Closing the yield gap while ensuring water sustainability

Water is a major factor limiting crop production in many regions around the world. Irrigation can greatly enhance crop yields, but the local availability and timing of freshwater resources constrains the ability of humanity to increase food production. Innovations in irrigation infrastructure have allowed humanity to utilize previously inaccessible water resources, enhancing water withdrawals for agriculture while increasing pressure on environmental flows and other human uses. While substantial additional water will be required to support future food production, it is not clear whether and where freshwater availability is sufficient to sustainably close the yield gap in cultivated lands. The extent to which irrigation can be expanded within presently rainfed cropland without depleting environmental flows remains poorly understood. Here we perform a spatially explicit biophysical assessment of global consumptive water use for crop production under current and maximum attainable yield scenarios assuming current cropping practices. We then compare these present and anticipated water consumptions to local water availability to examine potential changes in water scarcity. We find that global water consumption for irrigation could sustainably increase by 48% (408 km 3 H 2 O yr -1 ) - expanding irrigation to 26% of currently rainfed cultivated lands (2.67 × 10 6 km 2 ) and producing 37% (3.38 × 10 15 kcal yr -1 ) more calories, enough to feed an additional 2.8 billion people. If current unsustainable blue water consumption (336 km 3 yr -1 ) and production (1.19 × 10 15 kcal yr -1 ) practices were eliminated, a sustainable irrigation expansion and intensification would still enable a 24% increase in calorie (2.19 × 10 15 kcal yr -1 ) production. Collectively, these results show that the sustainable expansion and intensification of irrigation in selected croplands could contribute substantially to achieving food security and environmental goals in tandem in the coming decades.