This paper argues that successful adaptation of agriculture to ongoing climate changes would help to maintain productivity growth and reduce pressure to bring new lands into agriculture. It explores the potential co-benefits of adaptation in terms of the avoided emissions from land use change. A model of global agricultural trade and land use, SIMPLE, is utilised to link adaptation investments, yield growth rates, land conversion rates and land use emissions. The study finds that although investing in the least developed areas may be a desirable objective for adaptation, it has little net effect on mitigation because production gains are offset by greater rates of land clearing in the benefited regions, which are relatively low yielding and land abundant. Overall, broad-based efforts to adapt agriculture to climate change have mitigation co-benefits that, even when forced to shoulder the entire expense of adaptation, are relatively inexpensive compared to many mitigation activities.