CO2 emissions caused by changes of land use may possibly be higher than assumed so far. This is the outcome of a study made by the team of Professor Almut Arneth of the Karlsruhe Institute of Technology (KIT). The work presented in Nature Geoscience (DOI: 10.1038/NGEO2882) for the first time considers processes, such as slash-and–burn agriculture or different ways of managing forests and cropland. The results also imply that reforestation is important to increase the ecologically important CO2 uptake by land ecosystems.