Another Silent Spring
In 1962 Rachel Carson wrote Silent Spring. Indiscriminate use of pesticides was the book's focus and its title referred to springs without the songs of birds. While the arrival of birds may signal spring for others, the sound of frogs in a nearby wetland usually heralds spring for herpers. Unfortunately, frogs and amphibians in general are experiencing a world-wide decline and in many areas these heralds of spring have already been silenced. In February of 1990, the World Congress of Herpetology met in Irvine, California and concluded that 16 countries, representing five continents, reported massive declines in amphibian populations.

Though no one common cause has been linked to these declines, several theories have been put forward, among them are acid rain, global warming, increased UV radiation, pesticides and, of course, habitat destruction. The only commonality to the whole story seems to be the amphibians themselves. It may be that amphibians simply react to environmental stress earlier than most organisms. Their biology requires that they come in contact with both land and water-based contaminants and predators. Additionally, their permeable skins, unprotected by scales, hair or feathers increases susceptibility to environmental stressors.

Amphibians have been around for more than 350 million years and in that time have evolved to fill varied niches in ecosystems around the globe. This diverse biology makes studying the problem all the more difficult. As an example, one study indicates that frog eggs bathed in slightly acidic water either fail to hatch or produce deformed tadpoles. Many frogs from the Eastern U.S. however, are well adapted to life in acidic boggy habitats and a Swedish study indicates that moor frogs showed increased adaptation to high acidity after only 15 generations. For every theory, there are similar examples of how one species or another has been able to survive despite increases of any one environmental stressor.

Possibly the most ominous factor to this entire situation is the almost over-night extinction of amphibian species from remote protected areas. Both the gastric brooding frog of Australia and the Costa Rican golden toad experienced sudden extinction though they lived in seemingly secure protected habitats. Ironically, efforts to protect these species from the pet trade left biologists with zero options once the animals became extinct in the wild. Had numbers of these frogs been allowed to enter private collections there may have been a recoverable living resource available making repopulation a possibility. Unfortunately, the animals that were collected were only preserved in jars.

The most likely explanation behind the sudden decline of amphibian populations is that they have been assaulted along to many fronts for to long. The 1980's brought six of the ten hottest years since 1855. Perhaps this severity of weather was too much to handle for populations already suffering from other stressors.

The story is not entirely bleak however, the very diversity that makes studying amphibians difficult also insures that many species will survive. In the north west portion of the U.S. wood frogs thrive in areas that have experienced declines in leopard frog populations. Additionally, many biologists view amphibians as the "canaries of the global coal mine". With their sudden decline people are starting to take notice of just how severely we are affecting our environment.

Locally there is much that can be done to help amphibian populations. Through judicious use of pesticides we can decrease runoffs that pollutes wetland habitats. Energy conservation and recycling reduce dependance on fossil fuels and decrease emissions of green house gasses. Populations can be monitored by civic organizations to help alert officials of local declines. In the end, however, it is the collective impact of every individual considering the environmental impact of his or her everyday decisions that will most benefit the frogs, and us.