Exploring zonation strategy in land management of urban agglomeration

Land use/cover change (LUCC), especially of urban expansion, drives terrestrial carbon stock change in urban agglomeration. Due to the spatial heterogeneity of urban agglomeration, zonation supplies a possible way for land management in metropolises to achieve land use sustainability. In this study, we took Beijing-Tianjin-Hebei (BTH) region, known as the Capital Economic Zone, as an example and proposed a zonation strategy, as well as land management of each zone, to better adjust LUCC planning. BTH region was divided as Ecological Barrier (EB) zone, Potential Carbon Sequestration (PCS) zone and Potential Carbon Loss (PCL) zone, by evaluating topography, carbon storage and historic carbon stock change from 1990 to 2020. The EB zone was characterized as area of high carbon density, storing around 50% of carbon stock of BTH region. It experienced 52 Mt carbon stock loss from 1990 to 2020. PCL zone was characterized as area of high carbon stock loss of 122 Mt from 1990 to 2020. PCS zone was characterized as area of carbon stock increase by 7.23 MtC from 1990 to 2020. We analysed LUCC for each zone and found distinct drivers of carbon stock change. Based on zonation analysis, ecological engineering projects should continue in the PCS zone, leading to a carbon increase of 0.18 Mt C per year. Revegetation and strict ecological conservation policies were suggested to the EB zone, giving a potential of 58.9-186 Mt C carbon gain. Internal conversion between urban and rural construction land was proposed to the PCL zone, which can possibly achieve zero carbon loss of urban sprawl.