During the last 20 years, scientists worldwide have begun to notice some disturbing trends among amphibian populations. Moreover, the most troubling changes have occurred within the last decade. It seems that certain of the globe's 5,130 amphibian species have rapidly declined in number. Several species, in fact, may have already become extinct. To date, researchers do not know the reasons for this occurrence. However, some believe that atmospheric ozone depletion is responsible for the animals' decline. It could be that different amphibian species are highly vulnerable to ultraviolet radiation. Regardless of the underlying mechanisms though, the amphibians' plight may have serious implications. As "indicator" species, their decline could foretell major future environmental problems. Although amphibian population declines were first observed during the 1970s, they did not receive widespread attention until relatively recently (7:422-424). In 1989, scientists at the International Herpetologists Congress noticed an abundance of reports on amphibian declines, and even complete disappearances. Moreover, the researchers observed that the phenomena were occurring on a global scale. In the last several years, amphibian population decreases have been reported in eastern and western Canada, the western United States, the southeastern U.S., France, Italy, Central America, South America, and Australia (8:1694). Furthermore, the magnitude of some of these declines has been quite considerable: it seems that highland and northern frogs are more severely affected than other species (9:860).
Unfortunately, any analyses of these declines has been hampered by the lack of long-term census data on amphibians (6:253). Therefore, most conclusions regarding population trends tend to be based on anecdotal observations. For example, in the Rocky Mountains of Colorado and Wyoming, there used to be so many boreal toads that "you had to ki...