Terrestrial bioshere is absorbing about 1/4 of the carbon dioxide emissions from human activities. So far, rainforests have been considered to be playing the absolute key role in carbon dioxide uptake. However, allover there is a yearly variation in the amount uptaken globally. Ahlström and colleagues has now shown that this variation is depending on the semi-arid ecosystems. These areas, such as savannahs and shrublands, actually stands for the major increase in uptake of carbon dioxide of terrestrial ecosystems. These findings are important in understanding the global carbon cycling, and how the ecosystems will respond the climate change in the future.