Land Use Carbon Budget Evolution and Functional Spatial Associations: An Empirical Analysis of the Pearl River Delta Urban Agglomeration in China

Rapid urban expansion has increasingly reshaped the carbon budgets of urban agglomerations through land use change. However, the role of functional heterogeneity within construction land remains insufficiently considered when examining the spatial differentiation of construction expansion-related carbon increases. Using the Pearl River Delta Urban Agglomeration in China as the study area, this research traced the spatiotemporal changes in land use carbon budgets between 2000 and 2024, evaluated how the expansion of construction land contributed to the growth of regional carbon emissions, and further examined the spatial associations between six construction land functional categories and expansion-related carbon increases over the period of 2010–2024. The results show the following. (1) During 2000–2024, approximately 15,200 km2 of land experienced use transitions, representing 28.2% of the regional land area. These transitions generated an accumulated increase of 15.46 million t in net carbon emissions, largely driven by the conversion of cultivated land, forest land, and other non-construction land into construction land. (2) Approximately 96.2% of the carbon increase from land use transitions was attributed to the conversion of other land use types into construction land, confirming construction land expansion as the dominant pathway of regional carbon increases. (3) From 2010 to 2024, expansion-related carbon increases showed significant spatial clustering, with high-value clusters mainly concentrated in the Guangzhou–Foshan–Dongguan–Shenzhen corridor and low-value clusters in peripheral areas. (4) Functional space variables were further associated with the spatial differentiation of carbon increases. Industrial and transportation spaces showed the strongest spatial associations, and their interaction showed the strongest explanatory effect, while GWR results revealed stronger local associations in peripheral areas and weaker associations in core areas. These findings provide empirical support for carbon-focused land use governance, functional optimization of construction land, and differentiated territorial spatial regulation in rapidly urbanizing urban agglomerations.