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An extinction that leaves sameness in its wake


(Read caption) A red-eyed tree frog. Nearly one-third of amphibians worldwide are threatened with extinction, according to the Global Amphibian Assessment.

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Amphibians around the world are in trouble.

Nearly one-third worldwide are threatened with extinction, according to the Global Amphibian Assessment. And in the face of massive die-offs in the wild, scientists are scrambling to preserve what they can in captivity. A network of zoos and laboratories operating under the moniker "Amphibian Ark" is laboring to save amphibians with the aim of one day reintroducing them to the wild.

Scientists often liken amphibians to the proverbial canary in the coal mine.

Human activity on earth is causing a mass extinction, and amphibians are among the first species to begin disappearing en masse. (The last mass extinction occurred when an asteroid slammed into earth 65 million years ago, ending the dinosaurs' reign.)

That's partially because amphibians, who interface with their surroundings through highly permeable skin, are extremely sensitive to pollutants and to changes in the environment. And so scientists aren't sure which of several possible culprits -- more ultraviolet light from a thinner ozone layer, pesticides, habitat loss, global warming -- is most responsible for the observed amphibian die-offs. Most likely, all of them contribute.

Nonetheless, a prime suspect is a fungus called Batrachochytrium dendrobatidis, or chytrid for short.

Scientists aren't sure where it came from exactly, but they suspect that it was accidentally spread around the world from Southern Africa in the early 20th Century. At that time, African clawed frogs were in demand for pharmaceutical uses. Many were captured in Southern Africa and exported.


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