Global sustainable irrigation expansion potential under climate change

Climate change is expected to affect crop production worldwide, particularly rain-fed agricultural regions. It is still unclear to what extent the global patterns of rain-fed agriculture will be reshaped by the projected changes in precipitation and evapotranspiration and how changes in water availability will limit the ability to sustainably expand irrigation into rain-fed croplands. Here we map agricultural regions where water would be available for irrigation expansion under climate change. Using projections of sub-annual runoff and irrigation water demand under warming scenarios, we identify target regions where irrigation expansion may be used as an adaptation strategy to sustain crop production under climate change. We find that an additional 70 million hectares of rain-fed cropping systems, mostly in developing countries, will be exposed to additional green water scarcity. Our results show that there is substantial potential for adaptation of agriculture to climate change by sustainably expanding irrigation in Eastern Europe, Central Asia, sub-Saharan Africa, and Latin America. Even though large tracts of contemporary agricultural land are not suitable for irrigation in a warmer climate, in up to 35% of currently rain-fed croplands, water resources will be locally available for an expansion of irrigation without negative environmental externalities on freshwater resources. Our results also show that different irrigation strategies have different irrigation expansion potentials. Under climate change, we show that a soft-path irrigation expansion have the potential to expand irrigation over ~70 million hectares and feed ~300 million more people globally. We also find that a hard-path irrigation expansion can produce food for 1.4 billion more people globally.