Timothy F. H. Allen is Professor of Botany at the University of Wisconsin, Madison.He is the author of A Hierarchical Concept of Ecosystems (Princeton UP, 1986), and a co-author ofEcology (Oxford UP, 1998) and our ownToward a Unified Ecology(2e 2015).Timothy F. H. Allen is a professor of botany at the University of Wisconsin, Madison. Joseph Tainter is a project leader at the Rocky Mountain Research Station in the USDA Forest Service in Albuquerque. Thomas W. Hoekstra is director of the Inventory and Monitoring Institute of the National Resources Research Center of the USDA Forest Service.