1 “Modeling Feedback between Economic and Biophysical Systems in Smallholder Agriculture in Kenya: The C rops, L ivestock a nd S oils in S mallholder E conomic S ystems (CLASSES) model.” Emma C. Stephens a,* , Christopher B. Barrett b , Douglas R. Brown c , Johannes Lehmann d , David Mbugua e , Solomon Ngoze f , Charles F. Nicholson g , David Parsons h , Alice N. Pell i , Susan J. Riha j a Pitzer College, 1050 N. Mills Avenue, Claremont, CA 91711, USA b Cornell University, Applied Economics and Management, 315 Warren Hall, Ithaca, NY 14853 USA c World Vision Canada, 1 World Drive, Mississauga, Ontario L5T 2Y4, Canada d Cornell University, Crop and Soil Sciences, 909 Bradfield Hall , Ithaca, NY 14853 USA e World Argoforestry Centre (ICRAF), P.O. Box 30677-00100 GPO, Nairobi, Kenya f Cornell University, Ithaca, NY 14853 USA g Cornell University, Applied Economics and Management, 315 Warren Hall, Ithaca, NY 14853 USA h University of Tasmania, Agricultural Science, Private Bag 54, Hobart, Tasmania 7001 i Cornell University, Animal Science, 149 Morrison Hall, Ithaca, NY 14853 j Cornell University, Earth and Atmospheric Science, Bradfield Hall, Ithaca, NY 14853 Draft – Not for citation March 2009 * Corresponding author: emma_stephens@pitzer.edu . This work was supported by the Coupled Natural and Human Systems Program of the Biocomplexity Initiative of the National Science Foundation, through grant BCS – 0215890, with additional support from the USAID BASIS CRSP project on Rural Markets, Natural Capital and Dynamic Poverty Traps in East Africa. The Rockefeller Foundation is providing key financial support for many of the Kenyan doctoral students involved in the project.