In this chapter, I will explore the concept of sustainability, as viewed in the United States and around the world, and examine how we have arrived at our current thinking about conservation practices in a continually evolving, complex geopolitical sphere. I will do this to link delta restoration with the broader, global issues of providing food and clean water as described in the United Nations Millennium Development Goals (http:// www.un.org/millenniumgoals). Many people have written on global environmental sustainability, so I will only briefly summarize these views here and conclude with a brief statement about delta sustainability. During the short time that humans have been on this planet, we have altered nearly 50% of the land surface, and 50% of the wetlands in the world have been lost—a consequence of the unsustainable mindset of human civilizations. Sustainability embodies “stewardship” and “design with nature,” with well-defined goals and an agreed upon “carrying capacity,” that can be developed and modeled by scientists and planners. The most popular definition of sustainability can be traced to a 1987 United Nations conference, in which sustainable development programs were described as those that “meet present needs without compromising the ability of future generations to meet their needs.” Robert Gillman, editor of In Context magazine, extends this goal-oriented definition by stating “sustainability refers to a very old and simple concept (The Golden Rule) … do unto future generations as you would have them do unto you.” These well-established definitions set forth an ideal premise, but they do not specify the human and environmental parameters needed to model and measure sustainable development. So, here are some more specific definitions: “Sustainable means using methods, systems and materials that won’t deplete resources or harm natural cycles.” Sustainability “identifies a concept and attitude in development that looks at a site’s natural land, water, and energy resources as integral aspects of the development.”