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Biodiversity & Human Well-being

5. How might biodiversity change in the future under various plausible scenarios?

  • 5.1 Which scenarios have been explored in this assessment?
  • 5.2 How much biodiversity might be lost on land by 2050 and beyond?
  • 5.3 How much biodiversity might be lost in the aquatic environment by 2050 and beyond?
  • 5.4 How might human well-being be affected by ecosystem degradation?
    • 5.4.1 Ecological degradation and human well-being
    • 5.4.2 Implications and opportunities for trend reversion

The source document for this Digest states:

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

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

Source & ©: Millennium Ecosystem Assessment
 Ecosystems and Human Well-being: Biodiversity Synthesis (2005),
Chapter 4, p.60

5.1 Which scenarios have been explored in this assessment?

The source document for this Digest states:

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

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

Box 4.1: An Outline of the Four MA Scenarios

Source & ©: Millennium Ecosystem Assessment
 Ecosystems and Human Well-being: Biodiversity Synthesis (2005),
Chapter 4, p.60

5.2 How much biodiversity might be lost on land by 2050 and beyond?

The source document for this Digest states:

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

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

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

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

Source & ©: Millennium Ecosystem Assessment
 Ecosystems and Human Well-being: Biodiversity Synthesis (2005),
Chapter 4, p.60

5.3 How much biodiversity might be lost in the aquatic environment by 2050 and beyond?

The source document for this Digest states:

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

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

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

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

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

Source & ©: Millennium Ecosystem Assessment
 Ecosystems and Human Well-being: Biodiversity Synthesis (2005),
Chapter 4, p.60

5.4 How might human well-being be affected by ecosystem degradation?

    • 5.4.1 Ecological degradation and human well-being
    • 5.4.2 Implications and opportunities for trend reversion

5.4.1 Ecological degradation and human well-being

The source document for this Digest states:

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

Source & ©: Millennium Ecosystem Assessment
 Ecosystems and Human Well-being: Biodiversity Synthesis (2005),
Chapter 4, p.64

5.4.2 Implications and opportunities for trend reversion

The source document for this Digest states:

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

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

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

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

Source & ©: Millennium Ecosystem Assessment
 Ecosystems and Human Well-being: Biodiversity Synthesis (2005),
Chapter 4, p.67


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