In the largest such study to date, researchers reported today that the world's frogs, toads and other amphibians are disappearing, and the decline began long before scientists first sounded the alarm in the 1980s.
Researchers reported that overall numbers of amphibians dropped 15 percent each year from 1960 to 1966, and continued to decline about 2 percent annually through 1997.
''This should put the last nail in the coffin for anyone who doesn't think there are some population declines for amphibians,'' said Andrew Blaustein, a professor of zoology at Oregon State University.
The findings, published in today's issue of the journal Nature, were compiled by a University of Ottawa researcher, using Internet contacts with some 200 scientists around the world.
Since the late 1980s, scientists have been concerned about catastrophic declines in populations of frogs, toads, salamanders and other amphibian species, particularly in Australia, South America, Central America and high-altitude regions of the American West.
Because they are more vulnerable than many other creatures, amphibians are considered a ''canary in the coal mine'' for environmental damage.
Scientists have yet to zero in the causes but suspect a combination of factors: loss of wetlands to development; use of fertilizers and pesticides; increased ultraviolet light from an ozone layer thinned by industrial pollutants; and the introduction of exotic predators.
''It's just society doing its thing,'' said Michael Lannoo, a professor of anatomy at the Indiana University School of Medicine.
The study was initiated by Jeff Houlahan, a Ph.D candidate in biology.
''By and large the evidence has been anecdotal. No one had ever quantitatively tried to say is there truly a global decline,'' Houlahan said. ''I thought the best way to do that was simply to pile the data up as high as you can get it and see what it tells you.''
Houlahan gleaned studies from obscure scientific journals and combed university Web sites for the names of scientists studying amphibians, then e-mailed them to ask if they had data to share.
He contacted more scientists through Froglog, the Internet newsletter of the Declining Amphibian Population Taskforce of the World Conservation Union's Species Survival Commission.
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