1. U.S. Geological Survey, Western Geographic Science Center, 345 Middlefield Road MS 531, Menlo Park, California 94025
2. Irving B. Harris Graduate School of Public Policy, University of Chicago, 1155 East 60th Street, Chicago, Illinois 60637
3. U.S. Geological Survey, Lake Michigan Ecological Research Station, 1100 North Mineral Springs Road, Porter, Indiana 46304