1. Princeton University, Princeton, NJ 08544, USA.
2. Environmental Defense Fund, Boston, MA 02108, and Washington, DC 20009, USA.
3. Marine Biological Laboratory, Woods Hole, MA 02543, USA.
4. Duke University, Durham, NC 27708, USA.
5. International Institute for Applied Systems Analysis, Laxenburg 2361, Austria.
6. University of California at Berkeley, Berkeley, CA 94720, USA.
7. Cary Institute of Ecosystem Studies, Millbrook, NY 12545, USA.
8. Michigan State University, Hickory Corners, MI 49060, USA.
9. University of Minnesota, St. Paul, MN 55108, USA.