William Rees is a Professor Emeritus and former Director of the University of British Columbia's School of Community and Regional Planning. H. Sapiens is capable of exponential population growth and tends to use up accessible resources. These tendencies are held in check by 'negative feedback' - disease, food shortages, conflict. However, modern technology has freed humans from negative feedback and humanity's natural expansionism is being reinforced by growth-oriented economics. As a result the human enterprise is in 'overshoot'.