Although social sciences are gaining increasing recognition as being integral to successful conservation, this article argues that the social science of psychology is imperative. Understanding human behavior and human relationships to nature is essential, considering that it is humans who have the greatest impact on ecological sustainability. The challenges discussed include communicating the importance of nature to human beings, diminishing the human-nature dichotomy, encouraging humans to think globally (not nationally) and for the long-term, resolving environmental conflicts, and encouraging collaboration through appreciation of different value systems. Conservation psychology can play a critical role in linking social sciences and biological sciences in a way that encourages effective conservation.