For more than a century, nature lovers have held fast to the belief that preserving the wild means keeping people out. Today, policies that dictate everything from the regulation of ocean fisheries to the protection of endangered species are founded on an almost religious conviction that nature is constant, eternal, self-regulating - "in balance" - save only when man intrudes. But as Stephen Budiansky dramatically illustrates, these credos of modern environmentalism are flatly contradicted by modern ecological research and have led to spectacular disasters. Because paradoxes abound in nature, many of the straightforward solutions that have been proposed to save endangered species, eliminate pests, or enlarge populations of game animals have backfired again and again. Based on a mythical view of a natural world where man never treads, such policies threaten to destroy the very things they claim to preserve - biodiversity, endangered species, unique wilderness landscapes. Now, however, modern ecological research is providing the tools for effective environment management by revealing for the first time how ecosystems really work and interact. This new science of nature management, rooted in the mathematical relationships that link the fates of all plants and animals, is being applied to actual problems, such as elk overpopulation in Yellowstone, management of game bird populations and fisheries, and ecological restoration.