National Wildlife Refuge System

Amphibian Numbers Drop Sharply, Finds Study

Sierra Nevada yellow-legged frog
Credit: USGS

A new USGS study, using data collected at national wildlife refuges and other sites, finds a steep drop in the numbers of frogs, toads and salamanders across the country. The study shows widespread species declines even in protected areas such as refuges.

On average, amphibian populations studied vanished from habitats at a rate of 3.7 percent each year. At that rate, these species would disappear from half of their current habitats in about 20 years. More threatened species disappeared from their studied habitats at a rate of 11.6 percent each year. At that rate, these species would disappear from half of their current habitats in about six years.

Scientists with the USGS Amphibian Research and Monitoring Initiative analyzed nine years of data from 34 sites − including 10 national wildlife refuges – and covering 48 species.  

Refuge monitoring sites included those at:
Buenos Aires National Wildlife Refuge, AZ
Coldwater River National Wildlife Refuge, MS
Great Bay National Wildlife Refuge, WI
Neal Smith National Wildlife Refuge, IA
Rachel Carson National Wildlife Refuge, ME
Upper Mississippi River National Wildlife and Fish Refuge
William L. Finley National Wildlife Refuge, OR
Eastern Massachusetts National Wildlife Refuge
Canaan Valley National Wildlife Refuge, WV
Klamath Marsh National Wildlife Refuge, OR

The study found declines even in species presumed to be relatively stable and widespread. Declines were documented in all regions, from the swamps in Louisiana and Florida to the high mountains of the Sierras and the Rockies.

The study did not evaluate causes of decline, but researchers speculated disease and climate warming were among contributing factors. The decline in amphibian numbers affects humans because amphibians control pests, provide medicines, feed other animals and help make ecosystems work.

The study – reportedly the first to measure the rate at which amphibians are disappearing − appears in the scientific journal PLOS ONE: 

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Last updated: May 23, 2013