A Land-Sea integrated ecological compensation framework based on carbon sequestration service flows: Evidence from a Coastal City

Ecological compensation (EC) is an important policy instrument for coordinating ecological conservation and economic development and promoting carbon neutrality. However, existing EC policies in coastal regions remain largely terrestrial-oriented, making it difficult to identify cross-regional dependence on land-sea carbon sequestration services (CSs) and the corresponding compensation responsibilities. Using Qingdao, China, as a case study, this study develops a land-sea integrated EC framework that combines random forest, the IPCC inventory method, and a spatial interaction model to identify land-sea CSs supply-demand patterns and carbon sequestration service flows (CSF), and to allocate EC responsibilities accordingly. The results show that: (1) from 2004 to 2023, the imbalance between CSs supply and demand continuously intensified, with pronounced spatial mismatches; (2) CSF exhibited clear land-sea coupling, with the sea area and coastal mountainous area (Laoshan District) serving as the major CSF sources. CSF outflows from the sea area accounted for 29.02%–47.81% of the total positive regional CSF and primarily flowed to the rapidly urbanizing area of Huangdao District; and (3) actual EC payments differed markedly from ideal responsibilities across county-level administrative units, while the sea area received 78.10% of total inter-county compensation receipts. The Ecological Compensation Priority Index (ECPI) further indicated that the sea area and key terrestrial CSs supply areas should be prioritized for compensation. By integrating land-sea ecological contributions, external CSs dependence, compensation responsibilities, and implementation priorities into a unified analysis, the framework can support more equitable and efficient EC decision-making in coastal regions.