We propose a new domain for sociotechnical system design: creating new ecosystems for food production that are sustainable while producing high yields. Drawing on the field of agroecology, we discuss techniques for allowing a range of users to design sustainable food ecosystems that can overcome the environmental costs of industrial agriculture. Industrial agriculture, relying on declining reserves of fossil fuels and generating increasingly costly externalities, is unsustainable. Agroecology cannot scale until practitioners have access to detailed knowledge of local conditions and appropriate agricultural strategies. This paper reviews the agricultural and sustainability challenges that motivate our research. It describes design problems that must be addressed to scale agroecology. We discuss our initial work, and sketch a program of research we believe will contribute to global food security.