A review of the role of contaminants in amphibian declines

For the past decade, there has been growing concern about worldwide declines in amphibian populations,^1,2 and a general phenomenon of declining populations was recognized in the mid-1990's. Subsequent research has validated this concern.^3,4 These population declines have been defined either as decreases in numbers of individuals in an area or, preferably because of greater reliability, a decrease in the number of sites occupied by breeding amphibians. Widespread population declines have occurred in North America,^5-7 Europe,^3,8,9 Australia,¹⁰ and Central and South America.^11,12 Population declines in eastern Europe, Asia, and Africa have been suggested but are not as well documented. Worldwide, more than 500 populations of frogs and salamanders have been listed as declining or of concern.^4,13 In the United States, a third of known amphibian species are thought to be in trouble.14 While the most severely affected populations are in the mountains of the western United States, serious declines have also been observed among some species in the Midwest and Southeast.²