• We modelled rural symbiosis system and its chain drivers for China’s grain import. • Symbiosis degree had a direct effect of -0.190 and indirect of -0.013 on imports. • China’s adaptation shows significant spatial spillover effects on global grain trade. Existing research on global grain trade has largely neglected the micro-level drivers embedded in rural human-land systems. Filling this gap, this study constructs a cross-scale causal framework to trace how the symbiosis degree between rural settlements and cropland at China’s county level cascades through cropping structure adjustments and domestic supply-demand imbalances, ultimately producing spillover effects on the global grain trade network. The results indicated a significant chain mediation effect: a higher symbiosis degree between rural settlements and cropland is associated with a lower non‑grain level, which in turn increases the grain supply‑demand ratio, and ultimately reduces China’s grain imports. Specifically, the direct effect of the symbiosis degree on grain imports was -0.190 ( p < 0.05), the indirect effect was -0.013 ( p < 0.01), and the total effect was -0.203 ( p < 0.01). From 2000 to 2020, the symbiosis degree in rural China exhibited a distinct spatial differentiation pattern, characterized by higher values in the three major plains compared to other regions. This divergence has led to a grain conversion production in the three major plains, while other areas have shown a shift toward non-grain conversion production. Consequently, the respective grain supply patterns in these regions reflect situations of excess supply and insufficient supply, respectively. Under scenarios of 30 % and 50 % increase in symbiosis degree, grain imports are projected to decline by 7.99 % and 13.31 %, respectively, attributable to the enhanced optimization of human-land systems in rural China. Driven by this contraction in Chinese imports, grain exports from key partner countries (including the United States, Australia, and Canada etc.) are increasingly redirected toward East and Southeast Asia. By revealing the transnational spillover effects of rural system optimization in China on global grain trade, this study offers valuable insights for other import-dependent nations.
Zhang et al. (Wed,) studied this question.