Above: Bee with legs full of pollen on blooming Echinacea purpurea, or purple cone flower. 

Three Circles Model of Sustainability

The Three Circles Model for Sustainability is a useful way to convey and discuss the meaning of the term "sustainability".  We prepared this document in 2002 while Tania was director of the Penn State Center for Sustainability, but it continues to have use and meaning for us and others, and so we make it available to read in pdf form (click on the blue, underlined title above).

In this note we describe the model, how it should be interpreted, how it is misinterpreted, and the implications for decision-making and design.