Spatial Evolution and Policy Mechanisms of Green Belts in Metropolis

Green belts in metropolis face an inherent conflict between ecological protection and urban expansion, which requires effective planning and management strategies. This study develops a systematic framework for multidimensional quantitative analysis. By applying methods such as average nearest neighbor analysis, landscape ecological in-dex analysis, land use transfer matrices, kernel density estimation, and spatial auto-correlation models, the paper examines the spatial evolution of Shijiazhuang’s green belt from 2015 to 2024. The results show that rapid urbanization has accelerated the expansion of fragmented industrial land, intensified ecological space fragmentation, promoted the encroachment of agricultural land, driven spatially uneven growth of the service sector, and fueled the sprawling expansion of both rural and urban resi-dential areas. These dynamics have generated ecological risks, widened urban–rural disparities, and delayed infrastructure development. To address these challenges, the study proposes a spatial policy of “adjusting the primary industry, restricting the sec-ondary industry, and promoting the tertiary indust” to restructure land-use dynamics. Specifically, it suggests enhancing the value of agricultural space, encouraging the ag-glomeration of industrial land, guiding balanced growth of the service sector, and simultaneously strengthening the integration of ecological spaces and the intensifica-tion of residential land use. This approach aims to reconcile the tension between eco-logical protection and economic development, promote the long-term and orderly evolution of green belts in metropolis, and provide a reference for sustainable urban development in rapidly urbanizing cities of developing countries.