Digital-green integration and urban synergistic pollution and carbon reduction: Effects, mechanisms, and spatial spillovers

Unraveling the synergistic effects of the digital economy and green finance, conceptualized here as digital-green integration, is crucial for driving urban green transformation and achieving dual carbon goals. Treating the overlapping implementation of the National Big Data Comprehensive Pilot Zone and the Green Finance Reform and Innovation Pilot Zone as a quasi-natural experiment, this study utilizes panel data from 284 Chinese prefecture-level cities between 2011 and 2022. Employing Lasso-based synthetic control and regression control methods, we comprehensively investigate the dual impacts, underlying mechanisms, and spatial spillover effects of digital-green integration on urban pollution and carbon reduction. The findings reveal the following: (1) Digital-green integration has significantly facilitated urban pollution mitigation and carbon reduction. Furthermore, the synergistic effect of the dual policies outweighs the net effect of either single policy, thereby unleashing substantial superimposed policy effects. Using Guangzhou as a representative case, the synergistic shock of the digital-green policies led to an average post-policy reduction of 2.89% in carbon emission intensity and 0.2984 log points in PM2.5 concentration relative to the 2017 baseline. (2) The mechanism analysis reveals that digital-green integration facilitates urban pollution and carbon reduction primarily through four core pathways: enhancing energy utilization efficiency, accelerating technological progress, strengthening government science and technology expenditures, and optimizing digital talent. (3) Spatial effect estimates demonstrate that digital-green integration not only improves the local ecological environment but also exerts a significant positive spillover effect on neighboring cities, effectively fostering regionally coordinated pollution and emission reductions. These conclusions provide robust empirical evidence for evaluating the efficacy of macroeconomic policy combinations in environmental governance, highlighting the pivotal role of cross-sectoral policy synergy in driving urban green transformation. Future efforts should deepen the institutional synergy between digital technologies and green finance while fully accounting for differences in cities’ digital foundations, green financial resources, and policy absorption capacities, so as to prudently release the combined dividends and demonstration effects of the dual-pilot policies.