Two-thirds of 110 species of the colorful harlequin frogs of South America have vanished since the 1980’s. The article in Nature quotes the lead researcher:
"Disease is the bullet killing frogs, but climate change is pulling the trigger," says Alan Pounds, an ecologist at the Monteverde Cloud Forest Preserve and Tropical Science Center in Costa Rica.
Discussing the study, Andrew Revkin in the NY Times (reg. required) points out that the climate change/species extinction link is challenged by a few researchers, on the grounds that the mechanism–which appears to be linked paradoxically to a fungus–isn’t clearly understood.
Searching for balance, Revkin writes:
Several scientists criticized the paper yesterday, saying it glossed over significant sources of uncertainty; others said it was important evidence that warming caused by humans was already harming wildlife.
But take a look at the piece in Nature. Here’s how the explain what they found:
The team first mapped the timing of species disappearances against changes in sea-surface and air temperature over the past few decades, and found that the frogs are disappearing almost exactly in step with climate change.
But it was not clear how the link between species loss and climate change worked: the world is generally warming, but the fungus is thought to be more deadly in cooler climes.
So the team looked at 50 sites from Costa Rica to Peru. It found that the frogs were doing worst in areas where night-time temperatures are getting warmer, but day-time temperatures are cooler – conditions that favour the fungus.
The most likely connection, say the researchers in Nature2, is that large-scale warming is accelerating the formation of clouds. This in turn makes local conditions kinder on the fungus, and spells bad news for the frogs.
To me that sounds very convincing, and–even more interestingly–unusually blunt.
Fortunately, to keep everything in perspective, we have Tom Toles.