McClatchy newspapers, guardian.co.uk 14 Aug 08;
New research led by two University of California at Berkeley biologists finds frogs and other amphibians worldwide need help, because they are dying at alarming rates.
The researchers find that some frog populations are at 2 to 5% of their former size - that's a decline of 95 to 98% - which they argue is a warning sign of a larger global issue.
An article published this week in the journal Proceedings of the National Academy of Sciences reports that scientists are not yet sure what the long-term implications might be.
They are sure, however, of the varied causes of the die-off, and say mankind is to blame for most of them.
David Wake, a professor of integrative biology at the University of California at Berkeley, said the die-off can be pinned to three factors - habitat destruction; a naturally occurring fungus, which researchers say is not unique to dead frogs they found in the Sierra Nevada; and introduced species, which present an imbalance in amphibious habitats. For example, the first hint of frog decline in California came in the 1990s, when scientists believed rainbow trout introduced in the area by humans were feeding on tadpoles and frog eggs.
"It's not a one-two punch," Wake said. "It's more of a one, two, three, four punch."
The "fourth punch," Wake said, is climate change, which is showing dramatic effects on aquatic-dwelling species worldwide.
"There is no place in California where frogs are still thriving," Wake said.
Fewer frogs eating insects - like West Nile-carrying mosquitoes - is just one example of how a major blow to global ecology could cause a shift in the grand food chain, though Wake would not equate the possible spreading of West Nile virus to the frog die-off.
Wake and his colleague Vance Vredenburg studied amphibian populations in the Sierra Nevada and say they have observed frogs carcasses in remote peaks - places they are expected to thrive.
In 2004, researchers found that one-third of amphibian species around the world are threatened with extinction, according to a University of California-Berkeley release on the subject at that time.
Wake suggested mass extinctions should prompt more focus on the study of pathology, as decimated frog populations could easily mean a change in the ways diseases are transmitted in human populations.
"We've got to invest a lot more in research of the ecology of infectious disease," Wake said. Drastic shifts in the ecology affects "how it spreads through the environment".
