Amphibian Extinctions: Is Global Warming Off the Hook?

Brian Handwerk
for National Geographic News
December 1, 2008

The world's amphibians are in dire straits—but global warming may not be the problem, a new study suggests.

Previous research has pinned steep declines in amphibian species on rising global temperatures, which are said to be fueling the growth of a deadly fungus.

(Related: "Frog Extinctions Linked to Global Warming" [January 12, 2006].)

Most experts agree that the disease-causing chytrid fungus Batrachochytrium dendrobatidis is taking a terrible toll on frogs and toads. One in three species worldwide is threatened with extinction.

"There seems to be convincing evidence that chytrid fungus is the bullet killing amphibians," said University of South Florida biologist Jason Rohr, lead author of the study, published in a recent issue of the journal Proceedings of the National Academy of Sciences.

"But the evidence that climate change is pulling the trigger is weak at this point."

Beer to Blame?

Rohr and colleagues don't completely discount the role of global warming in amphibian declines.

But they say decades of data show only that some correlation exists between rising air temperatures and Latin American amphibian extinctions—and that data are well short of proving causation.

In fact, the researchers found that, in the Latin American countries they studied, beer and banana production were actually better predictors of amphibian extinctions than tropical air temperature.

While beer and bananas are certainly not to blame, the whimsical comparison makes a point.

"We can't jump to conclusions of causality based on a correlation—especially when we're talking about 60 or 70 species," Rohr said.

Continued on Next Page >>




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