May 25, 2013
Amphibian Populations Declining More Rapidly Than Previously Reported
redOrbit Staff & Wire Reports - Your Universe Online
The number of frogs, toads and salamanders in the US could be falling at an even more severe and widespread rate than previously believed, and even amphibian populations thought to be stable are actually on the decline, according to new research for the US Geological Survey (USGS).
The study, which was published earlier this week in the journal PLOS ONE, is believed to be the first-ever estimate of how quickly amphibians across the country are disappearing from their habitats. In the study, USGS scientists and their colleagues found dropping numbers of amphibians in populations everywhere, from the swamps of the southeast to high mountain ranges like the Rockies and the Sierras.
“Amphibians have been a constant presence in our planet's ponds, streams, lakes and rivers for 350 million years or so, surviving countless changes that caused many other groups of animals to go extinct,” USGS Director Suzette Kimball said in a statement Wednesday. “This is why the findings of this study are so noteworthy; they demonstrate that the pressures amphibians now face exceed the ability of many of these survivors to cope.”
Furthermore, the USGS study reports that the frogs, toads and lizards population numbers are even dropping in supposed safe-havens — locations like wildlife refuges and protected national parks.
“The declines of amphibians in these protected areas are particularly worrisome because they suggest that some stressors — such as diseases, contaminants and drought — transcend landscapes,” added USGS ecologist and lead author Michael Adams. “The fact that amphibian declines are occurring in our most protected areas adds weight to the hypothesis that this is a global phenomenon with implications for managers of all kinds of landscapes, even protected ones.”
According to the USGS, populations of all amphibian types examined disappeared from their habitats at an average annual rate of 3.7 percent. If that rate remains unchanged, the researchers believe that those species would vanish from half of their current habitats in approximately two decades.
The news is even bleaker for amphibians facing the possibility of extinction. Amphibian types on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species have disappeared from their studied habitats at a rate of 11.6 percent each year, the agency reported, and would disappear from half of their currently occupied habitats in about six years.
“Even though these declines seem small on the surface, they are not,” Adams explained. “Small numbers build up to dramatic declines with time. We knew there was a big problem with amphibians, but these numbers are both surprising and of significant concern.”
The scientists behind the research analyzed a total of nine years worth of data involving 48 different amphibian species at 34 different locations. They studied the rate of change in the number of ponds, lakes and other habitat features occupied by amphibians, but did not examine possible causes of the decreasing populations.
The study was conducted under the auspices of the USGS Amphibian Research and Monitoring Initiative (ARMI), which was formed in order to research amphibian trends and causes of decline. It discovered that amphibians appeared to be experiencing the most severe declines among vertebrates, but that all major groups of freshwater animals were having similar issues.