Climate change and large-scale land acquisitions in Africa: Quantifying the future impact on acquired water resources

Pressure on agricultural land has markedly increased since the start of the century, driven by demographic growth, changes in diet, increasing biofuel demand, and globalization. To better ensure access to adequate land and water resources, many investors and countries began leasing large areas of agricultural land in the global South, a phenomenon often termed "large-scale land acquisition" (LSLA). To date, this global land rush has resulted in the appropriation of 41million hectares and about 490km3 of freshwater resources, affecting rural livelihoods and local environments. It remains unclear to what extent land and water acquisitions contribute to the emergence of water-stress conditions in acquired areas, and how these demands for water may be impacted by climate change. Here we analyze 18 African countries - 20Mha (or 80%) of LSLA for the continent - and estimate that under present climate 210km3year-1of water would be appropriated if all acquired areas were actively under production. We also find that consumptive use of irrigation water is disproportionately contributed by water-intensive biofuel crops. Using the IPCCA1B scenario, we find only small changes in green (-1.6%) and blue (+2.0%) water demand in targeted areas. With a 3°C temperature increase, crop yields are expected to decrease up to 20% with a consequent increase in the water footprint. When the effect of increasing atmospheric CO2concentrations is accounted for, crop yields increase by as much as 40% with a decrease in water footprint up to 29%. The relative importance of CO2 fertilization and warming will therefore determine water appropriations and changes in water footprint under climate change scenarios