National Geographic News
Silent and secretive creatures, salamanders are just as quietly falling off the map in tropical forests throughout Central America, a new study says.
The tiny amphibians seem to be on the same downward spiral as their frog cousins, which have been mysteriously declining for years.
Scientists have identified chytrid, a fast-killing fungus that may spread in waves, as responsible for wiping out frogs around the world. Others have said that climate change is shifting temperatures and humidity, factors intricately tied to amphibian survival.
But among the Central American salamanders, "we have no evidence that either chytrid or climate change is responsible for the declines," said study author David Wake, an biologist at the University of California, Berkeley.
In the 1970s, Wake spent several years researching lungless salamanders in the San Marcos region of western Guatemala, one of the most diverse and well-studied salamander communities in the American tropics.
Between 2005 and 2007, he and colleagues returned to that region and previous study sites in Mexico to survey salamanders and compare their results to the historical data.
Their data-collecting strategy remained the same: Spot as many salamanders as possible in a standard amount of time.
The results, published this week in the journal Proceedings of the National Academy of Sciences, shocked Wake.
"Cold facts written on a piece of paper don't convey the impact on my psyche when I went there," he said. Species that could be seen 10 to 15 times an hour in the 1970s were "completely gone."
These species lived in forests at mid-elevations, up to 9,184 feet (about 2,800 meters)—a zone where global warming is most intense, Wake said.
Seven out of 62 salamanders tested showed signs of chytrid fungus—not enough to rule out chytrid, but not enough evidence it was the culprit.
Karen Lips, a biologist at the University of Maryland, College Park, who has studied amphibian decline, said the disappearance "sounds like chytrid."
For instance, a 2008 study in the journal EcoHealth found that the fungus is very prominent in Mexican amphibians.
She also pointed out there is "no data that climate change is killing frogs and causing this level of disaster."
(Related: "Amphibian Extinctions: Is Global Warming Off the Hook?" [December 1, 2008].)
Lips believes that in the 1980s, an epidemic wave of chytrid fungus passed through Central America, when civil strife had kept researchers out of those countries. The 2006 level of chytrid infection—11 percent—bears out this theory, she said.
Out of Whack
An unseen "carpet of salamanders" make up the most biomass in some forests—more than birds and mammals, Lips said.
If the amphibians—which also eat large volumes of insects—are gone, "things go out of whack," Lips said.
As for saving the elusive creatures, there are few solutions, study author Wake said. But it's clear that "locking up nature" in reserves is not going to work.
Climate change and chytrid fungus don't respect borders, Wake said. "We need to promote activities that reduce the impact of climate change."
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