AbstractSociologist Robert Nisbet has conjectured that: “It is entirely possible that when the history of the twentieth century is finally written, the single most important social movement of the period will be judged to be environmentalism.” The unique character of the environmental movement makes this possibility plausible. Among the many social movements of this century, the reorientation of human attitudes toward the global environment represents the most far-reaching break with the past. Other social developments—such as those related to civil and political rights—had their roots in the past. The environmental movement, however, offers a new perspective on humanity's relationship to planet Earth, and increased awareness of its vulnerability has popularized the protection of the biosphere.