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Amphibian Declines

Gray Tree Frog (Hyla versicolor)

Scientists from the U.S. Geological Survey have published the first quantitative estimate of the rate of change in amphibian occurrence across the conterminous United States. Results show that on average, amphibians disappeared from known habitats at a rate of 3.7 percent each year during the decade-long study. The most threatened species disappeared at an annual rate of 11.6 percent. If this trend continues, sensitive species could vanish from half their currently occupied habitats in less than a decade. Even populations of species believed to be the least vulnerable were found to be dwindling. Amphibians are ecologically important for several reasons. They are critical predators of invertebrates, helping to stabilize insect populations, and they serve as prey to other animals, such as birds. Amphibians are also indicator species; that is, they are sensitive to specific environmental factors and their fate can help predict the health of the ecosystem. Scientists are only beginning to realize the potential amphibians have for providing potentially lifesaving medicines to fight infections.

Blanchard's cricket frog (Acris blanchardi)

Amphibians have been a national conservation concern for some time. In the United States, 26 amphibian species are Federally listed as threatened or endangered. In 2004, the first comprehensive Global Amphibian Assessment of the world's approximately 6,000 known species of frogs, toads, salamanders, and caecilians suggested that 32.5 percent of global species and 31.7 percent of U.S. species were in decline. Another assessment in 2007 estimated that the current extinction rate for amphibians was 211 times the background rate estimated from the fossil record. While these studies reveal that many amphibian species have conservation problems, they do not show the rate of population loss. The 2013 USGS study provides quantitative data about the rate of amphibian population decline in the United States.

The 2013 analysis was conducted by the USGS Amphibian Research and Monitoring Initiative (ARMI) which studies local amphibian management questions while simultaneously producing metrics that can be synthesized nationally. This survey used 612 estimates of amphibian occupancy generated from ten years of research (2002-2011) at 34 study sites across the United States. Scientists examined the rate of change in amphibian occurrence in ponds and other suitable habitats. In addition to the overall synthesis, researchers examined changes in occupancy by geographic region, land owner (Federal and private), taxa (frogs and salamanders), and conservation status. Conservation status is defined by the International Union for Conservation of Nature (IUCN) which maintains the Red List, the world's most comprehensive inventory of the conservation status of plant and animal species. IUCN categories and criteria for species in the wild span five levels and range from "critically endangered" to "least concern." While this study did not investigate causes of amphibian losses, declining trends in even the most protected areas suggest continental or global processes could be important factors in U.S. amphibian declines.

Spring peeper (Pseudacris crucifer)

Additional Resources

IUCN Amphibian Links
The IUCN has gathered a list of online information sources on amphibians and organized them into categories (institutions, general, regional, bibliographic, and general biodiversity).

NatureServe 2004 Global Amphibian Assessment
NatureServe provides a brief synopsis of the 2004 assessment along with links to related materials. References include fact sheets, articles, and assessment data, available through a searchable database.

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