1. Centre for Biodiversity Dynamics; Norwegian University of Science and Technology; Trondheim NO-7491 Norway
2. Department of Environmental Science, Policy and Management; University of California; Berkeley California 94720-3114 USA
3. Arctic Ecology Department; Norwegian Institute for Nature Research, Fram Centre; Tromsø NO-9296 Norway
4. The James Hutton Institute; Craigiebuckler Aberdeen AB15 8QH UK
5. Ecology and Natural Resource Management; Norwegian University of Life Sciences; Ås NO-1432 Norway