Impervious Surface Expansion and Urban Carbon Emissions: Negative Spatial Spillovers in the Yangtze River Delta, China

Low-carbon sustainable development requires a better understanding of how urban land expansion reshapes carbon emission patterns within and across cities. Impervious surface expansion is a visible land use expression of urbanization and a key carrier of energy consumption, industrial activity, and ecological loss. Yet, its cross-city effects on carbon emissions remain insufficiently understood, particularly in highly integrated urban agglomerations. Using a balanced panel of 41 cities in the Yangtze River Delta (YRD), China, from 2008 to 2022, this study combines EDGAR gridded CO2 emissions, annual land cover data, global and local spatial autocorrelation analysis, and a two-way fixed-effects Spatial Durbin Model (SDM) to examine the local and spillover effects of impervious surface expansion. The results show that impervious surfaces and carbon emissions both evolved from core agglomeration toward peripheral diffusion, while carbon emissions maintained significant positive spatial autocorrelation, with Moran’s I remaining positive and significant throughout the study period. SDM estimates indicate that local impervious surface expansion significantly increases local carbon emissions, whereas the estimated indirect effect on neighboring cities is significantly negative. Effect decomposition confirms a positive direct effect and a negative indirect effect under both inverse-distance and contiguity weight matrices. A rolling-window analysis further shows that the negative spillover effect strengthened over time. These findings demonstrate that urban land hardening should be evaluated not only as a local emission driver but also as a spatially embedded process within regional carbon governance. By linking impervious surface expansion with spatial carbon emission interactions, this study contributes to sustainability research by providing empirical evidence for sustainable urban agglomeration development.