Global Environment Outlook 3 (GEO 3)

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STATE OF THE ENVIRONMENT AND POLICY RETROSPECTIVE: 1972–2002

UNEP, Soo Wee Ming, Malaysia, Still Pictures

Biodiversity

Global overview Biodiversity resources

million (see table), although this is highly uncertain, due to a lack of information about the number of insect, nematode, bacteria and fungus species. Living organisms contribute to a wide variety of environmental services, such as regulation of the gaseous composition of the atmosphere, protection of coastal zones, regulation of the hydrological cycle and climate, generation and conservation of fertile soils, dispersal and breakdown of wastes, pollination of

Biodiversity refers to the variability among living organisms from all sources, including terrestrial, marine and other aquatic ecosystems, and the ecological complexes of which they are part. This includes diversity within species (genetic diversity), between species and of ecosystems. There is no universally accepted classification of ecosystems at the global scale (UNEP 1995) but Olson (1994) defined 94 ecosystem classes based on land cover, vegetation and climate. This framework provides a mechanism for summarizing data at the global level, while recognizing the distinctiveness of ecosystems within each individual region. Tropical forest ecosystems are the most species- rich environments. Although they cover less than 10 per cent of the world’s surface, they may contain 90 per cent of the world’s species. Coral reefs and Mediterranean heathland are also highly species-rich. Around 1.75 million species have been named by taxonomists to date (UNEP-WCMC 2000). The total number of species has recently been estimated as 14

Estimated number of described species

Kingdom

Described species

Bacteria

4 000

Protoctists (algae, protozoa, etc.)

80 000 52 000

Animals: vertebrates Animals: invertebrates

1 272 000

Fungi Plants

72 000 270 000

Total described species

1 750 000 14 000 000

Possible total including unknown species

Source: UNEP-WCMC 2000