Langues:
The source document for this Digest states:
The MA developed four global scenarios to explore plausible futures for ecosystems and human well-being. (See Box 5.1.) The scenarios were developed with a focus on conditions in 2050, although they include some information through the end of the century. They explored two global development paths, one in which the world becomes increasingly globalized and the other in which it becomes increasingly regionalized, as well as two different approaches to ecosystem management, one in which actions are reactive and most problems are addressed only after they become obvious and the other in which ecosystem management is proactive and policies deliberately seek to maintain ecosystem services for the long term:
The source document for this Digest states:
- Global Orchestration - This scenario depicts a globally-connected society that focuses on global trade and economic liberalization and takes a reactive approach to ecosystem problems. However, it also takes strong steps to reduce poverty and inequality and to invest in public goods such as infrastructure and education. (More in Box 5.1) Economic growth is the highest of the four scenarios, while this scenario is assumed to have the lowest population in 2050.
- Order from Strength - This scenario represents a regionalized and fragmented world, concerned with security and protection, emphasizing primarily regional markets, paying little attention to public goods, and taking a reactive approach to ecosystem problems. (More in Box 5.1) Economic growth rates are the lowest of the scenarios (particularly low in developing countries) and decrease with time, while population growth is the highest.
- Adapting Mosaic - In this scenario, regional watershed-scale ecosystems are the focus of political and economic activity. Local institutions are strengthened and local ecosystem management strategies are common, and societies develop a strongly proactive approach to the management of ecosystems. (More in Box 5.1) Economic growth rates are somewhat low initially but increase with time, and the population in 2050 is nearly as high as in Order from Strength.
- TechnoGarden - This scenario depicts a globally-connected world relying strongly on environmentally sound technology, using highly managed, often engineered, ecosystems to deliver ecosystem services, and taking a proactive approach to the management of ecosystems in an effort to avoid problems. (More in Box 5.1.) Economic growth is relatively high and accelerates, while population in 2050 is in the mid-range of the scenarios.
Source & ©: MA 
Chapter 5, p.71
The source document for this Digest states:
The scenarios are not predictions; instead, they were developed to explore the unpredictable and uncontrollable features of change in ecosystem services and a number of socioeconomic factors. No scenario represents business as usual, although all begin from current conditions and trends. The future will represent a mix of approaches and consequences described in the scenarios, as well as events and innovations that have not yet been imagined. No scenario is likely to match the future as it actually occurs. These four scenarios were not designed to explore the entire range of possible futures for ecosystem services—other scenarios could be developed with either more optimistic or more pessimistic outcomes for ecosystems, their services, and human well-being.
The scenarios were developed using both quantitative models and qualitative analysis. For some drivers (such as land use change, and carbon emissions) and some ecosystem services (such as water withdrawals and food production), quantitative projections were calculated using established, peer-reviewed global models. Other drivers (such as economic growth and rates of technological change), ecosystem services (particularly supporting and cultural services such as soil formation and recreational opportunities), and human well-being indicators (such as human health and social relations) were estimated qualitatively. In general, the quantitative models used for these scenarios addressed incremental changes but failed to address thresholds, risk of extreme events, or impacts of large, extremely costly, or irreversible changes in ecosystem services. These phenomena were addressed qualitatively, by considering the risks and impacts of large but unpredictable ecosystem changes in each scenario.
Source & ©: MA
Chapter 5, p.71
The source document for this Digest states:
Projected Changes in Indirect and Direct Drivers under MA scenarios
In the four MA scenarios, during the first half of the twenty-first century the array of both indirect and direct drivers affecting ecosystems and their services is projected to remain largely the same as over the last half-century, but the relative importance of different drivers will begin to change. Some factors (such as global population growth) will begin to decline in importance and others (distribution of people, climate change, and changes to nutrient cycles) will gain more importance. (See Tables 5.1, 5.2, and 5.3.) Statements of certainty associated with findings related to the MA scenarios are conditional statements; they refer to level of certainty or uncertainty in the particular projection should that scenario and its associated changes in drivers unfold. They do not indicate the likelihood that any particular scenario and its associated projection will come to pass. With that caveat in mind, the four MA scenarios describe these changes between 2000 and 2050 (or in some cases 2100):
- Population is projected to grow to 8.1–9.6 billion in 2050 (medium to high certainty) and to 6.8–10.5 billion in 2100, depending on the scenario (S7.2.1). (See Figure 5.1.) The rate of global population growth has already peaked, at 2.1% per year in the late 1960s, and had fallen to 1.35% per year in 2000, when global population reached 6 billion (S7.ES). Population growth over the next several decades is expected to be concentrated in the poorest, urban communities in sub-Saharan Africa, South Asia, and the Middle East (S7.ES).
- Per capita income is projected to increase two- to fourfold, depending on the scenario (low to medium certainty) (S7.2.2). Gross world product is projected to increase roughly three to sixfold in the different scenarios. Increasing income leads to increasing per capita consumption in most parts of the world for most resources and it changes the structure of consumption. For example, diets tend to become higher in animal protein as income rises.
- Land use change (primarily the continuing expansion of agriculture) is projected to continue to be a major direct driver of change in terrestrial and freshwater ecosystems (medium to high certainty) (S9.ES). At the global level and across all scenarios, land use change is projected to remain the dominant driver of biodiversity change in terrestrial ecosystems, consistent with the pattern over the past 50 years, followed by changes in climate and nitrogen deposition (S10.ES). However, other direct drivers may be more important than land use change in particular biomes. For example, climate change is likely to be the dominant driver of biodiversity change in tundra and deserts. Species invasions and water extraction are important drivers for freshwater ecosystems.
- Nutrient loading is projected to become an increasingly severe problem, particularly in developing countries. Nutrient loading already has major adverse effects on freshwater ecosystems and coastal regions in both industrial and developing countries. These impacts include toxic algae blooms, other human health problems, fish kills, and damage to habitats such as coral reefs. Three out of the four MA scenarios project that the global flux of nitrogen to coastal ecosystems will increase by 10–20% by 2030 (medium certainty) (S9.3.7.2). (See Figure 5.2.) River nitrogen will not change in most industrial countries, while a 20–30% increase is projected for developing countries, particularly in Asia.
Source & ©: MA
Chapter 5, pp.71-77
The source document for this Digest states:
- Climate change and its impacts (such as sea level rise) are projected to have an increasing effect on biodiversity and ecosystem services (medium certainty) (S9.ES). Under the four MA scenarios, global temperature is expected to increase significantly—1.5–2.0° Celsius above preindustrial level in 2050 and 2.0–3.5° Celsius above it in 2100, depending on the scenario and using a median estimate for climate sensitivity (2.5°C for a doubling of the CO2 concentration) (medium certainty).
The IPCC reported a range of temperature increase for the scenarios used in the Third Assessment Report of 2.0-6.4° Celsius compared with preindustrial levels, with about half of this range attributable to the differences in scenarios and the other half to differences in climate models. The smaller, somewhat lower, range of the MA scenarios is thus partly a result of using only one climate model (and one estimate of climate sensitivity) but also the result of including climate policy responses in some scenarios as well as differences in assumptions for economic and population growth. The scenarios project an increase in global average precipitation (medium certainty), but some areas will become more arid while others will become more moist. Climate change will directly alter ecosystem services, for example, by causing changes in the productivity and growing zones of cultivated and noncultivated vegetation. It is also projected to change the frequency of extreme events, with associated risks to ecosystem services. Finally, it is projected to 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.
Climate change is projected to further adversely affect key development challenges, including providing clean water, energy services, and food; maintaining a healthy environment; and conserving ecological systems, their biodiversity, and their associated ecological goods and services (R13.1.3).
- Climate change is projected to exacerbate the loss of biodiversity and increase the risk of extinction for many species, especially those already at risk due to factors such as low population numbers, restricted or patchy habitats, and limited climatic ranges (medium to high certainty).
- Water availability and quality are projected to decrease in many arid and semiarid regions (high certainty).
- The risk of floods and droughts is projected to increase (high certainty).
- Sea level is projected to rise by 8-88 centimeters.
- The reliability of hydropower and biomass production is projected to decrease in some regions (high certainty).
- The incidence of vector-borne diseases such as malaria and dengue and of waterborne diseases such as cholera is projected to increase in many regions (medium to high certainty), and so too are heat stress mortality and threats of decreased nutrition in other regions, along with severe weather traumatic injury and death (high certainty).
- Agricultural productivity is projected to decrease in the tropics and sub-tropics for almost any amount of warming (low to medium certainty), and there are projected adverse effects on fisheries.
- Projected changes in climate during the twenty-first century are very likely to be without precedent during at least the past 10,000 years and, combined with land use change and the spread of exotic or alien species, are likely to limit both the capability of species to migrate and the ability of species to persist in fragmented habitats.
- By the end of the century, climate change and its impacts may be the dominant direct drivers of biodiversity loss and the change in ecosystem services globally (R13). Harm to biodiversity will grow with both increasing rates in change in climate and increasing absolute amounts of change. For ecosystem services, some services in some regions may initially benefit from increases in temperature or precipitation expected under climate scenarios, but the balance of evidence suggests that there will be a significant net harmful impact on ecosystem services worldwide if global mean surface temperature increases more than 2° Celsius above preindustrial levels or at rates greater than 0.2° Celsius per decade (medium certainty).
There is a wide band of uncertainty in the amount of warming that would result from any stabilized greenhouse gas concentration, but based on IPCC projections this would require an eventual CO2 stabilization level of less than 450 parts per million carbon dioxide (medium certainty).- This judgment is based on the evidence that an increase of about 2° Celsius above preindustrial levels in global mean surface temperature would represent a transition between the negative effects of climate change being felt in only some regions of the world to most regions of the world. For example, below an increase of about 2° Celsius, agricultural productivity is projected to be adversely affected in the tropics and sub-tropics, but beneficially affected in most temperate and high-latitude regions, whereas more warming than that is projected to have adverse impacts on agricultural productivity in many temperate regions. A 2° increase would have both positive and negative economic impacts, but most people would be adversely affected—that is, there would be predominantly negative economic effects. It would pose a risk to many unique and threatened ecological systems and lead to the extinction of numerous species. And it would lead to a significant increase in extreme climatic events and adversely affect water resources in countries that are already water-scarce or water-stressed and would affect human health and property.
Source & ©: MA
Chapter 5, pp.77-78
For more information on climate change, read the GreenFacts Digest on Climate Change and Global Warming, a faithful summary of the IPCC Third Assessment Report.
The source document for this Digest states:
Rapid conversion of ecosystems is projected to continue under all MA scenarios in the first half of the twenty-first century. Roughly 10–20% (low to medium certainty) of current grassland and forestland is projected to be converted to other uses between now and 2050, mainly due to the expansion of agriculture and, secondarily, because of the expansion of cities and infrastructure (S9.ES). The biomes projected to lose habitat and local species at the fastest rate in the next 50 years are warm mixed forests, savannas, scrub, tropical forests, and tropical woodlands, as Figure 1.2 illustrated (S10ES). Rates of conversion of ecosystems are highly dependent on future development scenarios and in particular on changes in population, wealth, trade, and technology.
Habitat loss in terrestrial environments is projected to accelerate decline in local diversity of native species in all four scenarios by 2050 (high certainty) (S.SDM). Loss of habitat results in the immediate extirpation of local populations and the loss of the services that these populations provided.
Source & ©: MA
Chapter 5, pp.78-79
The source document for this Digest states:
The habitat losses projected in the MA scenarios will lead to global extinctions as numbers of species approach equilibrium with the remnant habitat (high certainty) (S.SDM, S10.ES). The equilibrium number of plant species is projected to be reduced by roughly 10-15% as a result of habitat loss from 1970 to 2050 in the MA scenarios (low certainty). Other terrestrial taxonomic groups are likely to be affected to a similar extent. The pattern of extinction through time cannot be estimated with any precision, because some species will be lost immediately when their habitat is modified but others may persist for decades or centuries. Time lags between habitat reduction and extinction provide an opportunity for humans to deploy restoration practices that may rescue those species that otherwise may be in a trajectory towards extinction. Significant declines in freshwater fish species diversity are also projected due to the combined effects of climate change, water withdrawals, eutrophication, acidification, and increased invasions by non-indigenous species (low certainty). Rivers that are expected to lose fish species are concentrated in poor tropical and sub-tropical countries.
Source & ©: MA
Chapter 5, p.79
The source document for this Digest states:
Changes in Ecosystem Services and Human Well-being
In three of the four MA scenarios, ecosystem services show net improvements in at least one of the three categories of provisioning, regulating, and cultural services (S.SDM). These three categories of ecosystem services are all in worse condition in 2050 than they are today in only one MA scenario-Order from Strength. (See Figure 5.3.) However, even in scenarios showing improvement in one or more categories of ecosystem services, biodiversity loss continues at high rates.
Source & ©: MA
Chapter 5, p.79
The source document for this Digest states:
The following changes to ecosystem services and human well-being were common to all four MA scenarios and thus may be likely under a wide range of plausible futures (S.SDM):
- Human use of ecosystem services increases substantially under all MA scenarios during the next 50 years. In many cases this is accompanied by degradation in the quality of the service and sometimes, in cases where the service is being used unsustainably, a reduction in the quantity of the service available. (See Appendix A. Ecosystem Service Reports) The combination of growing populations and growing per capita consumption increases the demand for ecosystem services, including water and food. For example, demand for food crops (measured in tons) is projected to grow by 70–85% by 2050 (S9.4.1) and global water withdrawals are increased by 20–85% across the MA scenarios (S9 Fig. 9.34). Water withdrawals are projected to increase significantly in developing countries but to decline in OECD countries (medium certainty) (S.SDM). In some cases, this growth in demand will be met by unsustainable uses of the services, such as through continued depletion of marine fisheries. Demand is dampened somewhat by increasing efficiency in use of resources. The quantity and quality of ecosystem services will change dramatically in the next 50 years as productivity of some services is increased to meet demand, as humans use a greater fraction of some services, and as some services are diminished or degraded. Ecosystem services that are projected to be further impaired by ecosystem change include fisheries, food production in drylands, quality of fresh waters, and cultural services.
- Food security is likely to remain out of reach for many people. Child malnutrition will be difficult to eradicate even by 2050 (low to medium certainty) and is projected to increase in some regions in some MA scenarios, despite increasing food supply under all four scenarios (medium to high certainty) and more diversified diets in poor countries (low to medium certainty) (S.SDM). Three of the MA scenarios project reductions in child undernourishment by 2050 of between 10% and 60%, but undernourishment increases by 10% in Order from Strength (low certainty) (S9.4.1). (See Figure 5.4.) This is due to a combination of factors related to food supply systems (inadequate investments in food production and its supporting infrastructure resulting in low productivity increases, varying trade regimes) and food demand and accessibility (continuing poverty in combination with high population growth rates, lack of food infrastructure investments).
- Vast, complex changes with great geographic variability are projected to occur in world freshwater resources and hence in their provisioning of ecosystem services in all scenarios (S.SDM). Climate change will lead to increased precipitation over more than half of Earth’s surface, and this will make more water available to society and ecosystems (medium certainty). However, increased precipitation is also likely to increase the frequency of flooding in many areas (high certainty). Increases in precipitation will not be universal, and climate change will also cause a substantial decrease in precipitation in some areas, with an accompanying decrease in water availability (medium certainty). These areas could include highly populated arid regions such as the Middle East and Southern Europe (low to medium certainty). While water withdrawals decrease in most industrial countries, they are expected to increase substantially in Africa and some other developing regions, along with wastewater discharges, overshadowing the possible benefits of increased water availability (medium certainty).
- 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 in developing countries under the scenarios that are reactive to environmental problems (S9.ES). Less severe but still important declines are expected in the scenarios that are more proactive about environmental problems (medium certainty).
- Growing demand for fish and fish products leads to an increasing risk of a major and long-lasting collapse of regional marine fisheries (low to medium certainty) (S.SDM). Aquaculture may relieve some of this pressure by providing for an increasing fraction of fish demand. However, this would require aquaculture to reduce its current reliance on marine fish as a feed source.
Source & ©: MA
Chapter 5, p.79-80
The source document for this Digest states:
The future contribution of terrestrial ecosystems to the regulation of climate is uncertain (S9.ES). Carbon release or uptake by ecosystems affects the CO2 and CH4 content of the atmosphere at the global scale and thereby affects global climate. Currently, the biosphere is a net sink of carbon, absorbing about 1-2 gigatons a year, or 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 generates uncertainty about the future of the carbon sink. There is medium certainty that climate change will increase terrestrial fluxes of CO2 and CH4 in some regions (such as in Arctic tundra).
Source & ©: MA
Chapter 5, p.81
The source document for this Digest states:
Dryland ecosystems are particularly vulnerable to changes over the next 50 years. The combination of low current levels of human well-being (high rates of poverty, low per capita GDP, high infant mortality rates), a large and growing population, high variability of environmental conditions in dryland regions, and high sensitivity of people to changes in ecosystem services means that continuing land degradation could have profoundly negative impacts on the well-being of a large number of people in these regions (S.SDM). Subsidies of food and water to people in vulnerable drylands can have the unintended effect of increasing the risk of even larger breakdowns of ecosystem services in future years. Local adaptation and conservation practices can mitigate some losses of dryland ecosystem services, although it will be difficult to reverse trends toward loss of food production capacity, water supplies, and biodiversity in drylands.
Source & ©: MA
Chapter 5, p.82
The source document for this Digest states:
While human health improves under most MA scenarios, under one plausible future health and social conditions in the North and South could diverge (S11). In the more promising scenarios related to health, the number of undernourished children is reduced, the burden of epidemic diseases such as HIV/AIDS, malaria, and tuberculosis would be lowered, improved vaccine development and distribution could allow populations to cope comparatively well with the next influenza pandemic, and the impact of other new diseases such as SARS would also be limited by well-coordinated public health measures.
Under the Order from Strength scenario, however, it is plausible that the health and social conditions for the North and South could diverge as inequality increases and as commerce and scientific exchanges between industrial and developing countries decrease. In this case, health in developing countries could become worse, causing a negative spiral of poverty, declining health, and degraded ecosystems. The increased population in the South, combined with static or deteriorating nutrition, could force increased contact between humans and nonagricultural ecosystems, especially to obtain bushmeat and other forest goods. This could lead to more outbreaks of hemorrhagic fever and zoonoses. It is possible, though with low probability, that a more chronic disease could cross from a nondomesticated animal species into humans, at first slowly but then more rapidly colonizing human populations, as HIV is thought to have done.
Source & ©: MA
Chapter 5, p.82
The source document for this Digest states:
Each scenario yields a different package of gains, losses, and vulnerabilities to components of human well-being in different regions and populations (S.SDM). Actions that focus on improving the lives of the poor by reducing barriers to international flows of goods, services, and capital tend to lead to the most improvement in health and social relations for the currently most disadvantaged people. But human vulnerability to ecological surprises is high. Globally integrated approaches that focus on technology and property rights for ecosystem services generally improve human well-being in terms of health, security, social relations, and material needs. If the same technologies are used globally, however, local culture can be lost or undervalued. High levels of trade lead to more rapid spread of emergent diseases, somewhat reducing the gains in health in all areas. Locally focused, learning-based approaches lead to the largest improvements in social relations.
Order from Strength, which focuses on reactive policies in a regionalized world, has the least favorable outcomes for human well-being, as the global distribution of ecosystem services and human resources that underpin human well-being are increasingly skewed. (See Figure 5.5.) Wealthy populations generally meet most material needs but experience psychological unease. Anxiety, depression, obesity, and diabetes have a greater impact on otherwise privileged populations in this scenario. Disease creates a heavy burden for disadvantaged populations.
Source & ©: MA
Chapter 5, p.83
The source document for this Digest states:
Proactive or anticipatory management of ecosystems is generally advantageous in the MA scenarios, but it is particularly beneficial under conditions of changing or novel conditions (S.SDM). (See Table 5.4.) Ecological surprises are inevitable because of the complexity of the interactions and because of limitations in current understanding of the dynamic properties of ecosystems. Currently well understood phenomena that were surprises of the past century include the ability of pests to evolve resistance to biocides, the contribution to desertification of certain types of land use, biomagnification of toxins, and the increase in vulnerability of ecosystem to eutrophication and unwanted species due to removal of predators. While we do not know which surprises lie ahead in the next 50 years, we can be certain that there will be some.
In general, proactive action to manage systems sustainably and to build resilience into systems will be advantageous, particularly when conditions are changing rapidly, when surprise events are likely, or when uncertainty is high. This approach is beneficial largely because the restoration of ecosystems or ecosystem services following their degradation or collapse is generally more costly and time-consuming than preventing degradation, if that is possible at all. Nevertheless, there are costs and benefits to both proactive and reactive approaches, as Table 5.4 indicated.
Source & ©: MA
Chapter 5, p.83
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