Frogs Are Finding the Planet an Increasingly Hostile Pad
by James Gerstenzang, Los Angeles Times, August 6, 1998
EVERGLADES NATIONAL PARK, Fla. -- Kermit the frog may live on in all his felt-green Muppet glory. But scientists fear that real frogs are disappearing around the world.
Consider, for example, the experience one swamp-dark night a few weeks ago when Walter Meshaka and Joe Pechmann were looking for frogs while mosquitoes were looking for them.
The mosquitoes were successful; so, too, were Meshaka and Pechmann, two leading herpetologists. There are, after all, 14 species of frogs in the Everglades National Park.
But had the two scientists moved just a few miles north, beyond two drainage canals and into the milo fields that border the park entrance, the results of their hunt would have been much different: Only two species, both of them alien to South Florida, survive in the heavily farmed, pesticide-sprayed and drained fields.
Herpetologists -- students of frogs, toads and salamanders, as well as reptiles -- are crawling through reeds, turning over rocks and reaching into tree branches in their search for amphibians in such disparate but pristine locations as the Sierra Nevada in California, Australia, Puerto Rico and Costa Rica. But with increasing frequency, they are coming up empty-handed.
The significance, they say, is frightening.
In the view of such experts, frogs are ubiquitous indicators of global environmental health: They play the same role as a canary in a mine, whose death signals that poisonous or explosive gases have reached a dangerous level.
Thus, because the amphibians -- with their permeable skin and complex life cycles in water and on land -- are particularly sensitive to pollution, ultraviolet light and microscopic organisms, their decline may signal a wide range of as-yet-undetected environmental ills.
“If all the animals were dying in a pond, would you want to drink the water? That’s basically what’s happening,” said Kenneth Dodd, a research zoologist at the Interior Department’s Florida-Caribbean Science Center. “We breathe the same air, we drink the same water. We live in the same environment. If something is affecting them, it’s affecting us.”
Among those who are concerned -- and baffled -- by the frog shortage is Kathleen Freel, a U.S. Geological Survey biologist at Point Reyes, north of San Francisco. She studies the aptly named mountain yellow-legged frog.
The three-inch frog could once be found with ease, its yellow-tinted limbs giving it a distinctive look as it leaped along the water’s edge in higher elevations of the Sierra Nevada, above 5,000 feet or so.
“You’d find a mountain yellow-legged frog every meter around a pond,” Freel says, in “drainages” -- river valleys and hillsides -- in such clean-air, clear-water conditions as those in the Sequoia National Forest and Kings Canyon and Yosemite national parks.
“In these pristine national parks, we’ve definitely noticed major declines. Major. Like entire drainages. No frogs,” she says. “The crazy thing is this is in the national parks. They’re getting the best protection they can from human disturbances.”
Similarly, concern is being raised about the Pacific tree frog, once as common in California as the original Volkswagen beetle -- and now in decline.
“That’s scarier,” Freel says, because its territory, from the coastline to the Sierra, is so geographically diverse that it encompasses nearly all of the state’s human population.
In this ecological whodunit, the detectives of the biological world have yet to figure out why the decline is occurring. Among the questions they are trying to answer”
Are the frogs, toads, and salamanders of the world being weakened by an invisible pollutant, a pesticide or herbicide migrating in water and wind to even the most isolated quarters? Is a naturally occurring fungus attacking immune systems that are under stress from acid rain or from ultraviolet light that has increased as the protective atmospheric ozone layer has narrowed overhead? Is the phenomenon connected to the doubling of the number of frogs in the upper Midwest with deformed limbs? Are rejuvenated populations of trout gobbling up the larvae? Or are the frogs and their cousins suffering from a naturally occurring cycle that will eventually restore a new balance to the environment?
Biologists also are considering the possibility that there is no single answer that applies globally.
“Maybe it’s a longtime process, but we’re only seeing the end of it,” Dodd said. “Ultraviolet radiation may not be lethal, but something else comes along and, bang, they’re gone. What we’re seeing is a pervasive collapse in the biosphere.”
As in most such occurrences in the natural world, the shift is generally taking place very slowly -- over years and perhaps decades.
Biologists working individually began noticing evidence of the decline as long as a decade ago. But they only recently began pooling their data and recognizing the potentially global extent of the mystery.
The problem has also caught the attention of Interior Secretary Bruce Babbitt, who said it illuminates “a landscape of extinction that goes all the way around the world.”
“My experience repeatedly has been when you see one species in trouble, there are others waiting to cascade into the extinction process,” he said.
Over the 15-year period beginning in 1980, according to the Interior Department, the number of amphibian species in the United States suffering losses or suspected of being threatened has increased from 33 to 52. Up to one-third of the amphibians native to the United States may be in decline.
Babbitt recently convened a meeting of the nation’s top environmental and health officials, including Kathleen McGinty, who heads the White House Council on Environmental Quality, Carol Browner, administrator of the Environmental Protection Agency, and Donna Shalala, the secretary of Health and Human Services.
They spent an evening in a seminar conducted by some of the government’s leading herpetologists. Since then, Babbitt has journeyed to the Great Smoky Mountains National park for a frog-oriented field trip. The Geological Survey is beginning a five-year study there because the park has the greatest diversity of amphibians in North America.
Although some species losses are easily explained as the result of habitat destruction, says Stephen Corn, a U.S. Geological Survey herpetologist, it does not explain the mysterious 75% decline in the California red-legged frog and the arroyo toad, which were once common in the central and southern regions of the state.
And in the forests of Costa Rica’s Monteverde National Park, he says, one-half of the frog species has disappeared.
It was there, where the now-unseen golden toad once lived seemingly out of danger, that the phenomenon was discovered.
“Why did these things go from being everywhere to nowhere? We don’t know why,” said Meshaka, the curator of the Everglades Regional Collections Center. “But if it happened there, it could happen anywhere.”
But finding frogs in the Everglades with Meshaka and Pechmann, a post-doctoral associate at Florida International University, isn’t very difficult. Meshaka can mimic the mating call of each -- the deep wump, wump of the pig frog, the metronome-like tick, tick, tick, tick, tick of the cricket frog, the mid-range brunk, brunk, brunk of the green tree frog.
At 10 on a moonless night along the Anhinga Trail, they are all sounding off at once. Meshaka, who spends about 100 nights a year wandering the park to check on its frogs, can distinguish each.
So far, Meshaka has found no evidence that a decline is occurring within the boundaries of the park itself. But he is monitoring his frogs from season to season to determine whether the threat has reached into the waving muhly grass, cypress hammocks and gator holes here.
In any good mystery, the answer to one question brings more questions. So, too, in the case of the world’s missing amphibians.