May 23, 2013
A new U.S. Geological Survey study reveals an "alarming" finding that "amphibian declines may be more widespread and severe than previously realized."
In their study, Trends in Amphibian Occupancy in the United States in the journal PLOS ONE, the team of scientists looked at 34 sites and 48 species to see how fast clusters of amphibians disappeared from ponds, lakes and other amphibian habitats from 2002 - 2011.
What they found, said Brian Gratwicke, an amphibian conservation biologist with the Smithsonian Conservation Biology Institute, "is very bad news for amphibians."
Over the 9-year period, the researchers discovered that overall occupancy by amphibians declined 3.7% annually. Occupancy by species "red-listed" by the International Union for Conservation of Nature (IUCN) declined 11.6% annually over the same period. Species designated by IUCN as under "Least Concern" also dropped. The researchers write:
An average loss of 2.7% of occupied sites each year for the species of Least Concern monitored by ARMI [the USGS Amphibian Research and Monitoring Initiative] is alarming given that these species are thought to be relatively unaffected by global amphibian declines. This finding suggests that the IUCN threat status has been underestimated for some of these species.
Declines were observed even in protected areas like wildlife refuges and national parks, and this is "particularly worrisome because they suggest that some stressors - such as diseases, contaminants and drought - transcend landscapes," stated lead author and USGS ecologist 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."
The authors conclude:
Our trend estimates are consistent with other analyses showing that amphibians are declining, and go further by suggesting that species for which there has been little conservation concern or assessment focus (e.g., common species) may also be declining. While there was some variation across the U.S., the trend was consistently negative. Furthermore, declines are occurring on lands managed by federal agencies with the greatest observed rate of decline on National Park Service lands where management policy prescribes protection of natural ecosystem processes. Overall, the trends we documented suggest that amphibian declines may be more widespread and severe than previously thought.
"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," said USGS Director Suzette Kimball. "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."
"It's a loss of biodiversity. You lose them and you can't get them back. That seems like a problem," Adams told the Washington Post.
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