United Nations Environment Programme (UNEP)
Global  Environment Outlook-1 - The Web version

Chapter 4: Looking to the Future

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Pressures on Natural Habitats

Projected Pressures on Natural Habitats

Projections were made for the changes in total quantity and geographic distribution of non-domesticated areas. These areas have been broken down into six groups one group for areas covered by ice plus five vegetation categories: all forest, including tropical woodland and regrowth forest; grassland/savannah, which includes steppe and shrubland but excludes extensively used grassland; extensively used grassland, including all (marginal) land used for grazing; tundra and wooded tundra; and hot desert. [Note that marginal land used for grazing has been defined and included here as "non-domesticated" but has also been included as agricultural land in the previous section ("Use of Land").]

The percentages of non-domesticated land for each region for 1990, 2015, and 2050 are summarized in Table 4.6. Figure 4.16 then shows the extent for each of the six non-domesticated land categories from 1970 to 2050, as well as for domesticated land; both for the world and for each region. (For 1970-80, these figures differ from those in Figure 4.15, because two different data sources have been used.) Figure 4.17 a, b, and c shows the geographical distribution of domesticated and non-domesticated areas in 1990, 2015, and 2050.

Quantification of combined pressures on the remaining non-domesticated areas allows projections of the future risks for global and regional biodiversity. The four pressures used in this analysis are population density, consumption and production rates (gross national product per square kilometer per year), forest clearance for timber, and climate change.

The individual pressures were determined and given a preliminary grading from 0 to 10 for each non-domesticated area grid cell. A class of 0 meant no pressure, whereas class 10 meant extremely high pressure and subsequent high chances of extremely poor biodiversity compared with the original state. The total pressure was calculated by aggregating the four pressures per grid cell, which could theoretically result in a cumulative pressure class of 40 (though this value was never reached). The smaller the remaining non-domesticated area and the higher the total pressures on it, the greater the risk of poor biodiversity quality. A similar pressure-based approach has also been applied by Hannah et al. (1994) and Bryant et al. (1995) for, respectively, the current situation of natural habitats and coastal ecosystems.

Figure 4.18 shows the share of non-domesticated land globally that is under pressure in 1990, 2015, and 2050, based on the aggregated pressures of population density, consumption and production rate, forest clearance, and climate change.

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