Present and future water requirements for feeding humanity

Abstract

The Comprehensive Assessment of Water Man- agement in Agriculture recommended that future food production should be concentrated on existing agricultural land in order to avoid further loss of ecosystem functions from terrestrial lands. This paper is a green-blue water analysis of water constraints and opportunities for global food production on current croplands (including permanent pasture). It assesses, for the target year 2050, (1) how far improved land and water management would go towards achieving global food security, (2) the water deficits that would remain in water scarce regions aiming at food self- sufficiency, (3) how those water deficits may be met by food imports, (4) the cropland expansion required in low income countries without the needed purchasing power for such imports, and (5) the proportion of that expansion pressure which will remain unresolved due to potential lack of accessible land. The water surplus remaining on current cropland is compared with water requirements for biofuel production as a competing activity.