How have ecosystems changed?

Ecosystem Structure

The structure of the world’s ecosystems changed more rapidly in the second half of the twentieth century than at any time in recorded human history, and virtually all of Earth’s ecosystems have now been significantly transformed through human actions. The most significant change in the structure of ecosystems has been the transformation of approximately one quarter (24%) of Earth’s terrestrial surface to cultivated systems (C26.1.2). (See Box 1.1.) More land was converted to cropland in the 30 years after 1950 than in the 150 years between 1700 and 1850 (C26).

Figure 1.1. Time Series of Intercepted Continental Runoff and Large Reservoir Storage, 1900–2000 (C7 Fig 7.8) Source: Millennium Ecosystem Assessment

Between 1960 and 2000, reservoir storage capacity quadrupled (C7.2.4); as a result, the amount of water stored behind large dams is estimated to be three to six times the amount held by natural river channels (this excludes natural lakes) (C7.3.2). (See Figure 1.1.) In countries for which sufficient multi-year data are available (encompassing more than half of the present-day mangrove area), approximately 35% of mangroves were lost in the last two decades (C19.2.1). Roughly 20% of the world’s coral reefs were lost and an additional 20% degraded in the last several decades of the twentieth century (C19.2.1). Box 1.1 and Table 1.1 summarize important characteristics and trends in different ecosystems.

Although the most rapid changes in ecosystems are now taking place in developing countries, industrial countries historically experienced comparable rates of change. Croplands expanded rapidly in Europe after 1700 and in North America and the former Soviet Union particularly after 1850 (C26.1.1). Roughly 70% of the original temperate forests and grasslands and Mediterranean forests had been lost by 1950, largely through conversion to agriculture (C4.4.3). Historically, deforestation has been much more intensive in temperate regions than in the tropics, and Europe is the continent with the smallest fraction of its original forests remaining (C21.4.2). However, changes prior to the industrial era seemed to occur at much slower rates than current transformations.

Box 1.1. Characteristics of the World’s Ecological Systems

We report assessment findings for 10 categories of the land and marine surface, which we refer to as “systems”: forest, cultivated, dryland, coastal, marine, urban, polar, inland water, island, and mountain. Each category contains a number of ecosystems. However, ecosystems within each category share a suite of biological, climatic, and social factors that tend to be similar within categories and differ across categories. The MA reporting categories are not spatially exclusive; their areas often overlap. For example, transition zones between forest and cultivated lands are included in both the forest system and cultivated system reporting categories. These reporting categories were selected because they correspond to the regions of responsibility of different government ministries (such as agriculture, water, forestry, and so forth) and because they are the categories used within the Convention on Biological Diversity. Marine, Coastal, and Island Systems Source: Millennium Ecosystem Assessment Marine systems are the world’s oceans. For mapping purposes, the map shows ocean areas where the depth is greater than 50 meters. Global fishery catches from marine systems peaked in the late 1980s and are now declining despite increasing fishing effort (C18.ES). Coastal systems refer to the interface between ocean and land, extending seawards to about the middle of the continental shelf and inland to include all areas strongly influenced by proximity to the ocean. The map shows the area between 50 meters below mean sea level and 50 meters above the high tide level or extending landward to a distance 100 kilometers from shore. Coastal systems include coral reefs, intertidal zones, estuaries, coastal aquaculture, and seagrass communities. Nearly half of the world’s major cities (having more than 500,000 people) are located within 50 kilometers of the coast, and coastal population densities are 2.6 times larger than the density of inland areas. By all commonly used measures, the human well-being of coastal inhabitants is on average much higher than that of inland communities (C19.3.1). Islands are lands (both continental and oceanic) isolated by surrounding water and with a high proportion of coast to hinterland. For mapping purposes, the MA uses the ESRI ArcWorld Country Boundary dataset, which contains nearly 12,000 islands. Islands smaller than 1.5 hectares are not mapped or included in the statistics. The largest island included is Greenland. The map includes islands within 2 kilometers of the mainland (e.g., Long Island in the United States), but the statistics provided for island systems in this report exclude these islands. Island states, together with their exclusive economic zones, cover 40% of the world’s oceans (C23.ES). Island systems are especially sensitive to disturbances, and the majority of recorded extinctions have occurred on island systems, although this pattern is changing, and over the past 20 years as many extinctions have occurred on continents as on islands (C4.ES). Urban, Dryland, and Polar Systems Source: Millennium Ecosystem Assessment Urban systems are built environments with a high human density. For mapping purposes, the MA uses known human settlements with a population of 5,000 or more, with boundaries delineated by observing persistent night-time lights or by inferring areal extent in the cases where such observations are absent. The world’s urban population increased from about 200 million in 1900 to 2.9 billion in 2000, and the number of cities with populations in excess of 1 million increased from 17 in 1900 to 388 in 2000 (C27.ES). Dryland systems are lands where plant production is limited by water availability; the dominant human uses are large mammal herbivory, including livestock grazing, and cultivation. The map shows drylands as defined by the U.N. Convention to Combat Desertification, namely lands where annual precipitation is less than two thirds of potential evapotranspiration— from dry sub-humid areas (ratio ranges 0.50–0.65) through semiarid, arid, and hyperarid (ratio <0.05), but excluding polar areas. Drylands include cultivated lands, scrublands, shrublands, grasslands, savannas, semi-deserts, and true deserts. Dryland systems cover about 41% of Earth’s land surface and are inhabited by more than 2 billion people (about one third of the total population) (C22.ES). Croplands cover approximately 25% of drylands (C22 Table 22.2), and dryland rangelands support approximately 50% of the world’s livestock (C22). The current socioeconomic condition of people in dryland systems, of which about 90% are in developing countries, is worse than in other areas. Fresh water availability in drylands is projected to be further reduced from the current average of 1,300 cubic meters per person per year in 2000, which is already below the threshold of 2,000 cubic meters required for minimum human wellbeing and sustainable development (C22.ES). Approximately 10–20% of the world’s drylands are degraded (medium certainty) (C22.ES). Polar systems are high-latitude systems frozen for most of the year, including ice caps, areas underlain by permafrost, tundra, polar deserts, and polar coastal areas. Polar systems do not include high-altitude cold systems in low latitudes. Temperature in polar systems is on average warmer now than at any time in the last 400 years, resulting in widespread thaw of permafrost and reduction of sea ice (C25.ES). Most changes in feedback processes that occur in polar regions magnify trace gas–induced global warming trends and reduce the capacity of polar regions to act as a cooling system for Earth (C25.ES). Tundra constitutes the largest natural wetland in the world (C25.1). Forest Systems Source: Millennium Ecosystem Assessment Forest systems are lands dominated by trees; they are often used for timber, fuelwood, and non-wood forest products. The map shows areas with a canopy cover of at least 40% by woody plants taller than 5 meters. Forests include temporarily cut-over forests and plantations but exclude orchards and agroforests where the main products are food crops. The global area of forest systems has been reduced by one half over the past three centuries. Forests have effectively disappeared in 25 countries, and another 29 have lost more than 90% of their forest cover (C21.ES). Forest systems are associated with the regulation of 57% of total water runoff. About 4.6 billion people depend for all or some of their water on supplies from forest systems (C7 Table 7.2). From 1990 to 2000, the global area of temperate forest increased by almost 3 million hectares per year, while deforestation in the tropics occured at an average rate exceeding 12 million hectares per year over the past two decades (C.SDM). Cultivated Systems Source: Millennium Ecosystem Assessment Cultivated systems are lands dominated by domesticated species and used for and substantially changed by crop, agroforestry, or aquaculture production. The map shows areas in which at least 30% by area of the landscape comes under cultivation in any particular year. Cultivated systems, including croplands, shifting cultivation, confined livestock production, and freshwater aquaculture, cover approximately 24% of total land area. In the last two decades, the major areas of cropland expansion were located in Southeast Asia, parts of South Asia, the Great Lakes region of eastern Africa, the Amazon Basin, and the U.S. Great Plains. The major decreases of cropland occurred in the southeastern United States, eastern China, and parts of Brazil and Argentina (C26.1.1). Most of the increase in food demand of the past 50 years has been met by intensification of crop, livestock, and aquaculture systems rather than expansion of production area. In developing countries, over the period 1961– 99 expansion of harvested land contributed only 29% to growth in crop production, although in sub-Saharan Africa expansion accounted for two thirds of growth in production (C26.1.1). Increased yields of crop production systems have reduced the pressure to convert natural ecosystems into cropland, but intensification has increased pressure on inland water ecosystems, generally reduced biodiversity within agricultural landscapes, and it requires higher energy inputs in the form of mechanization and the production of chemical fertilizers. Cultivated systems provide only 16% of global runoff, although their close proximity to humans means that about 5 billion people depend for all or some of their water on supplies from cultivated systems (C7 Table 7.2). Such proximity is associated with nutrient and industrial water pollution. Inland Water and Mountain Systems Source: Millennium Ecosystem Assessment Inland water systems are permanent water bodies inland from the coastal zone and areas whose properties and use are dominated by the permanent, seasonal, or intermittent occurrence of flooded conditions. Inland waters include rivers, lakes, floodplains, reservoirs, wetlands, and inland saline systems. (Note that the wetlands definition used by the Ramsar Convention includes the MA inland water and coastal system categories.) The biodiversity of inland waters appears to be in a worse condition than that of any other system, driven by declines in both the area of wetlands and the water quality in inland waters (C4 and C20). It is speculated that 50% of inland water area (excluding large lakes) has been lost globally (C20.ES). Dams and other infrastructure fragment 60% of the large river systems in the world (C20.4. Mountain systems are steep and high lands. The map is based on elevation and, at lower elevations, a combination of elevation, slope, and local topography. Some 20% (or 1.2 billion) of the world’s people live in mountains or at their edges, and half of humankind depends, directly or indirectly, on mountain resources (largely water) (C24.ES). Nearly all—90%—of the 1.2 billion people in mountains live in countries with developing or transition economies. In these countries, 7% of the total mountain area is currently classified as cropland, and people are often highly dependent on local agriculture or livestock production (C24.3.2). About 4 billion people depend for all or some of their water on supplies from mountain systems. Some 90 million mountain people—almost all those living above 2,500 meters—live in poverty and are considered especially vulnerable to food insecurity (C24.1.4).

The ecosystems and biomes that have been most significantly altered globally by human activity include marine and freshwater ecosystems, temperate broadleaf forests, temperate grasslands, Mediterranean forests, and tropical dry forests. (See Figure 1.2 and C18, C20.) Within marine systems, the world’s demand for food and animal feed over the last 50 years has resulted in fishing pressure so strong that the biomass of both targeted species and those caught incidentally (the “bycatch”) has been reduced in much of the world to one tenth of the levels prior to the onset of industrial fishing (C18.ES). Globally, the degradation of fisheries is also reflected in the fact that the fish being harvested are increasingly coming from the less valuable lower trophic levels as populations of higher trophic level species are depleted. (See Figure 1.3.)

Figure 1.2. Conversion of Terrestrial Biomes^a (Adapted from C4, S10) Source: Millennium Ecosystem Assessment

Freshwater ecosystems have been modified through the creation of dams and through the withdrawal of water for human use. The construction of dams and other structures along rivers has moderately or strongly affected flows in 60% of the large river systems in the world (C20.4.2). Water removal for human uses has reduced the flow of several major rivers, including the Nile, Yellow, and Colorado Rivers, to the extent that they do not always flow to the sea. As water flows have declined, so have sediment flows, which are the source of nutrients important for the maintenance of estuaries. Worldwide, although human activities have increased sediment flows in rivers by about 20%, reservoirs and water diversions prevent about 30% of sediments from reaching the oceans, resulting in a net reduction of sediment delivery to estuaries of roughly 10% (C19.ES).

Within terrestrial ecosystems, more than two thirds of the area of 2 of the world’s 14 major terrestrial biomes (temperate grasslands and Mediterranean forests) and more than half of the area of 4 other biomes (tropical dry forests, temperate broadleaf forests, tropical grassland, and flooded grasslands) had been converted (primarily to agriculture) by 1990, as Figure 1.3 indicated. Among the major biomes, only tundra and boreal forests show negligible levels of loss and conversion, although they have begun to be affected by climate change.

Globally, the rate of conversion of ecosystems has begun to slow largely due to reductions in the rate of expansion of cultivated land, and in some regions (particularly in temperate zones) ecosystems are returning to conditions and species compositions similar to their pre-conversion states. Yet rates of ecosystem conversion remain high or are increasing for specific ecosystems and regions. Under the aegis of the MA, the first systematic examination of the status and trends in terrestrial and coastal land cover was carried out using global and regional datasets. The pattern of deforestation, afforestation, and dryland degradation between 1980 and 2000 is shown in Figure 1.4. Opportunities for further expansion of cultivation are diminishing in many regions of the world as most of the land well-suited for intensive agriculture has been converted to cultivation (C26. ES). Increased agricultural productivity is also diminishing the need for agricultural expansion.

Figure 1.3. Decline in Trophic Level of Fisheries Catch since 1950 (C18) Source: Millennium Ecosystem Assessment

As a result of these two factors, a greater fraction of land in cultivated systems (areas with at least 30% of land cultivated) is actually being cultivated, the intensity of cultivation of land is increasing, fallow lengths are decreasing, and management practices are shifting from monocultures to polycultures. Since 1950, cropland areas have stabilized in North America and 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 2.9 million hectares per year in the 1990s, of which approximately 40% was forest plantations (C21.4.2). In some cases, rates of conversion of ecosystems have apparently slowed because most of the ecosystem has now been converted, as is the case with temperate broadleaf forests and Mediterranean forests (C4.4.3)

Ecosystem Processes

Ecosystem processes, including water, nitrogen, carbon, and phosphorus cycling, changed more rapidly in the second half of the twentieth century than at any time in recorded human history. Human modifications of ecosystems have changed not only the structure of the systems (such as what habitats or species are present in a particular location), but their processes and functioning as well. The capacity of ecosystems to provide services derives directly from the operation of natural biogeochemical cycles that in some cases have been significantly modified.

• Water Cycle: Water withdrawals from rivers and lakes for irrigation or for urban or industrial use doubled between 1960 and 2000 (C7.2.4). (Worldwide, 70% of water use is for agriculture (C7.2.2).) Large reservoir construction has doubled or tripled the residence time of river water—the average time, that is, that a drop of water takes to reach the sea (C7.3.2). Globally, humans use slightly more than 10% of the available renewable freshwater supply through household, agricultural, and industrial activities (C7.2.3), although in some regions such as the Middle East and North Africa, humans use 120% of renewable supplies (the excess is obtained through the use of groundwater supplies at rates greater than their rate of recharge) (C7.2.2).

Figure 1.4. Locations Reported by Various Studies as Undergoing High Rates of Land Cover Change in the Past Few Decades (C.SDM) Source: Millennium Ecosystem Assessment

• Carbon Cycle: Since 1750, the atmospheric concentration of carbon dioxide has increased by about 34% (from about 280 parts per million to 376 parts per million in 2003) (S7.3.1). Approximately 60% of that increase (60 parts per million) has taken place since 1959. The effect of changes in terrestrial ecosystems on the carbon cycle reversed during the last 50 years. Those ecosystems were on average a net source of CO₂ during the nineteenth and early twentieth centuries (primarily due to deforestation, but with contributions from degradation of agricultural, pasture, and forestlands) and became a net sink sometime around the middle of the last century (although carbon losses from land use change continue at high levels) (high certainty). Factors contributing to the growth of the role of ecosystems in carbon sequestration include afforestation, reforestation, and forest management in North America, Europe, China, and other regions; changed agriculture practices; and the fertilizing effects of nitrogen deposition and increasing atmospheric CO₂ (high certainty) (C13.ES).

• Nitrogen Cycle: 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 fertilizers (S7.3.2). (See Figures 1.5 and 1.6.) A recent study of global human contributions to reactive nitrogen flows projected that flows will increase from approximately 165 teragrams of reactive nitrogen in 1999 to 270 teragrams in 2050, an increase of 64% (R9 Fig 9.1). More than half of all the synthetic nitrogen fertilizer (which was first produced in 1913) ever used on the planet has been used since 1985 (R9.2). Human activities have now roughly doubled the rate of creation of reactive nitrogen on the land surfaces of Earth (R9.2). The flux of reactive nitrogen to the oceans increased by nearly 80% from 1860 to 1990, from roughly 27 teragrams of nitrogen per year to 48 teragrams in 1990 (R9). (This change is not uniform over Earth, however, and while some regions such as Labrador and Hudson’s Bay in Canada have seen little if any change, the fluxes from more developed regions such as the northeastern United States, the watersheds of the North Sea in Europe, and the Yellow River basin in China have increased ten- to fifteenfold.)
• Phosphorus Cycle: The use of phosphorus fertilizers and the rate of phosphorus accumulation in agricultural soils increased nearly threefold between 1960 and 1990, although the rate has declined somewhat since that time (S7 Fig 7.18). The current flux of phosphorus to the oceans is now triple that of background rates (approximately 22 teragrams of phosphorus per year versus the natural flux of 8 teragrams) (R9.2)

Figure 1.5. Global Trends in the Creation of Reactive Nitrogen on Earth by Human Activity, with Projection to 2050 (R9 Fig 9.1) Source: Millennium Ecosystem Assessment

Species

A change in an ecosystem necessarily affects the species in the system, and changes in species affect ecosystem processes.

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 on the planet and the set at another location are, on average, diminishing. The natural process of evolution, and particularly the combination of natural barriers to migration and local adaptation of species, led to significant differences in the types of species in ecosystems in different regions. But these regional differences in the planet’s biota are now being diminished.

Two factors are responsible for this trend. First, the extinction of species or the loss of populations results in the loss of the presence of species that had been unique to particular regions. Second, the rate of invasion or introduction of species into new ranges is already high and continues to accelerate apace with growing trade and faster transportation. (See Figure 1.7.) For example, a high proportion of the roughly 100 non-native species in the Baltic Sea are native to the North American Great Lakes, and 75% of the recent arrivals of about 170 non-native species in the Great Lakes are native to the Baltic Sea (S10.5). When species decline or go extinct as a result of human activities, they are replaced by a much smaller number of expanding species that thrive in human-altered environments. One effect is that in some regions where diversity has been low, the biotic 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.)

Figure 1.6. Estimated Total Reactive Nitrogen Deposition from the Atmosphere (Wet and Dry) in 1860, Early 1990s, and Projected for 2050 (milligrams of nitrogen per square meter per year) (R9 Fig 9.2) Source: Millennium Ecosystem Assessment

Across a range of taxonomic groups, either the population size or range or both of the majority of species is currently declining. Studies of amphibians globally, African mammals, birds in agricultural lands, British butterflies, Caribbean corals, and fishery species show the majority of species to be declining in range or number. Exceptions include species that have been protected in reserves, that have had their particular threats (such as overexploitation) eliminated, or that tend to thrive in landscapes that have been modified by human activity (C4.ES).

Between 10% and 30% of mammal, bird, and amphibian species are currently threatened with extinction (medium to high certainty), based on IUCN–World Conservation Union criteria for threats of extinction. As of 2004, comprehensive assessments of every species within major taxonomic groups have been completed for only three groups of animals (mammals, birds, and amphibians) and two plant groups (conifers and cycads, a group of evergreen palm-like plants). Specialists on these groups have categorized species as “threatened with extinction” if they meet a set of quantitative criteria involving their population size, the size of area in which they are found, and trends in population size or area. (Under the widely used IUCN criteria for extinction, the vast majority of species categorized as “threatened with extinction” have approximately a 10% chance of going extinct within 100 years, although some long-lived species will persist much longer even though their small population size and lack of recruitment means that they have a very high likelihood of extinction.) Twelve percent of bird species, 23% of mammals, and 25% of conifers are currently threatened with extinction; 32% of amphibians are threatened with extinction, but information is more limited and this may be an underestimate. Higher levels of threat have been found in the cycads, where 52% are threatened (C4.ES). In general, freshwater habitats tend to have the highest proportion of threatened species (C4.5.2).

Figure 1.7. Growth in Number of Marine Species Introductions (C11) Source: Millennium Ecosystem Assessment

Over the past few hundred years, humans have increased the species extinction rate by as much as 1,000 times background rates typical over the planet’s history (medium certainty) (C4.ES, C4.4.2.). (See Figure 1.8.) Extinction is a natural part of Earth’s history. Most estimates of the total number of species today lie between 5 million and 30 million, although the overall total could be higher than 30 million if poorly known groups such as deep-sea organisms, fungi, and microorganisms including parasites have more species than currently estimated. Species present today only represent 2–4% of all species that have ever lived. The fossil record appears to be punctuated by five major mass extinctions, the most recent of which occurred 65 million years ago.

The average rate of extinction found for marine and mammal fossil species (excluding extinctions that occurred in the five major mass extinctions) is approximately 0.1–1 extinctions per million species per year. There are approximately 100 documented extinctions of birds, mammal, and amphibians over the past 100 years, a rate 50–500 times higher than background rates. Including possibly extinct species, the rate is more than 1,000 times higher than background rates. Although the data and techniques used to estimate current extinction rates have improved over the past two decades, significant uncertainty still exists in measuring current rates of extinction 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 time lags between the impact of a threatening process and the resulting extinction.

Figure 1.8. Species Extinction Rates (Adapted from C4 Fig 4.22) Source: Millennium Ecosystem Assessment

Genes

Genetic diversity has declined globally, particularly among cultivated species. The extinction of species and loss of unique populations has resulted in the loss of unique genetic diversity contained by those species and populations. For wild species, there are few data on the actual changes in the magnitude and distribution of genetic diversity (C4.4), although studies have documented declining genetic diversity in wild species that have been heavily exploited. 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 the crop varieties planted by farmers have shifted from locally adapted and developed populations (land races) to more widely adapted varieties produced through formal breeding systems (modern varieties). Roughly 80% of wheat area in developing countries and three quarters of the rice area in Asia is planted with modern varieties (C26.2.1). (For other crops, such as maize, sorghum and millet, the proportion of area planted to modern varieties is far smaller.) The on-farm losses of genetic diversity of crops and livestock have been partially offset by the maintenance of genetic diversity in seed banks.

How have ecosystem services and their uses changed?

Figure 2.1. Estimated Global Marine Fish Catch, 1950–2001 (C18 Fig 18.3) Source: Millennium Ecosystem Assessment

Ecosystem services are the benefits provided by ecosystems. These include provisioning services such as food, water, timber, fiber, and genetic resources; regulating services such as the regulation of climate, floods, disease, and water quality as well as waste treatment; cultural services such as recreation, aesthetic enjoyment, and spiritual fulfillment; and supporting services such as soil formation, pollination, and nutrient cycling. (See Box 2.1.)

Human use of all ecosystem services is growing rapidly. Approximately 60% (15 out of 24) of the ecosystem services evaluated in this assessment (including 70% of regulating and cultural services) are being degraded or used unsustainably. (See Table 2.1.) Of 24 provisioning, cultural, and regulating ecosystem services for which sufficient information was available, the use of 20 continues to increase. The use of one service, capture fisheries, is now declining as a result of a decline in the quantity of fish, which in turn is due to excessive capture of fish in past decades. Two other services (fuelwood and fiber) show mixed patterns. The use of some types of fiber is increasing and others decreasing; in the case of fuelwood, there is evidence of a recent peak in use.

Humans have enhanced production of three ecosystem services – crops, livestock, and aquaculture – through expansion of the area devoted to their production or through technological inputs. Recently, the service of carbon sequestration has been enhanced globally, due in part to the re-growth of forests in temperate regions, although previously deforestation had been a net source of carbon emissions. Half of provisioning services (6 of 11) and nearly 70% (9 of 13) of regulating and cultural services are being degraded or used unsustainably.

• Provisioning Services: The quantity of provisioning ecosystem services such as food, water, and timber used by humans increased rapidly, often more rapidly than population growth although generally slower than economic growth, during the second half of the twentieth century. And it continues to grow. In a number of cases, provisioning services are being used at unsustainable rates. The growing human use has been made possible by a combination of substantial increases in the absolute amount of some services produced by ecosystems and an increase in the fraction used by humans. World population doubled between 1960 and 2000, from 3 billion to 6 billion people, and the global economy increased more than sixfold. During this time, food production increased by roughly two-and-a-half times (a 160% increase in food production between 1961 and 2003), water use doubled, wood harvests for pulp and paper tripled, and timber production increased by nearly 60% (C9.ES, C9.2.2, S7, C7.2.3, C8.1). (Food production increased fourfold in developing countries over this period.)
  
  The sustainability of the use of provisioning services differs in different locations. However, the use of several provisioning services is unsustainable even in the global aggregate. The current level of use of capture fisheries (marine and freshwater) is not sustainable, and many fisheries have already collapsed. (See Figure 2.1.) Currently, one quarter of important commercial fish stocks are overexploited or significantly depleted (high certainty) (C8.2.2). From 5% to possibly 25% of global freshwater use exceeds longterm accessible supplies and is maintained only through engineered water transfers or the overdraft of groundwater supplies (low to medium certainty) (C7.ES). Between 15% and 35% of irrigation withdrawals exceed supply rates and are therefore unsustainable (low to medium certainty) (C7.2.2). Current agricultural practices are also unsustainable in some regions due to their reliance on unsustainable sources of water, harmful impacts caused by excessive nutrient or pesticide use, salinization, nutrient depletion, and rates of soil loss that exceed rates of soil formation.
• Regulating Services: Humans have substantially altered regulating services such as disease and climate regulation by modifying the ecosystem providing the service and, in the case of waste processing services, by exceeding the capabilities of ecosystems to provide the service. Most changes to regulating services are inadvertent results of actions taken to enhance the supply of provisioning services. Humans have substantially modified the climate regulation service of ecosystems—first through land use changes that contributed to increases in the amount of carbon dioxide and other greenhouse gases such as methane and nitrous oxide in the atmosphere and more recently by increasing the sequestration of carbon dioxide (although ecosystems remain a net source of methane and nitrous oxide). Modifications of ecosystems have altered patterns of disease by increasing or decreasing habitat for certain diseases or their vectors (such as dams and irrigation canals that provide habitat for schistosomiasis) or by bringing human populations into closer contact with various disease organisms. Changes to ecosystems have contributed to a significant rise in the number of floods and major wildfires on all continents since the 1940s. Ecosystems serve an important role in detoxifying wastes introduced into the environment, but there are intrinsic limits to that waste processing capability. For example, aquatic ecosystems “cleanse” on average 80% of their global incident nitrogen loading, but this intrinsic self-purification capacity varies widely and is being reduced by the loss of wetlands (C7.2.5).
• Cultural Services: Although the use of cultural services has continued to grow, the capability of ecosystems to provide cultural benefits has been significantly diminished in the past century (C17). Human cultures are strongly influenced by ecosystems, and ecosystem change can have a significant impact on cultural identity and social stability. Human cultures, knowledge systems, religions, heritage values, social interactions, and the linked amenity services (such as aesthetic enjoyment, recreation, artistic and spiritual fulfillment, and intellectual development) have always been influenced and shaped by the nature of the ecosystem and ecosystem conditions. Many of these benefits are being degraded, either through changes to ecosystems (a recent rapid decline in the numbers of sacred groves and other such protected areas, for example) or through societal changes (such as the loss of languages or of traditional knowledge) that reduce people’s recognition or appreciation of those cultural benefits. Rapid loss of culturally valued ecosystems and landscapes can contribute to social disruptions and societal marginalization. And there has been a decline in the quantity and quality of aesthetically pleasing natural landscapes.

Global gains in the supply of food, water, timber, and other provisioning services were often achieved in the past century despite local resource depletion and local restrictions on resource use by shifting production and harvest to new underexploited regions, sometimes considerable distances away. These options are diminishing. This trend is most distinct in the case of marine fisheries. As individual stocks have been depleted, fishing pressure has shifted to less exploited stocks (C18.2.1). Industrial fishing fleets have also shifted to fishing further offshore and in deeper water to meet global demand (C18.ES). (See Figure 2.2.) A variety of drivers related to market demand, supply, and government policies have influenced patterns of timber harvest. For example, international trade in forest products increases when a nation’s forests no longer can meet demand or when policies have been established to restrict or ban timber harvest.

Figure 2.2. Trend in Mean Depth of Catch Since 1950. (Source: Millennium Ecosystem Assessment)

Although human demand for ecosystem services continues to grow in the aggregate, the demand for particular services in specific regions is declining as substitutes are developed. For example, kerosene, electricity, and other energy sources are increasingly being substituted for fuelwood (still the primary source of energy for heating and cooking for some 2.6 billion people) (C9.ES). The substitution of a variety of other materials for wood (such as vinyl, plastics, and metal) has contributed to relatively slow growth in global timber consumption in recent years (C9.2.1). While the use of substitutes can reduce pressure on specific ecosystem services, this may not always have positive net environmental benefits. Substitution of fuelwood by fossil fuels, for example, reduces pressure on forests and lowers indoor air pollution, but it may increase net greenhouse gas emissions. Substitutes are also often costlier to provide than the original ecosystem services.

Both the supply and the resilience of ecosystem services are affected by changes in biodiversity. Biodiversity is the variability among living organisms and the ecological complexes of which they are part. When a species is lost from a particular location (even if it does not go extinct globally) or introduced to a new location, the various ecosystem services associated with that species are changed. More generally, when a habitat is converted, an array of ecosystem services associated with the species present in that location is changed, often with direct and immediate impacts on people (S10). Changes in biodiversity also have numerous indirect impacts on ecosystem services over longer time periods, including influencing the capacity of ecosystems to adjust to changing environments (medium certainty), causing disproportionately large and sometimes irreversible changes in ecosystem processes, influencing the potential for infectious disease transmission, and, in agricultural systems, influencing the risk of crop failure in a variable environment and altering the potential impacts of pests and pathogens (medium to high certainty) (C11.ES, C14.ES).

The modification of an ecosystem to alter one ecosystem service (to increase food or timber production, for instance) generally results in changes to other ecosystem services as well (CWG, SG7). Trade-offs among ecosystem services are commonplace. (See Table 2.2.) For example, actions to increase food production often involve one or more of the following: increased water use, degraded water quality, reduced biodiversity, reduced forest cover, loss of forest products, or release of greenhouse gases. Frequent cultivation, irrigated rice production, livestock production, and burning of cleared areas and crop residues now release 1,600±800 million tons of carbon per year in CO₂ (C26. ES). Cultivation, irrigated rice production, and livestock production release between 106 million and 201 million tons of carbon per year in methane (C13 Table 13.1). About 70% of anthropogenic nitrous oxide gas emissions are attributable to agriculture, mostly from land conversion and nitrogen fertilizer use (C26. ES). Similarly, the conversion of forest to agriculture can significantly change flood frequency and magnitude, although the amount and direction of this impact is highly dependent on the characteristics of the local ecosystem and the nature of the land cover change (C21.5.2).

Many trade-offs associated with ecosystem services are expressed in areas remote from the site of degradation. For example, conversion of forests to agriculture can affect water quality and flood frequency downstream of where the ecosystem change occurred. And increased application of nitrogen fertilizers to croplands can have negative impacts on coastal water quality. These trade-offs are rarely taken fully into account in decision-making, partly due to the sectoral nature of planning and partly because some of the effects are also displaced in time (such as long-term climate impacts).

The net benefits gained through actions to increase the productivity or harvest of ecosystem services have been less than initially believed after taking into account negative trade-offs. The benefits of resource management actions have traditionally been evaluated only from the standpoint of the service targeted by the management intervention. However, management interventions to increase any particular service almost always result in costs to other services. Negative trade-offs are commonly found between individual provisioning services and between provisioning services and the combined regulating, cultural, and supporting services and biodiversity. Taking the costs of these negative trade-offs into account reduces the apparent benefits of the various management interventions. For example:

• Expansion of commercial shrimp farming has had serious impacts on ecosystems, including loss of vegetation, deterioration of water quality, decline of capture fisheries, and loss of biodiversity (R6, C19).
• Expansion of livestock production around the world has often led to overgrazing and dryland degradation, rangeland fragmentation, loss of wildlife habitat, dust formation, bush encroachment, deforestation, nutrient overload through disposal of manure, and greenhouse gas emissions (R6.ES).
• Poorly designed and executed agricultural policies led to an irreversible change in the Aral Sea ecosystem. By 1998, the Aral Sea had lost more than 60% of its area and approximately 80% of its volume, and ecosystem-related problems in the region now include excessive salt content of major rivers, contamination of agricultural products with agrochemicals, high levels of turbidity in major water sources, high levels of pesticides and phenols in surface waters, loss of soil fertility, extinctions of species, and destruction of commercial fisheries (R6 Box 6.9).
• Forested riparian wetlands adjacent to the Mississippi River in the United States had the capacity to store about 60 days of river discharge. With the removal of the wetlands through canalization, leveeing, and draining, the remaining wetlands have a storage capacity of less than 12 days discharge, an 80% reduction in flood storage capacity (C16.1.1).

However, positive synergies can be achieved as well when actions to conserve or enhance a particular component of an ecosystem or its services benefit other services or stakeholders. Agroforestry can meet human needs for food and fuel, restore soils, and contribute to biodiversity conservation. Intercropping can increase yields, increase biocontrol, reduce soil erosion, and reduce weed invasion in fields. Urban parks and other urban green spaces provide spiritual, aesthetic, educational, and recreational benefits as well as such services such as water purification, wildlife habitat, waste management, and carbon sequestration. Protection of natural forests for biodiversity conservation can also reduce carbon emissions and protect water supplies. Protection of wetlands can contribute to flood control and also help to remove pollutants such as phosphorus and nitrogen from the water. For example, it is estimated that the nitrogen load from the heavily polluted Illinois River basin to the Mississippi River could be cut in half by converting 7% of the basin back to wetlands (R9.4.5). Positive synergies often exist among regulating, cultural, and supporting services and with biodiversity conservation.

How have ecosystem changes affected human well-being and poverty alleviation?

Figure 3.1. Net National Savings in 2001 Adjusted for Investments in Human Capital, Natural Resource Depletion, and Damage Caused by Pollution Compared with Standard Net National Savings Measurements (C5.2.6) Source: Millennium Ecosystem Assessment

Relationships between Ecosystem Services and Human Well-being

Changes in ecosystem services influence all components of human well-being, including the basic material needs for a good life, health, good social relations, security, and freedom of choice and action (CF3). (See Box 3.1.) Humans are fully dependent on Earth’s ecosystems and the services that they provide, such as food, clean water, disease regulation, climate regulation, spiritual fulfillment, and aesthetic enjoyment. The relationship between ecosystem services and human well-being is mediated by access to manufactured, human, and social capital. Human well-being depends on ecosystem services but also on the supply and quality of social capital, technology, and institutions. These factors mediate the relationship between ecosystem services and human well-being in ways that remain contested and incompletely understood. The relationship between human well- being and ecosystem services is not linear. When an ecosystem service is abundant relative to the demand, a marginal increase in ecosystem services generally contributes only slightly to human well-being (or may even diminish it). But when the service is relatively scarce, a small decrease can substantially reduce human well-being (S.SDM, SG3.4).

Ecosystem services contribute significantly to global employment and economic activity. The ecosystem service of food production contributes by far the most to economic activity and employment. In 2000, the market value of food production was $981 billion, or roughly 3% of gross world product, but it is a much higher share of GDP within developing countries (C8 Table 8.1). That year, for example, agriculture (including forestry and fishing) represented 24% of total GDP in countries with per capita incomes less than $765 (the low-income developing countries, as defined by the World Bank) (C26.5.1). The agricultural labor force contained 1.3 billion people globally—approximately a fourth (22%) of the world’s population and half (46%) of the total labor force—and some 2.6 billion people, more than 40% of the world, lived in agriculturally based households (C26.5.1). Significant differences exist between developing and industrial countries in these patterns. For example, in the United States only 2.4% of the labor force works in agriculture.

Other ecosystem services (or commodities based on ecosystem services) that make significant contributions to national economic activity include timber (around $400 billion), marine fisheries (around $80 billion in 2000), marine aquaculture ($57 billion in 2000), recreational hunting and fishing ($50 billion and $24–37 billion annually respectively in the United States alone), as well as edible forest products, botanical medicines, and medicinal plants (C9.ES, C18.1, C20.ES). And many other industrial products and commodities rely on ecosystem services such as water as inputs.

The degradation of ecosystem services represents a loss of a capital asset (C5.4.1). (See Figure 3.1.) Both renewable resources such as ecosystem services and nonrenewable resources such as mineral deposits, soil nutrients, and fossil fuels are capital assets. Yet traditional national accounts do not include measures of resource depletion or of the degradation of renewable resources. As a result, a country could cut its forests and deplete its fisheries, and this would show only as a positive gain to GDP despite the loss of the capital asset. Moreover, many ecosystem services are available freely to those who use them (fresh water in aquifers, for instance, or the use of the atmosphere as a sink for pollutants), and so again their degradation is not reflected in standard economic measures.

When estimates of the economic losses associated with the depletion of natural assets are factored into measurements of the total wealth of nations, they significantly change the balance sheet of those countries with economies especially dependent on natural resources. For example, countries such as Ecuador, Ethiopia, Kazakhstan, Republic of Congo, Trinidad and Tobago, Uzbekistan, and Venezuela that had positive growth in net savings (reflecting a growth in the net wealth of the country) in 2001 actually experienced a loss in net savings when depletion of natural resources (energy and forests) and estimated damages from carbon emissions (associated with contributions to climate change) were factored into the accounts. In 2001, in 39 countries out of the 122 countries for which sufficient data were available, net national savings (expressed as a percent of gross national income) were reduced by at least 5% when costs associated with the depletion of natural resources (unsustainable forestry, depletion of fossil fuels) and damage from carbon emissions were included.

Box 3.1. Linkages between Ecosystem Services and Human Well-being

Box Figure A. Illustration of Linkages between Ecosystem Services and Human Well-being. (Source: Millennium Ecosystem Assessment) Human well-being has five main components: the basic material needs for a good life, health, good social relations, security, and freedom of choice and action. (See Box Figure A.) This last component is influenced by other constituents of well-being (as well as by other factors including, notably, education) and is also a precondition for achieving other components of well-being, particularly with respect to equity and fairness. Human well-being is a continuum— from extreme deprivation, or poverty, to a high attainment or experience of well-being. Ecosystems underpin human well-being through supporting, provisioning, regulating, and cultural services. Well-being also depends on the supply and quality of human services, technology, and institutions. Basic Materials for a Good Life This refers to the ability to have a secure and adequate livelihood, including income and assets, enough food and water at all times, shelter, ability to have energy to keep warm and cool, and access to goods. Changes in provisioning services such as food, water, and fuelwood have very strong impacts on the adequacy of material for a good life. Access to these materials is heavily mediated by socioeconomic circumstances. For the wealthy, local changes in ecosystems may not cause a significant change in their access to necessary material goods, which can be purchased from other locations, sometimes at artificially low prices if governments provide subsidies (for example, water delivery systems). Changes in regulating services influencing water supply, pollination and food production, and climate have very strong impacts on this element of human well-being. These, too, can be mediated by socioeconomic circumstances, but to a smaller extent. Changes in cultural services have relatively weak linkages to material elements of well-being. Changes in supporting services have a strong influence by virtue of their influence on provisioning and regulating services. The following are some examples of material components of well-being affected by ecosystem change. Box Table. Selected Water-related Diseases. Income and Employment: Increased production of crops, fisheries, and forest products has been associated with significant growth in local and national economies. Changes in the use and management of these services can either increase employment (as, for example, when agriculture spreads to new regions) or decrease it through gains in productivity of labor. In regions where productivity has declined due to land degradation or over-harvesting of fisheries, the impacts on local economies and employment can be devastating to the poor or to those who rely on these services for income. Food: The growth in food production and farm productivity has more than kept pace with global population growth, resulting in significant downward pressure on the price of foodstuffs. Following significant spikes in the 1970s caused primarily by oil crises, there have been persistent and profound reductions in the price of foodstuffs globally (C8.1). Over the last 40 years, food prices have dropped by around 40% in real terms due to increases in productivity (C26.2.3). It is well established that past increases in food production, at progressively lower unit cost, have improved the health and well-being of billions, particularly the most needy, who spend the largest share of their incomes on food (C8.1). Increased production of food and lower prices for food have not been entirely positive. Among industrial countries, and increasingly among developing ones, diet-related risks, mainly associated with over-nutrition, in combination with physical inactivity now account for one third of the burden of disease (R16.1.2). At present, over 1 billion adults are overweight, with at least 300 million considered clinically obese, up from 200 million in 1995 (C8.5.1). Water Availability: The modification of rivers and lakes through the construction of dams and diversions has increased the water available for human use in many regions of the world. However, the declining per capita availability of water is having negative impacts on human well-being. Water scarcity is a globally significant and accelerating condition for roughly 1–2 billion people worldwide, leading to problems with food production, human health, and economic development. Rates of increase in a key water scarcity measure (water use relative to accessible supply) from 1960 to the present averaged nearly 20% per decade globally, with values of 15% to more than 30% per decade for individual continents (C7.ES). Box Figure B. Proportion of Population with Improved Drinking Water Supply in 2002 (C7 Fig 7.13) Source: World Health Organization Health By health, we refer to the ability of an individual to feel well and be strong, or in other words to be adequately nourished and free from disease, to have access to adequate and clean drinking water and clean air, and to have the ability to have energy to keep warm and cool. Human health is both a product and a determinant of well-being. Changes in provisioning services such as food, water, medicinal plants, and access to new medicines and changes in regulating services that influence air quality, water quality, disease regulation, and waste treatment also have very strong impacts on health. Changes in cultural services can have strong influences on health, since they affect spiritual, inspirational, aesthetic, and recreational opportunities, and these in turn affect both physical and emotional states. Changes in supporting services have a strong influence on all of the other categories of services. These benefits are moderately mediated by socioeconomic circumstances. The wealthy can purchase substitutes for some health benefits of ecosystems (such as medicinal plants or water quality), but they are more susceptible to changes affecting air quality. The following are some examples of health components of well-being affected by ecosystem change. Nutrition: In 2000, about a quarter of the burden of disease among the poorest countries was attributable to childhood and maternal under-nutrition. Worldwide, under-nutrition accounted for nearly 10% of the global burden of disease (R16.1.2). Water and Sanitation: The burden of disease from inadequate water, sanitation, and hygiene totals 1.7 million deaths and results in the loss of at least 54 million healthy life years annually. Along with sanitation, water availability and quality are well recognized as important risk factors for infectious diarrhea and other major diseases. (See Box Table.) Some 1.1 billion people lack access to clean drinking water, and more than 2.6 billion lack access to sanitation (C7.ES). (See Box Figures B and C.) Globally, the economic cost of pollution of coastal waters is estimated to be $16 billion annually, mainly due to human health impacts (C19.3.1). Box Figure C. Proportion of Population with Improved Sanitation Coverage in 2002 (C7 Fig 7.14) Source: World Health Organization Vector-borne Disease: Actions to reduce vector-borne diseases have resulted in major health gains and helped to relieve important constraints on development in poor regions. Vector-borne diseases cause approximately 1.4 million deaths a year, mainly due to malaria in Africa. These infections are both an effect and a cause of poverty (R12.ES). Prevalence of a number of infectious diseases appears to be growing, and environmental changes such as deforestation, dam construction, road building, agricultural conversion, and urbanization are contributing factors in many cases (C14.2). Medicines: The use of natural products in the pharmaceutical industry has tended to fluctuate widely, with a general decline in pharmaceutical bioprospecting by major companies. Historically, most drugs were obtained from natural products. Even near the end of the twentieth century, approximately 50% of prescription medicines were originally discovered in plants (C10.2). Natural products still are actively used in drug exploration. Medicinal plants continue to play an important role in health care systems in many parts of the world. One MA sub-global assessment in the Mekong wetlands identified more than 280 medically important plant species, of which 150 are still in regular use (C10.2.2). Medicinal plants have generally declined in availability due to over-harvesting and loss of habitats (C10.5.4). Good Social Relations Good social relations refer to the presence of social cohesion, mutual respect, and the ability to help others and provide for children. Changes in provisioning and regulating ecosystem services can affect social relations, principally through their more direct impacts on material well-being, health, and security. Changes in cultural services can have a strong influence on social relations, particularly in cultures that have retained strong connections to local environments. Changes in provisioning and regulating services can be mediated by socioeconomic factors, but those in cultural services cannot. Even a wealthy country like Sweden or the United Kingdom cannot readily purchase a substitute to a cultural landscape that is valued by the people in the community. Changes in ecosystems have tended to increase the accessibility that people have to ecosystems for recreation and ecotourism. There are clear examples of declining ecosystem services disrupting social relations or resulting in conflicts. Indigenous societies whose cultural identities are tied closely to particular habitats or wildlife suffer if habitats are destroyed or wildlife populations decline. Such impacts have been observed in coastal fishing communities, Arctic populations, traditional forest societies, and pastoral nomadic societies (C5.4.4). Source: Millennium Ecosystem Assessment Security By security, we refer to safety of person and possessions, secure access to necessary resources, and security from natural and human-made disasters. Changes in regulating services such as disease regulation, climate regulation, and flood regulation have very strong influences on security. Changes in provisioning services such as food and water have strong impacts on security, since degradation of these can lead to loss of access to these essential resources. Changes in cultural services can influence security since they can contribute to the breakdown or strengthening of social networks within society. Changes in supporting services have a strong influence by virtue of their influence on all the other categories of services. These benefits are moderately mediated by socioeconomic circumstances. The wealthy have access to some safety nets that can minimize the impacts of some ecosystem changes (such as flood or drought insurance). Nevertheless, the wealthy cannot entirely escape exposure to some of these changes in areas where they live. One example of an aspect of security affected by ecosystem change involves influences on the severity and magnitude of floods and major fires. The incidence of these has increased significantly over the past 50 years. Changes in ecosystems and in the management of ecosystems have contributed to these trends. The canalization of rivers, for example, tends to decrease the incidence and impact of small flood events and increase the incidence and severity of large ones. On average, 140 million people are affected by floods each year—more than all other natural or technological disasters put together. Between 1990 and 1999, more than 100,000 people were killed in floods, which caused a total of $243 billion in damages (C7.4.4). Freedom of Choice and Action Freedom of choice and action refers to the ability of individuals to control what happens to them and to be able to achieve what they value doing or being. Freedom and choice cannot exist without the presence of the other elements of well-being, so there is an indirect influence of changes in all categories of ecosystem services on the attainment of this constituent of well-being. The influence of ecosystem change on freedom and choice is heavily mediated by socioeconomic circumstances. The wealthy and people living in countries with efficient governments and strong civil society can maintain freedom and choice even in the face of significant ecosystem change, while this would be impossible for the poor if, for example, the ecosystem change resulted in a loss of livelihood. In the aggregate, the state of our knowledge about the impact that changing ecosystem conditions have on freedom and choice is relatively limited. Declining provision of fuelwood and drinking water have been shown to increase the amount of time needed to collect such basic necessities, which in turn reduces the amount of time available for education, employment, and care of family members. Such impacts are typically thought to be disproportionately experienced by women (although the empirical foundation for this view is relatively limited) (C5.4.2).

Figure 3.2. Annual Flow of Benefits from Forests in Selected Countries (Adapted from C5 Box 5.2) Source: Millennium Ecosystem Assessment

The degradation of ecosystem services often causes significant harm to human well-being (C5 Box 5.2). The information available to assess the consequences of changes in ecosystem services for human well-being is relatively limited. Many ecosystem services have not been monitored and it is also difficult to estimate the relative influence of changes in ecosystem services in relation to other social, cultural, and economic factors that also affect human well-being. Nevertheless, the following evidence demonstrates that the harmful effects of the degradation of ecosystem services on livelihoods, health, and local and national economies are substantial.

• Most resource management decisions are most strongly influenced by ecosystem services entering markets; as a result, the non-marketed benefits are often lost or degraded. Many ecosystem services, such as the purification of water, regulation of floods, or provision of aesthetic benefits, do not pass through markets. The benefits they provide to society, therefore, are largely unrecorded: only a portion of the total benefits provided by an ecosystem make their way into statistics, and many of these are mis-attributed (the water regulation benefits of wetlands, for example, do not appear as benefits of wetlands but as higher profits in water-using sectors). Moreover, for ecosystem services that do not pass through markets there is often insufficient incentive for individuals to invest in maintenance (although in some cases common property management systems provide such incentives). Typically, even if individuals are aware of the services provided by an ecosystem, they are neither compensated for providing these services nor penalized for reducing them. These non-marketed benefits are often high and sometimes more valuable than the marketed benefits. For example:
• Total economic value of forests. One of the most comprehensive studies to date, which examined the marketed and non-marketed economic values associated with forests in eight Mediterranean countries, found that timber and fuelwoodgenerally accounted for less than a third of total economic value in each country. (See Figure 3.2.)
• Recreational benefits of protected areas: The annual recreational value of the coral reefs of each of six Marine Management Areas in the Hawaiian Islands in 2003 ranged from $300,000 to $35 million.
• Water quality: The net present value in 1998 of protecting water quality in the 360-kilometer Catawba River in the United States for five years was estimated to be $346 million.
• Water purification service of wetlands: About half of the total economic value of the Danube River Floodplain in 1992 could be accounted for in its role as a nutrient sink.
• Native pollinators: A study in Costa Rica found that forest- based pollinators increased coffee yields by 20% within 1 kilometer of the forest (as well as increasing the quality of the coffee). During 2000–03, pollination services from two forest fragments (of 46 and 111 hectares) thus increased the income of a 1,100-hectare farm by $60,000 a year, a value commensurate with expected revenues from competing land uses.
• Flood control: Muthurajawela Marsh, a 3,100-hectare coastal peat bog in Sri Lanka, provides an estimated $5 mil- lion in annual benefits ($1,750 per hectare) through its role in local flood control.
• The total economic value associated with managing ecosystems more sustainably is often higher than the value associated with the conversion of the ecosystem through farming, clear-cut logging, or other intensive uses. Relatively few studies have compared the total economic value (including values of both marketed and non-marketed ecosystem services) of ecosystems under alternate management regimes, but a number of studies that do exist have found that the benefit of managing the ecosystem more sustainably exceeded that of converting the ecosystem (see Figure 3.3), although 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 total economic value of maintaining some “green space” can be greater than development of these sites.)

Figure 3.3. Economic Benefits under Alternate Management Practices (C5 Box 5.2) Source: Millennium Ecosystem Assessment

• The economic and public health costs associated with damage to ecosystem services can be substantial.
• The early 1990s collapse of the Newfoundland cod fishery due to overfishing (see Figure 3.4) resulted in the loss of tens of thousands of jobs and has cost at least $2 billion in income support and retraining.
• The cost of U.K. agriculture in 1996 resulting from the damage that agricultural practices cause to water (pollution, eutrophication), air (emissions of greenhouse gases), soil (off-site erosion damage, carbon dioxide loss), and biodiversity was $2.6 billion, or 9% of average yearly gross farm receipts for the 1990s. Similarly, the damage costs of freshwater eutrophication alone in England and Wales was estimated to be $105–160 million per year in the 1990s, with an additional $77 million per year being spent to address those damages.
• The burning of 10 million hectares of Indonesia’s forests in 1997/98 cost an estimated $9.3 billion in increased health care, lost production, and lost tourism revenues and affected some 20 million people across the region.
• The total damages for the Indian Ocean region over 20 years (with a 10% discount rate) resulting from the long-term impacts of the massive 1998 coral bleaching episode are estimated to be between $608 million (if there is only a slight decrease in tourism-generated income and employment results) and $8 billion (if tourism income and employment and fish productivity drop significantly and reefs cease to function as a protective barrier).
• The net annual loss of economic value associated with invasive species in the fynbos vegetation of the Cape Floral region of South Africa in 1997 was estimated to be $93.5 million, equivalent to a reduction of the potential economic value without the invasive species of more than 40%. The invasive species have caused losses of biodiversity, water, soil, and scenic beauty, although they also provide some benefits, such as provision of firewood.
• The incidence of diseases of marine organisms and emergence of new pathogens is increasing, and some of these, such as ciguatera, harm human health (C19.3.1). Episodes of harmful (including toxic) algal blooms in coastal waters are increasing in frequency and intensity, harming other marine resources such as fisheries and harming human health (R16 Figure 16.3). In a particularly severe outbreak in Italy in 1989, harmful algal blooms cost the coastal aquaculture industry $10 million and the Italian tourism industry $11.4 million (C19.3.1).
• The number of both floods and fires has increased significantly, in part due to ecosystem changes, in the past 50 years. Examples are the increased susceptibility of coastal populations to tropical storms when mangrove forests are cleared and the increase in downstream flooding that followed land use changes in the upper Yangtze River (C.SDM). Annual economic losses from extreme events increased tenfold from the 1950s to approximately $70 billion in 2003, of which natural catastrophes—floods, fires, storms, drought, and earthquakes—accounted for 84% of insured losses.
• Significant investments are often needed to restore or maintain non-marketed ecosystem services.
• In South Africa, invasive tree species threaten both native species and water flows by encroaching into natural habitats, with serious impacts for economic growth and human well-being. In response, the South African government established the “Working for Water Programme.” Between 1995 and 2001 the program invested $131 million (at 2001 exchange rates) in clearing programs to control the invasive species.
• The state of Louisiana has put in place a $14-billion wetland restoration plan to protect 10,000 square kilometers of marsh, swamp, and barrier islands in part to reduce storm surges generated by hurricanes.

Figure 3.4. Collapse of Atlantic Cod Stocks off the East Coast of Newfoundland in 1992 (CF Box 2.4) Source: Millennium Ecosystem Assessment

Although degradation of ecosystem services could be significantly slowed or reversed if the full economic value of the services were taken into account in decision-making, economic considerations alone would likely lead to lower levels of biodiversity (medium certainty) (CWG). Although most or all biodiversity has some economic value (the option value of any species is always greater than zero), that does not mean that the protection of all biodiversity is always economically justified. Other utilitarian benefi