GRANTS PASS, Ore. — A new study has determined for the first time just how quickly frogs and other amphibians are disappearing around the United States, and the news is not good.
The U.S. Geological Survey said Thursday that populations of frogs, salamanders and toads have been vanishing from places where they live at a rate of 3.7 percent a year.
That puts them on a path to disappearing from half their inhabited sites nationwide in 20 years.
USGS ecologist Michael J. Adams said the alarming news is that even species thought to be doing OK are declining, though at a slower rate, 2.7 percent a year.
"These are really ancient species that have been surviving a long time on earth through all kinds of changes," Adams said. "It's just a concern to see."
The data showed that species on the International Union for Conservation of Nature red list of declining species were disappearing from sites at an even higher rate, 11.6 percent a year. That would result in half the sites being unoccupied in six years. A third of amphibian species are on the red list.
"They just disappear," Admas said. "Populations are going away."
It has been known for a long time that amphibians are in trouble around the world from a killer fungus, habitat loss and a changing climate, but this is the first time that decline has been measured, Adams said.
"We are not making predictions," he added. "We are just trying to document the current trend."
Researchers plan to continue monitoring amphibians, giving scientists a way to measure how effective future efforts are in protecting and restoring the animals, Adams said
The study conducted by the USGS Amphibian Research and Monitoring Initiative was published Wednesday in the online journal PLOS One.
Scientists from USGS monitored hundreds of ponds, streams and other sites in 34 study areas around the country for the past nine years, returning two or three times a year to see if they were occupied and by what species. Most of the sites were on public lands with some level of protection.
"It's troubling that even on what are basically protected areas, we are seeing declines on average," Adams said.
Andrew Blaustein, a professor of zoology at Oregon State University not involved in the study, said the results were not surprising, because scientists have been worried about amphibians since the early 1990s.
"Now we need to continue to look at the causes, which will not be simple, because as the study suggest, they may involve factors that are not limited to local regions," he said in an email. "Many agents, including disease, atmospheric changes, pollutants, changes in climate etc. may interact with one another.
"We should continue our efforts to save these animals because of their importance in ecosystems."
Adams said it was difficult to help amphibians cope with something as big as climate change, but steps were being taking to remove more localized threats, such as non-native species of fish that eat amphibians.
The study published on PLOS One: http://bit.ly/12Nxina