According to this article, in the past, deforestation, mainly driven by the conversion of natural forests to agricultural land, contributed up to one fifth of global human-induced carbon dioxide (CO2) emissions. Substitution of bioenergy for fossil energy is an intensely discussed option for mitigating CO2 emissions. This article, by applying a global land use model and a global energy-economy-climate model, explores how demand for cellulosic bioenergy crops will add an additional pressure on the land system in the future. In accordance with other studies, this article finds that CO2 emissions from land use change caused by energy crop production will be an important factor in the greenhouse gas balance of bioenergy if natural forests will not be protected. But, restricting land availability for biomass plantations by conserving natural forests requires additional efforts in the agricultural sector. First, the simulation results indicate that significant additional crop yield increases will be needed because of the combination of forest conservation and the cultivation of dedicated bioenergy crops. Second, the simulation results show that forest conservation in combination with increasing demand for dedicated bioenergy crops will lead to higher agricultural production costs of approximately 20%.