Can Digital–Green Synergy Enhance Tourism Carbon Emission Efficiency? Evidence from Chinese Coastal Cities

As the core driving force behind the new wave of technological revolution and industrial transformation, digital–green synergy (DGS) has become a crucial pathway of low-carbon development in the tourism industry. On the basis of panel data from 54 coastal cities in China from 2011 to 2023, this study employs baseline regression models, moderation effect models, threshold effect models, and spatial spillover effect models to empirically examine the impact mechanisms of DGS on tourism carbon emission efficiency (TCEE), and its spatial spillover effects. The results indicate that (1) DGS can effectively enhance TCEE. (2) Environmental regulation (ER) and tourism industry agglomeration (TIA) play positive moderating roles in the relationship between DGS and TCEE. (3) The effect of DGS on TCEE exhibits nonlinearity, with a double-threshold characteristic, which leads to leap-like changes. (4) DGS has spatial spillover effects on TCEE, facilitating coordinated emission reductions across regions. (5) The results of the heterogeneity analysis indicate that the promoting effect of DGS on TCEE is more pronounced in the southern marine economic circles and economically advanced regions. The present study offers theoretical evidence and policy insights for promoting the deep integration of digitalization and greening development and for achieving high-quality development of the tourism industry in Chinese coastal regions.