1. World Wildlife Fund, 1250 24th St NW, Washington, DC 20037-1193, USA; and WWF-UK, Panda House, Weyside Park, Goldalming, Surrey GU7 1XR, England
2. Gund Institute for Ecological Economics, University of Vermont, 617 Main Street, Burlington, VT 05405, USA
3. World Wildlife Fund, 1250 24th St NW, Washington, DC 20037-1193, USA; and Center for Public Policy and Administration, University of Massachusetts Amherst, Gordon Hall 1st Floor, 418 North Pleasant Street, Amherst, MA 01002, USA
4. Department of Zoology and Biodiversity Research Centre, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia V6T 1ZT, Canada
5. World Wildlife Fund, 1250 24th St NW, Washington, DC 20037-1193, USA; and School of Natural Resources and Environment, University of Michigan, 440 Church Street, Ann Arbor, MI 48109-1041, USA
6. World Wildlife Fund, 1250 24th St NW, Washington, DC 20037-1193, USA