GROWING ALARM ABOUT vanishing wildlife and wilderness, and the health threats posed to humans from pollutants in the air, water, and earth, led to an overwhelming sense of environmental crisis in the 1960s and 1970s. The bald eagle was on the edge of extinction and the coastal fisheries were dying from overfishing and pollution. Even closer to home for many people was the toxic waste and sludge poisoning the Hudson River in New York and the yellow smog choking Los Angeles. Rachel Carson's 1962 book, Silent Spring, about the harmful effects of the widely used pesticide DDT, mobilized public opinion and sparked a new era of environmental activism.

The early conservationists and preservationists were concerned with protecting wildlife, natural resources, and wilderness. Now people were worried about the effects of pollution on human health. While conservationists had historically been in a...