http://www.time.com/time/magazine/article/0,9171,1149382,00.htmlHardy and plentiful as they seem, frogs are actually very frail things, with a semipermeable skin that leaves them vulnerable to even the slightest hiccup in their environment. So when entire species of brightly colored harlequin frogs started dying off in the cloud forests of Central and South America about 25 years ago, scientists suspected that something in the amphibians' ecosystems--they weren't sure what--had gone awry.
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The critters in question are favorites of scientists studying climate change. Quick and polychromatic, the frogs spend their days near stream banks, where their constant motion and vibrant hues make it easy for researchers to count them. Previous studies have shown that it's not heat alone that kills harlequins but also a pathogen--the chytrid fungus--that attacks their skin. The chytrid is actually a cool-weather organism, doing best at temperatures from 63°F to 77°F. Paradoxically, an effect of global warming is to increase cloud cover in the tropical forests, lowering daytime temperatures and making the frogs more vulnerable to fungal assault.
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Frogs are what scientists call an indicator species: particularly sensitive animals that are the first to go when the climate starts to change. Their extinction may increase pressure on government and industry to dial back greenhouse gases. The harlequins, after all, are only the beginning.
