One of the environmental impacts of land-use change (LUC) is a change in the net exchange of the greenhouse gases (GHGs) carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O). Here we summarize data of changes in soil organic carbon (SOC) stocks and net soil CH 4 and N 2 O emissions associated with LUC. We combine that with estimates of biomass carbon (C) stock changes and enteric CH 4 emissions following LUC. Data were expressed in common units by converting net CH 4 and N 2 O fluxes to CO 2 equivalents (CO 2 eq) using established 100-year global warming potentials, and carbon-stock changes were converted to annual net fluxes by averaging stock changes over 100 years. Conversion from natural forest to cropland or grassland resulted in a change in net emissions of 7.3±0.6 (mean±95% confidence intervals) or 5.9±0.3tCO 2 eqha −1 y −1 , respectively, while conversion of cropland or grassland to secondary forest reduced emissions by 5.3±0.9 or 3.6±0.7tCO 2 eqha −1 y −1 , respectively. In all LUCs involving forests, changes in biomass C dominated the overall change in net GHG emissions. A retrospective analysis indicated that LUC from natural forests to agricultural lands contributed a cumulative 1569±43GtCO 2 eq between 1765 and 2005, which is equivalent to average emissions of 6.5±0.2GtCO 2 eq per year.