Amphibian populations are declining at an alarming rate in the United States.
In fact, a new study from the U.S. Geological Survey (USGS) finds that if the rate of decline they're seeing is accurate, and continues unchecked, "these species would disappear from half of the habitats they currently occupy in about 20 years."
Amphibians have been with us for nearly 400 million years, but according to USGS Director Suzette Kimball, "the findings of this study... demonstrate the pressures amphibians now face exceed the ability of many of these survivors to cope."
According to the study, overall occupancy by amphibians in the U.S. declined by an average of 3.7 per cent each year from 2002 to 2011. This includes frogs, salamanders and other amphibians.
Researchers from the USGS, as well as Penn State and Colorado State Universities, used Amphibian Research and Monitoring Initiative (ARMI) data to estimate the rate of change in the probability that amphibians would occupy ponds and other comparable habitats.
Scientists analyzed 34 sites over the course of nine years, spanning 48 species.
The study's lead author, ecologist Michael Adams, says "even though these declines seem small on the surface, they are not. Small numbers build up to dramatic declines with time."
And for species on the International Union for Conservation's "red list," the numbers were bigger. On average, those species experienced 11.6 per cent declines each year.
The study doesn't directly touch on what may have caused the decline, but the authors suggest climate change, disease and drought may all have played a role.
According to scientists, the species and areas monitored by ARMI were generally selected to evaluate the status and trends of amphibians on federally-managed land and nature preserves.
According to the study, published in the Public Library of Science (PLOS), such lands are sometimes perceived as better protected than private lands. Unfortunately, this was not the case as declines even occurred at these sites.
In Canada, researchers at the Vancouver Aquarium have bred northern leopard frogs in an aquarium setting, creating an assurance (backup) population.
Adult northern leopard frogs at the Vancouver Aquarium (Photo: AP/Vancouver Aquarium)
The Rocky Mountain species began to experience a precipitous decline in the 1970s.
Aquarium director Dennis Thoney says "Frogs... are facing probably the largest extinction since the dinosaurs right now. Of the 6,000 species, a third to more are threatened or endangered now."
The Smithsonian Conservation Biology Institute's Brian Gratwicke says the USGS study is "very bad news for amphibians."
"Now, more than ever," says Gratwicke, "we need to confront amphibian declines in the U.S. and take actions to conserve our incredible frog and salamander biodiversity."