America's Frogs, Toads and Salamanders Disappearing Rapidly: Amphibian Decline

First Posted: May 23, 2013 10:23 AM EDT

When people think of species decline, their minds often wander toward the polar bear or the tiger--charismatic mega fauna that look good on posters. Yet there are other species that are going extinct far more rapidly--amphibians. Researchers have made the first ever estimate of how fast frogs, toads and salamanders in the United States are disappearing from their habitats.

Amphibians play an important role in ecosystems. They act as efficient predators of insects and also provide valuable nutrients to creatures further up the food chain. In addition, some play an important role in nutrient cycling. They're a constant presence in watery ecosystems, so the new findings are especially worrisome. It turns out that even the species of amphibians presumed to be relatively stable and widespread are declining.

In order to actually measure this decline, researchers looked at the rate of change in the number of ponds, lakes and other habitat features that amphibians occupied. In all, they analyzed nine years of data from 34 sites spanning 48 species. They found that amphibian populations are declining everywhere--from the swamps of Louisiana and Florida to the high mountains of the Sierras and the Rockies.

"Amphibians have been a constant presence in our planet's ponds, streams, lakes and rivers for 350 million years or so, surviving countless changes that caused many other groups of animals to go extinct," said USGS Director Suzette Kimball in a news release. "This is why the findings of this study are so noteworthy; they demonstrate that the pressures amphibians now face exceed the ability of many of these survivors to cope."

On average, populations of all of the amphibians examined vanished from habitats at a rate of about 3.7 percent each year. If this rate continues, these species would disappear from half of the habitats they currently occupy in about 20 years. Not all species disappeared at the same rate, though. Those that were Red-Listed disappeared at a phenomenal rate of 11.6 percent per year, which means that they would be gone from half of their habitats in about six years.

Those weren't the only findings, though. The researchers also discovered that declines occurred even in areas that are managed for conservation of natural resources. These included national parks and national wildlife refuges.

"The declines of amphibians in these protected areas are particularly worrisome because they suggest that some stressors--such as diseases, contaminants and drought--transcend landscapes, "said USGS ecologist Michael Adams, lead author of the study, in a news release. "The fact that amphibian declines are occurring in our most protected areas adds weight to the hypothesis that this is a global phenomenon with implications for managers of all kinds of landscapes, even protected ones."

Although this particular study didn't focus on why amphibians are declining, there are some theories out there that explain the phenomenon. There's no real single reason for the population plummets. However, some contributing factors include habitat destruction, environmental contamination, invasive species and climate change, according to Oregon State. Currently, amphibians seem to be experiencing the worst declines documented among all vertebrates; if this decline continues, we may see the last of some species in just a few short years.

The findings are published in the journal PLOS One.

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