Soil organic carbon (SOC) is vital for ecosystem and agro-ecosystem function. Any sustainable land management strategy should, therefore, include a consideration of long-term effects on SOC. In the future, we have the opportunity to adopt land management strategies that lead to greater C storage in the soil. However, to do so, we need consistent estimates of SOC stocks and changes under varying land use and climate change scenarios. A Global Environment Facility (GEF) project developed a generically applicable system (the GEFSOC Modelling System) for making such estimates. The system links two dynamic SOC models, designed for site scale applications (Century and RothC) and an empirical method, to spatial databases, giving spatially explicit results that allow geographic areas of change in SOC stocks to be identified. The system was developed using data from four contrasting eco-regions (The Brazilian Amazon, Jordan, Kenya and the Indian part of the Indo-Gangetic Plains). These areas were chosen, as they are located in regions previously underrepresented by soil C models. The system was then used to estimates SOC stocks and changes between 1990 and 2030 under likely land use change scenarios in each of the four regions. Losses in SOC of between 5 and 16 % were projected for each of the four areas over a 30-year period (2000-2030), driven by a range of factors including deforestation, overgrazing and conversion of grazing land to agriculture. Implications for sustainable land management and future land use policy are discussed for The Brazilian Amazon, Jordan, Kenya and the Indian Indo-Gangetic Plains.