Applying a global carbon tax on fossil was shown to lead to increased bioenergy production in four out of five scenarios. Increased bioenergy production led to global cropland changes that were up to 50 % larger by 2100 compared to the reference case (without global carbon tax). For scenarios with strong cropland expansion due to high population growth coupled with low technological change or bioenergy production, the biosphere was simulated to switch from a carbon sink into a carbon source.