THE BIOLOGY BOOK
Paul Müller (1899–1965), Rachel Carson (1907–1964)
In 1962, Silent Spring appeared and was instrumental in launching the environmental movement in the United States. Rachel Carson, a marine biologist and former science editor for the US Fish and Wildlife Service, previously authored a number of natural history books, including The Sea Around Us (1951), a New York Times best seller for eighty-six weeks.
Four years in preparation, Silent Spring documented evidence that pesticides had an adverse effect on the environment that spread far beyond their intended insect targets and extended to fish, birds, and even humans; Carson thought that these chemicals should be called biocides. The book’s title alludes to a spring in which bird songs are absent as all birds had vanished because of pesticides. She called not for a ban but for more responsible use and careful management of pesticides and greater awareness of their impact on the ecosystem.
Of these pesticides, she focused particular attention on DDT, invented by Paul Müller in 1939, and used highly effectively during World War II in eradicating mosquito-carriers of the malaria parasite in the Pacific and controlling lice responsible for typhus in Europe. When a single application was applied to crops, DDT killed insect pests for weeks and even months. However, runoffs containing DDT were often deposited in nearby waterways and ingested by fish that were the prey of bald eagles—the national symbol since 1782. DDT interfered with the eagle’s calcium metabolism and impaired its ability to produce strong eggshells; shells were so thin they broke during incubation. The population of bald eagles, peregrine falcons, and brown pelicans fell precipitously, and these birds were classified as endangered species.
Notwithstanding a firestorm of criticism by the chemical industry, Silent Spring was critically acclaimed by both the scientific community and the public. In 1970, the Environmental Protection Agency was created, and, in 1972, the use of DDT was banned in the US and, thereafter, throughout most of the world. The bald eagle has since returned to healthy numbers. Critics of the ban continue to assert that DDT’s removal from the market is responsible for the millions of deaths caused by malaria.
SEE ALSO: Food Webs (1927), Factors Affecting Population Growth (1935), Green Revolution (1945), Biological Magnification (1979), Depletion of the Ozone Layer (1987).
It is generally accepted among scientists that DDE, a metabolic breakdown product of DDT, causes eggshell thinning in many bird species, including bald eagles, with eggshells unable to support the weight of the incubating bird.