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Although nuclear war was once perceived as the greatest threat to the health of the human race, environmental degradation and uncontrolled population growth pose an even greater threat today, Dr. Eric Chivian said in an IAP talk on January 26.
Dr. Chivian, a psychiatrist with the MIT Medical Department and assistant clinical professor at Harvard Medical School, is a co-editor ofCritical Condition: Human Health and the Environment recently published by the MIT Press. He helped revive Physicians for Social Responsibility in 1978 and, with Drs. Bernard Lown, James Muller and Herbert Abrams, won the Nobel Peace Prize in 1985 as founders of International Physicians for the Prevention of Nuclear War. His talk was sponsored by the Medical Department and the MIT Women's League.
As was the case earlier with nuclear war, the general public and even the government have little understanding of the consequences to themselves of harming the environment, Dr. Chivian said. There is "a very basic misunderstanding about man's place in ecosystems," he said. "Many if not most people believe that we're somehow separate from our environment, that it's there for our plunder and that we can change the atmosphere and we can destroy habitats and forests and wetlands and the oceans without these changes affecting us; that we can disrupt complex ecosystems and extinguish species and somehow get away with it scot-free."
The destruction of species will prove detrimental to the human race because it results in the loss of valuable medical resources, Dr. Chivian said. Medical benefits from plants and animals (some of them endangered species), are continually being discovered. For example, the toxin from a dart-poison rainforest frog has proved "totally invaluable" in neurophysiological research, and may lead to drugs for treating heart arrhythmias and diseases of the nervous system, including Alzheimer's disease, he said. "As these frogs disappear, so may also new breakthroughs in these diseases."
Similarly, research on bears and their hibernation processes may lead to more understanding of osteoporosis and kidney failure in people. Although the animals don't move or urinate for several months at a time, they do not lose bone mass or suffer kidney damage and poisoning as people would under those circumstances. And from the bark of the Pacific yew-a tree found in old-growth forests in the American northwest that was formerly believed to be almost useless-comes taxol, a drug that is now the best-known treatment for ovarian cancer, he added.
The most diverse concentration of life forms is in rainforests, which occupy six percent of the world's land area but contain 58 percent of plant and animal species, Dr. Chivian said. At the current rate of destruction (142,000 square kilometers a year), extinction of one-quarter of the earth's species could occur within the next 50 years-the largest loss since the end of the dinosaur era 65 million years ago, he said.
A direct cause of deforestation is population growth, Dr. Chivian said. The current world census of 5.5 billion people is increasing by 90 million people a year (the present population of Mexico), and if nothing is done to alter this trend, the total population will double in 50 years. Most of this growth is occurring in the developing world and in cities, he noted.
Atmospheric degradation, particularly ozone depletion, is also causing damage to human health, Dr. Chivian said. From 1982 to 1989, the incidence of malignant melanoma (a potentially fatal skin cancer often caused by exposure to the sun's ultraviolet light, which ozone helps filter out) has increased by 83 percent in the United States, he said. Deterioration of the protective ozone layer can also damage crops and ocean phytoplankton, which occupy the bottom of the marine food chain and produce half of the atmosphere's oxygen, he added. However, many countries have agreed to ban use of ozone-damaging chlorofluorocarbons, and readings last summer showed no decrease in ozone levels for the first time, he said.
Global warming poses another threat to human health, Dr. Chivian said. The average prediction of the Intergovernmental Panel on Climate Change is that temperatures will increase by three to four degrees Centigrade by the year 2100. "This amount of warming would be unprecedented for the last one million years," he said. If nothing is done, "it will constitute a crisis of unimaginable proportions."
A major educational effort on the individual and governmental levels is necessary to undertsand and begin to solve environmental problems that are damaging human health, Dr. Chivian said. "Really protecting the environment is going to demand from all of us some changes in the way we use the world and interact with it. we're all involved in this issue."
A version of this article appeared in the February 2, 1994 issue of MIT Tech Talk (Volume 38, Number 2).