An examination of amphibian sensitivity to environmental contaminants: Are amphibians poor canaries?

Background/Question/Methods Nearly two decades ago, the global biodiversity crisis was catapulted to the front pages of newspapers with the recognition of worldwide amphibian declines. Amphibians earned the appellation, “canaries in a coal mine,” because of their apparent high sensitivity to human-mediated environmental change. For amphibians, the most frequently cited causes for high susceptibility include permeable skin, a dual aquatic-terrestrial life cycle and a relatively rudimentary immune system. There has been, however, no systematic evaluation of amphibian sensitivity to environmental challenges relative to other taxa. Here, we apply a database representing thousands of toxicity tests to compare the sensitivity of amphibians relative to that of other taxonomic groups. The use of standardized methods combined with large numbers of identical challenges enables a particularly powerful test of relative effect size.

Results/Conclusions Overall, we found that amphibians only exhibit moderate relative responses to water-borne toxins. These results mean that, as far as chemical contaminants are concerned, amphibians are not particularly sensitive and might more aptly represent “miners in a coal mine.” To the extent that amphibian declines have been mediated by chemical contaminants, our findings suggest that population losses and extinctions may have already occurred in a variety of taxa much more sensitive than amphibians.