For 35 years, Art Ludwig has been working on integrated “systems of systems” for water, wastewater, energy, shelter, transportation, food production, and more. He has worked on building codes in three states and has helped craft gray-water codes in New York, Arizona, New Mexico, and Santa Barbara, Calif. Art consults regularly with health, zoning, and elected officials about sustainability policy. He is also the author of Principles of Ecological Design, Water Storage, and Create an Oasis with Greywater. His Web site is www.oasisdesign.net.