Speculates that almost half of the world's wildlife species may become extinct in the next fifty years as a result of loss of habitat, climate change, predation by humans, and other human activities. Suggests possible strategies for averting such a catastrophe. Examines the situations of lowland gorillas in Africa and in the Bronx Zoo, grizzly bears in the Blackfoot River valley of Montana, migrating birds and wetlands habitat in the Florida everglades,...