Multidimensional mechanisms through which urban sprawl aggravates co‑emissions of carbon dioxide and air pollutants: empirical evidence from the Yangtze River Delta urban agglomeration in China

Amid the dual pressures of global climate change and China’s ‘dual carbon’ goals, achieving synergistic reductions in pollution and carbon has become a strategic priority. As a prevalent spatial pattern, urban sprawl significantly influences this synergy. Using long‑term night-time light and LandScan population data, this study quantifies urban sprawl levels across 41 cities in China’s Yangtze River Delta from 2005 to 2023. Panel data analysis, threshold regression, and spatial Durbin models are employed to systematically examine the impact of urban sprawl on the intensity of co-emissions of carbon dioxide and air pollutants (ICE). The results indicate that urban sprawl substantially increases ICE, primarily through industrial structure and electricity consumption. Moreover, this effect is nonlinear with respect to the jobs–housing ratio (JHR), and is significantly positive only within a moderately balanced range. Urban sprawl also generates significant spatial spillover effects, increasing ICE in neighbouring cities. These findings suggest that differentiated spatial planning should be adopted to curb disorderly expansion, promote compact urban forms, and strengthen regional coordination, thereby advancing high-quality urban development and synergistic reductions in carbon and air pollutant emissions.