Andy Kerr - Amphibians on Earth

By Andy Kerr

Column #38 - Go to next column

Length: 748 words

Published: 1 January 1998, Wallowa County Chieftain

During the last decade, scientists have noticed both sharp declines in populations and marked increases in deformities in amphibians around the world. Declines of several local populations can be traced to habitat loss: the destruction of wetlands and forests, etc. Droughts are often a cause of declines, but droughts don't happen simultaneously everywhere in the world. Many population declines have also been documented from apparently pristine areas .

That got scientists searching for a global factor or factors. Is it due to global warming from atmospheric carbon dioxide caused by burning fossil fuels and logging forests? What is the role of acid rain formed from smokestack pollutants? What about the loss of the protective ozone layer due to the release of ozone depleting chemicals?

For amphibians, scientists are focusing on this last factor, though the first two might be problems as well. Amphibians depend upon plenty of water with an adequate pH balance. Global warming is causing more droughts and acid rain, not surprisingly, acidifies surface water.

The lifestyles of amphibians make them very sensitive to environmental changes and they can serve the role of the canary in the coal mine. Their eggs have no protective shell and are most often laid in shallow water and direct sunlight. The eggs are permeable and can easily absorb contaminants. The thin skin of adults has no protective covering of hair or feathers.

While most press attention has focused on the hole in the ozone layer over the Antarctic, there is also a hole of a smaller magnitude over the Arctic. Canadian scientists have detected a significant thinning of the ozone layer over the Pacific Northwest.

A band of ultraviolet sunlight known as UV-B penetrates the atmosphere in greater amounts as the protective ozone layer thins. Ultraviolet light wavelengths are shorter than the visible violet light and longer than X-rays. Several species of plants, insects, birds and mammals are known to be sensitive to UV-B radiation.

Oregon State University zoology professor Andrew R. Blaustein and others have published a paper in the Proceedings of the National Academy of Sciences about their study of long-toed salamanders in a Cascade Range pond. They took 200 eggs and shielded them from 94% of UV-B radiation and compared them to another 200 eggs in direct sunlight. 85% of the unshielded embryos died and the rest had deformities. Of the shielded embryos, 5% died and another 1% had deformities. The deformed that lived were much more susceptible to later mortality.

Also participating in the study were scientists from the University of Maine, Yale University and the US Geological Survey. Similar studies by the Environmental Protection Agency in Duluth, Minnesota, Pepperdine University in Malibu, California have found similar results.

Scientists suspect ozone layer depletion and are continuing to study the effect on humans. Skin cancer cases are rising dramatically, as are cataracts and immune system dysfunction. Can these aliments be attributed to the depletion of the protective ozone layer? It's very plausible, and increasingly likely, but no "smoking gun" exists.

Several years ago, most nations met in Montreal and agreed to phase-out the use certain particularly egregious ozone-eating chemicals. Some of the substitutes being phased-in also chemically consume ozone, but at lower rates. Ozone-friendly options exist, but they are more common chemical compounds. They are somewhat less efficient, but most importantly, unpatented, so they sell for less.

Should society wait until a "smoking gun" is found? Keep in mind that no comparable "smoking gun" has yet been found for tobacco. In the case of the killer weed, it was the overwhelming preponderance of the scientific evidence. There is still a little scientific evidence that tobacco isn't harmful.

Is it rational to always presume that the placement of a man-made chemical into our environment is a safe and sane thing to do? That is the default setting of our society now. When questions do arise, should the burden be on government agencies to prove something is harmful or upon the chemical's maker to prove that it is safe?

The analogy between amphibians in nature and canaries in coal mines breaks down because of the differing time scales. The time between the poisonous gas killing the canary and then killing the miners was relatively brief, but nonetheless time to act. UV-B is a much slower killer than mine gas.

It is also a different scale of space. Miners can evacuate a mine, but Earthlings can't evacuate the Earth.

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