Amphibians, reigning survivors of past mass extinctions, are sending a clear, unequivocal signal that something is wrong, as their extinction rates rise to unprecedented levels, according to a paper published by the Proceedings of the National Academy of Sciences (PNAS). Amphibians are among the oldest organisms on earth, having survived the last four mass extinctions. The current extinction rate of amphibians is cause for alarm, according to biologists.
The authors of the paper confront the question of whether Earth is experiencing its sixth mass extinction and suggest that amphibians, as a case study for terrestrial life, provide a clear answer. "A general message from amphibians is that we may have little time to stave off a potential mass extinction," said co-authors Vance T. Vredenburg and David B. Wake.
"An ancient organism, which has survived past extinctions, is telling us that something is wrong right now," said Vredenburg. "We - humans - may be doing fine right now, but they are doing poorly. The question, really, is whether we'll listen before it's too late," he added. While many factors have been cited for the profound change in global amphibian populations, a new emerging infectious disease, chytridiomycosis, is thought to be directly responsible for wiping out more than 200 species.
It poses the greatest threat to biodiversity of any known disease. An aquatic fungus of unknown origin, it's the first of its kind to infect vertebrates, and only amphibians. Understanding the ecology of chytridiomycosis may not only help amphibians, but human health as well. Scientists seek to map how the pathogen is transmitted from one species to another to develop ways to prevent or control outbreaks. The fungus is surprisingly virulent, according to authors, and how it causes death is not yet known.
"It's important for people to understand what's infecting and killing these frogs," said Vredenburg. "This disease is a remarkable example of a pathogen jumping boundaries and causing havoc. If we can understand how it is able to do so, we may be able to help the frogs as well as ourselves," he added.