1. Department of Food and Resource Economics; University of Copenhagen; 25 Rolighedsvej Frederiksberg 1958 Denmark
2. School of Natural Resources and Environment; University of Michigan; 440 Church St. Ann Arbor MI 48109 USA
3. Department of Anthropology; University of Michigan; 1085 University Avenue Ann Arbor MI 48109 USA
4. Department of Afroamerican and African Studies; University of Michigan; 505 S. State St. Ann Arbor MI 48109 USA
5. Department of Geography; University of Dar es Salaam; P.O. Box 35049 Dar es Salaam Tanzania
6. Institute of Resource Assessment; University of Dar es Salaam; P.O. Box 35097 Dar es Salaam Tanzania
7. Department of Urban and Rural Development; Swedish University for Agricultural Sciences; P.O. Box 7012 Uppsala SE-750 07 Sweden