Examining spatio-temporal variations in carbon budget and carbon compensation zoning in Beijing-Tianjin-Hebei urban agglomeration based on major functional zones

Research on the carbon budget and zoning for carbon compensation in major functional zones (MFZs) is important for formulating strategies for low-carbon development for each functional zone, promoting the collaborative governance of the regional ecological environment, and achieving high-quality development. Such work can also contribute to achieving peak emissions and carbon neutrality. This paper constructs a theoretical framework for the carbon budget and carbon compensation from the perspective of the MFZ, uses 157 county-level units of the Beijing-Tianjin-Hebei urban agglomeration (BTHUA) as the study area, and introduces the concentration index, normalized revealed comparative advantage index, and Self Organizing Mapping-K-means (SOM-K-means) model to examine spatio-temporal variations in the carbon budget and carbon compensation zoning for the BTHUA from the perspective of MFZs. The authors propose a scheme for the spatial minimization of carbon emissions as oriented by low-carbon development. The results show that: (1) From 2000 to 2017, the carbon budget exhibited an upward trend of volatility, its centralization index was higher than the "warning line" of 0.4, and large regional differences in it were noted on the whole. (2) There were significant regional differences in the carbon budget, and carbon emissions exhibited a core-periphery spatial pattern, with a high-value center at Beijing-Tianjin-Tangshan that gradually decreased as it moved outward. However, the spatial pattern of carbon absorption tended to be stable, showing an inverted "U-shaped" pattern. It was high in the east, north, and west, and was low in the middle and the south. (3) The carbon budget was consistent with the strategic positioning of the MFZ, and the optimized development zone and key development zone were the main pressure-bearing areas for carbon emissions, while the key ecological functional zone was the dominant zone of carbon absorption. The difference in the centralization index of carbon absorption among the functional zones was smaller than that in the centralization index of carbon emissions. (4) There were 53 payment areas, 64 balanced areas, and 40 obtaining areas in the study area. Nine types of carbon compensation zones were finally formed in light of the strategic objectives of the MFZ, and directions and strategies for low-carbon development are proposed for each type. (5) It is important to strengthen research on the carbon balance and horizontal carbon compensation at a microscopic scale, enrich the theoretical framework of regional carbon compensation, integrate it into the carbon trading market, and explore diversified paths for achieving peak emissions and carbon neutrality.