Accelerator or Not? The Impact of Port Integration Reform on Carbon Emissions with Evidence from Chinese Ports

Port integration reforms constitute an important institutional arrangement for promoting green development in the shipping sector and achieving China’s carbon peaking and carbon neutrality goals. Assessing their carbon-mitigation effect is crucial for improving the governance framework of port integration and promoting high-quality port development. Using panel data for 55 Chinese port cities from 2011 to 2022, this study exploits the staggered implementation of port integration strategies as a quasi-natural experiment and applies a multi-period Difference-in-Differences (DID) approach to estimate their effects on port carbon emissions. The results indicate that port integration reforms significantly reduce carbon emissions, implying that integration acts as a substantive driver for low-carbon transformation. Heterogeneity analysis shows that the emission-abatement effect is stronger for ports outside the Yangtze River Economic Belt, coastal and southern ports, large-scale and small-scale ports, regions with weaker environmental regulation, cities with more advanced industrial structures, and major national hub ports. In contrast, the policy effect is relatively muted for medium-sized ports, highly regulated regions, cities with less advanced industrial structures, and non-core hub ports, where port integration delivers merely weak marginal emission reduction effects. Further mechanism tests reveal that green technological innovation plays a certain mediating role. This study contributes to the literature by providing dynamic causal evidence on how port governance reforms shape green development outcomes. It also offers policy implications for designing differentiated port integration strategies that align with regional development conditions and national low-carbon transition objectives.