Global agricultural green and blue water consumption under future climate and land use changes

Abstract

Agriculture accounts for 90% of global freshwater consumption and it is expected to intensify in the future. Climate and land use changes are two major factors affecting crop green and blue water consumption, and in this study we explicitly consider the effects of both factors in a consistent modeling framework. Two important research questions are addressed: 1) How will global crop green and blue water consumption evolve over the 21st century under climate and land use changes; and 2) what are the individual and combined effects of climate and land use changes on future crop green and blue water consumption? To tackle these two questions, a crop water use module is developed based on the Global Change Assessment Model (GCAM) and its hydrology module (i.e., Xanthos). Crop specific green and blue water consumption are then calculated at global 0.5° × 0.5° grid scale. Results show that global crop green water consumption increases by 12% in 2090s when compared with that in 1971–2000, and climate change dominates over land use change in determining the trend of global crop green water consumption. However, expansion in global irrigated area dominates the changing trend of global crop blue water consumption which increases 70% by 2090s, especially in regions with significant irrigated land expansion (e.g. northern Africa, central Asia, China, Mexico, the Middle East, Russia, southern Asia, and Argentina). Furthermore, global crop blue water dependence will increase under climate and land use changes, especially in arid regions.