A social-ecological network approach to quantify the supply-demand-flow of grain ecosystem service

The supply-demand flow of food is crucial for accurately assessing ecosystem services and human well-being. However, quantifying the direction and intensity of dynamic ecosystem service (ES) flows is challenge. This study establishes a social-ecological network (SEN) framework to quantify the supply-demand flow of grain ES, which involves analyzing spatiotemporal patterns of supply and demand to distinguish between social and ecological aspects, identifying supply and demand nodes to define administrative boundaries, building a socialecological network between supply and demand nodes, and measuring the intensity and direction of the supplydemand flow of grain ES. Taking the Pearl River Basin of China as an example, the supply-demand flow of grain ES was analyzed across three different scales during 2000-2019. The results indicated that there are significant spatial differences and mismatches in the supply-demand-flow of grain ES. The grain supply ranges from 29.18 Mt to 32.42 Mt, while grain demand ranges from 19.51 Mt to 25.28 Mt, respectively. The evolution of grain SEN reveals that most flow exhibits local characteristics, six prefecture-level city demand nodes were expected, and five prefecture-level city supply nodes with the highest flow intensity contributed a total flow intensity of 8.06-10.10 Mt. The supply nodes increased from 74.5% to 82.5% and demand nodes decreased from 25.5% to 17.5% during 2000-2019. The SEN approach can be effectively and visually used to quantify the supply-demandflow of grain ES, support ecosystem management, and promote decision-making on food resource allocation.