Rising water pressure from global crop production—A 26-yr multiscale analysis

Crop production with intensive water use is burdening global water resources system. From the perspective of production, this study focuses on investigating world's water challenge from crop cultivation based on a 26-yr multi-scale analysis. Blue water footprint (BWF) dynamics covering 146 crops over 180 countries are examined during 1992–2017, applying a fast-track based BWF assessment and a modified dynamic decomposition analysis (DDA). Results show that global crop BWF has increased by 10.8% during 1992–2017 with increased growth rate after 2002, indicating rising water pressure from crop farming. About three-fifths of world's regions/nations have grown crop BWFs, especially in Southeast Asia, Oceania, and North-Central-West Africa (grown by over 30% each). Absolute changing rates of national crop BWFs trend to increase along with the decrease of population and BWF scales, with developing countries presenting large crop BWF increases, especially India, Pakistan, and Egypt (> 9 billion m3 each). The crop BWF growths come mainly from the farming of fruits, cereals, and sugar crops, with contribution proportions of 32.4%, 19.6%, and 12.8%, respectively. Decomposition results show that world's growing crop BWF is dominantly driven by population (27.5%) and yield-improving technology (24.8%) while water-saving technology (-24.8%) and proportion of rural population (-18.9%) contribute to offsetting the BWF growth. Efforts towards water sustainable cropping should be made in technological development and planting structure adjustment, especially in those countries with high or largely grown BWFs. Based on these, we expect to provide useful and informative findings for building a better water conservation system on earth.