Influence of land use intensity on urban carbon efficiency under a carbon neutrality target: Evidence from the Yangtze River Delta urban agglomeration, China

Urban carbon efficiency (UCE) is a critical measure for guiding cities in reducing carbon emissions while sustaining economic growth. Enhancing UCEs through efficient urban land use is considered a key strategy. However, while previous research has explored the impact of urban land use on carbon efficiency, the influence under the constraints of carbon neutrality targets remains underexamined. To fill this gap, we apply a super-efficiency slack-based measure (SBM) model combined with a seemingly unrelated regression (SUR) model to assess the heterogeneous effects of land use intensity on UCEs within the carbon neutrality framework. Additionally, we use a causal mediation effect model to identify the mediating factors. Using data from 2000 to 2019 for 41 prefecture-level cities in China's Yangtze River Delta urban agglomeration, we find the following: (1) A 1% decrease in land use intensity (urban land use per unit of GDP) leads to a 0.745% increase in UCE and a 0.227% increase in carbon neutrality potential (CNP) when carbon sequestration is included in the UCE calculation, both at a significance level of 1%. (2) The negative effects of land use intensity show significant heterogeneity across different city types. Specifically, it significantly impacts both UCE and CNP in cities with high economic levels and low ecological levels but significantly affects only UCE in other cities. (3) The urban population and built-up area amplify the influence of land use intensity on UCEs through mediating effects, whereas factors such as industrial structure, energy intensity, and foreign direct investment mitigate this influence. These findings underscore the importance of incorporating carbon sequestration in UCE assessments under carbon neutrality constraints. They also suggest that policy-makers should adopt differentiated urban land management strategies tailored to the socioeconomic and ecological conditions of different cities to enhance UCEs within urban agglomerations. • Urban land intensity contributes to both carbon efficiency and carbon neutrality. • High urban land use intensity considerably reduces urban carbon efficiency. • Improving urban carbon efficiency with carbon sequestration promotes carbon neutrality. • Scale, structure and technology effects are significant as the mediating effects. • Heterogeneous impacts exist among cities with different economic and ecological levels.