Marine ranching policy and inclusive green growth in coastal cities: evidence from China’s national marine ranching demonstration zone program

Introduction Marine development programs often pursue resource conservation and production objectives simultaneously, yet their broader implications for sustainable coastal development remain insufficiently understood. This study examines whether China’s National Marine Ranching Demonstration Zone (NMRDZ) program improves inclusive green growth (IGG) in coastal cities. Methods IGG is measured using an entropy-weighted composite index covering economic growth, social inclusion, and environmental sustainability. Treating staggered NMRDZ designation as a quasi-natural experiment, this study applies a staggered difference-in-differences (DID) model to panel data for 37 Chinese coastal cities from 2011 to 2024. The analysis examines the program’s overall effect, transmission mechanisms, heterogeneity, and moderating conditions. Results The results show that: (1) the program increases IGG by approximately 0.174 standard deviations, and the finding remains robust; (2) it increases mariculture output per unit area, generating a positive transmission effect, but reduces marine capture production, creating an offsetting effect; (3) it significantly promotes IGG both within and outside the Northern Marine Economic Circle and across initial and subsequent designation batches, while its gains are statistically evident in larger-population cities but not in smaller-population cities; and (4) the estimated program effect is larger in cities with higher levels of green technological innovation or a more advanced industrial structure. Discussion These findings reveal a dual production dynamic in marine ranching development: higher mariculture output per unit area reinforces IGG, whereas contraction in marine capture production partially offsets the overall improvement. By evaluating marine ranching through an integrated economic, social, and environmental framework, this study moves beyond separate ecological or economic outcomes and provides evidence for refining the NMRDZ program, guiding fisheries production restructuring, and advancing inclusive and sustainable development in coastal cities.