Benefits of tropical crops for food security.

West et al.’s recent paper (1) compared tradeoffs of carbon and crop production in temperate and tropical zones. We welcome the empirical evidence in support of agricultural intensification rather than extensification. We strongly caution against the implicit conclusion that food production might need to be concentrated in the temperate zone, however. First, this has implications for food security. People vulnerable to food insecurity live largely in low-income tropical countries and depend predominantly on local agriculture both for food supplies and to provide the livelihoods that underpin food security (2). Second, as the maps of West et al. (1) show, there is high variance in carbon losses and crop yields in both tropical and temperate zones, suggesting that other factors have more importance than latitude. We look forward to more detailed disaggregation through the application of the authors’ high-resolution tool to assist local land use decisions, and we stress the importance of food security in assessment of tradeoffs in agriculture and land use. Sonja J. Vermeulen and Eva K. Wollenberg CGIAR Research Program on Climate Change, Agriculture, and Food Security, University of Copenhagen, 21 Rolighedsvej, DK1958 Frederiksberg, Denmark; and University of Vermont, VT