BIODIVERSITY:
So Long, Salamanders
By Stephen Leahy*
SAN DIEGO, U.S. (Tierramérica) - Mesoamerica's salamanders appear to
be joining the global decline in amphibian species, like frogs,
adding to the evidence of ecological change around the planet.
"What's happening to salamanders and other amphibians may be a
strong lesson for humans," says lead researcher David Wake, of the
University of California at Berkeley.
There are global changes that are altering ecosystems and disease
patterns, thus creating new elements of biological pressure, he
said.
Wake and his colleagues have discovered that several salamander
species have vanished or have become very rare since the 1970s in
closely studied areas in western Guatemala and the southern Mexican
state of Chiapas. These findings were published last week in the
Proceedings of the National Academy of Sciences.
Climate change and disease are likely causing the declines but
scientists do not know why, Wake, one of the world's salamander
experts, told Tierramérica.
"We don't know what the impacts are on local ecosystems, but they
could be significant," he said.
Two of the most common lungless salamander species that Wake and
others studied in the San Marcos region of Guatemala in the 1970s -
Pseudoeur brunata and Pseudoeur goebeli - could no longer be found
anywhere.
"They were just gone," said Sean Rovito, a herpetologist at
University of California, Berkeley, who did the field research with
local experts between 2005 and 2007.
They appear to have gone extinct sometime after 1978, Rovito says.
"Some of the local Guatemalans who helped do the 1970s surveys took
us to the same locations, the same tree stumps, and the salamanders
just weren't there," Rovito told Tierramérica.
Researchers combed the flanks of the Tajumulco volcano on the west
coast of Guatemala and found signs of two of the three species that
were commonest 40 years ago, while there was no trace of the third.
This was a completely unexpected finding: "We thought the
salamanders would be doing okay," he says.
In addition, several other species were found in far lower numbers
than in the past.
In Mexico, the decline was most evident in Cerro San Felipe, a
reserve in Oaxaca, among species living around 2,800-3,000 metres
above sea level. The commonest species, Pseudoeurycea smithi, has
virtually disappeared.
Where once hundreds could be found in a single morning, researchers
have only found only one or two in last 10 years.
The problem extends all the way to Mexico City. North of the
capital, in the Parque Nacional El Chico, formerly "a paradise for
salamanders," populations are radically reduced.
Wake noted that species that depend on salamanders, such as a
salamander-eating snake, have also declined significantly.
In some areas, the habitat has been significantly altered in the
past 30 years by logging or expansion of agricultural areas.
However, since the declines were so widespread, affecting protected
areas such as Guatemala's Chicabal volcano, that researchers suspect
the frog-killing chytrid fungus, climate change or a combination of
the both is responsible, he said.
Abrupt and widespread declines in frog populations in the Americas
since the 1980s have been blamed on chytrid, a fast-killing fungus
that may spread in waves.
But alterations to local climate conditions - drier or warmer - can
also affect amphibians, which are often unable to adjust or move
fast enough to more suitable climate zones.
Most of the hardest hit salamanders in the survey live in mid to
higher elevations, suggesting that the warming climate is pushing
them to higher and less hospitable elevations. If the dry season in
the cloud forests lasts longer than normal it could be enough to
stress salamanders and make them more susceptible to the fungus,
Rovito speculates.
Salamanders go largely unnoticed except by curious children. And yet
in most forests there is an unseen carpet of salamanders that make
up the most biomass - more than birds and mammals combined, says
Wake.
"You can't remove something like that without a profound effect on
the ecosystem," said the scientist, who conducted the surveys of
prime salamander habitat in Mexico and Guatemala between 1969 and
1978.
Wake recalls finding many thousands of salamanders per hectare in
San Marcos and elsewhere in the 1970s. The civil war in Guatemala
(1960-1996) forced Wake to end his field studies.
Guatemalan scientist Carlos R. Vasquez-Almaza, of the Museum of
Natural History at the University of San Carlos, invited Wake and
his colleagues to re-survey the sites studied last in 1978.
Gabriela Parra-Olea, of the Instituto de Biología, Autonomous
National University of Mexico (UNAM), led researchers to re-survey
the Mexican sites.
The lungless salamanders (family Plethodontidae) breathe through
their skin like frogs and are found from Canada into South America.
Although not very well studied in the tropics, "salamanders are
enormously important in forest ecosystems," Wake says.
For example, they eat a lot of insects. And in areas that lost their
frogs, another major insect eater, studies have shown that the
creeks became overgrown by algae, he said.
Salamanders are a very diverse group and have been around for 150
million years. "And here they are, apparently dying out in my
lifetime," says Wake. "There is definitely something wrong."
(*This story was originally published by Latin American newspapers
that are part of the Tierramérica network. Tierramérica is a
specialised news service produced by IPS with the backing of the
United Nations Development Programme, United Nations Environment
Programme and the World Bank.) |
|
|
|
|
|
|
