Assessment of water-carbon effects on the evolution of spatial patterns of grain production in China

With the growth of global population and sustained socio-economic development, the demand for food continues to rise. However, increasing water scarcity poses significant challenges to agricultural production, coupled with environmental issues such as greenhouse gas (GHG) emissions. As the world's most populous country, China faces even more severe water and environmental challenges in food production. Changes in the spatial patterns of food cultivation have implications for regional water consumption and GHG emissions. This study, based on the virtual water theory, explored the water-carbon effects resulting from the evolving spatial patterns of grain production and assessed their impact on sustainability goals in China. The findings reveal that the spatial pattern of grain production is influenced not only by regional meteorological conditions and arable land resources but also by shifts in industrial structure. Due to changes in industrial patterns and population movement, the center of grain production moved opposite to that of the economy and population, gradually shifting northward. While inter-regional grain transportation yields water-saving benefits, it simultaneously increases water resource pressure in the northern output areas by over 20%, creating a conflict between global water conservation and regional water use escalation. Changes in the spatial pattern of grain cultivation also affect the regional water environment and GHG emissions. The gray water footprint of the grain export region is higher, doubling with the increase in the scale of grain exports. The larger the scale of grain cultivation and transportation, the higher the GHG emissions of the region. Notably, the increase in GHG emissions for the grain export region surpasses that of the import region. In terms of sustainability goals, the current evolution of the spatial pattern of grain cultivation contributes to eradicating hunger, ensuring water resource security, promoting economic development, and enhancing infrastructure, but with obvious spatial heterogeneity. Considering national development planning, regional industrial structure, and population flow trends, the long-term operation of the "north-south water transfer" project – a virtual water trade pattern – poses a crucial challenge. Balancing overall development with local sustainability is paramount. In addition to adopting water-saving and emission-reduction measures in the production chain, optimizing the virtual water trade pattern, constructing a water-saving dietary structure, and optimizing the planting structure through demand-side guidance and macro policies are essential. This holistic approach will yield a counter effect on the production side, ultimately achieving water-saving and emission-reduction goals in both production and consumption.