1. State Key Laboratory of Earth Surface Processes and Resource Ecology, Beijing Normal University, 19 Xinjiekouwai Street, Beijng, China 100875
2. Faculty of Environment, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L3G1, Canada
3. Centre for Studies of Technology and Sustainable Development, Faculty of Management and Governance (MB), University of Twente, PO Box 217, 7500 AE, Enschede, The Netherlands
4. Institute on the Environment, University of Minnesota, Twin Cities, 325 Learning and Environmental Sciences, 1954 Buford Avenue, St. Paul, MN 55108, USA