Relationships between the greenhouse effect and agricultural activity are usually and firstly considered in terms of the impact of climate change on agriculture. But in reverse, farmers and herders may react to a climate policy imposing a carbon price to GHG-emitting activities, and possibly contribute to the emissions mitigation as well as to carbon sequestration. The degree of efficiency of the reactions will vary across regions of the world and across activities. A methodology considering risk associated with technology changes is proposed for estimating and accounting these reactions under production and resource constraints. For a business-as-usual scenario quantified by the integrated assessment model Image, decisions concerning land-use and alternative practices are modeled. Results indicate that main agricultural activities provide little room for manoeuvre for emissions mitigation.