Assessment of horizontal ecological compensation in China based on ecosystem service flows

Ecological compensation has been regarded as a key mechanism for promoting the coordinated development of regional social-ecological systems and addressing environmental justice. The scientific identification of compensation priorities and amounts is recognized as fundamental for the effective implementation of horizontal compensation schemes. The spatiotemporal dynamics of supply and demand for water, grain, and carbon ecosystem service values were assessed, together with coupling coordination and supply-demand balance. A national horizontal compensation framework for China integrated flow models for individual services, network topology analysis, and compensation accounting to link providers and beneficiaries across cities and estimate reference amounts. Supply generally increased, whereas demand rose for water and carbon but remained relatively stable for grain. Across 2000, 2010, and 2020, the average proportions of cities where local supply exceeded local demand were 80%, 86%, and 22% for water yield, grain production, and carbon sequestration, respectively. Substantial variations in network structure and node characteristics were observed among the compensation networks, with the number of modeled flow paths increasing for water and decreasing for grain and carbon. The numbers of ecological-provision and ecological-beneficiary cities decreased, while their respective average modeled net ecological benefits and net compensation payments were higher in 2020 than in 2000. Meanwhile, the number of cities with unresolved service deficits and no modeled compensation inflows or outflows increased. By linking supply-demand imbalances with flows of individual services, the framework provides a quantitative basis for identifying compensation partners and negotiating differentiated payment responsibilities using estimated amounts as references. • Proposed an ecological compensation framework based on ecosystem service flows. • Nine cities showed high coordination among water, grain and carbon service. • Modeled flow paths increased for water but decreased for grain and carbon. • Provider benefits rose to 2.90 and beneficiary payments to 3.61 billion yuan per city. • Ecological compensation-required cities rose to about 2.9 times the 2000 count by 2020.