Strongest Link Yet To Climate, Disease Synergies Wiping Out Frogs Globally

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Also, if you link to the site, you'll notice four different versions of Newsweek. One of them is not like the other. See if you can guess which regional edition it is?

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There's one member of this pageant that won't be turning up, however: the Monteverde harlequin frog. Named after its palette of yellow, red and black, this miniature amphibian—a member of the genus Atelopus—had thrived in these Costa Rican mountains for perhaps a million years. Yet the last time J. Alan Pounds, an ecologist who has studied the cloud forest's wildlife for 25 years, spotted one in Monteverde was in 1988. Its cousin, the golden toad, went missing about the same time. Indeed, the more scientists search, the grimmer the situation looks. A study by 75 scientists published earlier this year in the journal Nature estimated that two thirds of the 110 known species of harlequins throughout Central and South America have vanished. And that may be just the beginning.

The loss of a species is sad enough, not least a jewel like the harlequin, which one researcher described as a tropical Easter egg. What has puzzled scientists is why. For millennia, this denizen of tropical America survived by adapting to whatever changes nature threw its way. Suckers lining the underbelly of tadpoles allow them to cling to rocks without being flushed downstream. The adult's carnival-like costume warns potential predators to stand clear or risk a deadly dose of tetrodotoxin. But apparently there's one peril the harlequin couldn't trump: climate change.

Monteverde gets its lifeblood from the trade winds, which blow moisture uphill where the air cools and condenses into clouds. An ark of plants, insects and animals flourishes in the cool misty mountains. Gradually, though, a warming trend has raised nighttime temperatures and increased cloud cover, which makes for cooler days by blocking solar radiation. The subtle change, which might go unnoticed by us bipeds, is thought to have been ideal for chytridomycosis, a disease caused by a waterborne fungus that has flared up throughout tropical Central and South America. Scientists believe the chytrid disease kills the frogs by blocking their natural ability to absorb water through their porous skin (and perhaps also by releasing a toxin), essentially causing them to die of dehydration. What really frightens researchers, however, is the potential implications of the die-off. "There's basically a mass extinction in the making," says Pounds. "I think amphibians are just the first wave."

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The trouble at Monteverde only heightened a mystery that had scientists stumped for years: why do whole species of wildlife disappear in apparently pristine parks and nature preserves? There had been no shortage of theories to explain the demise of the harlequins, from acid rain to an overdose of ultraviolet rays. By the late nineties, attention shifted to the chytrid fungus outbreaks, which many amphibian experts concluded were the smoking gun. But Pounds wasn't satisfied. After all, it wasn't just harlequins, but all kinds of amphibians that were dying. And if the chytrid disease was killing the frogs, what was behind the deadly outbreak? In time, Pounds learned that the fungus flourished in the wet season and turned lethal in warm (17 to 25 degrees Celsius) weather—exactly the conditions that climate change was bringing to the cloud forest. More important, he found that 80 percent of the extinctions followed unusually warm years. "The disease was the bullet killing the frogs, but climate was pulling the trigger," says Pounds. "Alter the climate and you alter the disease dynamic."

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http://www.msnbc.msn.com/id/15176444/site/newsweek/