Global Environment Outlook 3 (GEO 3)

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BIODIVERSITY

many crops, and absorption of pollutants (UNEP 1995). Many of these services are neither widely recognized nor properly valued in economic terms; however, the combined economic value of 17 ecosystem services has recently been estimated in the range US$16–54 trillion per year (Costanza and others 1997). Human health and well-being are directly dependent on biodiversity. For example, 10 of the world’s 25 top-selling drugs in 1997 were derived from natural sources. The global market value of pharmaceuticals derived from genetic resources is estimated at US$75 000–150 000 million annually. Some 75 per cent of the world’s population rely for health care on traditional medicines, which are derived directly from natural sources (UNDP, UNEP, World Bank and WRI 2000). Biodiversity also provides genetic resources for food and agriculture, and therefore constitutes the biological basis for world food security and support for human livelihoods. A number of wild crop relatives are of great importance to national and global economies. For example, Ethiopian varieties have provided protection from viral pathogens to California’s barley crop, worth US$160 million per year. Genetic resistance to disease obtained from wild wheat varieties in Turkey has been valued at US$50 million per year (UNEP 1995). Decline and loss of species Global biodiversity is changing at an unprecedented rate (Pimm and others 1995), the most important drivers of this change being land conversion, climate change, pollution, unsustainable harvesting of natural resources and the introduction of exotic species (Sala and others 2000). The relative importance of these drivers differs between ecosystems. For example, land conversion is most intensive in tropical forests and less intensive in temperate, boreal and Arctic regions; atmospheric nitrogen deposition is largest in northern temperate areas close to cities; introduction of exotic species is related to patterns of human activity — those areas remote from human intervention generally receive fewer introduced species. The ultimate causes of biodiversity loss are human population growth together with unsustainable patterns of consumption, increasing production of waste and pollutants, urban development, international conflict, and continuing inequities in the distribution of wealth and resources.

Over the past three decades, decline and extinction of species have emerged as major

environmental issues. The current rate of extinction is many times higher than the ‘background’ rate — that which has prevailed over long periods of geological time. Estimates based on the fossil record suggest that the background extinction rate in mammals and birds has been one species lost every 500-1 000 years (May, Lawton and Stork 1995). Information on the conservation status of species is provided by the World Conservation Union (IUCN) which regularly publishes ‘Red Lists’ of species considered to be threatened with extinction. The latest IUCN Red List (Hilton-Taylor 2000) indicates that about 24 per cent (1 130) of mammals and 12 per cent (1 183) of bird species are currently regarded as globally threatened (see table). Since the Red List assessment in 1996, the number of critically endangered species has increased from 169 to 180 mammals and from 168 to 182 birds (Hilton-Taylor 2000). Analyses suggest that over the next 100 years the extinction rate of vertebrate groups could be as high as 15-20 per cent (Mace 1995). However, species trends derived from Red List data should be interpreted with caution because the criteria for listing have changed over time and some of the changes in status reflect taxonomic revisions (May, Lawton and Stork 1995). Insufficient information is available to determine precisely how many species have become extinct in

Globally threatened vertebrate species by region

Mammals Birds Reptiles Amphibians Fishes Total

Africa

294

217

47

17

148 723

Asia and the Pacific Europe

526

523 106

67

247 1 469

82

54

31

10

83 260

Latin America 275 and Caribbean North America 51

361

77

28

132

873

50

27

24

117 269

West Asia

0

24

30

8

9

71

Polar

0

6

7

0

1

14

Note: ‘Threatened species’ include those categorized by IUCN in 2000 as Critically Endangered, Endangered and Vulnerable (Hilton-Taylor 2000); adding totals for each region does not give a global total because a species may be threatened in more than one region Source: compiled from the IUCN Red List database (Hilton-Taylor 2000) and the UNEP-WCMC species database (UNEP-WCMC 2001a)