Christine Dell'Amore, National Geographic News 9 Feb 09;
Silent and secretive creatures, salamanders are just as quietly falling off the map in tropical forests throughout Central America, a new study says.
Two common species surveyed in the 1970s in cloud forests of southern Mexico and Guatemala are extinct, and several others have plummeted in number, researchers say.
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.
But among the Central American salamanders, "there's no way we can attribute the declines we've found to chytrid," said study author David Wake, an biologist at the University of California, Berkeley.
Instead, Wake said global warming "makes perfect sense."
"Completely Gone"
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.
(See a photo of the world's largest land salamander.)
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 2,800 feet (853 meters)—a zone where global warming is most intense, Wake said.
Seven out of 62 salamanders tested showed signs of chytrid fungus—not enough direct evidence to link the fungus to the drop in numbers, the authors said.
But Karen Lips, a biologist at the University of Maryland, College Park, who has studied amphibian decline, said the disappearance "sounds like chytrid."
She 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 combined, 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."
Salamander Losses in Mexico, Guatemala Cause Worry
Will Dunham, PlanetArk 10 Feb 09;
WASHINGTON - Many salamander species in Mexico and Guatemala have suffered dramatic population declines since the 1970s, driven to the brink probably by a warming climate and other factors, US scientists said on Monday.
The salamanders' fate provides the latest evidence of striking losses among the world's amphibians, a phenomenon some experts see as a harbinger of doom for many types of animals.
Biologist David Wake of the University of California Berkeley and colleagues tracked about two dozen species of salamanders at several sites in Guatemala and southern Mexico.
They put a special emphasis on the San Marcos region of Guatemala, boasting one of the most thoroughly studied and diverse salamander populations in the tropics.
Compared to levels measured in the 1970s, the population of half of the species in the two countries declined markedly. Four species were apparently completely gone and a fifth virtually wiped out, Wake said.
The cause is probably a complex combination of factors including climate change -- with warming temperatures forcing salamanders to higher and less hospitable elevations -- as well as habitat destruction and a fungal disease, Wake said.
"We have documented what has long been feared -- that tropical salamanders are being hit hard by something and are disappearing," Wake, whose findings appear in the journal Proceedings of the National Academy of Sciences, said in a telephone interview.
The species that formerly were the most common were the ones hit the hardest, Wake said.
Many scientists worry that climate change will have a terrible impact on animal populations, with those in the most sensitive places, like polar bears in the Arctic, hit first.
Some experts view today's amphibians, whose ancestors were the first land vertebrates, as sort of a canary in the coal mine, warning of future disaster for the animal kingdom.
"If we are convinced there is something going wrong and these are canaries in the coal mine, what are you going to do about it? This is a problem," Wake said. "One major avenue is global climate change. That is clearly a factor."
While not included in this study, Wake said similar losses are occurring in salamanders in Costa Rica.
A lot of the research into amphibian losses had focused on frogs. This study adds valuable data on salamanders.
The various species in this study ranged from about 1.5 inches to 5 inches long. Ground-dwelling salamanders were found to be the hardest hit, as opposed to those living in trees and other types of vegetation.
(Writing and reporting by Will Dunham; Editing by Bill Trott)
