Biologist Wendy Palen says "it now earns the moniker of the most deadly pathogen known to science." She's referring to an amphibian fungus responsible for wiping out at least 90 species in recent decades, reports the New York Times. It's called Batrachochytrium dendrobatidis or Bd, and it was first identified 20 years ago among declining frog populations. In addition to the species it has wiped out, the fungus has caused decline in another 501 species, or 6.5% of the known total, more than double earlier estimates, according to a study in the journal Science. Of those, 124 have declined by more than 90% and may not recover, per the Atlantic. "We knew that frogs were dying all around the world, but no one had gone back to the start and actually assessed what the impact was," says lead author Benjamin Scheele of Australian National University.
The study describes Bd as first appearing in Asia, where amphibians seem unaffected. It then spread—via water, amphibian contact, and international trade beginning in the early 20th century—to five continents, wiping out huge populations before scientists could even name it. "I don't think we fully appreciate what was lost," researcher Karen Lips tells the Atlantic, adding that "we haven't come up with a viable solution." While the worst effects were seen in the 1980s, and 12% of species are showing signs of recovery, 39% are still in decline. As Bd can't be removed from a habitat, researchers say limiting the wildlife trade is key. Especially warm areas might be in the clear, however. The Guardian reports Bd can't survive at temperatures above 82 degrees. (Read more frogs stories.)