The frogs are croaking.

From Tampa, Fla., to Tasmania, more and more frog species are joining the lists of threatened and endangered animals. Rocked by a great amphibian pandemic, frogs are disappearing in alarming numbers, say biologists who fear the worst: an ongoing wave of extinctions.

"They're dying, honestly, and many species already are extinct in the wild," said Eric Hovland, husbandry supervisor at The Florida Aquarium in Tampa.

Global warming and habitat destruction are culprits, but the amphibian disease chytridiomycosis has taken a noticeable toll on global populations. Caused by a virulent fungus, the disease can cause 100 percent mortality in some species, yet its origin and impact are unknown, says the Association of Zoos and Aquariums, a wildlife conservation group based in Maryland.

So the association is reaching out by encouraging its 200 national members to hop on the frog bandwagon. The association also has declared 2008 as the Year of the Frog.

"We could lose 30 to 50 of the world's frog species," Hovland said. "They haven't had time to develop immunity to the fungus."

Chytridiomycosis is an infectious disease that has spread like wildfire over the past 15 years. But even if scientists found a way to prevent it, frogs would still be threatened by changes to their environment, and by air and water pollution, said Dan Costell, keeper of amphibians and reptiles at Tampa's Lowry Park Zoo.

"Frogs are the canary in a coal mine," he said. "They breathe and take in fluids through their skin, so whatever bad things are going on in the environment, they absorb them through their bodies."

Scientists say complications from global warming, deforestation and industrial runoff are pushing dozens upon dozens of amphibian species to the brink, with more than 100 species disappearing in the past 25 years, according to a recent study published in the journal Nature.

As more frog populations die off, experts say more ecosystems that depend on a delicate balance of animals, plants, temperatures and natural filters will slip into disharmony. Frogs are a critical part of that balance and a natural enemy of mosquitoes that spread malaria and other diseases.

About 2,000 species of frogs and amphibians currently are in peril of being lost forever, said Shelly Grow, a conservation biologist with the association in Maryland.

"No other class of organisms -- birds, mammals or plants -- has faced such a high risk of widespread extinction," she said.

But the rate of loss can be slowed, one reason The Florida Aquarium and Lowry Park are working to educate visitors, encourage conservation projects and take part in captive breeding programs. Both have built new homes for such threatened species as the poison dart frog, the Puerto Rican crested toad, Florida gopher frog and Panamanian golden frog.

"People have to be cautious of their own footprint," Hovland said. "We need to be responsible for the animals we bring into our lives."
Kurt Loft is a staff writer for The Tampa Tribune in Florida.