Frog Extinctions Linked to Global Warming

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Study Skeptic

But not all experts are ready to pin amphibian deaths on climate change just yet.

Cynthia Carey, an amphibian-disease expert at the University of Colorado, warns that the study may have shown a circumstantial correlation between temperature data and amphibian deaths. But the report has not shown cause and effect.

"[The study authors] haven't met the rigorous criteria for proving that the frogs in Monteverde even died from chytrid," she said.

"And while the globe is certainly warming, [researchers] haven't proven that the fungal outbreaks are driven by increases in temperature."

Carey cited several research studies that document the ability of chytrid fungus to kill at temperatures near the freezing point. She noted that many documented amphibian deaths from such outbreaks occur in winter.

Frogs in the Coal Mine?

Climate scientists have long warned that global warming could spur deadly disease epidemics. The study suggests that such a scenario may already be unfolding in the amphibian world.

If so, humans and other species should consider themselves duly warned.

Because amphibians are particularly sensitive to environmental change, they may serve as proverbial "canaries in a coal mine" that warn of such climate change dangers.

A two-year-old study by a scientist at Britain's University of Leeds suggests that some 15 to 35 percent of land-dwelling plants and animals, or about a million species, would be extinct or committed to extinction by 2050.

Other climate scientists have calculated that half of the planet's species are already affected by global climate change.

The news for amphibians is particularly bad.

In 2004 a global amphibian assessment by the World Conservation Union, Conservation International, and NatureServe reported that about one-third of all amphibian species were in decline.

New data will soon supplement that study, and those data will tell a familiar and sad story, according to lead author Simon Stuart, of Washington, D.C.-based Conservation International.

"They'll show a continuing deterioration, I'm afraid," he said. "Things have gotten worse."

Important Clue?

Though his 2004 report did not specify a cause for amphibian extinctions, Stuart believes Pounds's new research is an important clue.

The new study of harlequin frog species has "certainly taken us much further down the road towards understanding what's going on, towards getting the mechanism of this decline clarified," Stuart said.

If the data can be verified, that may hold a ray of hope for beleaguered frogs.

Bruce Young, a NatureServe zoologist and study co-author, said: "The good news, such as it is, is that the new findings will open up avenues of research that could provide conservationists with the means to save the amphibians that still survive. If this cloud has any silver lining, that's it."

Meanwhile, extinctions in protected and otherwise pristine environments such as Monteverde could illustrate global risks associated with a warming climate.

"Most of the studies that have been done on the impacts of climate change on species have focused on shifting habitats on a habitat moving higher up a mountainside or closer to the poles," " Stuart said.

"What we're seeing now is a much more rapid impact of climate change, not just climate change per se but climate change rendering species vulnerable to another threat."

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