Note: This is the 1997 edition of UNEP's Global Environment Outlook. If you are interested in more recent information, please see the 2000 and 2002 editions.

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

Habitats the world over are under threat, with dire consequences for plant and animal species. The distribution and sizes of populations of many species are declining significantly, leading to local or regional extinctions and ultimately to global extinction. At the same time, a small number of mostly opportunistic species are increasing substantially. According to the Global Biodiversity Assessment, species have been becoming extinct since 1600 at 50-100 times the average estimated natural rate, while the extinction rate is expected to rise to between 1,000 and 10,000 times the natural rate (UNEP, 1995a).

The Global Biodiversity Assessmentidentifies the five major causes of biodiversity loss as the fragmentation, degradation, or outright loss of habitats (through the conversion of land for agriculture, infrastructure, or urbanization, for example); overexploitation; the introduction of non-native species; pollution; and climate change (UNEP, 1995). (See Figure 4.14.) Some positive initiatives have also been identified, however, such as the establishment of protected areas, habitat regeneration, and measures that mitigate pressures from human activities.

This section provides the results of a specific study on the projected changes in pressures that will affect biodiversity at the regional and global levels as a result of possible socio-economic developments. This is predominantly achieved by quantifying the projected conversion of non-domesticated into domesticated land and by assessing some of the pressures on the remaining natural habitat that affect its quality.

The domestication of land is one of the major causes of biodiversity loss on a global scale. For the purpose of this study, non-domesticated land is defined as those areas not dominated by human activity, irrespective of whether they are pristine or degraded. Examples of this include virgin land; nature reserves; all forests, also production forest, except wood plantations planted with exotic species; areas with shifting cultivation; all fresh-water areas and land covered with ice (excluding Antarctica); and extensive grasslands (marginal land used for grazing by nomadic livestock).

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