Charles Hall is a Systems Ecologist who received his PhD under Howard T. Odum at the University of North Carolina at Chapel Hill. Dr. Hall is Professor Emeritus at the College of Environmental Science and Forestry at the State University of New York, and the author or editor of twelve books and nearly 300 scholarly articles. He has worked or taught in some 30 different countries. He is best known for development of the concept of EROI, or energy return on investment, which is an examination of how organisms, including humans, invest energy into obtaining additional energy to improve biotic or social fitness. He has applied these approaches to fish migrations, carbon balance, tropical land use change, the extraction of petroleum and other fuels, and how EROI influences the ability of society to achieve different levels of economic and social development. Presently he is developing a new field, BioPhysical Economics, as a supplement or alternative to conventional neoclassical economics,while applying systems and EROI thinking to a broad series of resource and economic issues.