Pathways to carbon neutrality: Spatiotemporal evolution and policy-oriented zoning of carbon balance in China's urban agglomerations

In the context of escalating global climate change and China's commitment to its dual carbon goals, this study investigates the spatiotemporal dynamics of carbon balance across 296 prefecture-level and higher cities in mainland China from 2001 to 2022, using emission data from the EDGAR database. By integrating ecosystem carbon sequestration models with economic contribution coefficients (ECC), ecological support coefficients (ESC), and China's main functional zoning framework, we systematically analyze regional carbon sources and sinks and propose a spatially explicit optimization strategy. Results reveal a distinct "higher in the north than in the south, higher in the east than in the west" emission pattern, driven by economic agglomeration and energy structure, with industrial clusters such as Beijing-Tianjin-Hebei and the Yangtze River Delta acting as high-emission hotspots; notably, the Chengdu-Chongqing region exhibited a sharp emissions surge in 2022 due to accelerated industrialization. In contrast, carbon sequestration capacity forms a "northeast-southwest high axis," enhanced by ecological restoration in regions like the Yellow River Basin but diminished along the eastern coast due to urban expansion, thereby exacerbating regional carbon imbalance. Based on ECC and ESC, we classify areas into four dynamically adjusted carbon balance zones: (1) low-carbon maintenance zones (e.g., Beijing-Tianjin-Hebei, Chengdu-Chongqing), characterized by strong economic output and carbon sink potential; (2) economic development zones (e.g., Central Plains, Shandong Peninsula), reliant on high-carbon industries yet underpinned by relatively sound ecological foundations; (3) carbon sink development zones (middle reaches of the Yangtze River), combining significant economic contributions with fragile ecosystems; and (4) comprehensive optimization zones (e.g., Hohhot-Baotou-Ordos-Yulin, Hexi Corridor), facing dual economic and ecological pressures. These are further refined into 16 sub-zones aligned with national functional zoning to enable targeted policy implementation. We recommend zone-specific strategies: consolidating low-carbon technologies and ecological advantages in maintenance zones; accelerating industrial decarbonization and energy efficiency in development zones; strengthening ecological restoration and green industry cultivation in sink zones; and fostering coordinated socio-ecological development in optimization zones through policy incentives, interregional collaboration, and market mechanisms. Ultimately, achieving nationwide carbon balance hinges on two core pathways: optimized land-use planning and the implementation of differentiated, spatially tailored policies that account for local socioeconomic and ecological contexts.