Withinthe Kyoto Protocol,the clean developmentmechanism (CDM) isan instrument intended toreducegreenhousegas emissions,while assisting developing countries in achieving sustainable development, with the multiplegoals of poverty reduction, environmental benefits and cost-effective emission reductions. The CDM allows for a small percentage of emission reduction credits to come from afforestation and reforestation (CDM-AR) projects. We conducted a global analysis of land suitability for CDM-AR carbon ‘sink’ projects and identified large amounts of land (749 Mha) as biophysically suitable and meeting the CDM-AR eligibility criteria. Forty-six percent of all the suitable areas globallywere foundin SouthAmerica and27% in Sub-SaharanAfrica. In Asia,despite thelargerland mass,relativelyless landwasavailable. In South America and Sub-Saharan Africa the majority of the suitable land was shrubland/grassland or savanna. In Asia the majority of the land was low-intensity agriculture. The sociologic and ecological analyses showed that large amounts of suitable land exhibited relatively low population densities. Many of the most marginal areas were eliminated due to high aridity, which resulted in a generally Gaussian distribution of land productivity classes. If the cap on CDM-AR were raised to compensate for a substantially greater offset of carbon emission through sink projects, this study suggests that it will be increasingly important to consider implications on local to regional food security and local community livelihoods. # 2008 Elsevier B.V. All rights reserved.