Implications of Limiting CO₂ Concentrations for Land Use and Energy

Carbon dioxide is produced both by fossil fuel burning and by deforestation and other land-use changes. Limiting both sources of CO₂ 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 CO₂ 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 CO₂ 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 CO₂ as are approaches like CO₂ capture and storage.

Limiting atmospheric carbon dioxide (CO₂) concentrations to low levels requires strategies to manage anthropogenic carbon emissions from terrestrial systems as well as fossil fuel and industrial sources. We explore the implications of fully integrating terrestrial systems and the energy system into a comprehensive mitigation regime that limits atmospheric CO₂ concentrations. We find that this comprehensive approach lowers the cost of meeting environmental goals but also carries with it profound implications for agriculture: Unmanaged ecosystems and forests expand, and food crop and livestock prices rise. Finally, we find that future improvement in food crop productivity directly affects land-use change emissions, making the technology for growing crops potentially important for limiting atmospheric CO₂ concentrations.