Thursday, August 14, 2008

Dying frogs sign of a biodiversity crisis

University of California, Berkeley: Devastating declines of amphibian species around the world are a sign of a biodiversity disaster larger than just frogs, salamanders and their ilk, according to researchers from the University of California, Berkeley. In an article published online this week in the journal Proceedings of the National Academy of Sciences, the researchers argue that substantial die-offs of amphibians and other plant and animal species add up to a new mass extinction facing the planet.

"There's no question that we are in a mass extinction spasm right now," said David Wake, professor of integrative biology at UC Berkeley. "Amphibians have been around for about 250 million years. They made it through when the dinosaurs didn't. The fact that they're cutting out now should be a lesson for us."

The study, co-authored by Wake and Vance Vredenburg, research associate at the Museum of Vertebrate Zoology at UC Berkeley and assistant professor of biology at San Francisco State University, will appear in a special supplement to the journal featuring papers based on presentations from the December 2007 Arthur M. Sackler Colloquium of the National Academy of Sciences, "In the Light of Evolution II: Biodiversity and Extinction."

New species arise and old species die off all the time, but sometimes the extinction numbers far outweigh the emergence of new species. Extreme cases of this are called mass extinction events, and there have been only five in our planet's history, until now. The sixth mass extinction event, which Wake and others argue is happening currently, is different from the past events. "My feeling is that behind all this lies the heavy hand of Homo sapiens," Wake said.

There is no consensus among the scientific community about when the current mass extinction started, Wake said. It may have been 10,000 years ago, when humans first came from Asia to the Americas and hunted many of the large mammals to extinction. It may have started after the Industrial Revolution, when the human population exploded. Or, we might be seeing the start of it right now, Wake said…..

Carcasses of southern yellow-legged frogs in Sixty Lake Basin in Sierra Nevada, California. The frogs died of chytridiomycosis, an amphibian disease caused by a particularly virulent fungus. (Photo by Vance Vredenburg, from the UC Berkeley website)

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