Joel Sartore's Image

This is a crime scene in a remote corner of California, high in the Sixty Lakes Basin area of the Sierra Nevada: mountain yellow-legged frog corpses lie belly-up.

The culprit is a chytrid fungus, which causes the infectious disease chytridiomycosis, implicated in the decline or rapid extinction of at least 200 species of frogs and other amphibians worldwide. The disease was first seen in dying frogs in the Sierra Nevada in 2004, since when it has reduced the population of mountain yellow-legged frogs from tens of thousands to under a hundred. The death of the frogs is emblematic of a global amphibian decline. It's believed that the fungus is being spread in part by the international trade in amphibians for display, food and laboratory use, its effects enhanced by global warming. Its impact on frogs has resulted in the biggest loss of vertebrate life due to disease ever recorded.