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 Disappearance of frogs may signal the planet is out of whack
(CNN) -- Is the Earth so polluted, baked from global warming and suffocated by ozone depletion that species are dying? According to people who monitor frog populations it is. This summer, Jeff Houlahan, a Canadian student working toward a doctoral degree at the University of Ottawa, analyzed data on 936 frog populations collected from as far back as 1930. He found that between 1960 and 1966, the number of frogs decreased 15 percent each year. Since 1997, the population has dropped 2 percent each year. In some cases, species aren't just declining. They are disappearing. The Golden Toad has vanished from its cloud-shrouded home on Monte Verde in Costa Rica. And half a world away in Australia, no one has seen a Gastric Brooding Frog since the mid-1980s. Scientists theorize that disappearing and declining frog populations is one more indicator that Earth has more environmental stresses than it can handle. Are frogs like canaries?Some biologists say they believe that what happens to the frog population is a good predictor of what could happen to humans. They liken frogs to canaries that miners would use to detect fatal fumes. (During the 1800s, miners took the birds below ground with them to determine if the environment was safe. Mines sometimes contained invisible, odorless, poisonous gas. If the canaries died, the miners knew they had to leave the mine.) Frog abundance and visibility make them good "canaries," said David Green, a biology professor at McGill University in Montreal. "What makes a canary a good indicator is not that it just sits there and dies," Green said. "A flatworm would die in the mine, too. What makes canaries good in a mine is you notice when they are not there anymore. "Frogs sing. You know when they are not there," Green said. But not all scientists -- particularly herpetologists, or frog experts -- give the fate of frogs that much weight. "It makes sense in theory that what happens to frogs could happen to us. They have semipermeable skin. They have both aquatic and terrestrial life phases, so they are exposed to stuff in both places," Houlahan said. "But there is no evidence to show amphibians are more vulnerable than any other taxonomic group." Houlahan said he doesn't believe that frogs are the ultimate indicator of the planet's health, but they are one of many.
"It's like we used to have more fish on the planet, and if you look at a map from 100 years ago, we now have less forests," he said. "With amphibians, it's just one more indication we are overworking the planet." Fretting over frog fatalitiesA number of circumstances could be stressing out the planet and killing off frogs, said Joe Pechmann, a University of New Orleans assistant professor who has been in herpetology 18 years. These include increased pollution, habitat destruction, ozone depletion, global warming and species introduction. "Amphibians tend to live in wetlands and tropical rain forests," Pechmann said. "It's pretty obvious that anything living in wetlands and rain forests won't do well because they are being destroyed at a fast clip." Global warming and ozone depletion affect temperature and moisture on Earth. Some biologists said global warming had a role in the disappearance of the bright orange Golden Toad. "The theory is that global warming caused the clouds to lift up higher and higher off the mountains," Pechmann said. "The frogs ran out of mountain, and without the clouds, their environment might have gotten too dry." An increase in ultraviolet light and the introduction of new species also might have an adverse effect on amphibians. Too much UV light can kill frog embryos, and the rainbow trout that man moved into California's High Sierra proved to be a frog predator, Pechmann said. Where causes are known, such as pollution or habitat destruction, species disappearance isn't as frightening, Pechmann said. "They are all a concern from a conservationist point of view. But the ones we don't know the cause (of), they are very scary," he said. "If people don't know why, they have to wonder what else is next? Is it their dogs? Is it us?" 'A critical place in the food web'So who cares if there are less fly-zapping, bug-eating frogs around? Everyone should, Houlahan said. "They have a critical place in the food web. They eat a lot of things, and they get eaten by a lot of things," Houlahan said. "As they decline, there will be an effect up and down the web." Pechmann said people should care about amphibians for moral reasons. "We should be concerned about what happens to the food chain, but I think there is a bigger question, a more important reason we should care about what happens to these species," Pechmann said. "That is, 'Do we have a responsibility for taking care of the other life on this planet? Do we have the responsibility for making sure we don't kill off life on this planet?' " "Most people would feel that (killing off a species) is wrong or immoral," he said. "And I personally think that's the best argument." RELATED STORIES: World's reptile populations running thin RELATED SITES: North American Amphibian Monitoring Program | ||||||||||||||||||||||||
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