Amphibians Going Under

 

Frog -

     he croaked

     and soaked,

     then choked

     and croaked.

 

         Frogs, toads, newts, salamanders, and worm-like caecilians - 5,743 known species of amphibians - are facing unprecedented rates of decline and extinction. In fact, they are probably the most endangered class of animals on Earth with one-third of all species facing imminent extinction. This was the conclusion of a three-year international study, the first global amphibian assessment, conducted by over 500 scientists and published in Science magazine in December, 2004.

          Why are these creatures so vulnerable? At first glance, they might be expected to be unusually hardy. After all, they have been around for over 200 million years, having survived at least two major periods of mass extinction including the one that did in the dinosaurs. The answer appears to be complex as numerous causes are responsible. These include pesticides, global climate change, the thinning stratospheric ozone layer, destruction of fresh water and rainforest habitats, the introduction of non-native parasites and predators, and novel infectious diseases. All of these agents and conditions seem to contribute to the amphibian demise, and unfortunately, all appear to be caused by the current agent of mass extinction: man.

         Why should we be concerned about the loss of amphibians? After all, they are not of great economic importance to mankind compared with several other types of animals. Amphibians are thought to serve as sentinels for environmental problems that jeopardize entire ecosystems. These creatures spend their early months under water, breathing with gills, and the remainder on land, breathing with lungs. They have permeable sensitive skin that renders them particularly vulnerable to pesticides and other pollutants. Because of their sensitivities, they may be nature's best indicators of overall environmental health. Their catastrophic decline suggests that we may be experiencing the worst environmental crisis the Earth has endured in millions of years. "Amphibians are telling us that our planet is being harmed right where we live," reported Andrew Blaustein, Director of the Environmental Sciences Program of Oregon State University in Corvallis. We are in an age of accelerating unnatural extinction driven by human activities.

         While one-third of all amphibian species are known to be in peril, a majority could actually be on the verge of extinction. Only about 6% of known species are considered not threatened. In fact, the report suggests that the authors' own assessment of the amphibian threat is probably an underestimation as many species were probably wiped out before they were even discovered. The assessment did, however, remove any doubt about the magnitude of the problem. The loss of amphibians is occurring in "the blink of an eye," when viewed in geological time. These facts should clearly concern us all. It is obvious that we need greater protection of natural areas in addition to general environmental protection if we are to stem, or even slow down the tide of extinction. But unless we can control our population and curb our use of technologies that generate pollutants, conditions on Earth will become increasingly hostile towards life of almost all kinds.

 

 

Marla Cone. Threat to amphibians rising. Los Angeles Times, October 15, 2004, p. A5.

Stuart, S.N., Chanson, J.S., Cox, N.A., Young, B.E., Rodrigues, A.S., Fischman, D.L., and Waller, R.W. (2004). Status and trends of amphibian declines and extinctions worldwide. Science 306: 1783-1786.