Spatial decoupling and structural fragility of China's grain system: Long-term evolution and pathways toward resilient reconstruction, 1990-2050

Climate-driven instability and the spatial mismatch between grain production and consumption pose growing threats to national food security. In response to this challenge, we developed a comprehensive evaluation system combining dynamic centroid analysis, optimisation model and ensemble learning to quantify the structural vulnerability and evolution path of China's grain trade network from 1990 to 2050. The results show that, first of all, from 1990 to 2023, the spatial mismatch between the center of gravity of grain production moving northward (289 km) and the center of gravity of demand moving slightly (36 km) intensified. Secondly, although the contribution rate of inter-provincial transfer of the four provinces decreased from 88.59% in 2000 to 67.52% in 2023, it still maintained an absolute dominance; finally, the network vulnerability is aggravated under multi-scenario simulation. In the extreme SSP5-8.5 scenario, the supply and demand center potential is high (in-degree 28.621%, out-degree about 14.9%), indicating a potential risk of systemic failure rather than a complete collapse of the actual grain trade system. This study aims to provide an operable multi-scenario scientific basis for optimizing the future cross-regional grain transportation layout and improving the climate resilience of the national grain system.