Why are amphibian populations declining?

by the United States Geological Survey

Why are amphibian populations declining?

Research suggests that even though amphibians are severely declining worldwide, there is no smoking gun—and thus no simple solution—to halting or reversing these declines.

Though every region in the United States has suffered amphibian declines, threats differ among regions. They include:

• Human influence from the Mississippi River east, including the metropolitan areas of the Northeast and the agricultural-dominated landscapes of the Midwest
• Disease, particularly a chytrid fungus in the Upper Midwest and New England
• Pesticide applications east of the Colorado River
• Climate changes across the Southern U.S. and the West Coast

Amphibian declines are a global phenomenon that has continued unabated in the United States since at least the 1960's. Declines are occurring even in protected national parks and refuges.

The average decline in overall amphibian populations is 3.79 percent per year, though the decline rate is more severe in some regions of the U.S., such as the West Coast and the Rocky Mountains. If this rate remains unchanged, some species will disappear from half of the habitats they occupy in about 20 years.

Amphibians are good indicators of significant environmental changes. Amphibians, unlike people, breathe at least partly through their skin, which is constantly exposed to everything in their environment. Consequently, their bodies are much more sensitive to environmental factors such as disease, pollution, toxic chemicals, ultraviolet radiation, and habitat destruction. The worldwide occurrences of amphibian declines and deformities could be an early warning that some of our ecosystems, even seemingly pristine ones, are seriously out of balance.

The USGS coordinates and leads the Amphibian Research and Monitoring Initiative (ARMI), which was formed to determine the scope, severity, and causes of amphibian declines.