Vanishing of frogs, toads tied to global warming, study says
By Traci Watson, USA TODAY
A team of biologists and climate scientists says in a new study that it has linked the extinction of a widespread group of animals to global warming.
Writing in Thursday's issue of the journal Nature, the scientists say that more than 60 closely related frog and toad species have vanished from the tropical forests of Latin America during the last few decades, partly because of warming temperatures. The team says this is the first time such a connection has been made.
The research team found a "near lock-step (link) between the timing of losses and changes in climate," said lead scientist Alan Pounds of the Monteverde Cloud Forest Preserve and Tropical Science Center in Costa Rica. "It's a very striking pattern, and it's hard to find another explanation for it."
The group did not identify the other contributing causes. Pounds and his team say the warmer temperatures of the late 20th century led to better growing conditions for a fungus that kills frogs and toads.
Other scientists expressed skepticism about the findings. Stephen Corn of the U.S. Geological Survey said the dates recorded for extinctions may not be entirely reliable. The University of Colorado's Cynthia Carey questioned why the new work ignores extinctions of related species after 1998.
The Earth's average temperature rose roughly 1 degree in the 20th century and could rise 10 more degrees by 2100, according to an international group of scientists convened by the United Nations.
That group and other researchers attribute the warming trend to the use of coal, oil and other fossil fuels, which emit carbon dioxide when burned. Buildup of the gas in the atmosphere can trap heat.
Scientists already have evidence linking higher temperatures to changes in the behavior or range of hundreds of species, such as flowers that bloom earlier in the year.
Scientists in the U.N. group predicted in 2001 that global warming would produce a wave of extinctions. They did not predict they'd see evidence so quickly.
"None of us expected that we'd be seeing massive extinctions in five years," said Camille Parmesan of the University of Texas. She was not on the Pounds team but found the link between extinction and global warming "very convincing."
Pounds and his colleagues compared when a species was last seen with climate data. They found that roughly 80% of the extinct species were spotted for the last time just after a particularly hot year. For example, the Monteverde harlequin frog hasn't been seen since 1988, one year after a warm year.
Pounds and his team theorize that the changes in the region's climate are encouraging the growth of a parasite that spread around the world in the 1960s and is a known killer of frogs and toads. Pounds said more work needs to be done to nail down this possibility.