Ecosystems and Human Well-being: Biodiversity Synthesis: Key Questions on Biodiversity in the Millennium Ecosystem Assessment

Published: August 19, 2008, 3:13 pm

Updated: September 4, 2011, 6:24 am

Source: Millennium Ecosystem Assessment

Topics:

Human Health (main) Environmental Monitoring (main) Biodiversity (main) Environmental Assessment (main) Ecology (main) International Environmental Issues (main)

This is part of the Millennium Ecosystem Assessmentt report Ecosystems and Human Well-Being: Biodiversity Synthesis

Extended Writing Team: MA Coordinating Lead Authors, Lead Authors, Contributing Authors, and Sub-global Assessment Coordinators

Review Editors: José Sarukhán and Anne Whyte (co-chairs) and MA Board of Review Editors

Biodiversity: What is it, where is it, and why is it important?

• Biodiversity is the variability among living organisms from all sources, including terrestrial, marine (Biome), and other aquatic eco­systems and the ecological complexes of which they are part; this includes diversity within species, between species, and of ecosystems.
• Biodiversity forms the foundation of the vast array of eco­system services that critically contribute to human well-being.
• Biodiversity is important in human-managed as well as natu­ral ecosystems.
• Decisions humans make that influence biodiversity affect the well-being of themselves and others.

What Is Biodiversity?

Biodiversity is the foundation of ecosystem services to which human well-being is intimately linked. No feature of Earth is more complex, dynamic, and varied than the layer of living organisms that occupy its surfaces and its seas, and no feature is experiencing more dramatic change at the hands of humans than this extraordinary, singularly unique feature of Earth. This layer of living organisms—the biosphere—through the collective meta­bolic activities of its innumerable plants, animals, and microbes physically and chemically unites the atmosphere, geosphere, and hydrosphere into one environmental system within which millions of species, including humans, have thrived. Breathable air, potable water, fertile soils, productive lands, bountiful seas, the equitable climate of Earth’s recent history, and other ecosystem services (see Box 1.1 and Key Question 2) are manifes­tations of the workings of life. It follows that large-scale human influences over this biota have tremendous impacts on human well-being. It also follows that the nature of these impacts, good or bad, is within the power of humans to influence (CF2).

Defining Biodiversity

Biodiversity is defined as “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.” The importance of this definition is that it draws attention to the many dimensions of biodiversity. It explicitly recognizes that every biota can be characterized by its taxonomic, ecological, and genetic diversity and that the way these dimensions of diversity vary over space and time is a key feature of biodiversity. Thus only a multidi­mensional assessment of biodiversity can provide insights into the relationship between changes in biodiversity and changes in ecosystem functioning and ecosystem services (CF2).

Biodiversity includes all ecosystems—managed or unmanaged. Sometimes biodiversity is presumed to be a relevant feature of only unmanaged ecosystems, such as wildlands, nature preserves, or national parks. This is incorrect. Managed systems—be they planta­tions, farms, croplands, aquaculture sites, rangelands, or even urban parks and urban ecosystems—have their own biodiversity. Given that cultivated systems alone now account for more than 24% of Earth’s terrestrial surface, it is critical that any decision concerning biodiversity or ecosystem services address the maintenance of biodi­versity in these largely anthropogenic systems (C26.1).

Measuring Biodiversity: Species Richness and Indicators

In spite of many tools and data sources, biodiversity remains difficult to quantify precisely. But precise answers are seldom needed to devise an effective understanding of where biodiversity is, how it is changing over space and time, the drivers responsible for such change, the consequences of such change for ecosystem services and human well-being, and the response options avail­able. Ideally, to assess the conditions and trends of biodiversity either globally or sub-globally, it is necessary to measure the abun­dance of all organisms over space and time, using taxonomy (such as the number of species), functional traits (for example, the eco­logical type such as nitrogen-fixing plants like legumes versus non-nitrogen-fixing plants), and the interactions among species that affect their dynamics and function (predation, parasitism, compe­tition, and facilitation such as pollination, for instance, and how strongly such interactions affect ecosystems). Even more important would be to estimate turnover of biodiversity, not just point esti­mates in space or time. Currently, it is not possible to do this with much accuracy because the data are lacking. Even for the taxo­nomic component of biodiversity, where information is the best, considerable uncertainty remains about the true extent and changes in taxonomic diversity (C4).

There are many measures of biodiversity; species richness (the number of species in a given area) represents a single but important metric that is valuable as the common currency of the diversity of life—but it must be integrated with other metrics to fully capture biodiversity. Because the multidimensionality of biodiversity poses formidable challenges to its measurement, a variety of surrogate or proxy measures are often used. These include the species richness of specific taxa, the number of distinct plant functional types (such as grasses, forbs, bushes, or trees), or the diversity of distinct gene sequences in a sample of microbial DNA taken from the soil. Species- or other taxon-based measures of biodiversity, however, rarely capture key attributes such as vari­ability, function, quantity, and distribution—all of which provide insight into the roles of biodiversity. (See Box 1.2.)

Ecological indicators are scientific constructs that use quanti­tative data to measure aspects of biodiversity, ecosystem condi­tion, services, or drivers of change, but no single ecological indicator captures all the dimensions of biodiversity (C2.2.4). (See Box 1.3.) Ecological indicators form a critical component of monitoring (Environmental monitoring and assessment), assessment, and decision-making and are designed to communicate information quickly and easily to policy-makers. In a similar manner, economic indicators such as GDP are highly influential and well understood by decision-makers. Some envi­ronmental indicators, such as global mean temperature and atmo­spheric CO₂ concentrations, are becoming widely accepted as measures of anthropogenic effects on global climate. Ecological indicators are founded on much the same principles and therefore carry with them similar pros and cons (C2.2.4). (See Box 1.4.)

Where Is Biodiversity?

Biodiversity is essentially everywhere, ubiquitous on Earth’s surface and in every drop of its bodies of water. The virtual omnipresence of life on Earth is seldom appreciated because most organisms are small (<5 centimeters); their presence is sparse, ephemeral, or cryptic, or, in the case of microbes, they are invisible to the unaided human eye (CF2).

Documenting spatial patterns in biodiversity is difficult because taxonomic, functional, trophic, genetic, and other dimensions of biodiversity have been relatively poorly quanti­fied. Even knowledge of taxonomic diversity, the best known dimension of biodiversity, is incomplete and strongly biased toward the species level, megafauna, temperate systems, and components used by people. (See Figure 1.1.) This results in significant gaps in knowledge, especially regarding the status of tropical systems, marine and freshwater biota, plants, inverte­brates, microorganisms, and subterranean biota. For these rea­sons, estimates of the total number of species on Earth range from 5 million to 30 million. Irrespective of actual global species richness, however, it is clear that the 1.7–2 million species that have been formally identified represent only a small portion of total species richness. More-complete biotic inventories are badly needed to correct for this deficiency (C4).

Spatial Patterns of Biodiversity: Hotspots, Biomes,^[1] Biogeographic Realms, Ecosystems, and Ecoregions

While the data to hand are often insufficient to provide accu­rate pictures of the extent and distribution of all components of biodiversity, there are, nevertheless, many patterns and tools that decision-makers can use to derive useful approximations for both terrestrial and [[marine (Biome)] ecosystems]. North-temperate regions often have usable data on spatial distributions of many taxa, and some groups (such as birds, mammals, reptiles, plants, butterflies, and dragonflies) are reasonably well documented globally. Biogeographic principles (such as gradients in species richness associated with latitude, temperature, salinity, and water depth) or the use of indicators can supplement available biotic inventories. Global and sub-global maps of species richness, sev­eral of which are provided in the MA reports Current State and Trends and Scenarios, provide valuable pictures of the distribution of biodiversity (C4, S10).

Box 1.2. Measuring and Estimating Biodiversity: More than Species Richness

Measurements of biodiversity seldom capture all its dimensions, and the most common measure—species richness—is no excep­tion. While this can serve as a valuable surrogate measure for other dimensions that are difficult to quantify, there are several limitations associated with an emphasis on species. First, what constitutes a species is not often well defined. Second, although native species richness and ecosystem functioning correlate well, there is consid­erable variability surrounding this relationship. Third, species may be taxonomically similar (in the same genus) but [[ecological]ly] quite dis­tinct. Fourth, species vary extraordinarily in abundance; for most bio­logical communities, only a few are dominant, while many are rare. Simply counting the number of species in an ecosystem does not take into consideration how variable each species might be or its contribution to ecosystem properties. For every species, several properties other than its taxonomy are more valuable for assess­ment and monitoring. These properties include measures of genetic and ecological variability, distribution and its role in ecosystem pro­cesses, dynamics, trophic position, and functional traits. In practice, however, variability, dynamics, trophic position, and functional attributes of many species are poorly known. Thus it is both necessary and useful to use surrogate, proxy, or indicator measures based on the taxonomy or genetic information. Important attributes missed by species or taxon-based measures of diversity include: abundance—how much there is of any one type. For many pro­visioning services (such as food, fresh water, fiber), abundance mat­ters more than the presence of a range of genetic varieties, species, or ecosystem types. variation—the number of different types over space and time. For understanding population persistence, the number of different varieties or races in a species or variation in genetic composition among individuals in a population provide more insight than species richness. distribution—where quantity or variation in biodiversity occurs. For many purposes, distribution and quantity are closely related and are therefore generally treated together under the heading of quan­tity. However, quantity may not always be sufficient for services: the location, and in particular its availability to the people that need it, will frequently be more critical than the absolute volume or biomass of a component of biodiversity. Finally, the importance of variability and quantity varies, depending on the level of biodiversity measured. (See Table.)

Most macroscopic organisms have small, often clustered geo­graphical ranges, leading to centers of both high diversity and endemism, frequently concentrated in isolated or topographi­cally variable regions (islands, mountains, peninsulas). A large proportion of the world’s terrestrial biodiversity at the species level is concentrated in a small part of the world, mostly in the tropics. Even among the larger and more mobile species, such as terrestrial vertebrates, more than one third of all species have ranges of less than 1,000 square kilometers. In contrast, local and regional diversity of microorganisms tends to be more similar to large-scale and global diversity because of their large population size, greater dispersal, larger range sizes, and lower levels of regional species clustering (C4.2.3).

Biomes and biogeographic realms provide broad pictures of the distribution of functional diversity. Functional diversity (the variety of different ecological functions in a community independent of its taxonomic diversity) shows patterns of associ­ations (biota typical of wetlands, forests, grasslands, estuaries, and so forth) with geography and climate known as biomes (see Figure 1.2), with ecosystems and ecoregions being smaller divisions within biomes (see Figure 1.3). These can be used to provide first-order approximations of both expected functional diversity as well as possible changes in the distribution of these associations should environmental conditions change.

Box 1.3. Ecological Indicators and Biodiversity

The National Research Council in the United States identified three categories of ecological indicators, none of which adequately assesses the many dimensions of biodiversity: Ecosystem extent and status (such as land cover and land use) indicates the coverage of ecosystems and their ecologi­cal attributes. Ecological capital, further divided into biotic raw material (such as total species richness) and abiotic raw materials (such as soil nutrients), indicates the amount of resources available for providing services. Ecological functioning (such as lake trophic status) measures the performance of ecosystems. Care must therefore be taken not to apply ecological indica­tors to uses they were not intended for, especially when assess­ing biodiversity. For example, biotic raw ecological capital measures the amount and variability of species within a defined area (C2.2.4). This may seem related to biodiversity, but it mea­sures only taxonomic diversity. As such, this indicator does not necessarily capture many important aspects of biodiversity that are significant for the delivery of ecosystem services. The most common ecological indicator, total species rich­ness, is a case in point. TSR only partially captures ecosystem services. It does not differentiate among species in terms of sen­sitivity or resilience to change, nor does it distinguish between species that fulfill significant roles in the ecosystem (such as pol­linators and decomposers) and those that play lesser roles. That is, all species are weighted equally, which can lead assigning equal values to areas that have quite different biota. Moreover, the value of TSR depends on the definition of the area over which it was measured and may scale neither to smaller nor to larger areas. Finally, TSR does not differentiate between native and non-native species, and the latter often include exotic (Exotic species), introduced, or invasive species that frequently disrupt key ecosystem services. Ecosystem degradation by human activities may temporarily increase species richness in the limited area of the impact due to an increase in exotic or weedy species, but this is not a relevant increase in biodiversity (C2.2.4). Given the limitations of ecological indicators to serve as ade­quate indicators of biodiversity, work is urgently needed to develop a broader set of biodiversity indicators that are aligned against valued aspects of biodiversity. With the exception of diversity indices based on taxonomic or population measures, little attention has been paid to the development of indicators that capture all the dimensions of biodiversity (C4.5.1), although see Key Question 6 and C4.5.2 for more on indicators for the “2010 biodiversity target.”

Box 1.4. Criteria for Effective Ecological Indicators

An effective ecological indicator should: Provide information about changes in important processes Be sensitive enough to detect important changes but not so sensitive that signals are masked by natural variability Be able to detect changes at the appropriate temporal and spatial scale without being overwhelmed by variability Be based on well-understood and generally accepted con­ceptual models of the system to which it is applied Be based on reliable data that are available to assess trends and are collected in a relatively straightforward process Be based on data for which monitoring (Environmental monitoring and assessment) systems are in place Be easily understood by policy-makers

Temporal Patterns of Biodiversity: Background Rates of Extinction and Biodiversity Loss

Knowledge of patterns of biodiversity over time allow for only very approximate estimates of background rates of extinc­tion or of how fast species have become extinct over geological time. Except for the last 1,000 years, global biodiversity has been relatively constant over most of human history, but the history of life is characterized by considerable change. The estimated mag­nitude of background rates of extinction is roughly 0.1–1.0 extinctions per million species per year. Most measurements of this rate have come from assessing the length of species’ lifetimes through the fossil record: these range over 0.5–13 million years, and possibly 0.2–16 million years. These data probably underes­timate background extinction rates because they are necessarily largely derived from taxa that are abundant and widespread in the fossil record (C4.4.2). Current rates of extinction are dis­cussed in Key Question 3.

A mismatch exists between the dynamics of changes in natu­ral systems and human responses to those changes. This mis­match arises from the lags in ecological responses, the complex feedbacks between socioeconomic and ecological systems, and the difficulty of predicting thresholds. Multiple impacts (espe­cially the addition of climate change to the mix of forcing func­tions) can cause thresholds, or rapid and dramatic changes in ecosystem function even though the increase in environmental stress has been small and constant over time. Understanding such thresholds requires having long-term records, but such records are usually lacking or monitoring (Environmental monitoring and assessment) has been too infrequent, of the wrong periodicity, or too localized to provide the necessary data to analyze and predict threshold behavior (C28, S3.3.1).

Shifts to different regimes may cause rapid substantial changes in biodiversity, ecosystem services, and human well-being. Regime shifts have been commonly documented in pelagic systems due to thresholds related to temperature regimes and overexploitation (C19.2.1, C18). Some regime shifts are essentially irreversible, such as coral reef ecosystems that undergo sudden shifts from coral-dominated to algal-dominated reefs (C19.5). The trigger for such phase shifts usually includes increased nutrient inputs leading to eutrophic conditions and removal of herbivorous fishes that maintain the balance between corals and algae. Once the thresholds (both an upper and a lower threshold) for the two ecological processes of nutrient loading and herbivory are passed, the phase shift occurs quickly (within months), and the resulting ecosystem—though stable—is less productive and less diverse. Consequently, human well-being is affected not only by reductions in food supply and decreased income from reef-related industries (diving and snorkeling, aquarium fish collecting, and so on), but also by increased costs due to diminished ability of reefs to protect shorelines. (Algal reefs are more prone to being broken up in storm events, leading to shoreline erosion and seawater breaches of land) (C19.3). Such phase shifts have been documented in Jamaica, elsewhere in the Caribbean, and in Indo-Pacific reefs (C19, S3.3.1).

Introduced invasive species can act as a trigger for dramatic changes in ecosystem structure, function, and delivery of ser­vices. For example, the introduction of the carnivorous cteno­phore Mnemiopsis leidyi (a jellyfish-like animal) in the Black Sea caused the loss of 26 major fisheries (Fisheries and aquaculture) species and has been impli­cated (along with other factors) in the subsequent growth of the oxygen-deprived “dead” zone (C19.2.1).

Biodiversity and Its Link to Ecosystem Services

Biodiversity plays an important role in ecosystem functions that provide supporting, provisioning, regulating, and cultural services. These services are essential for human well-being. However, at present there are few studies that link changes in biodiversity with changes in ecosystem functioning to changes in human well-being. Protecting the Catskill watersheds that provide drinking water for New York City is one case where safeguarding ecosystem services paid a dividend of several billion dollars. Further work that demonstrates the links between biodi­versity, regulating and supporting services, and human well-being is needed to show this vital but often unappreciated value of biodiversity (C4, C7, C11).

Species composition matters as much or more than species richness when it comes to ecosystem services. Ecosystem func­tioning, and hence ecosystem services, at any given moment in time is strongly influenced by the ecological characteristics of the most abundant species, not by the number of species. The rela­tive importance of a species to ecosystem functioning is deter­mined by its traits and its relative abundance. For example, the traits of the dominant or most abundant plant species—such as how long they live, how big they are, how fast they assimilate carbon and nutrients, how decomposable their leaves are, or how dense their wood is—are usually the key species drivers of an ecosystem’s processing of matter and energy. Thus conserving or restoring the composition of biological communities, rather than simply maximizing species numbers, is critical to maintaining ecosystem services (C11.2.1, C11.3).

Local or functional extinction, or the reduction of popula­tions to the point that they no longer contribute to ecosystem functioning, can have dramatic impacts on ecosystem services. Local extinctions (the loss of a species from a local area) and functional extinctions (the reduction of a species such that it no longer plays a significant role in ecosystem function) have received little attention compared with global extinctions (loss of all individuals of a species from its entire range). Loss of ecosys­tem functions, and the services derived from them, however, occurs long before global extinction. Often, when the function­ing of a local ecosystem has been pushed beyond a certain limit by direct or indirect biodiversity alterations, the ecosystem-service losses may persist for a very long time (C11).

Changes in biotic interactions among species—predation, parasitism, competition, and facilitation—can lead to dispro­portionately large, irreversible, and often negative alterations of ecosystem processes. In addition to direct interactions, such as predation, parasitism, or facilitation, the maintenance of ecosys­tem processes depends on indirect interactions as well, such as a predator preying on a dominant competitor such that the dominant is suppressed, which permits subordinate species to coexist. Interactions with important consequences for ecosystem services include pollination; links between plants and soil com­munities, including mycorrhizal fungi and nitrogen-fixing micro­organisms; links between plants and herbivores (Herbivory) and seed dispersers; interactions involving organisms that modify habitat conditions (beavers that build ponds, for instance, or tussock grasses that increase fire frequency); and indirect interactions involving more than two species (such as top predators, parasites, or pathogens that control herbivores and thus avoid overgrazing of plants or algal communities) (C11.3.2).

Many changes in ecosystem services are brought about by the removal or introduction of organisms in ecosystems that dis­rupt biotic interactions or ecosystem processes. Because the net­work of interactions among species and the network of linkages among ecosystem processes are complex, the impacts of either the removal of existing species or the introduction of new species are difficult to anticipate (C11). (See Table 1.1.)

As in terrestrial and aquatic communities, the loss of individ­ual species involved in key interactions in [[marine (Biome)] ecosystems] can also influence ecosystem processes and the provisioning of ecological services. For example, [[coral reef]s] and the ecosystem services they provide are directly dependent on the maintenance of some key interactions between animals and algae. As one of the most species-rich communities on Earth, coral reefs are responsible for maintaining a vast storehouse of genetic and bio­logical diversity. Substantial ecosystem services are provided by coral reefs—such as habitat construction, nurseries, and spawn­ing grounds for fish; nutrient cycling and carbon and nitrogen fixing in nutrient-poor environments; and wave buffering and sediment stabilization. The total economic value of reefs and associated services is estimated as hundreds of millions of dollars. Yet all coral reefs are dependent on a single key biotic interaction: symbiosis with algae. The dramatic effects of climate change and variability (such as El Niño oscillations) on coral reefs are medi­ated by the disruption of this symbiosis (C11.4.2).

Supporting Services

Biodiversity affects key ecosystem processes in terrestrial eco­systems such as biomass production, nutrient and water cycling, and soil formation and retention—all of which govern and ensure supporting services (high certainty). The relationship between biodiversity and supporting ecosystem services depends on composition, relative abundance, functional diversity, and, to a lesser extent, taxonomic diversity. If multiple dimensions of biodiversity are driven to very low levels, especially trophic or functional diversity within an ecosystem, both the level and sta­bility (for instance, biological insurance) of supportive services may decrease (CF2, C11). (See Figure 1.4.)

Region-to-region differences in ecosystem processes are driven mostly by climate, resource availability, disturbance, and other extrinsic factors and not by differences in species richness (high certainty). In natural ecosystems, the effects of abiotic and land use drivers on ecosystem services are usually more important than changes in species richness. Plant productivity, nutrient retention, and resistance to invasions and diseases sometimes grow with increasing species numbers in experimental ecosystems that have been reduced to low levels of biodiversity. In natural ecosystems, however, these direct effects of increasing species richness are usually overridden by the effects of climate, resource availability, or disturbance regime (C11.3).

Even if losses of biodiversity have small short-term impacts on ecosystem function, such losses may reduce the capacity of ecosystems for adjustment to changing environments (that is, ecosystem stability or resilience, resistance, and biological insurance) (high certainty). The loss of multiple components of biodiversity, especially functional and ecosystem diversity at the landscape level, will lead to lowered ecosystem stability (high certainty). Although the stability of an ecosystem depends to a large extent on the characteristics of the dominant species (such as life span, growth rate, or regeneration strategy), less abundant species also contribute to the long-term preservation of ecosystem functioning. There is evidence that a large number of resident species, including those that are rare, may act as “insurance” that buffers ecosystem processes in the face of changes in the physical and biological environment (such as changes in precipitation, temperature, pathogens) (C11.3.2). As tragically illustrated by social conflict and humanitarian crisis over droughts, floods, and other ecosystem collapses, stability of ecosystems underpins most components of human well-being, including health, security, satisfactory social relations, and freedom of choice and action (C6; see also Key Question 2).

Regulating Services

Invasion resistance

The preservation of the number, types, and relative abun­dance of resident species can enhance invasion resistance in a wide range of natural and semi-natural ecosystems (medium cer­tainty). Although areas of high species richness (such as biodiver­sity hot spots) are more susceptible to invasion than species-poor areas, within a given habitat the preservation of its natural species pool appears to increase its resistance to invasions by non-native species. This is also supported by evidence from several marine ecosystems, where decreases in the richness of native taxa were correlated with increased survival and percent cover of invading species (C11.3.1, C11.4.1).

Pollination

Pollination is essential for the provision of plant-derived eco­system services, yet there have been worldwide declines in pol­linator diversity (medium certainty). Many fruits and vegetables require pollinators, thus pollination services are critical to the production of a considerable portion of the vitamins and miner­als in the human diet. Although there is no assessment at the continental level, documented declines in more-restricted geo­graphical areas include mammals (lemurs and bats, for example) and birds (hummingbirds and sunbirds, for instance), bumblebees in Britain and Germany, honeybees in the United States and some European countries, and butterflies in Europe. The causes of these declines are multiple, but habitat destruction and the use of pesticide are especially important. Estimates of the global annual monetary value of pollination vary widely, but they are in the order of hundreds of billions of dollars (C11.3.2, Box C11.2).

Climate regulation

Biodiversity influences climate at local, regional, and global scales, thus changes in land use and land cover that affect biodi­versity can affect climate. The important components of biodi­versity include plant functional diversity and the type and distribution of [[habitat]s] across landscapes. These influence the capacity of [[terrestrial] ecosystems] to sequester carbon, albedo (proportion of incoming radiation from the Sun that is reflected by the land surface back to space), evapotranspiration, tempera­ture, and fire regime—all of which influence climate, especially at the landscape, ecosystem, or biome levels. For example, forests have higher evapotranspiration than other ecosystems, such as grasslands, because of their deeper roots and greater leaf area. Thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems. In the Amazon, for example, 60% of precipitation comes from water transpired by upwind ecosystems (C11.3.3).

In addition to biodiversity within habitats, the diversity of habitats in a landscape exerts additional impacts on climate across multiple scales. Landscape-level patches (>10 kilometers in diameter) that have lower albedo and higher surface temperature than neighboring patches create cells of rising warm air above the patch (convection). This air is replaced by cooler moister air that flows laterally from adjacent patches (advection). Climate models suggest that these landscape-level effects can substantially modify local-to-regional climate. In Western Australia, for example, the replacement of native heath vegetation (Land-cover) by wheatlands increased regional albedo. As a result, air tended to rise over the dark (more solar-absorptive and therefore warmer) heathland, drawing moist air from the wheatlands to the heathlands. The net effect was a 10% increase in precipitation over heathlands and a 30% decrease in precipitation over croplands (C11.3.3).

Some components of biodiversity affect carbon sequestration and thus are important in carbon-based climate change mitiga­tion when afforestation, reforestation, reduced deforestation, and biofuel plantations are involved (high certainty). Biodiversity affects carbon sequestration primarily through its effects on spe­cies characteristics, which determine how much carbon is taken up from the atmosphere (assimilation) and how much is released into it (decomposition, combustion). Particularly important are how fast plants can grow, which governs carbon inputs, and woodiness, which enhances carbon sequestration because woody plants tend to contain more carbon, live longer, and decompose more slowly than smaller herbaceous plants. Plant species also strongly influence carbon loss via decomposition and their effects on disturbance. Plant traits also influence the probability of disturbances such as fire, windthrow, and human harvest, which temporarily change forests from accumulating carbon to releas­ing it (C11.3.3).

The major importance of marine biodiversity in climate reg­ulation appears to be via its effect on biogeochemical cycling and carbon sequestration. The ocean, through its sheer volume and links to the terrestrial biosphere, plays a huge role in cycling of almost every material involved in biotic processes. Of these, the anthropogenic effects on carbon (Carbon cycle) and nitrogen cycling are especially prominent. Biodiversity influences the effectiveness of the biological pump that moves carbon from the surface ocean and sequesters it in deep waters and sediments. Some of the car­bon that is absorbed by marine photosynthesis and transferred through food webs to grazers sinks to the deep ocean as fecal pellets and dead cells. The efficiency of this trophic transfer and therefore the extent of carbon sequestration is sensitive to the species richness and composition of the plankton community (C11.4.3).

Pest, disease, and pollution control

The maintenance of natural pest control services, which benefits food security, rural household incomes, and national incomes of many countries, is strongly dependent on biodiver­sity. Yields of desired products from agroecosystems may be reduced by attacks of animal herbivores (Herbivory) and microbial patho­gens, above and below ground, and by competition with weeds. Increasing associated biodiversity with low-diversity agroecosys­tems, however, can enhance biological control and reduce the dependency and costs associated with biocides. Moreover, high-biodiversity agriculture has cultural and aesthetic value and can reduce many of the externalized costs of irrigation, fertilizer, pesticide, and herbicide inputs associated with monoculture agriculture (C11.3.4, Boxes C11.3 and C11.4).

The marine microbial community provides critical detoxifi­cation services, but how biodiversity influences them is not well understood. There is very little information on how many species are necessary to provide detoxification services, but these services may critically depend on one or a few species. Some marine organisms provide the ecosystem service of filtering water and reducing effects of [[eutrophic]ation]. For example, American oysters in Chesapeake Bay were once abundant but have sharply declined—and with them, their filtering ecosystem services. Areas like the Chesapeake might have much clearer water if large populations of filtering oysters could be reintroduced. Some marine microbes can degrade toxic hydrocarbons, such as those in an oil spill, into carbon and water, using a process that requires oxygen. Thus this service is threatened by nutrient pollution, which generates oxygen deprivation (C11.4.4).

Why is biodiversity loss a concern?

• Biodiversity is essential for ecosystem services and hence for human well-being. Biodiversity goes beyond the provisioning for material welfare and livelihoods to include security, resil­iency, social relations, health, and freedoms and choices. Some people have benefited over the last century from the conversion of natural ecosystems to human-dominated ecosystems and from the exploitation of biodiversity. At the same time, however, these losses in biodiversity and associated changes in ecosys­tem services have caused other people to experience declining well-being, with some social groups being pushed into poverty.

Main Links among Biodiversity, Ecosystem Services, and Various Constituents of Human Well-being

The MA identifies biodiversity and the many ecosystem services that it provides as a key instrumental and constitutive factor determining human well-being. The MA findings support, with high certainty, that biodiversity loss and deteriorating ecosystem services contribute—directly or indirectly—to worsening health, higher food insecurity, increasing vulnerability, lower material wealth, worsening social relations, and less freedom for choice and action.

Food Security

Biological diversity is used by many rural communities directly as an insurance and coping mechanism to increase flex­ibility and spread or reduce risk in the face of increasing uncer­tainty, shocks, and surprises. The availability of this biological “safety net” has increased the security and resilience of some local communities to external economic and ecological perturbations, shocks, or surprises (C6.2.2, C8.2). In a world where fluctuating commodity prices are more the norm than the exception, eco­nomic entitlements of the poor are increasingly becoming precar­ious. The availability of an ecosystem-based food security net during times when economic entitlements are insufficient to pur­chase adequate nourishment in the market provides an important insurance program (C8.1, C6.7).

Coping mechanisms based on indigenous plants are particu­larly important for the most vulnerable people, who have little access to formal employment, land, or market opportunities (C6). For example, investigations of two dryland sites in Kenya and Tanzania report local communities using wild indigenous plants to provide alternative sources of food when harvests failed or when sudden expenses had to be met (such as a hospital bill). (See Table 2.1.)

Another pathway through which biodiversity can improve food security is the adoption of farming practices that maintain and make use of agricultural biodiversity. Biodiversity is impor­tant to maintaining agricultural production. Wild relatives of domestic crops provide genetic variability that can be crucial for overcoming outbreaks of pests and pathogens and new environ­mental stresses. Many agricultural communities consider increased local diversity a critical factor for the long-term pro­ductivity and viability of their agricultural systems. For example, interweaving multiple varieties of rice in the same paddy has been shown to increase productivity by lowering the loss from pests and pathogens.

Vulnerability

The world is experiencing an increase in human suffering and economic losses from natural disasters over the past sev­eral decades. Mangrove forests and [[coral reef]s]—a rich source of biodiversity—are excellent natural buffers against floods and storms. Their loss or reduction in coverage has increased the severity of flooding on coastal communities. Floods affect more people (140 million per year on average) than all other natural or technological disasters put together. Over the past four decades, the number of “great” disasters has increased by a factor of four, while economic losses have increased by a factor of ten. During the 1990s, countries low on the Human Development Index experienced about 20% of the hazard events and reported over 50% of the deaths and just 5% of economic losses. Those with high rankings on the index accounted for over 50% of the total economic losses and less than 2% of the deaths (C6, R11, C16).

A common finding from the various sub-global assessments was that many people living in rural areas cherish and promote ecosystem variability and diversity as a risk management strategy against shocks and surprises (SG11). They maintain a diversity of ecosystem services and are skeptical about solutions that reduce their options. The sub-global assessments found that diversity of species, food, and landscapes serve as “savings banks” that rural communities use to cope with change and ensure sustainable livelihoods (see Peruvian, Portuguese, Costa Rican, and India sub-global assessments).

Health

An important component of health is a balanced diet. About 7,000 species of plants and several hundred species of animals have been used for human food consumption at one time or another. Some indigenous and traditional communities currently consume 200 or more species. Wild sources of food remain par­ticularly important for the poor and landless to provide a some­what balanced diet (C6, C8.2.2). Overexploitation of marine fisheries worldwide, and of bushmeat in many areas of the trop­ics, has lead to a reduction in the availability of wild-caught ani­mal protein, with serious consequences in many countries for human health (C4.3.4).

Human health, particularly risk of exposure to many infec­tious diseases, may depend on the maintenance of biodiversity in natural ecosystems. On the one hand, a greater diversity of wildlife species might be expected to sustain a greater diversity of pathogens that can infect humans. However, evidence is accumu­lating that greater wildlife diversity may decrease the spread of many wildlife pathogens to humans. The spread of Lyme disease, the best-studied case, seems to be decreased by the maintenance of the biotic integrity of natural ecosystems (C11, C14).

Energy Security

Wood fuel provides more than half the energy used in developing countries. Even in industrial countries such as Swe­den and the United States, wood supplies 17% and 3% of total energy consumption respectively. In some African countries, such as Tanzania, Uganda, and Rwanda, wood fuel accounts for 80% of total energy consumption (SG-SAfMA). In rural areas, 95% is consumed in the form of firewood, while in urban areas 85% is in the form of charcoal. Shortage of wood fuel occurs in areas with high population density without access to alternative and affordable energy sources. In some provinces of Zambia where population densities exceed the national average of 13.7 persons per square kilometer, the demand for wood has already surpassed local supply. In such areas, people are vulnerable to illness and malnutrition because of the lack of resources to heat homes, cook food, and boil water. Women and children in rural poor communities are the ones most affected by wood fuel scarcity. They must walk long distances searching for fire­wood and therefore have less time for tending crops and school (C9.4).

Provision of Clean Water

The continued loss of cloud forests and the destruction of watersheds reduce the quality and availability of water supplied to household use and agriculture. The availability of clean drinking water is a concern in dozens of the world’s largest cities (C27). In one of the best documented cases, New York City took steps to protect the integrity of watersheds in the Catskills to ensure continued provision of clean drinking water to 9 million people. Protecting the ecosystem was shown to be far more cost-effective than building and operating a water filtration plant. New York City avoided $6–8 billion in expenses by protecting its watersheds (C7, R17).

Social Relations

Many cultures attach spiritual and religious values to ecosys­tems or their components such as a tree, hill, river, or grove (C17). Thus loss or damage to these components can harm social relations—for example, by impeding religious and social ceremo­nies that normally bind people. (See Box 2.1.) Damage to ecosys­tems, highly valued for their aesthetic, recreational, or spiritual values can damage social relations, both by reducing the bonding value of shared experience as well as by causing resentment toward groups that profit from their damage (S11, SG10).

Box 2.1. Social Consequences of Biodiversity Degradation (SG-SAfMA)

The basic needs of the AmaXhosa people in South Africa are met by ecosystem services, including fuelwood, medicinal plants, build­ing materials, cultural species, food supplements, and species of economic value. When asked by researchers about their relation­ship with the natural environment, a local responded “I am entirely dependent on [environment]. Everything that I need comes from this environment” and “environment will be important for­ever because if you have something from [environment] it does encourage you to love [environment].” Respondents often described positive emotional and physical symptoms when [environment] is healthy: “When [environment] is healthy, my body and spirit is also happy.” And when describ­ing people’s feelings toward a healthy environment, a respondent stated that “people love such an environment. They really adore it. Such an environment makes them feel free.” In addition, respon­dents described the feelings of peace when walking in the bush and how they would go into the natural environment to pray. The beliefs and traditions of the AmaXhosa play an important role in guiding resource use and management and encouraging values to be place-centered. The ancestors are central to this cosmology, where the very identity of a Xhosa person is based on performing traditions and rituals for ancestors. The majority of respondents stated that practicing traditions and thus communi­cating with ancestors is what is of value to a Xhosa person. A number of sites and species are fundamental to the perfor­mance of rituals and maintaining a relationship with the ances­tors. When respondents were asked what would happen if these sites were to be destroyed, they replied “It means that the ances­tors would be homeless.” “That can’t happen here at this village because our health depends entirely on these sites,” and “it means that our culture is dead.”

Freedom of Choice and Action

Freedom of choice and action within the MA context refers to individuals having control over what happens and being able to achieve what they value (CF3). Loss of biodiversity often means a loss of choices. Local fishers depend on man­groves (Mangrove ) as breeding grounds for local fish populations. Loss of mangroves translates to a loss in control over the local fish stock and a livelihood they have been pursuing for many generations and that they value. Another example is high-diversity agricul­tural systems. These systems normally produce less cash than monoculture cash crops, but farmers have some control over their entitlements because of spreading risk through diversity. High diversity of genotypes, [[population]s], species, functional types, and spatial patches decreases the negative effects of pests and pathogens on crops and keeps open possibilities for agrarian communities to develop crops suited to future environmental challenges and to increase their resilience to climate variability and market fluctuations (C11).

Another dimension of choices relates to the future. The loss of biodiversity in some instances is irreversible, and the value indi­viduals place on keeping biodiversity for future generations—the option value—can be significant (CF6, C2). The notion of having choices available irrespective of whether any of them will be actually picked is an essential constituent of the freedom aspect of well-being. However, putting a monetary figure on option values is notoriously difficult. We can only postulate on the needs and desires of future generations, some of which can be very different from today’s aspirations.

Basic Materials for a Good Life and Sustainable Livelihoods

Biodiversity offers directly the various goods—often plants, animals, and fungi—that individuals need in order to earn an income and secure sustainable livelihoods. In addition, it also contributes to livelihoods through the support it provides for ecosystem services: the agricultural labor force currently contains approximately 22% of the world’s population and accounts for 46% of its total labor force (C26.5.1). For example, apples are a major cash crop in the Himalayan region in India, accounting for 60–80% of total household income (SG3). The region is also rich in honeybee diversity, which played a signifi­cant role in pollinating field crops and wild plants, thereby increasing productivity and sustaining ecosystem functions. In the early 1980s, market demand for particular types of apples led farmers to uproot pollinated varieties and plant new, sterile cultivars. The pollinator populations were also negatively affected by excessive use of [[pesticide]s]. The result was a reduc­tion in overall apple productivity and the extinction of many natural pollinator species (SG3).

Nature-based tourism (“ecotourism”)—one of the fastest-growing segments of tourism worldwide—is a particularly important economic sector in a number of countries and a potential income source for many rural communities (C17.2.6). The aggregate revenue generated by nature-based tourism in Southern Africa was estimated to be $3.6 billion in 2000, roughly 50% of total tourism revenue (SG-SAfMA). Botswana, Kenya, Namibia, South Africa, Tanzania, Uganda, and Zimba­bwe each generated over $100 million in revenue annually from nature-based tourism in 2000. In Tanzania, tourism contributed 30% of the total GDP of the country.

Biodiversity also contributes to a range of other industries, including pharmaceuticals, cosmetics, and horticulture. Market trends vary widely according to the industry and country involved but many bioprospecting activities and revenues are expected to increase over the next decades (C10). The current economic climate suggests that pharmaceutical bioprospecting will increase, especially as new methods use evolutionary andecological knowledge.

Losses of biodiversity can impose substantial costs at local and national scales. For example, the collapse of the Newfound­land cod fishery in the early 1990s cost tens of thousands of jobs, as well as at least $2 billion in income support and retraining. Recent evidence suggests that the preservation of the integrity of local biological communities, both in terms of the identity and the number of species, is important for the maintenance of plant and animal productivity, soil fertility, and their stability in the face of a changing environment (C11). Recent estimates from the MA Portugal sub-global assessment indicate that environ­mental expenses in that country are increasing at a rate of 3% a year and are presently 0.7% of GDP (SG-Portugal).

Trade-offs among Biodiversity, Ecosystem Services, and Human Well-being

When society has multiple goals, many of which depend on biodiversity, ecosystem services, and the many constituents of well-being, difficult decisions involving trade-offs among com­peting goals have to be made. The value of ecosystem services lost to human society, in the long term, may greatly exceed the short-term economic benefits that are gained from transforma­tive activities. In Sri Lanka, for example, the clearing of tropical forest for agriculture initially reduced the habitat for forest-adapted anopheline mosquito vectors of malaria. But in due course, other vector species occupied the changed habitat, con­tributing to the resurgence of malaria (SG3).

Many of the changes in biodiversity and ecosystems have been made to enhance the production of specific ecosys­tem services such as food production. But only 4 of the 24 ecosystem services examined in this assessment have been enhanced: crops, livestock, aquaculture, and (in recent decades) carbon sequestration, while 15 services have been degraded. (See Table 2.2.) The degraded services include cap­ture fisheries (Fisheries and aquaculture), timber production, water supply, waste treatment and detoxification, water purification, natural hazard protec­tion, regulation of air quality, regulation of regional and local climate, regulation of erosion, and many cultural services (the spiritual, aesthetic, recreational, and other benefits of ecosys­tems). Modifications of ecosystems to enhance one service gen­erally have come at a cost to other services that the ecosystem provided. For example, while the expansion of agriculture and its increased productivity are a success story of enhanced pro­duction of one key ecosystem service, this success has come at high and growing costs in terms of trade-offs with other ecosystem services, both through the direct impact of land cover change and as a result of water withdrawals for irrigation and release of nutrients into rivers. Globally, roughly 15–35% of irrigation withdrawals are estimated to be unsustainable (low to medium uncertainty).The impacts of these trade-offs among ecosystem services affect people in different ways. An aquacul­ture farmer, for instance, may gain material welfare from man­agement practices that increase soil salinization and thereby reduce rice yields and threaten food security for nearby subsis­tence farmers.

Trade-off analysis aided by qualitative and quantitative values for biodiversity and ecosystem services can help decision-makers make intelligent decisions among competing goals (R17). (See Figure 2.1.) Such analysis can identify management strategies that generate efficient outcomes in which it is not possible to increase one objective without decreasing another. Second, it can show the extent to which current decisions are inefficient and help identify opportunities for improving the status quo. Third, it illustrates the nature of the trade-offs between goals once the effi­ciency frontier has been reached.

Values of Biodiversity and Ecosystem Services for Human Well-being

The importance of biodiversity and natural processes in pro­ducing ecosystem services that people depend on is not cap­tured in financial markets. Unlike goods bought and sold in [[market]s], many ecosystem services do not have markets or readily observable prices. However, lack of a price does not mean lack of value. A substantial body of research on nonmarket valuation is now available for some ecosystem services, including clean drink­ing water, recreation, or commercially harvested species. Exis­tence value of species and other “non-use” values pose a greater challenge to those who would try to measure the complete value of conserving biodiversity and natural processes. The fact that ecosystems are dynamic and complex, as well as the fact that human preferences change through time, also present difficulties for attempts to value natural systems. Combinations of irrevers­ible actions, such as species extinction, and uncertainty give rise to option value (such as the value of maintaining flexibility, keep­ing options open, until uncertainty is resolved). Though clear in theory, getting reasonable estimates of option value is difficult in practice (C2.3). Better quantification of the benefits derived from ecosystems would provide greater impetus for biodiversity protection and create a more transparent picture of the equitabil­ity of the distribution of benefits.

Private and social values of conserving biodiversity and natu­ral systems often differ widely. The private use value of biodiver­sity and ecosystem services by individuals will typically ignore the “external” benefits of conservation that accrue to society in general. For example, a farmer may benefit from intensive use of the land but generally does not bear all the consequences caused by leaching of excess nutrients and [[pesticide]s] into ground or surface water, or the consequences of loss of habitat for native species. If private decision-makers are not given the incentives to value the larger social benefits of conservation, their decisions will often result in inadequate conservation (C5.4).

The indirect values of biodiversity conservation can be highly significant in comparison with the direct economic values derived from a particular area. (See Box 2.2.) In existing eco­nomic studies of changes to biodiversity in specific locations (such as the conversion of mangrove forests, degradation of [[coral reef]s], and clear-felling of forests), the costs of ecosystem conver­sion are often found to be significant and sometimes exceed the benefits of the habitat conversion. Despite this, in a number of these cases conversion was promoted because the value of the lost ecosystem services—the indirect value of biodiversity conserva­tion—was not internalized. In other instances, subsidies (Perverse subsidies) dis­torted the relative costs and benefits and provided the incentives to destroy biodiversity (C5).

Box 2.2. Economic Costs and Benefits of Ecosystem Conversion (C5 Box 5.2)

Relatively few studies have compared the total economic value of ecosystems under alternate management regimes. The results of several that attempted to do so are shown in the Figure. In each case where the total economic value of sustainable management practices was compared with management regimes involving conversion of the ecosystem or unsustainable prac­tices, the benefit of managing the ecosys­tem more sustainably exceeded that of the converted ecosystem even though the pri­vate benefits—that is, the actual monetary benefits captured from the services enter­ing the market—would favor conversion or unsustainable management. These stud­ies are consistent with the understanding that market failures associated with eco­system services lead to greater conversion of ecosystems than is economically justi­fied. However, this finding would not hold at all locations. For example, the value of con­version of an ecosystem in areas of prime agricultural land or in urban regions often exceeds the total economic value of the intact ecosystem (although even in dense urban areas, the TEV of maintaining some “green space” can be greater than develop­ment of these sites) (C5). Conversion of tropical forest to small-scale agriculture or plantations (Mount Cam­eroon, Cameroon). Maintenance of the forest with low-impact logging provided social bene­fits (NWFPs, sedimentation control, and flood prevention) and global benefits (carbon stor­age plus option, bequest, and existence val­ues) across the five study sites totaling some $3,400 per hectare. Conversion to small-scale agriculture yielded the greatest private benefits (food production), of about $2,000 per hectare. Across four of the sites, con­version to oil palm and rubber plantations resulted in average net costs (negative ben­efits) of $1,000 per hectare. Private bene­fits from cash crops were only realized in this case because of market distortions. Conversion of a mangrove system to aquaculture (Thailand). Although conver­sion for aquaculture made sense in terms of short-term private benefits, it did not once external costs were factored in. The global benefits of carbon sequestration were con­sidered to be similar in intact and degraded systems. However, the substantial social ben­efits associated with the original mangrove cover—from timber, charcoal, NWFPs, off­shore fisheries, and storm protection—fell to almost zero following conversion. Summing all measured goods and services, the TEV of intact mangroves was a minimum of $1,000 and possibly as high as $36,000 per hect­are, compared with the TEV of shrimp farm­ing, which was about $200 per hectare. Draining freshwater marshes for agricul­ture (Canada). Draining freshwater marshes in one of Canada’s most productive agri­cultural areas yielded net private benefits in large part because of substantial drain­age subsidies (Perverse subsidies). However, the social benefits of retaining wetlands arising from sustain­able hunting, angling, and trapping greatly exceeded agricultural gains. Consequently, for all three marsh types considered, TEV was on average $5,800 per hectare, com­pared with $2,400 per hectare for con­verted wetlands. Use of forests for commercial timber extraction (Cambodia). Use of forest areas for swidden agriculture and extraction of non-wood forest products (including fuel­wood, rattan and bamboo, wildlife, malva nuts, and medicine) as well as ecological and environmental functions such as water­shed, biodiversity, and carbon storage pro­vided a TEV ranging of $1,300–4,500 per hectare (environmental services accounted for $590 of that while NWFPs provided $700–3,900 per hectare). However, the pri­vate benefits associated with unsustainable timber harvest practices exceeded private benefits of NWFP collection. Private bene­fits for timber harvest ranged from $400 to $1,700 per hectare, but after accounting for lost services the total benefits were from $150 to $1,100 per hectare, significantly less than the TEV of more sustainable uses.

The depletion and degradation of many ecosystem services represents the loss of a capital asset that is poorly reflected in conventional indicators of economic growth or growth in human well-being (C2.3.5). A country could cut its forests and deplete its fisheries (Fisheries and aquaculture), and this would show only as a positive gain to GDP, despite the loss of the capital asset. (GDP measures the flow of economic benefits from the use of these resources, but the depletion of the capital asset is not reflected.) Moreover, many ecosystem services are available freely to those who use them (fresh water in aquifers, for instance, and the use of the atmo­sphere as a sink for pollutants) and so again their degradation is not reflected in standard economic measures. When changes to these natural capital assets are factored into measures of the inclusive wealth of nations, they significantly change the balance sheet for countries with economies largely dependent on natural resources. Some countries that appeared to have positive growth in the 1970s and 1980s, for example, actually experienced a net loss of capital assets, effectively undermining the sustainability of any gains they may have achieved.

The Distributional Impacts of Biodiversity Loss and Ecosystem Change

Biodiversity use, change, and loss have improved well-being for many social groups and individuals. But people with low resilience to ecosystem changes—mainly the disadvantaged—have been the biggest losers and witnessed the biggest increase in not only monetary poverty but also relative, temporary poverty and the depth of poverty (C5, C6, R17). See Box 2.3 for a description of various types of poverty.

Box 2.3. Concepts and Measures of Poverty

Relative poverty is the state of deprivation defined by social stan­dards. It is fixed by a contrast with others in the society who are not considered poor. Poverty is then seen as lack of equal opportuni­ties. It is based on subjective measures of poverty. Depth of poverty is a measure of the average income gap of the poor in relation to a certain threshold. It defines how poor the poor are. It gives the amount of resources needed to bring all poor peo­ple to the poverty-line level. Temporary poverty is characterized by a short-term deprivation, usually seasonal, of water or food. Monetary poverty is an insufficiency of income or monetary resources. Most indicators like the U.S. dollar a day indicator or national poverty lines are defined in those terms. Multidimensional poverty is conceived as a group of irreducible deprivations that cannot be adequately expressed as income insuf­ficiency. It combines basic constituents of well-being in a composite measure, such as the Human Poverty Index. Other characteristics of poverty commonly used in the literature include rural and urban poverty, extreme poverty (or destitution), female poverty (to indicate gender discrimination), and food-ratio poverty lines (with calorie-income elasticities). Other indices such as the FGT (Foster, Greer, and Thorbecke) or the Sen Index, which combine both dimensions of incidence and depth of poverty, are also widely used. The type of poverty experienced by individuals will therefore differ for different rates and levels of biodiversity and ecosystem services loss and if the loss is transitory or permanent.

Many communities depend on a range of biological prod­ucts for their material welfare. In addition, the transfer of ownership or use rights to ecosystem services like timber, fish­ing, and mining to privileged groups by governments have also excluded local communities from the use of these ecosystem services (R8). Provisions for ensuring the equitable distribu­tion of monetary benefits from the use of biological products are an issue of major concern. Even in cases where equitable provisioning has been made, implementation is being impaired by weak and ineffective institutions (C10).

Poor people have historically disproportionately lost access to biological products and ecosystem services as demand for those services has grown. Coastal habitats are often converted to other uses, frequently for aquaculture ponds or cage cultur­ing of highly valued species such as shrimp and salmon. Despite the fact that the area is still used for food production, local residents are often displaced from their fishing grounds, and the fish produced are usually not for local consumption but for export. Coastal residents often no longer have access to cheap protein or sources of income (C18). The development of shrimp aquaculture has displaced local fishers who are not able to enter the capital- and technology-intensive shrimp fisheries (SG3). Food security and overall well-being is much better in situations where local communities—with particular focus on the poor and the disadvantaged—were involved and made partners in the access, use, and management of biodiversity.

Changes in the equity structure of societies can have impacts on ecosystem services. Differential access to resources may also help to explain why some people living in environmental resource-rich areas nevertheless rank low in measures of human well-being. For example, economic lib­eralization in Viet Nam resulted in the development of a class of entrepreneurs with markedly greater access to capital. The poorer fishers were unable to enter the capital and technology-intensive shrimp fishery that developed. Furthermore, the ecological changes precipitated by the expansion of shrimp aquaculture reduced the capacity of the ecosystem to support the traditional fish stocks, further exacerbating the inequity (SG3.7).

The increase in international trade of biological products has improved the well-being for many social groups and indi­viduals, especially in countries with well-developed [[market]s] and trade rules and among people in developing countries who have access to the biological products. However, many groups have not benefited from such trade. Some people who live near and are dependent on biodiversity-rich areas have experienced a drop in their well-being rather than an increase. Examples include the many indigenous groups and local com­munities who have relied on these products and the ecosystem services they support for many of the constituents of well- being. Weak and inefficient institutional structures that over­see the equitable distribution of benefits are key reasons for the inequitable distribution of benefits at the national and local levels. In addition, structural adjustment programs played a key role in pushing the poor further into destitution and forc­ing many to have no choice but to further stress ecosystem ser­vices (R17).

Conflicts between competing social groups or individuals over access to and use of biological products and ecosystem services have contributed to declines in well-being for some groups and improvements for others. Sometimes different social groups have a conflict over how a given bundle of eco­system services or biological products ought to be used and shared. Although many such conflicts have been managed cooperatively, it is also common for one group to impose its preferred outcome on the others, leading to an improvement in well-being for one group at the expense of others. For example, if mountain communities convert forests into agri­cultural lands, they may reduce downstream water quality. When ecosystem change is linked to well-being change through this highly complex structure of interdependencies, there are both winners and losers. Some groups improve and other groups decline (C6). Box 2.4 describes some con­flicts that emerged in Chile over the mining industry and local communities.

Box 2.4. Conflicts Between the Mining Sector and Local Communities in Chile

The Salar de Atacama, Chile, is a salty wetland within the driest desert in the world. Surface water is limited. The present major concern is over [[ground]water] usage and the extent to which the exploitation is sustainable. The economic activities in this region include mining, agriculture, and tourism, all of which depend on the quantity and quality of available water. The Salar de Atacama holds over 40% of world lithium reserves; mining provides 12% of local employment and two thirds of the regional GDP. It also consumes 65% of the water used in the region. Tourism is the second larg­est source of employment and income, and tourist facilities need fresh water. Local communities rely on water for subsistence agri­culture and livestock raising. Most subsistence farmers do not have enough resources to buy water rights when bidding against the mining companies. Hence the shortage of water is generating major conflicts over access and ownership rights among compet­ing users (SG.SDM).

One of the main reasons some countries, social groups, or individuals—especially the disadvantaged—are more severely affected by biodiversity and ecosystem changes is limited access to substitutes or alternatives. When the qual­ity of water deteriorates, the rich have the resources to buy personal water filters or imported bottled water that the poor can ill afford. Similarly, urban populations in developing countries have easier access to clean energy sources because of easy access to the electrical grid, while rural communities have fewer choices. Poor farmers often do not have the option of substituting modern methods for services provided by biodi­versity because they cannot afford the alternatives. And, sub­stitution of some services may not be sustainable, and may have negative environmental and human health effects. For example, the reliance on toxic and persistent [[pesticide]s] to control certain pests can have negative effects on the provision of services by the cultivated system and other ecosystems con­nected to the cultivated system (C.26.2). Many industrial countries maintain seed banks in response to the rapid rate of loss of crop genetic diversity and to make existing genetic diversity more readily available to plant breeders. Apart from the network of seed banks maintained in developing countries by the Consultative Group on International Agricultural Research, for many developing countries creating such banks could pose a problem when electricity supplies are unreliable, fuel is costly, and there is a lack of human capacity (R17).

Place-based or micro-level data and not macro-level or aggregated data provide more useful information to identify disadvantaged communities being affected by biodiversity and ecosystem changes. Most poverty statistics are only available at an aggregate level. These tend to hide pockets of poverty existing sometimes within traditionally defined “wealthy” regions or provinces. Therefore, using aggregate data to understand and establish links between biodiversity loss, ecosystem changes, and well-being can be quite mislead­ing (C5).

What are the current trends and drivers of biodiversity loss?

• Across the range of biodiversity measures, current rates of loss exceed those of the historical past by several orders of magnitude and show no indication of slowing.
• Biodiversity is declining rapidly due to land use change, climate change, invasive species, overexploitation, and pollu­tion. These result from demographic, economic, sociopolitical, cultural, technological, and other indirect drivers.
• While these drivers vary in their importance among ecosystems and regions, current trends indicate a continuing loss of biodiversity.

Recent and Current Trends in Biodiversity

Across the range of biodiversity measures, current rates of change and loss exceed those of the historical past by several orders of magnitude and show no indication of slowing. At large scales, across biogeographic realms and ecosystems ([[biome]s]), declines in biodiversity are recorded in all parts of the habitable world. Among well-studied groups of species, extinction rates of organisms are high and increasing (medium certainty), and at local levels both [[population]s] and [[habitat]s] are most commonly found to be in decline. (C4)

Virtually all of Earth’s ecosystems have now been dramat­ically transformed through human actions. More land was converted to cropland in the 30 years after 1950 than in the 150 years between 1700 and 1850 (C26). Between 1960 and 2000, reservoir storage capacity quadrupled (C7.2.4) and, as a result, the amount of water stored behind large dams is estimated to be three to six times the amount held by rivers (C7.3.2). Some 35% of mangroves have been lost in the last two decades in countries where adequate data are available (encompassing about half of the total mangrove area) (C19.2.1). Roughly 20% of the world’s [[coral reef]s] have been destroyed and an additional 20% have been degraded (C19.2.1). Although the most rapid changes in ecosystems are now taking place in developing countries, industrial countries historically experienced comparable changes.

The biomes with the highest rates of conversion in the last half of the 20th century were temperate, tropical, and flooded grasslands and tropical dry forests (Forest biome) (more than 14% lost between 1950 and 1990) (C4.4.3). Areas of particularly rapid change in [[terrestrial] ecosystems] over the past two decades include (C28.2):

• the Amazon basin and Southeast Asia (deforestation and expansion of croplands);
• Asia (land degradation in drylands); and
• Bangladesh, Indus Valley, parts of Middle East and Central Asia, and the Great Lakes region of Eastern Africa.

Habitat conversion to agricultural use has affected all biogeographical realms. In all realms (except Oceania and Antarc­tica), at least a quarter of the area had been converted to other land uses by 1950 (C4.4.4), and in the Indo-Malayan realm almost half of the natural habitat cover had been converted. In the 40 years from 1950 to 1990, habitat conversion has con­tinued in nearly all realms. (See Figure 3.1.) The temperate northern realms of the Nearctic and Palearctic are currently extensively cultivated and urbanized; how­ever, the amount of land under cultivation and pasture seems to have stabilized in the Nearctic, with only small increases in the Palearctic in the last 40 years. The decrease in extensification of land under agricul­tural use in these areas is counterbalanced by intensification of agricultural practices in order to ensure continued food produc­tion for expanding human population (Population growth rate)s (Population growth rate) (C8, C26). Within the tropics, rates of land conversion to agricul­tural use range from very high in the Indo-Malayan realm to moderate in the Neotropics and the Afrotropics, where large increases in cropland area have taken place since the 1950s. Aus­tralasia has relatively low levels of cultivation and urbanization, but these have also increased in the last 40 years at a similar rate to those of the Neotropics.

The majority of [[biome]s] have been greatly modified. Between 20% and 50% of 9 out of 14 global biomes have been trans­formed to croplands. Tropical dry forests were the most affected by cultivation between 1950 and 1990, although temperate grasslands, temperate broadleaf forests, and Mediterranean for­ests each experienced 55% or more conversion prior to 1950. Biomes least affected by cultivation include boreal forests (Forest biome) and tundra. (See Figure 3.2.) While cultivated lands provide many provisioning services (such as grains, fruits, and meat), habitat conversion to agriculture typically leads to reductions in local native biodiversity (C4.4.3).

Rates of human conversion among biomes have remained similar over at least the last century. For example, boreal forests had lost very little native habitat cover up to 1950 and have lost only a small additional percentage since then. In contrast, the temperate grasslands biome had lost nearly 70% of its native cover by 1950 and lost an additional 15.4% since then. Two biomes appear to be exceptions to this pattern: Mediterranean forests and temperate broadleaf forests. Both had lost the major­ity of their native habitats by 1950 but since then have lost less than 2.5% additional habitat. These biomes contain many of the world’s most established cities and most extensive surrounding agricultural development (Europe, the United States, the Medi­terranean basin, and China). It is possible that in these biomes the most suitable land for agriculture had already been converted by 1950 (C4.4.3).

Over the past few hundred years, humans have increased the species extinction rate by as much as three orders of magnitude (medium certainty). This estimate is only of medium certainty because the extent of extinctions of undescribed taxa is unknown, the status of many described species is poorly known, it is difficult to document the final disappearance of very rare species, and there are extinction lags between the impact of a threatening process and the resulting extinction. However, the most definite information, based on recorded extinctions of known species over the past 100 years, indicates extinction rates are around 100 times greater than rates characteristic of species in the fossil record (C4.4.2). Other less direct estimates, some of which model extinctions hundreds of years into the future, esti­mate extinction rates 1,000 to 10,000 times higher than rates recorded among fossil lineages. (See Figure 3.3.)

Between 12% and 52% of species within well-studied higher taxa are threatened with extinction, according to the IUCN Red List. Less than 10% of named species have been assessed in terms of their conservation status. Of those that have, birds have the lowest percentage of threatened species, at 12%. The patterns of threat are broadly similar for mammals and conifers, which have 23% and 25% of species threatened, respectively. The situation with amphibians looks similar, with 32% threatened, but information is more limited, so this may be an underesti­mate. Cycads have a much higher proportion of threatened species, with 52% globally threatened. In regional assessments, taxonomic groups with the highest proportion of threatened species tended to be those that rely on freshwater habitats (C4.4). Threatened species show continuing declines in conservation status, and species threat rates tend to be highest in the realms with highest species richness (C4.4). (See Figures 3.4 and 3.5.)

Threatened vertebrates are most numerous in the biomes with intermediate levels of habitat conversion. Low-diversity [[biome]s] (such as boreal forest and tundra) have low species richness and low threat rates and have experienced little conversion. Very highly converted habitats in the temperate zone had lower richness than tropical biomes, and many species vulnerable to conversion may have gone extinct already. It is in the high-diversity, moderately converted tropical biomes that the greatest number of threatened vertebrates are found (C4.4.3). (See Figure 3.6.)

Among a range of higher taxa, the majority of species are currently in decline. Studies of amphibians globally, African mammals, birds in agricultural lands, British butterflies, Carib­bean corals, waterbirds, and fishery species show the majority of species to be declining in range or number. Increasing trends in species can almost always be attributed to management interven­tions, such as protection in reserves, or to elimination of threats such as overexploitation, or they are species that tend to thrive in human-dominated landscapes (C4.4.1). An aggregate indicator of trends in species populations—the Living Planet Index—uses published data on trends in natural populations of a variety of wild species to identify overall trends in species abundance. Although more balanced sampling would enhance its reliability, the trends are all declining, with the highest rate in freshwater habitats. (See Figure 3.7.)

Genetic diversity has declined globally, particularly among domesticated species (C26.2.1). In cultivated systems, since 1960 there has been a fundamental shift in the pattern of intra-species diversity in farmers’ fields and farming systems as a result of the Green Revolution. Intensification of agricultural systems coupled with specialization by plant breeders and the harmonizing effects of globalization have led to a substantial reduction in the genetic diversity of domesticated plants and animals in agricultural systems. The on-farm losses of genetic diversity of crops have been partially offset by the maintenance of genetic diversity in gene banks. A third of the 6,500 breeds of domesticated animals are threatened with extinction due to their very small population sizes (C.26.2). In addition to culti­vated systems, the extinction of species and loss of unique pop­ulations that has taken place has resulted in the loss of unique genetic diversity contained in those species and populations. This loss reduces overall fitness and adaptive potential, and it limits the prospects for recovery of species whose populations are reduced to low levels (C4.4). Globally, the net rate of conversion of some ecosystems has begun to slow, and in some regions ecosystems are returning to more natural states largely due to reductions in the rate of expansion of cultivated land, though in some instances such trends reflect the fact that little habitat remains for further con­version. Generally, opportunities for further expansion of culti­vation are diminishing in many regions of the world as the finite proportion of land suitable for intensive agriculture continues to decline (C26.ES). Increased agricultural productivity is also low­ering pressures for agricultural expansion. Since 1950, cropland areas in North America, Europe, and China have stabilized, and even decreased in Europe and China (C26.1.1). Cropland areas in the former Soviet Union have decreased since 1960 (C26.1.1). Within temperate and boreal zones, forest cover increased by approximately 3 million hectares per year in the 1990s, although about half of this increase consisted of forest plantations (C21.4.2).

Translating biodiversity loss between different measures is not simple: rates of change in one biodiversity measure may underestimate or overestimate rates of change in another. The scaling of biodiversity between measures is not simple, and this is especially significant in the relationship between habitat area and species richness. Loss of habitat initially leads to less species loss than might be expected, but depending on how much habitat remains, rates of loss of habitat can underestimate rates of loss of species (C2.2.4, C4.5.1).

Biotic homogenization, defined as the process whereby species assemblages become increasingly dominated by a small number of widespread species, represents further losses in biodiversity that are often missed when only considering changes in absolute numbers of species. Human activities have both negative and positive impacts on species. The many species that are declining as a result of human activities tend to be replaced by a much smaller number of expanding species that thrive in human-altered environments. The outcome is a more homogenized biosphere with lower species diversity at a global scale. One effect is that in some regions where diversity has been low because of isolation, the species diversity may actually increase—a result of invasions of non-native forms (this is true in continental areas such as the Netherlands as well as on oceanic islands). Recent data also indicate that the many losers and few winners tend to be non-randomly distributed among higher taxa and ecological groups, enhancing homogenization (C4.4).

While biodiversity loss has been a natural part of the history of Earth’s biota, it has always been countered by origination and, except for rare events, has occurred at extremely slow rates. Currently, however, loss far exceeds origination, and rates are orders of magnitude higher than average rates in the past. Recall that biodiversity loss is not just global extinction, such as that faced by many threatened and endangered species, but declines in genetic, ecosystem, and landscape diversity are considered biodiversity loss as well. Even if every native species were retained in an ecological preserve, if the majority of the landscape has been converted to high-intensity monoculture cropland systems, then biodiversity has declined significantly. Landscape homogenization is linked to biotic homogenization (C4).

The patterns of threat and extinction are not evenly distributed among species but tend to be concentrated in particular ecological or taxonomic groups. Ecological traits shared by species facing high extinction risk include high trophic level, low population density, long lifespan, low reproductive rate, and small geographical range size (C4.4.2). The degree of extinction risk also tends to be similar among related species, leading to the likelihood that entire evolutionary radiations can and have been lost. The majority of recorded species extinctions since 1500 have occurred on islands. However, predictions of increasing numbers of future extinctions suggest a significant shift from island to continental areas (C4.4.2).

Drivers of Biodiversity Change and Their Trends

Biodiversity change is caused by a range of drivers. A driver is any natural or human-induced factor that directly or indirectly causes a change in an ecosystem. A direct driver unequivocally influences ecosystem processes. An indirect driver operates more diffusely, by altering one or more direct drivers. Important direct drivers affecting biodiversity are habitat change, climate change, invasive species, overexploitation, and pollution (CF4, C3, C4.3, S7).

No single measure or indicator represents the totality of the various drivers. Some direct drivers of change have relatively straightforward indicators, such as fertilizer usage, water consumption, irrigation, and harvests. Indicators for other drivers, including invasion by non-native species, climate change, land cover conversion, and landscape fragmentation, are not as well developed, and data to measure them are not as readily available (S7).

Changes in biodiversity and in ecosystems are almost always caused by multiple, interacting driv­ers. Changes are driven by combinations of drivers that work over time (such as population (Population growth rate) and income growth interacting with technological advances that lead to climate change) or level of organization (such as local zoning laws versus international environmental treaties) and that happen intermittently (such as droughts, wars, and economic crises). Reviews of case studies of deforestation and desertification reveal that the most common type of interaction is synergetic factor combinations: combined effects of multiple drivers that are amplified by reciprocal action and feedbacks (S7.4).

Drivers interact across spatial, temporal, and organizational scales, and any specific ecosystem change is driven by a network of interactions among different drivers. Though some of the elements of these networks are global, the actual set of interac­tions that brings about an ecosystem change is more or less spe­cific to a particular place. For example, a link between increasing producer prices and the extension of production can be found in many places throughout the world. The strength of this effect, however, is determined by a range of location-specific factors including production conditions, the availability of resources and knowledge, and the economic situation of the farmer (S7.4). No single conceptual framework captures the broad range of case study evidence about the interactions among driv­ers. Based on the findings of the sub-global assessments of the MA and recent literature, some examples of causal linkages for ecosystem change can be given (SG-Portugal, SG-SAfMA). (See Figures 3.8 and 3.9 and Box 3.1.)

Box 3.1. Direct Drivers: Example from Southern African Sub-global Assessment (SG-SAfMA)

The direct drivers of biodiversity loss in southern Africa include the impacts of land use change, alien invasives, overgrazing, and over-­harvesting—all of which have already had a large impact on the region’s biodiversity, ecosystem services, and human well-being, and all of which are likely to spread in the absence of interventions. The dominant direct driver of ecosystem change in southern Africa is considered to be widespread land use change that in some cases has led to degradation. Forests and woodlands are being converted to croplands and pastures at a rate somewhat slower than in Southeast Asia and the Amazon during the 1990s, but nev­ertheless sufficiently fast to endanger ecosystem services at a local scale. Half of the region consists of drylands, where overgraz­ing is the main cause of desertification. In the first half of the twenty-first century, climate change is a real threat to water supplies, human health, and biodiversity in southern Africa. The threats arise partly because the projected warming may, over large areas, be accompanied by a drying trend, and partly because of the low state of human welfare and weak governance, which increases vulnerability of humans to climate change. Although some of these threats have slowed in some regions (afforestation with monocultures of alien species in South Africa has decreased, for example), some have accelerated elsewhere (afforestation with alien species in Mozambique has increased, for instance, due to favorable growing conditions and weak regulation). Thus, the region’s biodiversity remains vulnerable to land use change. In addi­tion, the more subtle problem of land degradation is considered a bigger threat in the region. Several studies indicate that the biodiversity of southern Africa is at risk. There is now evidence, for example, that it is declining in the northern part of its range, but stable in the southern part, as pre­dicted by the global change models. In addition, there is experimen­tal evidence that the recorded expansion of woody invasions into grasslands and savannas may be driven by rising global CO2 concen­trations. The ability of species to disperse and survive these pres­sures will be hampered by a fragmented landscape made inhospi­table by human activities. The Assessments of Impacts and Adapta­tions to Climate Change in Multiple Regions and Sectors project is currently analyzing response options that may conserve biodiversity under future climate and land cover scenarios in southern Africa.

Indirect Drivers

Biodiversity change is most clearly a consequence of the direct drivers. However, these reflect changes in indirect drivers—the root causes of changes in ecosystems. These can be classified into the following broad categories: change in economic activity, demographic change, sociopolitical factors, cultural and religious factors, and scientific and technological change.

• Global economic activity increased nearly sevenfold between 1950 and 2000 (S7.SDM), and in the MA scenarios it is pro­jected to grow a further three- to sixfold by 2050. The many pro­cesses of globalization have amplified some driving forces of changes in ecosystem services and attenuated other forces by removing regional barriers, weakening national connections, and increasing the interdependence among people and between nations (S7.2.2).
• Global population (Population growth rate) doubled in the past 40 years, reaching 6 billion in 2000 (S7.2.1). It is projected to grow to 8.1–9.6 billion by 2050, depending on the scenario. Urbanization influences consumption, generally increasing the demand for food and energy and thereby increasing pressures on ecosystems globally.
• Over the past 50 years, there have been significant changes in sociopolitical drivers, including a declining trend in central­ized authoritarian governments and a rise in elected democra­cies, which allows for new forms of management, in particular adaptive management, of environmental resources (S7.2.3).

Culture conditions individuals’ perceptions of the world, and by influencing what they consider important, it has implica­tions for conservation and consumer preferences and suggests courses of action that are appropriate and inappropriate. The development and diffusion of scientific knowledge and technol­ogies can on the one hand allow for increased efficiency in resource use and on the other hand can provide the means to increase exploitation of resources (S7.2.4, S7.2.5).

Direct Drivers

Direct drivers vary in their importance within and among systems and in the extent to which they are increasing their impact. Historically, habitat and land use change have had the biggest impact on biodiversity across [[biome]s]. Climate change is projected to increasingly affect all aspects of biodiversity, from individual organisms, through [[population]s] and species, to eco­system composition and function. Pollution, especially the depo­sition of nitrogen and phosphorus, but also including the impact of other contaminants, is also expected to have an increasing impact, leading to declining biodiversity across biomes. Overex­ploitation and invasive species have been important as well and continue to be major drivers of changes in biodiversity (C4.3). (See Figure 3.10.)

For [[terrestrial] ecosystems], the most important direct driver of change in the past 50 years has been land cover change (C4.3, SG7). Only biomes relatively unsuited to crop plants, such as [[desert]s], boreal forests (Forest biome), and tundra, are relatively intact (C4). Deforestation and forest degradation are currently more exten­sive in the tropics than in the rest of the world, although data on boreal forests are especially limited (C21). Approximately 10–20% of drylands are considered degraded (medium certainty), with the majority of these areas in Asia (C22). A study of the southern African biota shows how degradation of habitats led to loss of biodiversity across all taxa. (See Figure 3.11.)

Cultivated systems (defined in the MA to be areas in which at least 30% of the landscape is in croplands, shifting cultivation, confined livestock production, or freshwater aquaculture in any par­ticular year) cover 24% of Earth’s surface. (See Figure 3.12.) In 1990, around 40% of the crop­land is located in Asia; Europe accounts for 16%, and Africa, North America, and South America each account for 13% (S7).

For [[marine (Biome)] ecosystems], the most important direct driver of change in the past 50 years, in the aggregate, has been fishing. Fishing is the major direct anthropogenic force affecting the structure, function, and biodiversity of the oceans (C18). Fishing pressure is so strong in some marine systems that over much of the world the biomass of fish targeted in fisheries (including that of both the target species and those caught inci­dentally) has been reduced by 90% relative to lev­els prior to the onset of industrial fishing. In these areas a number of targeted stocks in all oceans have collapsed—having been overfished or fished above their maximum sustainable levels. Recent studies have demonstrated that global fisheries landings peaked in the late 1980s and are now declining despite increasing effort and fishing power, with little evidence of this trend reversing under current practices (C18.3). In addition to the landings, the average trophic level of global landings is declining, which implies that we are increasingly relying on fish that originate from the lower part of marine food webs (C18.3). (See Figures 3.13 and 3.14.) Destructive fishing is also a factor in shallower waters; bottom trawling homogenizes three-dimensional benthic habitats and dramatically reduces biodiversity.

For freshwater ecosystems, depending on the region, the most important direct drivers of change in the past 50 years include physical changes, modification of water regimes, invasive spe­cies, and pollution. The loss of wetlands worldwide has been speculated to be 50% of those that existed in 1900. However, the accuracy of this figure has not been established due to an absence of reliable data (C20.3.1). Massive changes have been made in water regimes. In Asia, 78% of the total reservoir volume was constructed in the last decade, and in South America almost 60% of all reservoirs were built since the 1980s (C20.4.2). Water with­drawals from rivers and lakes for irrigation or urban or industrial use increased sixfold since 1900 (C7.2.2). Globally, humans now use roughly 10% of the available renewable freshwater supply, although in some regions, such as the Middle East and North Africa, humans use 120% of renewable supplies—the excess is obtained through mining [[ground]water] (C7.2.3). The introduc­tion of non-native invasive species is now a major cause of species extinction in freshwater systems. It is well established that the increased discharge of nutrients causes intensive [[eutrophic]ation] and potentially high levels of nitrate in drinking water and that pollution from point sources such as mining has had devastating impacts on the biota of inland waters (C20.4).

Apparently stable areas of habitat may suffer from fragmen­tation, with significant impacts on their biodiversity (C4.3.1). Fragmentation is caused by natural disturbance (such as fires or wind) or by land use change and habitat loss, such as the clearing of natural vegetation (Land-cover) for agriculture or road construction, which divides previously continuous habitats. Larger remnants, and remnants that are close to other remnants, are less affected by fragmentation. Small fragments of habitat can only support small [[population]s], which tend to be more vulnerable to extinction. Moreover, habitat along the edge of a fragment has a different climate and favors different species to the interior. Small frag­ments are therefore unfavorable for those species that require interior habitat, and they may lead to the extinction of those spe­cies. Species that are specialized to particular habitats and those whose dispersal abilities are weak suffer from fragmentation more than generalist species with good dispersal ability (C4.3.1). Fragmentation affects all [[biome]s], but especially forests (see Fig­ure 3.15) and major freshwater systems (see Figure 3.16).

Invasive alien species have been a major cause of extinction, especially on islands and in freshwater habitats, and they con­tinue to be a problem in many areas. In freshwater habitats, the introduction of alien species is the second leading cause of spe­cies extinction, and on islands it is the main cause of extinction over the past 20 years, along with habitat destruction. Awareness about the importance of stemming the tide of invasive alien spe­cies is increasing, but effective implementation of preventative measures is lacking. The rate of introductions continues to be extremely high; for example, in New Zealand plant introductions alone have occurred at a rate of 11 species per year since Euro­pean settlement in 1840 (C4.3.2).

Overexploitation remains a serious threat to many species and [[population]s]. Among the most commonly overexploited spe­cies or groups of species are marine fish and invertebrates, trees, and animals hunted for meat. Most industrial fisheries (Fisheries and aquaculture) are either fully or overexploited, and the impacts of over-harvesting are coupled to destructive fishing techniques that destroy habitat, as well as associated ecosystems such as estuaries and wetlands. Even recreational and subsistence fishing has contributed to what is known as the “shifting baselines” phenomenon, in which what we consider the norm today is dramatically different from pre-exploitation conditions.

Many of the current concerns with overexploitation of bush­meat (wild meat taken from the forests by local people for income or subsistence) are similar to those of fisheries, where sustainable levels of exploitation remain poorly understood and where the offtake is difficult to manage effectively. Although the true extent of exploitation is poorly known, it is clear that rates of offtake are extremely high in [[tropical forest]s]. The trade in wild plants and animals and their derivatives is poorly documented but is esti­mated at nearly $160 billion annually. It ranges from live animals for the food and pet trade to ornamental plants and timber. Because the trade in wild animals and plants crosses national borders, the effort to regulate it requires international cooperation to safeguard certain species from overexploitation (C4.3.4).

Over the past four decades, nutrient loading has emerged as one of the most important drivers of ecosystem change in ter­restrial, freshwater, and coastal ecosystems. While the intro­duction of nutrients into ecosystems can have both beneficial and adverse effects, the beneficial effects will eventually reach a plateau as more nutrients are added (for example, additional inputs will not lead to further increases in crop yield), while the harmful effects will continue to grow. Synthetic production of nitrogen fertilizer has been the key driver for the remarkable increase in food production of the past 50 years (S7.3). (See Fig­ure 3.17.) The total amount of reactive, or biologically available, nitrogen created by human activities increased ninefold between 1890 and 1990, with most of that increase taking place in the second half of the century in association with increased use of [[fertilizer]s] (C7.3.2).

More than half of all the synthetic nitrogen fertilizers ever used on Earth have been used since 1985 (R9.2). Humans now produce more reactive nitrogen than is produced by all natural pathways combined (R9.ES). Nitrogen application has increased fivefold since 1960, but as much as 50% of the nitrogen fertil­izer applied may be lost to [environment]. Phosphorus appli­cation has increased threefold since 1960, with steady increase until 1990, followed by leveling off at a level about equal to applications in 1980. (See Figure 3.18.) These changes are mir­rored by phosphorus accumulation in soils, which can serve as an indicator of [[eutrophic]ation] potential for freshwater lakes and phosphorus-sensitive estuaries. Potential consequences include eutrophication of freshwater ecosystems, hypoxia in coastal marine ecosystems, nitrous oxide emissions contributing to global climate change, and air pollution by NO_x in urban areas. Occur­rence of such problems varies widely in different regions (S7.3). (See Figure 3.19.)

Climate change in the past century has already had a measur­able impact on biodiversity. Observed recent changes in climate, especially warmer regional [[temperature]s], have already had signifi­cant impacts on biodiversity and ecosystems, including causing changes in species distributions, population sizes, the timing of reproduction or migration events, and an increase in the fre­quency of pest and disease outbreaks. Many [[coral reef]s] have undergone major, although often partially reversible, bleaching episodes when local sea surface temperatures have increased dur­ing one month by 0.5–1^o Celsius above the average of the hottest months (R13.1.3). Precipitation patterns have changed spatially and temporally, and global average sea level rose 0.1–0.2 meters (S7.ES). By the end of the century, climate change and its impacts may be the dominant direct driver of biodiversity loss and changes in ecosystem services globally.

Recent studies, using the climate envelope/species-area tech­nique, estimated that the projected changes in climate by 2050 could lead to an eventual extinction of 15–52% of the subset of 1,103 endemic species (mammals, birds, frogs, reptiles, butterflies, and plants) analyzed (R13.1.3). While the growing season in Europe has lengthened over the last 30 years, in some regions of Africa the combination of regional climate changes and anthropogenic stresses has led to decreased cereal crop pro­duction since 1970. Changes in fish populations have been linked to large-scale climate oscillations; El Niño events, for instance, have affected fisheries (Fisheries and aquaculture) off the coasts of South America and Africa, and decadal oscillations in the Pacific have affected fisheries off the west coast of North America (R13.1.3).

The scenarios developed by the Intergovernmental Panel on Climate Change (Intergovernmental Panel on Climate Change (IPCC)) project an increase in global mean surface tem­perature of 2.0–6.4^o Celsius above preindustrial levels by 2100, increased incidence of floods and droughts, and a rise in sea level of an additional 8–88 centimeters between 1990 and 2100. (See Figure 3.20.)

Harm to biodiversity will grow worldwide with increasing rates of change in climate and increasing absolute amounts of change. In contrast, some ecosystem services in some regions may initially be enhanced by projected changes in climate (such as increases in temperature or precipitation), and thus these regions may experience net benefits at low levels of climate change. As climate change becomes more severe, however, the harmful impacts on ecosystem services outweigh the benefits in most regions of the world. The balance of scientific evidence sug­gests that there will be a significant net harmful impact on eco­system services worldwide if global mean surface temperature increases more than 2^o Celsius above preindustrial levels or at rates greater than 0.2^o Celsius per decade (medium certainty).Cli­mate change is projected to further adversely affect key develop­ment challenges, including providing clean water, energy services, and food; maintaining a healthy environment; and con­serving ecological systems and their biodiversity and associated ecological goods and services (R13.1.3).

• Climate change is projected to exacerbate the loss of biodiversity and increase the risk of extinc­tion for many species, especially those already at risk due to factors such as low population num­bers, restricted or patchy [[habitat]s], and limited climatic ranges (medium to high certainty).
• Water availability and quality are projected to decrease in many arid and semiarid regions (high certainty).
• The risk of floods and droughts is projected to increase (high certainty).
• The reliability of hydropower and biomass production is projected to decrease in some regions (high certainty).
• The incidence of vector-borne diseases such as malaria and dengue and of waterborne diseases such as cholera is projected to increase in many regions (medium to high certainty), and so too are heat stress mortality and threats of decreased nutrition in other regions, along with severe weather traumatic injury and death (high certainty).
• Agricultural productivity is projected to decrease in the tropics and sub-tropics for almost any amount of warming (low to medium cer­tainty), and there are projected adverse effects on fisheries (Fisheries and aquaculture).
• Projected changes in climate during the twenty-first century are very likely to be without precedent during at least the past 10,000 years and, combined with land use change and the spread of exotic (Exotic species) or alien species, are likely to limit both the capability of species to migrate and the ability of species to persist in [[fragmented] habitats].

Present-day threats are often multiple and of greater intensity than historical threats. The susceptibility of an ecological community to a given threat will depend on the events of the past that have shaped the current biota. If the current threats are novel, they will have dramatic effects on [[population]s], since spe­cies will lack adaptations. Even if drivers are similar to past driv­ers (climate, for example, has always been variable to some degree), the intensity of some current-day drivers is unprece­dented (such as the rates and extent of habitat change). Further­more, today’s drivers of extinction are often multiple—land use change, emerging disease, and invasive species are all occurring together, for instance. Because exposure to one threat type often makes a species more susceptible to a second, exposure to a sec­ond makes a species more susceptible to a third, and so on, con­secutive, multiple threats to species may have unexpectedly dramatic impacts on biodiversity (S7.4, C4.3).

Each driver has a characteristic spa­tial and temporal scale at which it affects ecosystem services and human well-being. Climate change may oper­ate on a spatial scale of a large region; political change may operate at the scale of a nation or a municipal district. Sociocultural change typically occurs slowly, on a time scale of decades, while economic forces tend to occur more rapidly. Because of the variability in ecosystems, their services, and human well-being in space and time, there may be mismatches or lags between the scale of the driver and the scale of its effects on ecosystem services (S7, SG7.3.5).

The fate of declining species and [[habitat]s] will depend on sources of inertia and the speed of their response to management interventions. Natural sources of inertia correspond to the time scales inherent to natural systems; for example, recovery of a population cannot proceed more quickly than the average turnover or generation time, and established recovery will often take several generations. On top of this is anthropogenic inertia resulting from the time scales inherent in human institu­tions for decision-making and imple­mentation. For most systems, these two sources of inertia will lead to delays of years, and more often decades, in slow­ing and reversing a declining biodiver­sity trend. This analysis assumes that the drivers of change could indeed be halted or reversed in the near term. Yet currently there is little evidence that any of the direct or indirect drivers are slow­ing or that any are well controlled at the large to global scale. More significantly, we have net yet seen all of the conse­quences of changes that occurred in the past (C4, R5, S7, S10).

The delay between a driver affecting a system and its conse­quences for biodiversity change can be highly variable. In the relatively well studied case of species extinctions, habitat loss is known to be a driver with particularly long lag times. In studies of tropical forest bird species the time from habitat fragmenta­tion to species extinction has been estimated to have a half-life of decades to hundreds of years. Overall, these results suggest that about half of the species losses may occur over a period of 100 to 1,000 years. Therefore, humans have the opportunity to deploy active habitat restoration practices that may rescue some of the species that otherwise would have been in a trajectory toward extinction. Notwithstanding this, habitat restoration measures will not be likely to save the most sensitive species, which will become extinct soon after habitat loss (C4.5.2).

What is the future for biodiversity and ecosystem services under plausible scenarios?

• In the range of plausible scenarios explored by the MA, biodiversity will continue to be lost at extremely high rates over the next 50 years. Given inertia in the indirect drivers and in ecosystems, this loss cannot be halted over this time period. Nonetheless, opportunities exist to reduce the rate of loss of biodiversity and associated ecosystem services if society places an emphasis on ecosystem protection, restoration, and management.

Statements of certainty in the following conclusions are conditional statements in that they refer to level of certainty or uncertainty in the particular projection should that scenario and its associated changes in drivers unfold.

Global Scenarios and Ecosystem Change

The scenarios developed by the MA project continued loss of biodiversity, with attendant changes in ecosystems services and declines in human well-being in some regions and [[population]s]. The MA scenarios address the consequences of different plausible futures for ecosystem services and human well-being (S5). (See Box 4.1.) These futures were selected to explore a wide range of contexts under which development will be pursued, as well as a wide range of approaches to development. Two basic contrasts are explored, one in which the world becomes increasingly globalized and the other in which it becomes increasingly regionalized. In the first case we see a focus on global [[market]s] and policies and on supranational institutions fostering interna­tional cooperation, while in the regionalized world there is an emphasis on local and national institutions and on regional mar­kets, and little attention is paid to the global commons.

Box 4.1. An Outline of the Four MA Scenarios

It is important to remember that no scenario will match the future as it actually occurs. None of the scenarios represents a “best” path or a “worst” path. There could be com­binations of policies and practices that pro­duce significantly better or worse outcomes than any of these scenarios. The future will represent a mix of approaches and conse­quences described in the scenarios, as well as events and innovations that could not be imagined at the time of writing (S5). The focus on alternative approaches to sustaining ecosystem services distinguishes the MA scenarios from previous global sce­nario exercises. The four approaches were developed based on interviews with leaders in NGOs, governments, and business on five continents, on scenario literature, and on pol­icy documents addressing linkages between ecosystem change and human well-being. The approach to scenario development used in the MA consists of a combination of qual­itative storyline development and quantita­tive modeling based on assumptions about the evolution of indirect drivers such as eco­nomic and [[population (Population growth rate)] growth] (S6). The Global Orchestration scenario explores the possibilities of a world in which global economic and social poli­cies are the primary approach to sus­tainability. The recognition that many of the most pressing global problems seem to have roots in poverty and inequality evokes fair policies to improve the well-being of those in poorer countries by removing trade barriers and subsidies. Environmental problems are dealt with in an ad-hoc reactive manner, as it is assumed that improved economic well-being will eventually create demand for and the means to achieve environmental protec­tion. Nations also make progress on global environmental problems, such as greenhouse gas emissions and the depletion of pelagic marine fisheries. However, some local and regional environmental problems are exac­erbated. The results for ecosystem services are mixed. Human well-being is improved in many of the poorest countries (and in some rich countries), but a number of ecosystem services deteriorate by 2050, placing at risk the long-term sustainability of the well-being improvements. The Order from Strength scenario examines the outcomes of a world in which protection through boundaries becomes paramount. The policies enacted in this scenario lead to a world in which the rich protect their borders, attempting to con­fine poverty, conflict, environmental degrada­tion, and deterioration of ecosystem services to areas outside the borders. These prob­lems often cross borders, however, imping­ing on the well-being of those within. The Adapting Mosaic scenario explores the benefits and risks of envi­ronmentally proactive local and regional management as the primary approach to sustainability. In this scenario, lack of faith in global institutions, combined with increased understanding of the importance of resilience and local flexibility, leads to approaches that favor experimentation and local control of ecosystem management. The results are mixed, as some regions do a good job managing ecosystems but oth­ers do not. High levels of communication and interest in learning leads regions to compare experiences and learn from one another. Gradually the number of successful experi­ments begins to grow. While global problems are ignored initially, later in the scenario they are approached with flexible strategies based on successful experiences with locally adap­tive management. However, some systems suffer long-lasting degradation. The TechnoGarden scenario explores the potential role of technology in pro­viding or improving the provision of ecosystem services. The use of technol­ogy and the focus on ecosystem services is driven by a system of property rights and valuation of ecosystem services. In this sce­nario, people push ecosystems to their limits of producing the optimum amount of ecosys­tem services for humans through the use of technology. Often, the technologies they use are more flexible than today’s environmental engineering, and they allow multiple needs to be met from the same ecosystem. Provi­sion of ecosystem services in this scenario is high worldwide, but flexibility is low due to high dependence on a narrow set of opti­mal approaches. In some cases, unexpected problems created by technology and ero­sion of ecological resilience lead to vulner­able ecosystem services, which may break­down. In addition, the success in increasing the production of ecosystem services often undercuts the ability of ecosystems to sup­port themselves, leading to surprising inter­ruptions of some ecosystem services. These interruptions and collapses sometimes have serious consequences for human well-being.

In terms of approaches, the scenarios focus either on a reactive attitude toward environmental problems or on futures that emphasize proactive management of ecosystems and their ser­vices. In the reactive approach, [environment]al problems that threaten human well-being are dealt with only after they become apparent, and, in general, people believe that the necessary knowledge and technology to address environmental challenges will emerge or can be developed as needed. The proactive ecosys­tem management approach focuses on ecosystem engineering or adaptive management to maximize the delivery of ecosystem ser­vices while reducing the impact of human activities and to enhance ecosystem resilience.

Habitat loss caused by land use change will lead, with high certainty, to continuing decline in the local and global diversity of some taxa, especially vascular plants, in all four scenarios (S10.2). Habitat conversion between 1970 and 2050 ranges from 13% to 20% (see Figure 4.1) as projected by the IMAGE model, leading to local and global extinctions as [[population]s] approach equilibrium with the remnant habitat. Analysis using the well-established species-area relationship indicates that the number of species lost at equilibrium (that is, the number of species that can be supported by the habitat remaining by 2050) is likely to be approximately 10–15% of the species present in 1970 (low cer­tainty), and other factors such as over-harvesting, invasive species, pollution, and climate change will further increase the rate of extinction. The two scenarios that take a more proactive approach to [environment] (TechnoGarden and Adapting Mosaic) have more success in reducing terrestrial biodiversity loss in the near future than the two scenarios that take a reactive approach to environmental issues (S10.2). The scenario with a focus on security through boundaries (Order from Strength) has the highest rate of biodiversity loss. It is important to note that all the projected extinctions will not have occurred by 2050.

Habitat and vascular plant populations are projected to be lost in the MA scenarios at the fastest rate in warm mixed forests, savannas, scrub, [[tropical forest]s], and tropical woodlands (high certainty) (S10.2). In a few [[biome]s], expected changes post-1990 are greater that those seen in the past half-century. Regions that will lose species at the lowest rate include those with low human impact as well as those where major land use changes and human intervention have already occurred, such as the Palearctic (S10.2). (See Figures 4.2 and 4.3.) Tropical Africa is the region that will lose the most vascular plant species, mainly as a result of rapid [[population (Population growth rate)] growth] and strong increases in per capita food production in the region, much of which continues to rely on expansion of cultivated area. The Indo-Malayan region loses the second-most biodiversity. Past and projected future trends in habitat change indicate that the biomes that have already suffered the greatest change (Mediterra­nean forests and temperate grasslands) show the highest recover­ies over the next 50 years, while the biomes that suffered intermediate changes in the past have the highest rates of change in the near future. (See Figure 4.4.) Finally, biomes at higher lati­tudes that had not been converted to agriculture in the past will continue to be relatively unchanged.

Land use changes causing habitat loss are associated primarily with fur­ther expansion of agriculture and, sec­ondarily, with the expansion of cities and infrastructure (S9.8). This expan­sion is caused by increases in popula­tion, economic growth, and changing consumption patterns. By 2050, global population increases (medium to high certainty) to 8.1–9.6 billion, depending on the scenario. At the same time, per capita GDP expands by a factor of 1.9–4.4 depending on the scenario (low to medium certainty). Demand is damp­ened by increasing efficiency in the use of resources. The expansion of agricul­tural land occurs mainly in developing countries and arid regions, whereas in industrial countries, agricultural area declines. (See Figure 4.5.) The reverse pattern occurs in terms of forest cover, with some forest being regained in industrial countries but with 30% of the forest in the developing world being lost from 1970 to 2050, resulting in a global net loss of forest. The two scenarios with a proactive approach to [environment] (TechnoGarden and Adapting Mosaic) are the most land-conserving ones because of increasingly efficient agricultural production, lower meat consumption, and lower popula­tion increases. Existing wetlands and the services they provide (such as water purification) are at increasing risk in some areas due to reduced runoff or intensified land use.

For the three drivers tested across scenarios regarding terres­trial systems, land use change is projected to be the dominant driver of biodiversity loss, followed by changes in climate and nitrogen deposition. But there are differences between [[biome]s] (medium certainty) (S10.2). For example, climate change will be the dominant driver of biodiversity change in tundra, boreal for­est, cool conifer forest (Forest biome), savanna, and [[desert]s]. Nitrogen deposition will be an important driver in warm mixed forests and temperate deciduous forest. These two ecosystems are sensitive to nitrogen deposition and include densely populated areas. Considering these three drivers together, the total loss of vascular plant diver­sity from 1970 to 2050 ranges from 13% to 19%, depending on the scenario (low certainty). The impact of other important driv­ers, such as overexploitation and invasive species, could not be assessed as fully, suggesting that terrestrial biodiversity loss may be larger than the above projection.

Vast changes are expected in world freshwater resources and hence in their provisioning of ecosystem services (S9.4.5). (See Figure 4.6.) Under the two scenarios with a reactive approach to [environment] (Order from Strength and Global Orchestration), massive increases in water withdrawals in developing countries are projected to lead to an increase in untreated wastewater dis­charges, causing a deterioration of freshwater quality. Climate change leads to both increasing and declining river runoff, depending on the region. The combination of huge increases in water withdrawals, decreasing water quality, and decreasing run­off in some areas leads to an intensification of water stress over wide areas. In sum, a deterioration of the services provided by freshwater resources (such as aquatic habitat, fish production, and water supply for households, industry and agriculture) is expected under the two scenarios with a reactive approach to [environment], with a less severe decline under the other two sce­narios (medium certainty).

Fish populations are projected to be lost from some river basins under all scenarios due to the combined effects of cli­mate change and water withdrawals. Under all scenarios, water availability decreases in 30% of the modeled river basins from the combined effects of climate change and water withdrawal, as projected by the WaterGAP model (S10.3). Based on established but incomplete scientific understanding of fish species-discharge relationships, the decreased water discharge will result in eventual losses of up to 65% (by 2100) of fish species from these basins (low certainty).

Climate change rather than water withdrawal is the major driver for the species losses from most basins, with projected losses from climate change alone of up to 65% by 2100. Rivers that are projected to lose the most fish species are concentrated in poor tropical and sub-tropical countries, where the needs for human adaptation are most likely to exceed governmental and societal capacity to cope (S10.3). Many rivers and lakes also experience increased [[temperature]s], [[eutrophic]ation], acidification, and increased invasions by non-indigenous species, leading to loss of native biodiversity. No algorithms exist for estimating the numbers of species lost due to these drivers, but recent experi­ence suggests that they cause losses greater than those caused by climate change and water withdrawal.

Demand for fish as food expands under all scenarios, and the result will be an increasing risk of a major long-lasting collapse of regional marine fisheries (low to medium certainty). The demand for fish from both freshwater and marine sources, as well as from aquaculture, increases across all scenarios because of increasing human population (Population growth rate), income growth, and growing preferences for fish (S9.4.2). Increasing demand raises the pressure on marine fisheries, most of which are already above or near their maximum sustainable yield and could cause a long-term collapse in their productivity. The production of fish via aquaculture adds to the risk of collapse of marine fisheries, as aquaculture continues to depend on marine fish as a feed source.

However, the diversity of marine biomass is sensitive to changes in regional policy. Scenarios with policies that focus on maintaining or increasing the value of fisheries (Fisheries and aquaculture) result in declin­ing biomass diversity (that is, a few functional groups become much more abundant than others), while scenarios with policies that focus on maintaining the ecosystem responded with increasing biomass diversity (the biomass becomes more evenly distributed among the different functional groups). Rebuilding selected stocks does not necessarily increase biomass diversity as effectively as an ecosystem-focused policy (S10.4).

Ecological Degradation and Human Well-being

Biodiversity loss will lead to a deterioration of ecosystem services, increasing the likelihood of ecological surprises—with negative impacts on human well-being. Examples of ecological sur­prises include runaway climate change, desertifi­cation, fisheries collapse, floods, landslides, wildfires, eutrophication, and disease (S11.1.2, S11.7). Security and social relations are vulnera­ble to reductions in ecosystem services. Short­ages of provisioning services, such as food and water, are obvious and potent causes for conflict, thus harming social relations. But social relations can also be harmed by reduced ecosystem cul­tural services, such as the loss of iconic species or changes to highly valued landscapes. Likelihood of surprises, society preparedness, and ecosystem resilience interact to determine the vulnerability of human well-being to ecological and other forms of surprise in any given scenario. The vul­nerability of human well-being to adverse eco­logical, social, and other forms of surprise varies among the scenarios (S11.7), but it is greatest in Order from Strength, with a focus on security through boundaries and where the society is not proactive to [environment].

Scenarios that limit deforestation show relatively better preservation of regulating services. Tropical deforestation could be reduced by a combination of reduced tropical hard­wood consumption in the North, technological developments leading to substitution, and slower [[population (Population growth rate)] growth] in the South (TechnoGarden) or through greater protection of local ecosystems (Adapting Mosaic). In contrast, in the scenarios that are not proactive on [environment], a combination of market forces, undervaluation, and feedbacks lead to substan­tial deforestation not only in the tropics but also in large swaths of Siberia (Order from Strength and Global Orchestra­tion). Deforestation increasingly interacts with climate change in all scenarios, causing not only more flooding during storms but also more fires during droughts, greatly increasing the risk of runaway climate change (S11).

Terrestrial ecosystems currently absorb CO₂ at a rate of about 1–2 gigatons of carbon per year (with medium certainty) and thereby contribute to the regulation of climate, but the future of this service is uncertain (S9.5). Deforestation is expected to reduce the carbon sink most strongly in a globalized world with a focus on security through boundaries (Order from Strength) (medium certainty). Carbon release or uptake by ecosystems affects the CO₂ and CH₄ content of the atmosphere at the global scale and thereby global climate. Currently, the biosphere is a net sink of carbon, absorbing approximately 20% of fossil fuel emis­sions. It is very likely that the future of this service will be greatly affected by expected land use change. In addition, a higher atmo­spheric CO₂ concentration is expected to enhance net productiv­ity, but this does not necessarily lead to an increase in the carbon sink. The limited understanding of soil respiration processes, and their response to changed agricultural practices, generates uncer­tainty about the future of this sink.

The MA scenarios project an increase in global temperature between 2000 and 2050 of 1.0–1.5^o Celsius, and between 2000 and 2100 of 2.0–3.5^o Celsius, depending on the scenario (low to medium certainty) (S9.3). There is an increase in global average precipitation (medium certainty). Furthermore, according to the climate scenarios of the MA, there is an increase in precipitation over most of the land area on Earth (low to medium certainty). However, some arid regions (such as North Africa and the Mid­dle East) could become even more arid (low certainty). Climate change will directly alter ecosystem services, for example, by causing changes in the productivity and growing zones of culti­vated and non-cultivated vegetation (Land-cover). It will also indirectly affect ecosystem services in many ways, such as by causing sea level to rise, which threatens mangroves and other vegetation that now protect shorelines.

Acknowledging the uncertainty in climate sensitivity in accor­dance with the IPCC would lead to a wider range of temperature increase than 2.0–3.5^o Celsius. Nevertheless, both the upper and lower end of this wider range would be shifted downward some­what compared with the range for the scenarios in the IPCC Special Report on Emission Scenarios (1.5–5.5o Celsius). This is caused by the fact that the TechnoGarden scenario includes cli­mate policies (while the IPCC scenarios did not cover climate policies) and the highest scenarios (Global Orchestration and Order from Strength) show lower emissions than the highest IPCC scenario (S9.3.4).

The scenarios indicate (medium certainty) certain “hot spot regions” of particularly rapid changes in ecosystem ser­vices, including sub-Saharan Africa, the Middle East and Northern Africa, and South Asia (S9.8). To meet its needs for development, sub-Saharan Africa is likely to rapidly expand its withdrawal of water, and this will require an unprecedented investment in new water infrastructure. Under some scenarios (medium certainty), this rapid increase in withdrawals will cause a similarly rapid increase in untreated return flows to the freshwater systems, which could endanger public health and aquatic ecosystems. This region could experience not only accelerating intensification of agriculture but also further expansion of agricultural land onto natural land. Further intensification could lead to a higher level of contamination of surface and [[ground]waters].

Expansion of agriculture will come at the expense of the disappearance of a large fraction of sub-Saharan Africa’s natural forest and grasslands (medium certainty) as well as the ecosystem services they provide. Rising incomes in the Middle East and Northern African countries lead to greater demand for meat, which could lead to a still higher level of dependency on food imports (low to medium certainty). In South Asia, deforestation continues, despite increasingly intensive industrial-type agriculture. Here, rapidly increasing water withdrawals and return flows further intensify water stress.

While the GDP per person improves on aver­age in all scenarios, this can mask increased inequity and declines in some ecosystem ser­vices (S9.2). Food security improves in the South in all scenarios except in Order from Strength, a world with a focus on security through boundar­ies and reactive to [environment]. (See Figure 4.7.) Food security remains out of reach for many people, however, and child malnutrition cannot be eradicated even by 2050, with the number of malnourished children still at 151 million in Order from Strength. In a regionalized and envi­ronmentally proactive world, there is an improve­ment of provisioning services in the South through investment in social, natural, and, to a lesser extent, human capital at local and regional levels (Adapting Mosaic). Global health improves in a globalized world that places an emphasis on economic development (Global Orchestration) but worsens in a regionalized world with a focus on security, with new diseases affecting poor [[population]s] and with anxiety, depression, obesity and diabetes affecting richer populations (Order from Strength).

New health technologies and better nutrition could help unleash major social and economic improvements, especially among poor tropical populations, where it is increasingly well recog­nized that development is being undermined by numerous infectious diseases, widespread under­nutrition, and high birth rates. Good health depends crucially on institutions. The greatest improvements in social relations occur in a regionalized world with a focus on the environ­ment, as civil society movements strengthen (Adapting Mosaic). Curiously, security is poorest in a world with focus on security through bound­aries (Order from Strength). This scenario also sees freedom of choice and action reduced both in the North and the South, while other scenarios see an improvement, particularly in the South (S11).

Implications and Opportunities for Trend Reversion

The MA scenarios demonstrate the fundamen­tal interdependence between energy, climate change, biodiversity, wetlands, desertification, food, health, trade, and economy, since ecologi­cal change affects the scenario outcomes. This interdependence between environmental and development goals stresses the importance of partnerships and the potential for synergies among multilateral environ­mental agreements (S14). As the basis for international cooperation, all global environ­mental agreements operate under profoundly different cir­cumstances in the four scenar­ios, and their current instruments—exchange of sci­entific information and knowl­edge, technology transfer, benefit sharing, financial sup­port—might need to be revised and complemented by new ones according to changing sociopolitical conditions. The interdependence between socioeconomic development and ecosystems also requires national governments and intergovernmental organizations to influence and moderate the actions of the private sector, communities, and NGOs. The responsibility of national governments to establish good governance at the national and sub-national levels is complemented by their obligation to shape the international context by negotiating, endorsing, and imple­menting international environmental agreements.

Trade-offs between ecosystem services continue and may intensify. The gains in provisioning services such as food supply and water use will come partly at the expense of other ecosystem services (S12). Major decisions in the next 50–100 years will have to address trade-offs between agricultural production and water quality, land use and biodiversity, water use and aquatic biodiversity, current water use for irrigation and future agricul­tural production, and in fact all current and future use of nonre­newable resources (S12). Providing food to an increasing population (Population growth rate) will lead (with low to medium certainty) to the expan­sion of agricultural land, and this will lead to the loss of natural forest and grassland (S9.3) as well as of other services (such as genetic resources, climate regulation, and runoff regulation). While water use will increase in developing countries (with high certainty), this is likely to be accompanied by a rapid and perhaps extreme deterioration of water quality, with losses of the services provided by clean fresh waters (genetic resources, recreation, and fish production).

For a given level of socioeconomic development, policies that conserve more biodiversity will also promote higher aggregated human well-being through the preservation of regulating, cul­tural, and supporting services. Regulating and supporting ser­vices are essential for the steady delivery of provisioning services to humans and to sustain life on Earth, while cultural services are important for many people. Although trade-offs are common, various synergistic interactions can allow for the simultaneous enhancement of more than one ecosystem service (S12.4.4). Increasing the supply of some ecosystem services can enhance the supply of others (forest restoration, for instance, may lead to improvements in carbon sequestration, runoff regulation, polli­nation, and wildlife), although there are also trade-offs (in this case with reduced capacity to provide food, for example). Suc­cessful management of synergisms is a key component of any strategy aimed at increasing the supply of ecosystem services for human well-being.

The prospect of large unexpected shifts in ecosystem services can be addressed by adopting policies that hedge (by diversify­ing the services used in a particular region, for example), choos­ing reversible actions, monitoring to detect impending changes in ecosystems, and adjusting flexibly as new knowledge becomes available (S.SDM, S5, S14). More attention to indicators and monitoring (Environmental monitoring and assessment) for large changes in ecosystem services would increase society’s capacity to avert large disturbances of ecosystem services or to adapt to them more rapidly if they occur. Without monitoring and policies that anticipate the possi­bility of large ecosystem changes, society will face increased risk of large impacts from unexpected disruptions of ecosystem ser­vices. In the scenarios, the greatest risks of large, unfavorable eco­logical changes arise in dryland agriculture, marine fisheries, degradation in the quality of fresh waters and coastal marine waters, emergence of disease, and regional climate change. These are also some of the ecosystem attributes most poorly monitored at present.

What response options can conserve biodiversity and promote human well-being?

• Biodiversity loss is driven by local, regional, and global factors, so responses are also needed at all scales.
• Responses need to acknowledge multiple stakeholders with different needs.
• Given certain conditions, many effective responses are available to address the issues identified.
• Responses designed to address biodiversity loss will not be sustainable or sufficient unless relevant direct and indirect drivers of change are addressed.
• Further progress in reducing biodiversity loss will come through greater coherence and synergies among sectoral responses and through more systematic consideration of trade-offs among ecosystem services or between biodiversity conser­vation and other needs of society.

Some drivers of biodiversity loss are localized, such as overex­ploitation. Others are global, such as climate change, while many operate at a variety of scales, such as the local impacts of invasive species through global trade. Most of the responses assessed here were designed to address the direct drivers of biodi­versity loss. However, these drivers are better seen as symptoms of the indirect drivers, such as unsustainable patterns of con­sumption, demographic change, and globalization.

At the local and regional scale, responses to the drivers may promote both local biodiversity and human well-being by acting on the synergies between maintenance of local biodiversity and provision of key ecosystem services. Responses promoting local management for global biodiversity values depend on local “cap­ture” of the global values in a way that provides both ongoing incentives for management and support for local well-being (R5).

At the global scale, effective responses set priorities for conser­vation and development efforts in different regions and create shared goals or programs, such as the biodiversity-related conven­tions and the Millennium Development Goals. Effective trade-offs and synergies will be promoted when different strategies or instruments are used in an integrated, coordinated way (R5).

The MA assessment of biodiversity responses places human well-being as the central focus for assessment, recognizing that people make decisions concerning ecosystems based on a range of values related to well-being, including the use and non-use values of biodiversity and ecosystems. The assessment therefore has viewed biodiversity responses as addressing values at different scales, with strong links to ecosystem service values and well-being arising at each of these scales. The well-being of local people dom­inates the assessment of many responses, including those relating to protected areas, governance, wild species management, and var­ious responses related to local capture of benefits.

Focusing exclusively on values at only one level often hinders responses that could promote values at all levels or reconcile conflicts between the levels. Effective responses function across scales, addressing global values of biodiversity while identifying opportunity costs or synergies with local values. Local consider­ation of global biodiversity recognizes the value of what is unique at a place (or what is not yet protected elsewhere). The values of ecosystem services, on the other hand, do not always depend on these unique elements. Effective biodiversity responses recognize both kinds of values.

These considerations guide the assessment summarized in this section of a range of response strategies that to varying degrees integrate global and local values and that seek effective trade-offs and synergies for biodiversity, ecosystem services, and human well-being.

Difficulties in measuring biodiversity have complicated assessments of the impact of response strategies. Developing better indicators of biodiversity would enhance integration among strategies and instruments. For example, existing mea­sures often focus on local biodiversity and do not estimate the marginal gains in regional or global biodiversity values. Similarly, biodiversity gains from organic farming are typically expressed only as localized species richness, with no consideration of the degree of contribution to regional or global biodiversity or the trade-offs with high-productivity industrial agriculture.

How Effective Are Protected Areas for Biodiversity Conservation and Improved Human Well-being?

Protected areas are an extremely important part of programs to conserve biodiversity and ecosystems, especially for sensitive [[habitat]s] (R5). Recent assessments have shown that at the global and regional scales, the existence of current PAs, while essential, is not sufficient for conservation of the full range of biodiversity. Protected areas need to be better located, designed, and managed to deal with problems like lack of representativeness, impacts of human settlement within protected areas, illegal harvesting of plants and animals, unsustainable tourism, impacts of invasive alien species, and vulnerability to global change. Marine (Biome) and freshwater ecosystems are even less well protected than [[terrestrial] systems], leading to increasing efforts to expand PAs in these [[biome]s]. Efforts to expand marine protected areas are also spurred by strong evidence of positive synergies between conservation within PAs and sustainable use immediately outside their bound­aries (C18). However, marine protected area management poses special challenges, as enforcement is difficult and much of the world’s oceans lie outside national jurisdictions.

Based on a survey of management effectiveness of a sample of nearly 200 protected areas in 34 countries, only 12% were found to have implemented an approved management plan. The assess­ment concluded that PA design, legal establishment, boundary demarcation, resource inventory, and objective setting were rela­tively well addressed. But management planning, monitoring (Environmental monitoring and assessment) and evaluation, and budgets for security and law enforcement were generally weak among the surveyed areas. Moreover, the “paper park” problem remains, whereby geographic areas may be labeled as some category of protected area but not achieve the promised form of management (R5).

Protected areas may contribute to poverty where rural people are excluded from resources that have traditionally supported their well-being. However, PAs can contribute to improved live­lihoods when they are managed to benefit local people (R5). Relations with local people should be addressed more effectively through participatory consultation and planning. One possible strategy is to promote the broader use of IUCN protected areas management categories. Success depends on a collaborative man­agement approach between government and stakeholders, an adaptive approach that tests options in the field, comprehensive monitoring that provides information on management success or failure, and empowerment of local communities through an open and transparent system that clarifies access and ownership of resources.

Success of protected areas as a response to biodiversity loss requires better site selection and incorporation of regional trade-offs to avoid some ecosystems from being poorly repre­sented while others are overrepresented. Success of PAs depends on adequate legislation and management, sufficient resources, better integration with the wider region surrounding protected areas, and expanded stakeholder engagement (R5). Moreover, representation and management targets and performance indica­tors work best when they go beyond measuring the total area apparently protected. Indicators of percent-area coverage of PAs, as associated with the Millennium Development Goals and other targets, for example, only provide a broad indication of the actual extent of protection afforded by PA systems, but regional and national-level planning requires targets that take into account trade-offs and synergies with other ecosystem services.

Protected area design and management will need to take into account the impacts of climate change. The impacts of climate change will increase the risk of extinctions of certain species and change the nature of ecosystems. Shifts in species distribution as a result of climate change are well documented (C4, C19, C25). Today’s species conservation plans may incorporate adaptation and mitigation aspects for this threat, drawing on existing tools to help assess species’ vulnerability to climate change. Corridors and other habitat design aspects to give flexibility to protected areas are effective precautionary strategies. Improved manage­ment of habitat corridors and production ecosystems between protected areas will help biodiversity adapt to changing condi­tions (R5).

How Effective is Local Capture of Biodiversity Benefits?

The impact of market instruments in encouraging and achiev­ing conservation of biodiversity is unclear (R5). Although trad­able development rights offer the potential to achieve a conservation objective at a low cost by offering flexibility in achieving the objectives, they have been the subject of some criti­cisms—notably for being complex and involving high transac­tion costs and the establishment of new supporting institutions. For example, a situation could arise in which the most ecologi­cally sensitive land but also the least costly to develop would not be protected. To date, the TDR has not been designed to target specific habitat types and properties.

Transferring rights to own and manage ecosystem services to private individuals gives them a stake in conserving those ser­vices, but these measures can backfire without adequate levels of institutional support. For example, in South Africa, changes in wildlife protection legislation allowed a shift in landownership and a conversion from cattle and sheep farming to profitable game farming, enabling conservation of indigenous wildlife. On the other hand, the CAMPFIRE program in Zimbabwe, based on sustainable community-managed use of wildlife, has now become an example of how success can turn into failure, with the state repossessing the areas given to individuals and breaking the levels of trust and transparency—a form of instrumental free­dom—that are critically needed for these economic responses to work efficiently and equitably (R17).

Payments to local landowners for ecosystem services show promise of improving the allocation of ecosystem services and are applicable to biodiversity conservation. However, compen­sating mechanisms addressing the distributive and equitable aspects of these economic instruments may need to be designed in support of such efforts. By 2001, more than 280,000 hectares of forests had been incorporated in Costa Rica within reserves, at a cost of about $30 million per year, with typical annual pay­ments ranging from $35 to $45 per hectare for forest conserva­tion (R5 Box 5.3). However, the existence of direct payment initiatives does not guarantee success in achieving conservation and development objectives or benefits for human well-being. Empirical analyses about the distributive impacts across different social groups are rare.

Direct payments are often more effective than indirect incen­tives. For example, integrated conservation-development proj­ects—an indirect incentive—designed to allow local [[population]s] to improve their well-being by capturing international willing­ness to pay for biodiversity conservation have in practice rarely been integrated into ongoing incentives for conservation. Over­all, long-term success for these response strategies depends on meeting the economic and social needs of communities whose well-being already depends to varying degrees on biodiversity products and the ecosystem services biodiversity supports (R5).

However, direct payments have been criticized for requiring ongoing financial commitments to maintain the link between investment and conservation objectives. Furthermore they have led in some instances to inter- and intra-community conflict. Yet many success stories show the effectiveness of direct pay­ments and the transfer of property rights in providing incentives for local communities to conserve biodiversity. Effectiveness of payments in conserving regional biodiversity may be enhanced by new approaches that target payments based on estimated mar­ginal gains (“complementarity” values) (R5 Box 5.3).

Significant improvements can be made to mitigate biodiver­sity loss and ecosystem changes by removing or redirecting eco­nomic subsidies that cause more harm than good. Agricultural subsidies in industrial countries reduce world prices for many commodities that developing countries produce. Lower prices provide the wrong incentives, encouraging these countries to adopt unsustainable agricultural activities that destroy ecosystems as well as push many poor farmers into poverty. Therefore the removal or redirection of agricultural subsidies is highly likely by itself to produce major improvements in ecosystem services and to check the rate of biodiversity loss (R5).

The promotion of “win-win” outcomes has been politically correct at best and naive at worst. Economic incentives that encourage the conservation and sustainable use of biodiversity show considerable promise. However, trade-offs between biodi­versity, economic gains, and social needs have to be more realisti­cally acknowledged. The benefits of biodiversity conservation are often widespread, even global in the case of existence values or carbon sequestration, while the costs of restricting access to bio­diversity often are concentrated on groups living near biodiver­sity-rich areas (R5).

Why is the Management of Individual Species a Common Response Strategy for Harvestable and Invasive Species?

Direct management of invasive species will become an even more important biodiversity conservation response, typically calling for an ecosystem-level response if the invasive species has become established. Control or eradication of an invasive species once it is established is often extremely difficult and costly, while prevention and early intervention have been shown to be more successful and cost-effective. Common factors in suc­cessful eradication cases include particular biological features of the target species (for example, poor dispersal ability), early detection/response, sufficient economic resources devoted for a sufficient duration, and widespread support from the relevant agencies and the public. Successful prevention requires increased efforts in the control and regulation of the transportation of invasive species due to international trade (R5).

Chemical control of invasive plant species, sometimes com­bined with mechanical removal like cutting or pruning, has been useful for controlling at least some invasive plants, but has not proved particularly successful in eradication. In addition to its low efficiency, chemical control can be expensive. Biological control of invasive species has also been attempted, but results are mixed (R5). For example, the introduction of a non-native [[predator]y] snail to control the giant African snail in Hawaii led to extinction of many native snails. Some 160 species of biological agents, mainly insects and fungi, are registered for controlling invasive species in North America, and many of them appear highly effective. However, at least some of the biological agents used are themselves potential invaders. Environmental screening and risk assessment can minimize the likelihood of negative impacts on non-target native species.

Social and economic aspects of the control of invasive species have received less attention, perhaps because of difficulties in estimating these trade-offs. The Global Invasive Species Pro­gram is an international response to address the problem. The CBD has adopted Guiding Principles on Invasive Alien Species (Decision VI/23) as a basic policy response, but it is too early to assess the effectiveness of implementation (R5).

Sustainable use of natural resources is an integral part of any sustainable development program, yet its contribution to con­servation remains a highly controversial subject within the con­servation community. Conserving species when the management objective is ensuring resource availability to support human live­lihoods is frequently unsuccessful. This is because optimal man­agement for natural resource extraction frequently has negative impacts on species targeted for conservation. Therefore, care in establishing positive incentives for conservation and sustainable use is critical to successful biodiversity conservation (R5).

Where the goal is species conservation, and where a specific population has a distinct identity and can be managed directly, species management approaches can be effective. However, managing for a single species is rarely effective when the goal is ecosystem functioning, which is tied to the entire suite of species present in the area. Where human livelihoods depend on single species resources, species management can be effective (for exam­ple, some fisheries (Fisheries and aquaculture) and game species), but where people depend on a range of different wild resources, as is frequently the case, multiple species management is the appropriate approach (R5).

How Effective Are Strategies for Integrating Biodiversity Issues in Production Sectors?

At the national level, integrating biodiversity issues into agri­culture, fishery, and forestry management encourages sustain­able harvesting and minimizes negative impacts on biodiversity. Biodiversity will only be conserved and sustainably used when it becomes a mainstream concern of production sectors. Agricul­ture is directly dependent on biodiversity, but agricultural prac­tices in recent decades have focused on maximizing yields. Research and development have focused on few relatively pro­ductive species, thus ignoring the potential importance of biodi­versity. Effective response strategies include sustainable intensification, which minimizes the need for expanding total area for production, so allowing more area for biodiversity conservation. Practices such as integrated pest management, some forms of organic farming, and protection of field margins, riparian zones, and other noncultivated [[habitat]s] within farms can promote synergistic relationships between agriculture, domestic biodiversity, and wild biodiversity. However, assess­ments of biodiversity contributions from such management reveal little data about contributions to regional biodiversity conservation (C26, R5).

A review of 36 initiatives to conserve wild biodiversity while enhancing agricultural production demonstrated benefits to landscape and ecosystem diversity, while impacts on species diversity were very situation-specific. Assessing the impact of these approaches suffers from a lack of consistent, comprehen­sively documented research on the systems, particularly regarding interactions between agricultural production and ecosystem health (R5).

Tropical deforestation at a local level can be controlled most effectively when the livelihood needs of local inhabitants are addressed within the context of sustainable forestry. The early proponents of forest certification hoped it would be an effective response to tropical deforestation, but most certified forests are in the North, managed by large companies and exporting to Northern retailers (C9, C21). The proliferation of certification programs to meet the needs of different stakeholders has meant that no single program has emerged as the only credible or domi­nant approach internationally (R8.3.9). Forest management poli­cies should center on existing land and water ownership at the community level. Relevant legal tools include redesigning owner­ship to small-scale private control of forests, public-private part­nerships, direct management of forests by indigenous people, and company-community partnerships. New land tenure systems must be context-relevant and accompanied by enforcement if they are to be effective. They need to include elements of educa­tion, training, health, and safety to function effectively (R5, R8).

What Can the Private Sector Contribute to Biodiversity Objectives?

The private sector can make significant contributions to biodi­versity conservation. Some parts of the private sector are show­ing greater willingness to contribute to biodiversity conservation and sustainable use due to the influence of shareholders, custom­ers, and government regulation. Showing greater corporate social responsibility, many companies are now preparing their own biodiversity action plans, managing their own landholdings in ways that are more compatible with biodiversity conservation, supporting certification schemes that promote more sustainable use, working with multiple stakeholders, and accepting their responsibility for addressing biodiversity issues in their operations. Influence of shareholders or customers is limited in cases where the company is not publicly listed or is government-owned.

Further developments are likely to focus on two main areas. First, in addition to assessing the impact of companies on biodi­versity, important though this is, increasing emphasis will be given to ecosystem services and how companies rely on them. This will require development of mechanisms for companies to understand their risk exposure and to manage those risks. Sec­ond, greater collaboration is likely to take place between NGOs and business in order to more fully explore ways to reduce harm­ful trade-offs and identify positive synergies that could lead to more effective sustainable management practices (R5).

What Institutions, Forms of Governance, and Multilateral Processes Can Promote Effective Conservation of Biodiversity?

Governance approaches to support biodiversity conservation and sustainable use are required at all levels, with supportive laws and policies developed by central governments providing the security of tenure and authority essential for sustainable management at lower levels. The principle that biodiversity should be managed at the lowest appropriate level has led to decentralization in many parts of the world, with variable results. The key to success is strong institutions at all levels, with security of tenure and authority at the lower levels essential to providing incentives for sustainable management (R5).

At the same time that management of some ecosystem services is being devolved to lower levels, management approaches are also evolving to deal with large-scale processes with many stake­holders. Problems such as regional water scarcity and conserva­tion of large ecosystems require large-scale management structures. For example, most of the major rivers in Southern Africa flow across international borders, so international water co-management organizations are being designed to share the management of riparian resources and ensure water security for all members. However, political instability in one state may negatively affect others, and power among stakeholders is likely to be uneven.

Neither centralization nor decentralization of authority always results in better management. For example, the power of Catchment Management Agencies in South Africa is constrained to their catchment, but impacts may be felt from outside or upstream. The best strategy may be one with multi-subsidiar­ity—that is, functions that subordinate organizations perform effectively belong more properly to them (because they have the best information) than to a dominant central organization, and the central organization functions as a center of support, coordi­nation, and communication (R5).

Legal systems in countries are multilayered and in many countries, local practices or infor­mal institutions may be much stronger than the law on paper. Important customs relate to the local norms and traditions of managing property rights and the ecosystems around them. Since these are embedded in the local societies, changing these customs and customary rights through external incentive and disincen­tive schemes is very difficult unless the incen­tives are very carefully designed. Local knowledge, integrated with other scientific knowledge, becomes absolutely critical for addressing ways of managing local ecosystems.

More effort is needed in integrating biodi­versity conservation and sustainable use activi­ties within larger macroeconomic decision-making frameworks. New poverty reduction strategies have been developed in recent years covering a wide range of policies and different scales and actors. However, the integration or mainstreaming of ecosystems and ecosystem services is largely ignored. The focus of such strategies is generally on institutional and macroeconomic stability, the generation of sectoral growth, and the reduction of the number of people living on less than $1 a day in poor countries. It is well documented that many of the structural adjustment pro­grams of the mid- to late 1980s caused deterioration in ecosys­tem services and a deepening of poverty in many developing countries (R17).

International cooperation through multilateral environmen­tal agreements requires increased commitment to implementa­tion of activities that effectively conserve biodiversity and promote sustainable use of biological resources. Numerous mul­tilateral environmental agreements have now been established that contribute to conserving biodiversity. The Convention on Biological Diversity is the most comprehensive, but numerous others are also relevant, including the World Heritage Conven­tion, the Convention on International Trade in Endangered Spe­cies of Wild Fauna and Flora, the Ramsar Convention on Wetlands, the Convention on Migratory Species, the U.N. Con­vention to Combat Desertification, the U.N. Framework Con­vention on Climate Change, and numerous regional agreements. Their impacts at policy and practical levels depend on the will of the contracting parties (R5).

Effective responses may build on recent attempts (such as through joint work plans) to create synergies between conven­tions. The lack of compulsory jurisdiction for dispute resolution is a major weakness in international environmental law. How­ever, requirements to report to conventions put pressure on countries to undertake active measures under the framework of those treaties. An effective instrument should include incentives, plus sanctions for violations or noncompliance procedures to help countries come into compliance. Links between biodiversity conventions and other international legal institutions that have significant impacts on biodiversity (such as the World Trade Organization) remain weak (R5).

The international agreements with the greatest impact on bio­diversity are not in [environment]al field but rather deal with economic and political issues. These typically do not take into account their impact on biodiversity. Successful responses will require that these agreements are closely linked with other agree­ments and that solutions designed for one regime do not lead to problems in other regimes. For example, efforts to sequester car­bon under the Kyoto Protocol should seek to enhance biodiver­sity, not harm it (for example, by planting multiple species of native trees rather than monospecific plantations of exotic spe­cies) (R5).

Although biodiversity loss is a recognized global problem, most direct actions to halt or reduce loss need to be taken locally or nationally. Indirect drivers like globalization and inter­national decisions on trade and economics often have a negative effect on biodiversity and should be addressed at the interna­tional level, but the proximate responsibility to detect and act directly on biodiversity loss is at the local and national level. For threatened endemic species or ecosystems limited to an area within a single country or local administrative unit, the relevant agencies should give high priority to these species or ecosystems, with appropriate support from global, regional, or national sup­port systems (R5).

How Can the Identification, Design, and Implementation of Responses Be Improved?

Numerous response options exist to improve the benefits from ecosystem services to human societies without undermining biodiversity. The political and social changes now occurring in many parts of the world will have far-reaching consequences for the way ecosystem services and human well-being are managed in the future; it is thus imperative to develop an increased under­standing of the enabling conditions needed for choosing and implementing responses. (See Box 5.1.)

Responses do not work in a vacuum. A variety of enabling conditions—a combination of instrumental freedoms and insti­tutional frameworks—play critical roles in determining the suc­cess or failure of a response strategy. The success or failure of many responses is largely influenced by the various institutional frameworks in place in a country (CF3, R17).

Box 5.1. Key Factors of Successful Responses to Biodiversity Loss

Mobilize knowledge. Ensure that the available knowledge is presented in ways that can be used by decision-makers. Recognize complexity. Responses must serve multiple objec­tives and sectors; they must be integrated. Acknowledge uncertainty. In choosing responses, understand the limits to current knowledge, and expect the unexpected. Enable natural feedbacks. Avoid creating artificial feedbacks that are detrimental to system resilience. Use an inclusive process. Make information available and understandable to a wide range of affected stakeholders. Enhance adaptive capacity. Resilience is increased if institu­tional frameworks are put in place that allow and promote the capacity to learn from past responses and adapt accordingly. Establish supporting instrumental freedoms. Responses do not work in a vacuum, and it is therefore critical to build nec­essary supporting instrumental freedoms—enabling conditions like transparency, [[market]s], education—needed in order for the responses to work efficiently and equitably. Establish legal frameworks. A legally binding agreement is generally likely to have a much stronger effect than a soft law agreement. Have clear definitions. Agreements with clear definitions and unambiguous language will be easier to implement. Establish principles. Clear principles can help guide the parties to reach future agreement and guide the implementa­tion of an agreement. Elaborate obligations and appropriate rights. An agreement with a clear elaboration of obligations and rights is more likely to be implemented. Provide financial resources. Availability of financial resources increases the opportunities for implementation. Provide mechanisms for implementation. Where financial resources are not sufficient, market mechanisms may increase the potential for implementation. Establish implementing and monitoring (Environmental monitoring and assessment) agencies. The estab­lishment of subsidiary bodies with authority and resources to undertake specific activities to enhance the implementation of the agreements is vital to ensure continuity, preparation, and follow-up to complex issues. Establish good links with scientific bodies. As ecological issues become more complex, it becomes increasingly impor­tant to establish good institutional links between the legal pro­cess and the scientific community. Integrate traditional and scientific knowledge. Identify opportunities for incorporating traditional and local knowledge in designing responses.

Education and communication programs have both informed and changed preferences for biodiversity conservation and have improved implementation of biodiversity responses (R5). Scien­tific findings and data need to be made available to all of society. A major obstacle for knowing (and therefore valuing), preserving, sustainably using, and sharing benefits equitably from the biodi­versity of a region is the human and institutional capacity to research a country’s biota. The CONABIO initiative in Mexico and INBio in Cost Rica offer examples of successful national models for converting basic taxonomic information into knowl­edge for biodiversity conservation policies, as well as for other policies relating to ecosystems and biodiversity.

Ecosystem restoration activities are now common in many countries and include actions to restore almost all types of eco­systems, including wetlands, forests, grasslands, estuaries, [[coral reef]s], and mangroves. Restoration will become an increasingly important response as more ecosystems become degraded and as demands for their services continue to grow. Ecosystem restora­tion, however, is generally far more expensive an option than protecting the original ecosystem, and it is rare that all the biodi­versity and services of a system can be restored (R5).

Rather than the “win-win” outcomes promoted (or assumed) by many practitioners of integrated conservation and develop­ment projects, conflict is more often the norm, and trade-offs between conservation and development need to be acknowl­edged. Identifying and then negotiating trade-offs is complex, involving different policy options, different priorities for conser­vation and development, and different stakeholders. In the case of biodiversity conservation, the challenge is in negotiating these trade-offs, determining levels of acceptable biodiversity loss, and encouraging stakeholder participation. Where trade-offs must be made, decision-makers must consider and make explicit the con­sequences of all options. Better trade-offs from policies that remove perverse incentives or create [[market]s] for biodiversity protection can achieve a given level of biodiversity protection (regionally) at lower cost (R5).

The “ecosystem approaches” as developed by the CBD and others provide principles for integration across scales and across different responses. Central to the rationale is that the full range of measures is applied in a continuum from strictly protected to human-made ecosystems and that integration can be achieved through both spatial and temporal separation across the land­scape, as well as through integration within a site. The MA sub-global assessments highlight useful synergies and trade-offs where different responses are integrated into a coherent regional frame­work (SG9). While some effective approaches will not require quantification of biodiversity gains, quantifying marginal gains and losses from different sources can strengthen such integration and enable one strategy to complement another in a targeted, strategic way (R17).

Society may receive greater net benefits when opportunity costs of conservation in a particular location are adjusted to reflect positive gains from ecosystem services provided and when the setting of biodiversity targets takes all land and water use contributions into account (C5 Box 5.2, R5, R17). Debates about the relative value of formal protected areas versus lands that are more intensely used by people but that conserve at least some components of biodiversity are more constructive when conservation is seen as a continuum of possibilities. Weaknesses of both ends of the spectrum can be overcome by linking them in integrated regional strategies (R5).

For example, an area converted to agriculture can lead to loss of biodiversity but can still contribute to regional biodiversity if it contributes certain complementary elements of biodiversity to overall regional biodiversity conservation. Formal protected areas are criticized for foreclosing other opportunities for society, but an integrated regional approach can build on the biodiversity protec­tion gains from the surrounding lands, thereby reducing some of the pressure for biodiversity protection in the face of other antici­pated uses over the region. Many contributions to overall biodi­versity protection are made from production landscapes or other lands outside of protected areas, and integration allows these con­tributions to be credited at the regional planning scale and to increase regional net benefits. However, the ideal of measurable gains from production lands should not reduce the more general efforts to mainstream biodiversity into other sectors; even without formal estimates of complementarity values, mainstreaming poli­cies can be seen as important aspects of integration. (R5)

What Response Options Exist to Address Other Drivers of Biodiversity Loss?

Many of the responses designed with the conservation of bio­diversity or ecosystem service as the primary goal will not be sustainable or sufficient unless indirect and direct drivers of change are addressed. Numerous responses that address direct and indirect drivers would be particularly important for biodiver­sity and ecosystem services:

• Elimination of subsidies that promote excessive use of specific ecosystem services. Subsidies paid to the agricultural sectors of OECD countries between 2001 and 2003 averaged over $324 billion annually, or one third the global value of agricultural products in 2000 (S7). These subsidies lead to overproduction, reduce the profitability of agriculture in developing countries, and promote overuse of [[fertilizer]s] and [[pesticide]s]. Similar prob­lems are created by fishery (Fisheries and aquaculture) subsidies, which amounted to approx­imately $6.2 billion in OECD countries in 2002, or about 20% of the gross value of production (S7). Although removal of per­verse subsidies will produce net benefits, it will not be without costs. Some of the people benefiting from production subsidies (through either the low prices of products that result from the subsidies or as direct recipients of subsidies) are poor and would be harmed by their removal. Compensatory mechanisms may be needed for these groups. Moreover, removal of agricultural subsi­dies within the OECD would need to be accompanied by actions designed to minimize adverse impacts on ecosystem services in developing countries. But the basic challenge remains that the current economic system relies fundamentally on economic growth that disregards its impact on natural resources.
• Promotion of sustainable intensification of agriculture (C4, C26). The expansion of agriculture will continue to be one of the major drivers of biodiversity loss well into the twenty-first century. In regions where agricultural expansion continues to be a large threat to biodiversity, the development, assessment, and diffusion of technologies that could increase the production of food per unit area sustainably, without harmful trade-offs related to excessive consumption of water or use of nutrients or pesti­cides, would significantly lessen pressure on biodiversity. In many cases, appropriate technologies already exist that could be applied more widely, but countries lack the financial resources and intu­itional capabilities to gain and use these technologies. Where agriculture already dominates landscapes, the maintenance of biodiversity within these landscapes is an important component of total biodiversity conservation efforts, and, if managed appro­priately, can also contribute to agricultural productivity and sus­tainability through the ecosystem services that biodiversity provides (such as through pest control, pollination, soil fertility, protection of water courses against soil erosion, and the removal of excessive nutrients).
• Slowing and adapting to climate change (R13). By the end of the century, climate change and its impacts may be the dominant direct driver of biodiversity loss and change of ecosystem services globally. Harm to biodiversity will grow with both increasing rates in change in climate and increasing absolute amounts of change. For ecosystem services, some services in some regions may initially benefit from increases in temperature or precipita­tion expected under climate scenarios, but the balance of evi­dence indicates that there will be a significant net harmful impact on ecosystem services worldwide if global mean surface tempera­ture increase more than 2^o Celsius above preindustrial levels or faster than 0.2^o Celsius per decade (medium certainty). Given the inertia in the climate system, actions to facilitate the adaptation of biodiversity and ecosystems to climate change will be neces­sary to mitigate negative impacts. These may include the devel­opment of ecological corridors or networks.
• Slowing the global growth in nutrient loading (even while increasing fertilizer application in regions where crop yields are con­strained by the lack of fertilizers, such as parts of sub-Saharan Africa). Technologies already exist for reduction of nutrient pol­lution at reasonable costs, but new policies are needed for these tools to be applied on a sufficient scale to slow and ultimately reverse the increase in nutrient loading (R9).
• Correction of market failures and internalization of environ­mental externalities that lead to the degradation of ecosystem services (R17, R10, R13). Because many ecosystem services are not traded in [[market]s], markets fail to provide appropriate signals that might otherwise contribute to the efficient allocation and sus­tainable use of the services. In addition, many of the harmful trade-offs and costs associated with the management of one eco­system service are borne by others and so also do not weigh into decisions regarding the management of that service. In countries with supportive institutions in place, market-based tools can be used to correct some market failures and internalize externalities, particularly with respect to provisioning ecosystem services.
• Increased transparency and accountability of government and private-sector performance in decisions that affect ecosystems, includ­ing through greater involvement of concerned stakeholders in deci­sion-making (RWG, SG9). Laws, policies, institutions, and markets that have been shaped through public participation in decision-making are more likely to be effective and perceived as just. Stakeholder participation also contributes to the decision-making process because it allows for a better understanding of impacts and vulnerability, the distribution of costs and benefits associated with trade-offs, and the identification of a broader range of response options that are available in a specific context. And stakeholder involvement and transparency of decision-making can increase accountability and reduce corruption.
• Integration of biodiversity conservation strategies and responses within broader development planning frameworks. For example, protected areas, restoration ecology, and markets for ecosystem services will have higher chances of success if these responses are reflected in the national development strategies or in poverty reduction strategies, in the case of many developing countries. In this manner, the costs and benefits of these conservation strate­gies and their contribution to human development are explicitly recognized in the Public Expenditure Review and resources for the implementation of the responses can be set aside in national Mid-Term Budgetary Frameworks (R17).
• Increased coordination among multilateral environmental agreements and between environmental agreements and other inter­national economic and social institutions (R17). International agreements are indispensable for addressing ecosystem-related concerns that span national boundaries, but numerous obstacles weaken their current effectiveness. The limited, focused nature of the goals and mechanisms included in most bilateral and multi­lateral environmental treaties does not address the broader issue of ecosystem services and human well-being. Steps are now being taken to increase coordination among these treaties, and this could help broaden the focus of the array of instruments. How­ever, coordination is also needed between the multilateral envi­ronmental agreements and the more politically powerful international legal institutions, such as economic and trade agreements, to ensure that they are not acting at cross-purposes.
• Enhancement of human and institutional capacity for assessing the consequences of ecosystem change for human well-being and act­ing on such assessments (RWG). Technical capacity for agriculture, forestry, and fisheries (Fisheries and aquaculture) management is still limited in many coun­tries, but it is vastly greater than the capacity for effective man­agement for ecosystem services not derived from these sectors.
• Addressing unsustainable consumption patterns (RWG). Con­sumption of ecosystem services and nonrenewable resources affects biodiversity and ecosystems directly and indirectly. Total consumption is a factor of per capita consumption, population, and efficiency of resource use. Slowing biodiversity loss requires that the combined effect of these factors be reduced.

What are the prospects for reducing the rate of loss of biodiversity by 2010 or beyond and what are the implications for the Convention on Biological Diversity?

• Biodiversity will continue to decline during this century. While biodiversity makes important contributions to human well-being, many of the actions needed to promote economic devel­opment and reduce hunger and poverty are likely to reduce biodiversity. This makes the policy changes necessary to reverse these trends difficult to agree on and implement in the short term.
• Since biodiversity is essential to human well-being and sur­vival, however, biodiversity loss has to be controlled in the long term. A reduction in the rate of loss of biodiversity is a neces­sary first step. Progress in this regard can be achieved by 2010 for some components, but it is unlikely that it can be achieved for biodiversity overall at the global level by 2010.
• Many of the necessary actions to reduce the rate of biodi­versity loss are already incorporated in the programs of work of the Convention on Biological Diversity, and if fully implemented they would make a substantial difference. Yet even if existing measures are implemented, this would be insufficient to address all the drivers of biodiversity loss.

In April 2002, the Conference of the Parties of the Conven­tion on Biological Diversity adopted the target, subsequently endorsed in the Johannesburg Plan of Implementation adopted at the World Summit on Sustainable Development, to “achieve by 2010 a significant reduction of the current rate of biodiversity loss at the global, regional, and national level as a contribution to poverty alleviation and to the benefit of all life on earth” (CBD Decision VI/26). In 2004, the Conference of the Parties adopted a framework for evaluation, including a small number of global 2010 sub-targets, and a set of indicators that will be used in assessing progress (C4.5.2).

To assess progress toward the target, the Conference of the Parties defines biodiversity loss as the “long-term or permanent qualitative or quantitative reduction in components of biodiver­sity and their potential to provide goods and services, to be measured at global, regional, and national levels” (CBD Decision VII/30). The objectives of the Convention and the 2010 target are translated into policies and concrete action through the agreement of international guidelines and the implementation of work programs of the Convention and through National Biodi­versity Strategies and Action Plans.

An unprecedented effort would be necessary to achieve by 2010 a significant reduction of the current rate of biodiversity loss at global, regional, and national levels. The 2010 target implies that the rate of loss of biodiversity—as indicated by mea­sures of a range of components or attributes—would need to be significantly less in 2010 than the current or recent trends described in Key Question 3 of this report. This is unlikely to be achieved globally for various reasons: current trends show few indications of slowing the rate of loss; most of the direct drivers of biodiversity loss are projected to increase; and inertia in natural and human institutional systems implies lags of years, decades, or even centuries between actions taken and their impact on biodiversity and ecosystems (C4, S7, S10, R5).

With appropriate responses at global, regional, and especially national level, it is possible to achieve, by 2010, a reduction in the rate of biodiversity loss for certain components of biodiver­sity or for certain indicators, and in certain regions, and several of the 2010 sub-targets adopted by the CBD could be met. Overall the rate of habitat loss—the main driver of biodiversity loss in [[terrestrial] ecosystems]—is slowing in certain regions and could slow globally if proactive approaches are taken (S10). This may not necessarily translate into lower rates of species loss, how­ever, because of the nature of the relationship between numbers of species and area of habitat, because decades or centuries may pass before species extinctions reach equilibrium with habitat loss, and because other drivers of loss, such as climate change, nutrient loading, and invasive species, are projected to increase. While rates of habitat loss are decreasing in temperate areas, they are projected to continue to increase in tropical areas (C4, S10).

At the same time, if areas of particular importance for biodi­versity and functioning ecological networks are maintained within protected areas or by other conservation mechanisms, and if proactive measures are taken to protect endangered species, the rate of biodiversity loss of the targeted habitats and species could be reduced. Further, it would be possible to achieve many of the sub-targets aimed at protecting the components of biodiversity if the response options that are already incorporated into the CBD programs of work are implemented. However, it appears highly unlikely that the sub-targets aimed at addressing threats to biodi­versity—land use change, climate change, pollution, and invasive alien species—could be achieved by 2010. It will also be a major challenge to maintain goods and services from biodiversity to support human well-being (C4, S10, R5). (See Table 6.1.)

There is substantial scope for greater protection of biodiver­sity through actions justified on their economic merits for material or other benefits to human well-being. Conservation of biodiversity is essential as a source of particular biological resources, to maintain different ecosystem services, to maintain the resilience of ecosystems, and to provide options for the future. These benefits that biodiversity provides to people have not been well reflected in decision-making and resource manage­ment, and thus the current rate of loss of biodiversity is higher than what it would be had these benefits been taken into account (R5). (See Figure 6.1.)

However, the total amount of biodiversity that would be con­served based strictly on utilitarian considerations is likely to be less than the amount present today (medium certainty). Even if utilitarian benefits were taken fully into account, planet Earth would still be losing biodiversity, as other utilitarian benefits often “compete” with the benefits of maintaining greater diver­sity. Many of the steps taken to increase the production of spe­cific ecosystem services require the simplification of natural systems (in agriculture, for example). Moreover, managing eco­systems without taking into account the full range of ecosystem services may not necessarily require the conservation of biodiver­sity. (For example, a forested watershed could provide clean water and timber whether it was covered by a diverse native forest or a single-species plantation, but a single-species plantation may not provide significant levels of many other services, such as pollina­tion, food, and cultural services.) Ultimately, the level of biodi­versity that survives on Earth will be determined to a significant extent by ethical concerns in addition to utilitarian ones (C4, C11, S10, R5).

Trade-offs between achieving the MDG targets for 2015 and reducing the rate of biodiversity loss are likely. For example, improving rural road networks—a common feature of hunger reduction strategies—will likely accelerate rates of biodiversity loss (directly through habitat fragmentation and indirectly by facilitating unsustainable harvests of bushmeat and so on). More­over, one of the MA scenarios (Global Orchestration) suggests that future development paths that show relatively good progress toward the MDG of eradicating extreme poverty and improving health also showed relatively high rates of habitat loss and associ­ated loss of species over 50 years. (See Figure 6.2.) This does not imply that biodiversity loss is, in itself, good for poverty and hunger reduction. Instead, it indicates that many economic development activities aimed at poverty reduction are likely to have negative impacts on biodiversity unless the value of biodi­versity and related ecosystem services are factored in (S10, R19).

In fact, some short-term improvements in material welfare and livelihoods due to actions that lead to the loss of biodiversity that is particularly important to the poor and vulnerable may actually make these gains temporary—and may in fact exacerbate all con­stituents of poverty in the long term. To avoid this, efforts for the conservation and sustainable use of biodiversity need to be inte­grated into countries’ strategies for poverty reduction (S10, R5).

But there are potential synergies as well as trade-offs between the short-term MDG targets for 2015 and reducing the rate of loss of biodiversity by 2010. For a reduction in the rate of biodi­versity loss to contribute to poverty alleviation, priority would need to be given to protecting the biodiversity of particular importance to the well-being of poor and vulnerable people. Given that biodiversity underpins the provision of ecosystem ser­vices that are vital to human well-being, long-term sustainable achievement of the Millennium Development Goals requires that biodiversity loss is reduced controlled as part of MDG 7 (ensur­ing environmental sustainability).

Given the characteristic response times for human systems (political, social, and economic) and ecological systems, longer-term goals and targets—say, for 2050—are needed in addition to short-term targets to guide policy and actions. Biodiversity loss is projected to continue for the foreseeable future (S10). The indirect drivers of biodiversity loss are related to economic, demographic, sociopolitical, cultural, and technological factors. Consumption of ecosystem services and of energy and nonre­newable resources has an impact, directly and indirectly, on bio­diversity and ecosystems. Total consumption is a factor of per capita consumption, population, and efficiency of natural resource use. Halting biodiversity loss (or reducing it to a mini­mal level) requires that the combined effect of these factors in driving biodiversity loss be reduced (C4, S7).

Differences in the inertia of different drivers of biodiversity change and different attributes of biodiversity itself make it difficult to set targets or goals over a single time frame. For some drivers, such as the overharvesting of particular species, lag times are rather short; for others, such as nutrient loading and, especially, climate change, lag times are much longer. Addressing the indirect drivers of change may also require somewhat longer time horizons given political, socioeconomic, and demographic inertias. Population (Population growth rate) is projected to stabilize around the middle of the century and then decrease. Attention also needs to be given to addressing unsustainable consumption patterns. At the same time, while actions can be taken to reduce the drivers and their impacts on biodiversity, some change is inevitable, and adaptation to such change will become an increasingly important component of response measures (C4.5.2, S7, R5).

The world in 2100 could have substantial remaining biodi­versity or could be relatively homogenized and contain rela­tively low levels of diversity. Sites that are globally important for biodiversity could be protected while locally or nationally important biodiversity is lost. Science can help to inform the costs and benefits of these different futures and identify paths to achieve them, along with the risks and the thresholds. Where there is insufficient information to predict the consequences of alternative actions, science can identify the range of possible outcome. Science can thus help ensure that social decisions are made with the best available information. But ultimately the choice of biodiversity futures must be determined by society.

Notes

^ 1. Biomes represent broad habitat and vegetation (Land-cover) types, span across biogeographic realms, and are useful units for assessing global biodiversity and ecosystem services because they stratify the globe into [[ecological]ly] meaningful and contrasting classes. Throughout this report, and elsewhere in the MA, the 14 biomes of the WWF [[terrestrial] biome] classification are used, based on WWF terrestrial ecoregions (C4.2.2).

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(2011). Ecosystems and Human Well-being: Biodiversity Synthesis: Key Questions on Biodiversity in the Millennium Ecosystem Assessment. Retrieved from http://editors.eol.org/eoearth/wiki/Ecosystems_and_Human_Well-being:_Biodiversity_Synthesis:_Key_Questions_on_Biodiversity_in_the_Millennium_Ecosystem_Assessment