An assessment of major global agricultural breadbaskets reveals significant exposure to future climatic crop yield failures within water scarce regions

As the greatest water user in the world, the agricultural sector is vulnerable to changes in climate and water resource availability. Understanding these potentially limiting factors of agricultural yield is critical in order to achieve and maintain global food security. Here we analyze an ensemble of nitrogen-limited Agricultural Model Intercomparison and Improvement Project (AgMIP) models to project the probability of rice, soy, maize, and wheat yield failures throughout the 21st century. In the top five producing regions of each crop, otherwise known as breadbaskets, we define a yield failure as a 10% decrease from historical yield. We further analyze the effect of CO₂ fertilization. The probability of yield failure varies greatly across breadbaskets and when applying CO₂ fertilization within the models. A general trend indicates breadbasket failures will become more likely by the end of the century. The probability of breadbasket failures is higher when CO₂ fertilization is not applied. While CO₂ fertilization may decrease the magnitude of failure probability, it may also decrease the nutritional value of crop yields. To quantify water scarcity within the breadbaskets, we further develop the open-source Aqueduct Water Risk Atlas to create a water scarcity index using historical and future water risk. The index is a relative global percentile ranking system where each location (10 km²) is scored relative to all other locations. Cross-referencing the spatial extent of agricultural breadbaskets with this index, we identify major crop-producing regions that will face challenges in both crop yield and water scarcity with emphasis on the soybean and maize breadbaskets in China as well as soybean and wheat breadbaskets in India. Our analysis highlights agricultural regions that have historically provided the global food system with large quantities of one or more major grains, but will face challenges in continuing to do so due to changes in climate and/or water resource availability.