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 habitats 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 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 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 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 eutrophication. 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). Page 2Biodiversity 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 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 markets 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 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 pesticides 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 (C26.2). 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). Page 3
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 (biomes), 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 populations and habitats 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 reefs 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 (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):
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 populations (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 biomes 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 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 biomes (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 (C26.2). 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 bio-diversity 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 distrib-uted 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). Page 4
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 biomes. Climate change is projected to increasingly affect all aspects of biodiversity, from individual organisms, through populations 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 deserts, boreal forests, 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 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 groundwater (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 eutrophication 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). Page 5Biodiversity 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 the 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 growth in the South (TechnoGarden) or through greater protection of local ecosystems (Adapting Mosaic). In contrast, in the scenarios that are not proactive on the 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 1.0–1.5o Celsius, and between 2000 and 2100 of 2.0–3.5o 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 noncultivated vegetation. 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° 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 (1.5–5.5° 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 groundwaters. 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 the 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 populations 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). Page 6Governance 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 the environmental 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). Page 7
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) Table 6.1. Prospects for Attaining the 2010 Sub-targets Agreed to under the Convention on Biological Diversity 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 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. Page 8Finding 1. Human actions are fundamentally, and to a significant extent irreversibly, changing the diversity of life on Earth, and most of these changes represent a loss of biodiversity. Changes in important components of biological diversity were more rapid in the past 50 years than at any time in human history. Projections and scenarios indicate that these rates will continue, or accelerate, in the future. 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. Between 1960 and 2000, reservoir storage capac-ity quadrupled, and as a result the amount of water stored behind large dams is estimated to be three to six times the amount of water flowing through rivers at any one time. Some 35% of man-groves have been lost in the last two decades in countries where adequate data are available (encompassing about half of the total mangrove area). Already 20% of known coral reefs have been destroyed and another 20% degraded in the last several decades. Although the most rapid changes in ecosystems are now taking place in developing countries, industrial countries historically experienced comparable changes. Over half of the 14 biomes that the MA assessed have experi-enced a 20–50% conversion to human use, with temperate and Mediterranean forests and temperate grasslands being the most affected (approximately three quarters of these biome’s native habitat has been replaced by cultivated lands). In the last 50 years, rates of conversion have been highest in tropical and sub-tropical dry forests. Globally, the net rate of conversion of some ecosystems has begun to slow, although in some instances this is because 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. Increased agricul-tural productivity is also diminishing pressures for agricultural expansion. Since 1950, cropland areas in North America, Europe, and China have stabilized, and they even decreased in Europe and China. Cropland areas in the former Soviet Union have decreased since 1960. Within temperate and boreal zones, forest cover increased by approximately 3 million hectares per year in the 1990s, although about 40% of this increase consisted of forest plantations. Across a range of taxonomic groups, the population size or range (or both) of the majority of species is declining. Studies of amphibians globally, African mammals, birds in agricultural lands, British butterflies, Caribbean and IndoPacific corals, and commonly harvested fish species show declines in populations of the majority of species. Exceptions include species that have been protected in reserves, that have had their particular threats (such as overexploitation) eliminated, and that tend to thrive in land-scapes that have been modified by human activity. Marine and freshwater ecosystems are relatively less studied than terrestrial systems, so overall biodiversity is poorly understood; for those species that are well studied, biodiversity loss has occurred through population extirpation and constricted distributions. Over the past few hundred years, humans have increased species extinction rates by as much as 1,000 times background rates that were typical over Earth’s history. (See Figure 1) There are approximately 100 well-documented extinctions of birds, mammals, and amphibians over the last 100 years—a rate 100 times higher than background rates. If less well documented but highly probable extinctions are included, the rate is more than 1,000 times higher than background rates. The distribution of species on Earth is becoming more homogenous. By homogenous, we mean that the differences between the set of species at one location and the set of species at another location are, on average, diminishing. Two factors are responsible for this trend. First, species unique to particular regions are experiencing higher rates of extinction. Second, high rates of invasion by and introductions of species into new ranges are accelerating in pace with growing trade and faster transporta-tion. Currently, documented rates of species introductions in most regions are greater than documented rates of extinction, which can lead to anomalous, often transient increases in local diversity. The consequences of homogenization depend on the aggressiveness of the introduced species and the services they either bring (such as when introduced for forestry or agriculture) or impair (such as when loss of native species means loss of options and biological insurance). Between 10% and 50% of well-studied higher taxonomic groups (mammals, birds, amphibians, conifers, and cycads) are currently threatened with extinction, based on IUCN–World Conservation Union criteria for threats of extinction. Some 12% of bird species, 23% of mammals, and 25% of conifers are currently threatened with extinction. In addition, 32% of amphibians are threatened with extinction, but information is more limited and this may be an underestimate. Higher levels of threat (52%) have been found in the cycads, a group of evergreen palm-like plants. Aquatic (including both marine and freshwater) organisms, however, have not been tracked to the same degree as terrestrial ones, masking what may be similarly alarming threats of extinction (low certainty). Genetic diversity has declined globally, particularly among domesticated species. 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, has led to a substantial reduction in the genetic diversity of domesticated plants and animals in agricultural systems. Such declines in genetic diversity lower the resilience and adaptability of domesticated species. Some of these on-farm losses of crop genetic diversity have been partially offset by the maintenance of genetic diversity in seed banks. In addition to cultivated systems, the extinction of species and loss of unique populations (including commercially important marine fishes) 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. All scenarios explored in the Millennium Ecosystem Assessment project continuing rapid conversion of ecosystems in the first half of the twenty-first century.Roughly 10–20% (low to medium certainty) of current grassland and forestland is projected to be converted to other uses between now and 2050, mainly due to the expansion of agriculture and, second, due to the expansion of cities and infrastructure. The habitat losses projected in the MA scenarios will lead to global extinctions as species numbers approach equilibrium with the remnant habitat. The equilibrium number of plant species is projected to be reduced by roughly 10–15% as a result of habitat loss over the period 1970–2050 in the MA scenarios (low certainty), but this projection is likely to be an underestimate as it does not consider reductions due to stresses other than habitat loss, such as climate change and pollution. Similarly, modification of river water flows will drive losses of fish species. Page 9Home » Biodiversity (MA) » Level 2 » Question 8
Finding 1. Human actions are fundamentally, and to a significant extent irreversibly, changing the diversity of life on Earth, and most of these changes represent a loss of biodiversity. Changes in important components of biological diversity were more rapid in the past 50 years than at any time in human history. Projections and scenarios indicate that these rates will continue, or accelerate, in the future. Species extinction is a natural part of Earth's history. However, over the past 100 years, humans have increased the extinction rate by at least 100 times compared to the natural rate, leading to a net loss of biodiversity. Some 12% of bird species, 23% of mammals, 25% of conifers, and 32% of amphibians are currently threatened with extinction, and similarly alarming threats of extinction may apply to aquatic organisms. Many animal and plant populations have declined in numbers, geographical spread, or both. Genetic diversity has also declined globally, particularly among domesticated plants and animals in agricultural systems. The distribution of species on Earth is becoming more homogeneous. This is caused by the extinction of species or loss of populations that had been unique to particular regions, and by the invasion or introduction of species into new areas. Virtually all of Earth's ecosystems have now been dramatically transformed through human actions. Due to the expansion of agriculture, cities and infrastructure, the conversion of ecosystems is expected to continue between now and 2050. More...
Finding 2. Biodiversity contributes both directly and indirectly to many constituents of human well-being, including security, basic material for a good life, health, good social relations, and freedom of choice and action. Over the last century, many people have benefited from the transformation of natural ecosystems and the exploitation of biodiversity, but the losses in biodiversity and changes in ecosystem services have adversely affected the well-being of some people and exacerbated poverty in some social groups. Many of the actions that have caused the homogenization or loss of biodiversity have provided substantial benefits to humans. Agriculture, fisheries, and forestry, for example, have yielded revenues that have enabled investments in industrialization and economic growth. However, the benefits have not been fairly distributed among people and many of the costs of changes in biodiversity have not been taken into account by decision-makers. When humans modify an ecosystem to improve one of the services it provides, it generally results in changes to other ecosystem services. For example, actions to increase food production can lead to reduced water availability for other uses, and degraded water quality. Although a few ecosystem services have been enhanced by humans, many other ecosystem services have been degraded. Many costs associated with changes in biodiversity may be slow to become apparent, or may appear only at some distance from where biodiversity was changed. Some changes in ecosystems are gradual until a particular pressure on the ecosystem reaches a threshold, at which point rapid shifts to a new state occur. For instance, a steady increase in fishing pressure can cause the sudden collapse of fisheries. Biodiversity loss is important in its own right because biodiversity has spiritual, aesthetic, recreational, and other cultural values, because many people ascribe intrinsic value to biodiversity, and because it represents unexplored options for the future. More...
Finding 3. Although many individuals benefit from the actions and activities that lead to biodiversity loss and ecosystem change, the full costs borne by society is often higher. This is revealed by improved valuation techniques and information on ecosystem services. Even in cases where our knowledge of benefits and costs is incomplete, a precautionary approach may be justified when the costs associated with ecosystem changes may be high or the changes irreversible. Even in cases where the costs borne by society exceeded the benefits, ecosystem conversion has often been promoted because the cost associated with the loss of ecosystem services was not taken into account, because the private gains were significant (although less than the public losses), and also because subsidies sometimes distorted the market. The benefits that could be gained from better ecosystem management are poorly reflected in conventional economic indicators. A country could cut its forests and deplete its fisheries and this would show only as a positive gain in GDP despite the loss of the capital asset. The costs resulting from ecosystem "surprises", such as extreme events like floods and fire, can be very high. The costs and risks associated with biodiversity loss are expected to increase, and to affect disproportionately the poor who depend more heavily on local ecosystem service. New tools exist to better quantify the different values people place on biodiversity and ecosystem services. However, the value of some ecosystem services is difficult to quantify, and often not taken into account in decision making. More...
Finding 5. Many of the actions that have been taken to conserve biodiversity and promote its sustainable use have been successful in limiting biodiversity loss. Rates of loss are now lower than they would have been in the absence of such actions. Less biodiversity would exist today had not communities, NGOs, governments, and, to a growing extent, business and industry taken actions to conserve biodiversity, mitigate its loss, and support its sustainable use. To achieve greater progress toward biodiversity conservation, it will be necessary (but not sufficient) to strengthen a series of actions that focus primarily on conservation and sustainable use of biodiversity and ecosystem services. Actions that focus primarily on conservation include: protected areas; species protection and recovery measures for threatened species; conservation of genetic diversity; both on and off sites (such as in gene banks); and ecosystem restoration. Actions that focus primarily on sustainable use include: providing economic incentives; incorporating biodiversity considerations into management practices (for instance in agriculture, forestry, and fisheries); ensuring that local communities benefit from biodiversity. Actions that address both conservation and sustainable use include: increasing coordination between international agreements that affect biodiversity and resource use; increasing public awareness, communication, and education; improving our capacity to assess the consequences of ecosystem change for human well-being; and increasing the integration between different policy areas. However, many of all the above actions will not be sufficient unless other indirect and direct drivers of change are addressed and certain enabling conditions are met. More...
Finding 6. Unprecedented additional efforts would be needed to achieve, by 2010, a significant reduction in the rate of biodiversity loss at all levels. Indeed, the challenge is great, as it can take many years for human institutions to act and for positive and negative impacts of human actions on biodiversity and ecosystem to become apparent. Given appropriate actions, it is possible to achieve, by 2010, a reduction in the rate of biodiversity loss for certain aspects of biodiversity and in certain regions. The rate of habitat loss, for instance, is now slowing in some regions, though this may not necessarily translate into lower overall rates of species loss. Decision-making at all levels could be improved through a better understanding of the impacts of drivers on biodiversity, ecosystem functioning, and ecosystem services. Since changes take place over different time frames, longer-term goals and targets - say, for 2050 - are needed in addition to short-term targets to guide policy and actions. 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. Thus, the 2015 targets of the Millennium Development Goals of poverty alleviation and the 2010 target of reducing the rate of biodiversity loss need to be addressed jointly. People and decision-makers today still have the power to choose among a very wide array of possible approaches, and these choices will have different implications for biodiversity and human well-being of current and future generations. Depending on the path that will be taken, the world in 2100 could still have a substantial biodiversity or be relatively homogenized with relatively low levels of diversity. More... |
Which of the following best describes the relationship between habitat structure and biodiversity
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