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Science Frontiers ONLINE No. 69: May-Jun 1990 |
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Extinction Countdown
Some plants may, as described below, have environment-sensitive genes that help them adjust to external pressures. Amphibians and birds do not seem to be so pliable.
The worldwide precipitous decline of amphibian populations is alarming. Her-petologists are literally seeing species disappear before their eyes. Here is a typical anecdote:
"In 1974, Michael Tyler of the University of Adelaide, Australia, described a newly discovered frog species that broods its young in its stomach. The frog was once so commo 'an agile collector could have picked up 100 in a single night,' Tyler says. By 1980 it had completely disappeared from its habitat (a 100-square-kilometer area in the Conondale Ranges, 100 miles north of Brisbane). It has not been seen since."
Similar stories emanate from Brazil, Japan, Mexico, Norway, and elsewhere. Many environmental causes have been proposed, but it is significant that the frogs are also disappearing from nature preserves where environmental pressures are small. D. Wake, a biologist at Berkeley, has remarked:
"[Amphibians] were here when the dinosaurs were here, and [they] survived the age of mammals. If they're checking out now, I think it is significant."
In this context, Wake believes that there is a single, global, still-unidentified cause operating.
(Barinaga, Marcia; "Where Have All the Froggies Gone?" Science, 247:1033, 1990. Also: Cowen, Ron; "Tales from the Froglog and Others," Science News, 137:158, 1990.)
In the same issue of Science, S.A. Temple reviewed the book: Where Have All the Birds Gone? The situation for North American forest-dwelling song birds is not as critical as that for frogs and toads, but it is still very serious. The populations of warblers, vireos, and thrushes are declining rapidly, even though the North American forests are now expanding.
(Temple, Stanley A.; "Winter Absences," Science, 247: 1128, 1990.)