Dietary transitions intensify the decoupling between China’s grain flows and their environmental footprints

The socioeconomic development in China has fundamentally reshaped the patterns of grain supply, demand, and interregional flows, with significant implications for both national food security and global environmental sustainability. In this study, we constructed an integrated analytical framework to comprehensively assess and forecast the spatial dynamics of grain flows and their associated environmental impacts under multiple future consumption scenarios. Our findings reveal that by 2040, domestic grain supply will continue to fall short of demand, leading to sustained increases in interprovincial flows, alongside a decelerating trend in overseas grain inflows. Crucially, the environmental footprints along the grain flows, particularly in terms of virtual water and virtual greenhouse gas emissions are increasingly decoupled from flow intensity. This decoupling effect is strongly linked to dietary shifts. The more balanced and health-oriented the diet, the stronger the decoupling effect characterized by increased interprovincial flows but reduced environmental footprints, and reduced overseas flows but increased environmental footprints. These results underscore the environmental trade-offs embedded in dietary transitions, and call for systematic integration of environmental impact assessments into food and nutrition policies. Achieving a sustainable food system requires coordinated efforts in both total quantity control and dietary structural optimization.