Al Gore recently paid a visit to the home of Rachel Carson whose book Silent Spring played an important role in jump starting the environmental movement. Her home is being preserved as a shrine. On the day of the vice president?s visit, a fourteen-year-old student named Lauren delivered a speech paying tribute to Rachel Carson. Lauren told how Carson had publicized the claim that DDT was killing off bald eagles, peregrine falcons and brown pelicans because it was thinning the egg shells that were cracking under the mother birds?s weight.
Al Gore praised Lauren?s remarks and told how his mother had discussed Silent Spring with him and his sister for weeks. He said the main lesson he learned from it was that there are problems with the environment that are not always obvious such as the connection between those thinning egg shells and DDT.
Dr. J. Gordon Edwards, a distinguished biologist and entomologist, showed in a paper he wrote 20 years ago that the claim that DDT caused the thinning of bird egg shells and a decline in the bird population is false. The facts in this report are based on Dr. Edwards? paper. It points out that forty years ago a study of captive bald eagles in Alaska by the U.S. Fish and Wildlife Service included feeding the birds high levels of DDT for a prolonged period. The study concluded that the amount of DDT that eagles were likely to ingest in the wild were far less than the amounts they were fed that showed no ill effects.
Other Fish and Wildlife Service studies involved analysis of every bald eagle found dead in the lower 48 states from 1960 to 1972. Most of the dead eagles had died violently, mainly from being shot. No adverse effects caused by DDT were observed, but there were nineteen suspected cases of poisoning by other pesticides. The Environmental Protection Agency held lengthy hearings on DDT in 1972. William Ruckelshaus, the EPA administrator, ignored the scientific finding that DDT was safe and ordered it banned. In a 1979 letter to the president of the American Farm Bureau Federation he said the decision was political.
Edwards points out that in the scientific findings and in Ruckelshaus?s forty-page opinion “there is no mention of eagles and no indication that research on bird eggs and reproduction led to the banning of DDT.” He says that articles about the impending extinction of the bald eagle were published eighty years ago. That was also true of the brown pelicans in Texas. Edwards notes that in 1960, after DDT had been used for fifteen years, the Audubon annual bird census found that the bald eagle count per observer was twenty-five percent higher than before DDT was introduced.
The annual count of migrating hawks at Hawk Mountain, Pennsylvania rose 19 percent from 1946-48 to 1964-66, a period of heavy DDT usage, but media attention was focused on the decline of peregrine falcons. That also began long before DDT was used. It was reversed after a program of breeding the falcons in captivity and releasing them was launched in 1975. We will have more on DDT in our next commentary.