Global warming drives epidemic disease wiping out amphibian populations

A University of Alberta scientist is part of a research team offering the first evidence that global warming is behind an infectious disease epidemic wiping out entire frog populations and forcing many species to extinction. The work is published in the journal "Nature."

"When we talk about climate change, there is so much focus on industrialized countries, but people are ignoring other ecosystems that may be extremely sensitive to climate change, such as dry and cloud forest environments," says Dr. Arturo Sanchez-Azofeifa, from the U of A's Department of Earth and Atmospheric Sciences and one of the paper's co-authors. "Its impact goes beyond what we can observe here in Canada and the north, and the situation is obviously very grave."

Sanchez-Azofeifa is part of an international research team led by Dr. Alan Pounds from Costa Rica's Monteverde Cloud Forest Preserve and Tropical Science Centre. Accounting for such things as deforestation, the scientists investigated how the Monteverde harlequin frog vanished along with the golden toad 17 years ago from the mountains of Costa Rica. About 67 per cent of the 110 species of the particular frog--which only existed in the American tropics--have met the same fate due, say the researchers, to a pathogenic fungus called Batrachochytrium dendrobatidis.

Between 1975 and 2000, air temperature for the tropics increased by 0.18 degrees per decade, triple the average rate of warming for the 20th Century. That warming, the paper argues, has reduced mist frequency at Monteverde by raising the heights of cloud formation which may promote the survival, growth and reproduction of the fungi.

After analyzing the relationship and timing between the species' losses and the changes in surface and air temperatures, the scientists conclude "with high confidence," that large-scale warming is a key factor in the disappearances of many of the amphibian populations present in cloud forest environments.

"There is absolutely a linkage between global warming and this disease--they go hand-in-hand," says Sanchez-Azofeifa, who analyzed satellite images to extract deforestation rates and forest cover extent that were later used on the modeling component of the study. "With this increase in temperature, the bacteria has been able to increase its niche and wipe out large populations of amphibians in the Americas.

"Once a species is gone we can't do much to bring it back--what we need to do is worry about what will be happening in the future," says Sanchez-Azofeifa. "How many species in tropical environments are going to disappear before people realize how serious climate change is? This is not esoteric thing that is only important to the scientific community--it affects all of us. We are showing that there are real consequences to inaction."

There is much concern over the future of amphibians. In 2004, the Global Amphibian Assessment, found that nearly one-third of the world's 6,000 or so species of frogs, toads, and salamanders are threatened with extinction--a figure far greater than any other group of animals.

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Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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