Virtual water and land dynamics: Decoding their asymmetric effects on food security across China

The flow of virtual water and land impacts the spatial imbalance of food production and consumption through inter-regional transfer of water and land resources. Studying food security from the perspective of virtual water and land is of great significance for further optimizing resource allocation and achieving sustainable development. China has a large population and significant regional differences in water and land resources. Therefore, this study takes China as a case study, analyzing the spatial and temporal processes and patterns of both inter-provincial virtual water and land net transfer volume and food security index, based on the calculation of their values using spatiotemporal trend methods. A fixed-effects regression model combined with an improved four-quadrant diagram is used to analyze the nonlinear relationship, characteristic types, and causes of the flow of virtual water and land and food security. The study found that: (1) From 2012–2019, the trend of virtual water and land flow in China gradually strengthened from north to south, and the overall change in the food security index showed a "lower values lower, higher values higher, and stable intermediate values" pattern, with the centroid of both continuously moving northward. (2) Food security showed an "inverted U-shaped" fluctuation trend with the expansion of the net transfer volume of virtual water and land. (3) Based on the improved four-quadrant diagram, the zones can be divided into: Self-sufficient Food Security Improvement Zone, Dependency-based Food Security Decline Zone, Water-scarce and Land-rich Stable Food Security Zone, and Water-rich and Land-scarce Stable Food Security Zone. Among them, the Dependency-based Food Security Decline Zone occupies the largest proportion, which continues to increase. The distribution of provinces in each quadrant tends to be clustered, with each quadrant exhibiting distinct characteristics, causes of formation, and development trends. Based on this, the paper further elaborates on the impact mechanism of virtual water and land flow on food security, proposes targeted development strategies for each region, and provides new perspectives for localized virtual water and land trade strategies and enhancing food security's resilience to risks.