Carbon stocks in vegetation play a key role in the climate system. In a recent study, we showed the effect of land use on these carbon stocks. We found that vegetation currently stores around 450 petagrams of carbon, which is less than half of the potential vegetation that would prevail in the hypothetical absence of land use. While deforestation and other land-cover changes are responsible for a bit more than half of the difference between current and potential biomass stocks, land management effects contribute the other half. Forest management presently lowers carbon stocks by 100-150 petagrams of carbon compared potential carbon stocks in forests, which is the same effect as deforestation for cropland or 11 to 16 times the of current global annual GHG emissions. We will discuss the relevance of properly integrating these management effects into global carbon models. Overall, our results highlight trade-offs between conserving carbon stocks on managed land and raising the contribution of biomass to raw material and energy supply for the mitigation of climate change.