Climate change is expected to affect crop production worldwide, particularly in rain-fed agricultural regions. It is still unknown how irrigation water needs will change in a warmer planet and where freshwater will be locally available to expand irrigation without depleting freshwater resources. Here, we identify the rain-fed cropping systems that hold the greatest potential for investment in irrigation expansion because water will likely be available to suffice irrigation water demand. Using projections of renewable water availability and irrigation water demand under warming scenarios, we identify target regions where irrigation expansion may sustain crop production under climate change. Our results also show that global rain-fed croplands hold significant potential for sustainable irrigation expansion and that different irrigation strategies have different irrigation expansion potentials. Under a 3 °C warming, we find that a soft-path irrigation expansion with small monthly water storage and deficit irrigation has the potential to expand irrigated land by 70 million hectares and feed 300 million more people globally. We also find that a hard-path irrigation expansion with large annual water storage can sustainably expand irrigation up to 350 million hectares, while producing food for 1.4 billion more people globally. By identifying where irrigation can be expanded under a warmer climate, this work may serve as a starting point for investigating socioeconomic factors of irrigation expansion and may guide future research and resources toward those agricultural communities and water management institutions that will most need to adapt to climate change.

Meeting the increasing global demand for agricultural products without depleting the limited resources of the planet is a major challenge that humanity is facing. Most studies on global food security do not make projections past the year 2050, just as climate change and increasing demand for food are expected to intensify. Moreover, past studies do not account for the water sustainability limits of irrigation expansion to presently rainfed areas. Here we perform an integrated assessment that considers a range of factors affecting future food production and demand throughout the 21st century. We evaluate the self-sufficiency of 165 countries under sustainability, middle-of-the-road, and business-as-usual scenarios considering changes in diet, population, agricultural intensification, and climate. We find that under both the middle-of-the-road and business-as-usual trajectories global food self-sufficiency is likely to decline despite increased food production through sustainable agricultural intensification since projected food demand exceeds potential production. Contrarily, under a sustainability scenario, we estimate that there will be enough food production to feed the global population. However, most countries in Africa and the Middle East will continue to be heavily reliant on imports throughout the 21st century under all scenarios. These results highlight future hotspots of crop production deficits, reliance on food imports, and vulnerability to food supply shocks.

Although a wide body of scholarly research recognizes multiple kinds of values for water, water security assessments typically employ just some of them. In the present article, we integrate value scenarios into a planetary water security model to incorporate multiple water-related social values and illustrate trade-offs among them. Specifically, we incorporate cultural values for environmental flows needed to sustain ecosystem function (rights of waters), the water requirements of a human right to food (rights to water), and the economic value of water to commercial enterprise (commercial water rights). Pairing quantitative hydrological modeling with qualitative systems of valuing, we suggest how to depict the available water for realizing various combinations of the values underlying those rights. We account for population growth and dietary choices associated with different socioeconomic pathways. This pluralist approach incorporates multiple kinds of values into a water security framework, to better recognize and work with diversity in cultural valuation of water.

Africa is a major hotspot of food insecurity with climate change and population growth as major drivers. Irrigation expansion can sustainably increase agricultural productivity and adapt crops to climate change. We use agro‐hydrological, climate, and socio‐economic models to quantify crop production with irrigation expansion and perform food security analyses for different adaptation scenarios for African countries under baseline and 3°C warmer climate conditions. We find that under a 3°C warmer climate the total food production in Africa can only feed 1.35 billion people, when the continent's population is expected to reach 3.5 billion, leaving a food deficit equivalent to 2.15 billion people. Increasing agricultural productivity with irrigation alone will not be enough to achieve food self‐sufficiency. Therefore, future food demand will likely be met by other means such as cropland expansion or greater reliance on imports which would further expose African populations to uncertainty from the volatility in global food prices.