There is a plague ripping through the amphibian species of the world. It’s caused by fungus that’s invisible to the naked eye and spreads easily by many means.
It kills by disrupting the way these creatures breathe through their skin, essentially suffocating frogs and salamanders.
The disease is called chytridiomycosis, and according to a landmark study published recently in the journal Science, it’s even worse than first thought.
Scientists once estimated about 200 species of frogs and salamanders have been harmed by the disease, but the new study concludes that chytrid fungus has contributed to declines in at least 501 amphibian species. Ninety of the species are thought to have gone extinct because of the epidemic.
Populations in tropical Australia, Central and South American seem to be hit hardest, though Africa, Europe and North America are also affected. The epidemic has caused the biggest loss of biodiversity of any recorded disease, according to this new accounting.
“It’s a staggering thing to consider,” said Jonathan Kolby, one of the study’s authors and a herpetologist specializing in conservation and wildlife diseases at James Cook Univerbefore had a single disease that had the power to make multiple species extinct, on multiple continents, all at the same time.”
The scope of the chytrid fungus onslaught on the amphibian world, which began in the 1980s, is unprecedented. West Nile Virus, which is now a well-known pathogen, affects 23 bird species. The fungus laying waste to bat populations across North America, white nose syndrome, is attacking six species.
“You’ve got hundreds if not thousands of frog species that could go extinct, and they’re getting much less attention from a global health perspective,” said Kolby, who helped create the Honduras Amphibian Rescue and Conservation Center.
Kolby argues the United States and other countries need to enact stricter biosecurity measures for several reasons. It’s already been shown that frogs and toads can harbor the fungus that afflicts salamanders, so only banning certain salamander species may not be enough to protect native species.
In many ways, Kolby said, the U.S. already does a good job of preventing the spread of diseases that affect crops and livestock, thanks to agencies like the U.S. Department of Agriculture and the Centers for Disease Control and Prevention. But chytrid fungus may have slipped through the cracks because it doesn’t immediately affect humans.
“What concerns me is there’s going to be a next time,” he said. “By not using this as a learning experience about what happens when we aren’t being careful, it almost undoubtedly ensures that the wildlife trade is moving other pathogens right now, be it for mammals, birds, fish. You name it.”
It is also unclear how a global decline in amphibians will disrupt the ecosystems they inhabit. Many species improve water quality by clearing waterways of vegetation when they’re in the tadpole stage. Other frog species play a crucial role in keeping mosquito numbers in check by feasting on their larvae. Other species rely on frogs as a food sources.
There are glimmers of hope. Kolby and his co-authors found population trends for 292 frog species that have been thinned by chytrid, and of those, 60 species have shown evidence of recovery, possibly because they are evolving resistance to the fungus. The scientists note that these are mostly recoveries of individual populations, rather than rebounds for the species at large.
“It at least gives us something to look at in terms of why some species are recovering and why others are not,” said Wolz.