The Power of Green Carbon dioxide is produced both by fossil fuel burning and by deforestation and other land-use changes. Limiting both sources of CO ₂ is necessary if we are to curb global warming. Wise et al. (p. 1183 ) use an integrated assessment model to explore the consequences of limiting atmospheric CO ₂ concentrations at levels between 450 and 550 parts per million through a combination of fossil-fuel emissions reductions and land-use modification. Land-use modification strategies reduce the cost of limiting atmospheric CO ₂ concentrations, but can make crop prices rise and transform human diets, for example, when people consume less beef and other carbon-intensive protein sources. The rate at which crop productivity is improved has a strong influence on emissions from land-use change. Thus, the technology used for growing crops is potentially as important for limiting atmospheric CO ₂ as are approaches like CO ₂ capture and storage.