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Ecosystem service (ES) flow can address mismatches between the supply and demand of ESs. Nevertheless, how to improve ES flow considering spatial flow information and interactions among different flow systems is a research gap. Taking the Beijing-Tianjin-Hebei (BTH) urban agglomeration region of China as an example, this study combined both system and network perspectives to analyze the ES flow of grain provision before and after optimization. Metacoupling system analysis was adopted to assess intra-regional and extra-regional flow. Linear programming was used to calculate the optimal distance cost flow solution with constraints. A network model was finally applied to build and analyze flow and transmission networks. In 2020, BTH participated in nearly 10% of the national flow, among which 57% was extra-regional flow. After optimization, the proportion of extra-regional flow decreased to 36%, all of which was inflow from the nearest provinces, while intra-regional flow increased by 35%. The optimized flow reduced distance costs by 143% and decreased network complexity. Core transmission nodes with both high degree and betweenness centrality played prominent connection roles in the process of flow. Strengthening regional connections and simultaneously effectively managing core transmission nodes are of great significance for improving flow efficiency and ensuring food provision.
Fang et al. (Thu,) studied this question.