Intensification and Low-Carbon Performance: A Two-Stage Framework for Evaluating Urban Construction Land Use Efficiency Across 268 Chinese Cities

Evaluating urban construction land use efficiency (UCLUE) from the dual perspectives of intensification and low-carbon performance is critical for sustainable urban development. Previous studies often assess this efficiency from a single perspective, failing to capture potential conflicts and synergies between economic density and emission reduction goals. This study adopts a two-stage super-SBM approach to evaluate UCLUE of 268 Chinese cities from 2001 to 2021, systematically examining both intensification and low-carbon dimensions. Results show that (1) the average efficiency from an intensification perspective remains relatively low and exhibits a fluctuating pattern of initial increase, subsequent decline, and final rebound, with the eastern region ranking highest, followed by the western and central regions. (2) The low-carbon efficiency follows a U-shaped trajectory over the study period, with the eastern region again performing best, followed by the western and central regions. (3) Many cities exhibit relatively low efficiency in both dimensions, with 146 of the 268 cities (54.48%) falling into the Low–Low development mode and only 53 cities (19.78%) achieving the High–High development mode. Furthermore, cities with larger population sizes demonstrate stronger sustainable performance. These findings provide empirical evidence for identifying spatial heterogeneities and formulating differentiated, context-specific land use policies to coordinate urban expansion and carbon reduction.