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SOURCE: National Geographic

DATE: March 28, 2019

SNIP: For decades, a silent killer has slaughtered frogs and salamanders around the world by eating their skins alive. Now, a global team of 41 scientists has announced that the pathogen—which humans unwittingly spread around the world—has damaged global biodiversity more than any other disease ever recorded.

The new study, published in Science on Thursday, is the first comprehensive tally of the damage done by the chytrid fungi Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal). In all, the fungi have driven the declines of at least 501 amphibian species, or about one out of every 16 known to science.

Of the chytrid-stricken species, 90 have gone extinct or are presumed extinct in the wild. Another 124 species have declined in number by more than 90 percent. All but one of the 501 declines was caused by Bd.

“We’ve known that’s chytrid’s really bad, but we didn’t know how bad it was, and it’s much worse than the previous early estimates,” says study leader Ben Scheele, an ecologist at Australian National University.

“Chytrid fungus is the most destructive pathogen ever described by science—that’s a pretty shocking realization,” adds Wendy Palen, a biologist at Simon Fraser University in British Columbia who wrote about the study for Science.

What’s more, the study’s counts are conservative. Earlier die-offs from the 1950s and 1960s in Europe and North America aren’t included for lack of evidence. And the 501 species tallied are just the ones that scientists know about. Researchers keep identifying new species of frogs—even after they’ve been nearly wiped out in the wild.

There are hundreds of species of chytrid fungi, and most of them are unobtrusive decomposers. But Bd is an oddball: It has a fanatical taste for the proteins in amphibian skin. In the early 20th century, human activity—such as trade and war—accidentally spread the fungus around the world.