the processes in intact ecosystems are often more effective and less costly than those that do not. For example, forestry practices that mimic the frequencies of natural disturbances such as fires, appear to offer the best opportunities for maintaining the biodiversity associated with many forest ecosystems. In fisheries, better monitoring of fish stocks offers hope for increasing the sustainability of harvests and the conservation of marine biodiversity. Social and economic measures may be more important than technical measures for ensuring sustainable use. For example, the assignment or recognition of clearly defined property rights and tenure systems is vital to sustainable forestry and fisheries. Of particular concern are equitable measures to transform open access regimes to private, community or other ownership systems to bring to a halt the overexploitation of forest, freshwater and marine ecosystems. Many traditional resource management systems achieve effective conservation of biodiversity and sustainable use of its components. Small-scale farmers using traditional agricultural practices have long created varietal diversity and been stewards of genetic diversity (Fig. 16). Traditional forms of agriculture, particularly in developing countries, are the largest repositories of crop and livestock genetic diversity. On-farm conservation of crop genetic resources in traditional agroecosystems pro-
Fig. 16 Many traditional resource management systems
achieve effective conservation of biodiversity and sustainable
use of its components (from Primack, R.B. 1993. Essentials of
Conservation Biology.
Sinauer Associates, Sunderland, Massachusetts, USA).
vides unique benefits due to the potential for continued, dynamic adaptation of plants to the environment, especially in diversified agricultural areas where crops may be enriched by gene exchange with wild or 'weedy' relatives in fields or adjacent ecosystems. These resources can be lost, however, in regions where conversion to high-input, low-diversity agroecosystems is economically more advantageous. Market mechanisms or funds that compensate farmers for providing this 'service' could in principle reduce the loss of these resources. Tourism and other non-consumptive uses of biodiversity can provide opportu nities for sustainable use, and can also be combined with other uses, such as bioprospecting, so as to generate multiple income streams from single areas or resources. The success of such management schemes often depends on appropriating some of the benefits for the local communities. Appropriate incentives and enforcement of management decisions and policies must be ensured. For example, an appropriate balance between national and local control over resource management is vital to sustainable use of biodiversity in providing goods and services of direct economic benefit. Over-centralizing resource rights has often led to excessive resource harvesting and biodiversity loss. Conversely, similar destructive practices have also resulted from too much local control over resources, particularly among communities without a long traditional attachment to a region or among communities that are confronted by rapid change due to population gi,owth, expanding market forces and cultural breakdown. Finding the appropriate balance depends on the particular cultural, legal, economic, ownership, tenure and biological situations within countries. Wherever the balance lies in a particular case, incentives should be put in place to encourage adoption of the declared management policies, and enforcement of reasonable policies must be clear. No management prescriptions can possibly anticipate all the possible changes in ecological, climatic, social and economic conditions. Hence, flexible techniques are needed for managers to maintain the provision of goods and services and respond to changing social, biological and physical environments, while reducing uncertainty about the functioning of ecosystems and therefore the effectiveness of thei.actions. Adaptive management is an emerging philosophy for integrating these concerns. It has three primary elements:
Importance of research, monitoring and dissemination of information
Enhanced scientific research and monitoring are essential for countries to increase their ability to benefit from and sustainably manage their biodiversity and its components. Particular areas for research and monitoring include:
A considerable amount of inforniation on biodiversity does exist, but is difficult to gain access to, not always because of technological problems, but also because of differing policies on data ownership and control, and institutional rivalries. These policies must be analysed, and if necessary altered in such a way that benefits derived from the use of information help defray costs of providing information services. The rapid developments in information technology have provided new options for information access, use and management. Better software tools in local languages will facilitate the strengthening and decentralization of management systems and provide better support to decision-makers. The increased development of networks is opening new ways of accessing and exchanging information at national and global levels, and the emergence of new tools such as electronic publishing and multimedia will further facilitate the delivery of information. Careful analysis of technological options will help reduce the technology gap between countries and develop more efficient approaches to information management. Figure 17 illustrates how information needs to flow among different users.
Box 13 Monitoring biodiversity
Biological monitoring programmes can evaluate the trends in the status of species, communities and ecological systems over time. The conservation of biodiversity can be enhanced by monitoring programmes, providing a'feed-back loop'that signals to managers and policy-makers the need to make appropriate changes. Monitoring pro grammes should be designed at a scale relevant to the ecological processes being monitored and the pertinent conservation or management questions being asked. Often, regionalor landscape-scale monitoring is necessary to evaluate the aggregate impact on species or ecosystems of local activities or events. Similarly, both a national and a global scale are needed to understand and effectively manage such species as migratory birds. Monitoring programmes need to be evaluated over time to refine techniques and to test new technologies.
Remote sensing from satellites and aircraft can be used to monitor changes in the extent of land cover, the distribution of major vegetation types, and the function ing of some types of ecosystems (Fig. 1 8). It can be used to stratify ecological sam pling and to identify situations where more detailed, ground-based monitoring is war ranted. Carefully chosen, indicator species provide an efficient means for monitoring the status and trends in the populations of some other species and certain ecosystem services. However, no small subset of indicator species can be used to monitor all aspects of biodiversity relevant to management.
Building national capacity and public awareness
Human, institutional, financial and infrastructure components are often scarce in much of the world, but can be expanded with well focused investment and policy support. In many countries the existing telecommunications infrastructure is inadequate for the dissemination of information through electronic networks, and its improvement is an urgent priority. Committed and skilled people are the key to the successful maintenance and sustainable use of biodiversity. Training for the people who will manage protected areas, conduct biodiversity inventories and develop and safeguard ex situ collections must be provided through appropriate mechanisms. Of equal importance is to reorientate the training of the next generation of professionals who will manage biological resources such as forests, fisheries and agricultural lands in order to empha size the benefits of maintaining adequate levels of biodiversity. Because of the continued importance of scientific research and monitoring, it will be particularly important to have trained scientists in all countries. The current distribution of expertise is strongly skewed towards the northern industrialized countries. Training and exchange programmes should therefore concentrate on producing more skilled scientists in the developing world, and providing them with the necessary research and management tools. Important though scientific research and monitoring is, it is not sufficient by itself. The successful implementation of strategies to use biodiversity sustainably is
Fig. 17 Information flow on Biodiversity (from
WRI/IUCN/UNEP, 1992. Global Biodiversity Strategy: Guidelines
foraction to Save, Study and Use Earth's Biotic Wealth Sustainably
and Equitably. World Resources Institute, Washington DC, The World
Conservation Union, Gland, Switzerland, and the United Nations
Environment Programme, Nairobi, Kenya).
often constrained by lack of public understanding and support. Broad constituencies of informed people need to be built up, and local and national experience and knowledge will play a critical role in developing well-informed citizenries. Governments themselves need to become better informed about biodiversity so that they will be able to make more informed decisions concerning the management of their natural resources.
Fig 18: Remote sensing can be used to monitor changes in the vegetation (UNEP/GRID).