This Article is adapted from Chapter Fourteen of Rethinking Sustainability to Meet the Climate Change Challenge, edited by Jessica Owley and Keith Hirokawa and published by ELI Press. The author responds to critics of the concept of sustainability, and argues for its continued relevance by identifying a functional definition of sustainability as a framework for managing change. Contrary to the critics, sustainability programs do not rely on static conceptions of current circumstances or future conditions, but apply economic, environmental, and social considerations to a changing landscape. They utilize pragmatic, flexible ideas such as ecosystem services valuation to identify trade offs in our interactions with ecosystems. Even if adaptation is considered as a candidate governance tool for coping with unpredictable and extreme changes in the environment, it must face the same uncertainty as sustainability programs.