What Do We Have and What Are We Losing

At present there are 1.7 million described species, nearly a million of which are insects. There are many more. UNEP (1995) gives the best guess that there are six undescribed organisms for every one that has been described. These are very large numbers. The number of these species whose existence is threatened by the activities of humans is considerable. For the better-known groups, such as mammals, birds, fish, and higher plants, we have good estimates of the numbers of threatened species. For these groups, the percentages threatened of the total known species are 18, 11, 5, and 8%, respectively. A recent survey notes that 10% of tree species are threatened (Oldenfield et al, 1998). The earth has seen the origins and demise of species through time but the current extinction rates are up to three orders of magnitude over evolutionary background values.

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