The impact of urban agglomerations on carbon emissions in China: Spatial scope and mechanism

Urban agglomerations have emerged as the dominant form of regional growth, but are also responsible for a vast majority of carbon emissions, making it a global concern. With China undergoing rapid construction of urban agglomerations, reducing carbon emissions is a significant challenge for its urbanization development. This study considers the construction of China's urban agglomerations as a regional policy and utilizes the time-varying difference-in-differences method to investigate its impact on carbon emissions, as well as the effect's spatial scope, mechanism, and heterogeneity. The findings reveal that 1) urban agglomerations can effectively reduce carbon emissions; 2) the optimal spatial scope for the reduction effect is within 50–100 km; 3) urban agglomerations can partially impact carbon emissions through the regional digital economy development level; and 4) the reduction effect varies based on the regional economic development level and green innovation capability. The study offers policy recommendations for the rational design of urban agglomerations' spatial scope and the improvement of the digital economy level to achieve carbon emission reduction.