carnes@gargoyle.UUCP (Richard Carnes) (09/25/86)
[This article contains no philosophy. But in the 17th century it would have been described as "natural philosophy". Follow-ups are directed to net.sci.] [wex@milano.UUCP] >I seem to recall that experts now think that 98% of all species are >now extinct. It is hard to believe figures for species extinction >from the past because the information from that time is so poor. >Most species were not even known; how would we determine how many >species died out from say 1700-1799? There is evidence for species >known today but how does that compare with the past? Records of the disappearance of birds and mammals have been reasonably accurate since about 1600. Around 130 bird and mammal species became extinct between 1600 and 1975. In 1600 there were about 12,910 species of birds and mammals, and on this basis the average rate of extinction during this period is estimated to be 5 to 50 times as great as the average rate during the prehistoric past. [Sources: Fisher, Simon, and Vincent, *Wildlife in Danger* (1969); Ehrlich et al., *Ecoscience*.] No one knows or will ever know the exact number of species of all types of organisms that have become extinct since 1600. One difficulty is that we don't know how many living species there are even within an order of magnitude. About 1.6 million species have been catalogued and described, but this is probably well under half of the total. E.O. Wilson writes [*Biophilia* (1984), pp. 121-122]: Extinction is accelerating and could reach ruinous proportions during the next twenty years. Not only are birds and mammals vanishing but such smaller forms as mosses, insects, and minnows. A conservative estimate of the current extinction rate is one thousand species a year, mostly from the destruction of forests and other key habitats in the tropics. By the 1990s the figure is expected to rise past ten thousand species a year (one species per hour). During the next thirty years fully one million species could be erased. For the latest on prehistoric extinction rates, see David Raup's article in one of the March 1986 issues of *Science*. (Raup is the author of *The Nemesis Affair*.) Richard Carnes