Re-examining carbon source-sink differentiation and carbon compensation zoning in the Beijing-Tianjin-Hebei region

Regional carbon compensation faces the challenge of being more difficult to implement "one policy for one area" at the optimal scale, and current methods for monitoring of the spatial dimension of carbon effects are often imprecise. This study seeks to systematically reveal the spatiotemporal scale-dependent characteristics of land-use carbon sources and sinks in the Beijing-Tianjin-Hebei region from 2000 to 2020, based on a multi-scale analysis framework. Furthermore, we aims to propose a spatial carbon compensation zoning scheme—designating payment, balance, and compensation zones—using a SOM-K-Means hybrid clustering model. This approach effectively enhances the robustness and geographical identification accuracy of the carbon compensation zoning results. We attempt to address these limitations by exploring new approaches based on land use data, carbon emission data and various ancillary data. Our findings reveal significant spatio-temporal heterogeneity in carbon sources and sinks during 2000–2020. Carbon sinks increased to 354.89 million tonnes, while carbon sources initially rose and then declined. Spatially, the south-central region exhibited an expanding carbon sink area, while the northern and southwestern boundaries play more of a carbon source role. The 18 × 18 km grid scale was identified as optimal for studying land use-related carbon sinks in the region. The land-use carbon compensation payment area is concentrated in the southern region, with its share decreasing over time. Conversely, the received area have expanded towards the northern mountains and other areas; while the balanced area have gradually contracted from the northwest to the south-central part of the region. These findings suggest that land use management has significant potential for optimizing carbon compensation. The proposed approach offers valuable insights for developing spatially optimized carbon compensation policies, promoting low-carbon land use, and facilitating the practical application of these policies at the regional level.