JACKSONVILLE, Fla. -

Amphibians are said to have roamed the Earth for 350 million years, but many species face extinction.

Federal wildlife scientists say frogs, salamanders and toads are dying off at alarming rates nationwide, with the declines most dire among threatened species.

"Just the loss of one species could impact everything all the way up the line," said Mark Beshel, senior herpetologist at Jacksonville Zoo and Gardens.

A U.S. Geological Survey finds even in national parks thought to be islands of conservation, amphibians are dying off.

It finds overall numbers of frogs and their kin drop 3.7 percent every year, meaning they could disappear in half of the habitats they now occupy nationwide in 26 years. For 12 threatened species, things are even worse, with their numbers dropping 11.6 percent each year.

Worldwide, nearly a third of amphibian species are threatened with extinction. A spreading fungal syndrome and habitat destruction are seen as leading causes.

"Due to human encroachment, people build roads for development and make big pavements," Beshel said.

Not everyone wants to cuddle up next to these creatures, but scientists say they are crucial to helping make ecosystems work.

"Yeah, some people might not like frogs, but nobody likes mosquitoes," Beshel said.

Amphibians control pests, like mosquitoes, provide medicines and feed other animals.

"Toads eat cockroaches. Who wants more cock roaches around the house?" Beshel said.

One thing you can do at home to try to save the frogs and other amphibians is try not to treat your yard with as many pesticides or herbicides.