Carbon sink potential and planning and governance strategies of ecological space in megacities: A case study of Beijing

• Identified 3 types of potential spaces for carbon sink enhancement in Beijing. • Beijing's ecological carbon sink may rise to 10.84–11.48 million tons by 2035. • Additional afforestation offers minimal carbon sink benefits. • Sustainable forest management and restoration are key to carbon sink enhancement. • Systematic planning and governance strategies for ecological space were proposed. Beijing proposes to take the lead in achieving carbon neutrality by 2050, so the ecological carbon sink needs to be improved urgently, but there are still practical problems such as scattered layout and imperfect functions of ecological carbon sink spatial elements such as water, forest and farmland due to the lack of overall coordination. Based on establishing the relationship between the territorial ecological spaces and the ecosystem carbon pools, this paper systematically evaluated the current status of the ecological carbon sink across the entire area and all elements of the territorial space in capital Beijing, and identified potential spaces for carbon sink enhancement, including afforestation-suitable barren land and planned afforestation site, construction land retreat for ecological space recovery, and degraded forest. By combining the urban master plan and relevant departmental targets, the medium- and long- term carbon sink potential was simulated. The results showed that: (1) The current status of the ecological carbon sink in the whole territory is about 7.58 million tons, which is much smaller than the current carbon emission level, and its spatial difference gradient is obvious, but there is also a relative imbalance within the circle. (2) The reasonable range of the city's ecological carbon sink growth potential by 2035 is about 10.84–11.48 million tons, and the potential for increasing carbon sink mainly comes from sustainable forest management and the restoration of degraded forests, while the carbon sink increase from new afforestation is only <0.3 million tons. Accordingly, ecological restoration strategies for territorial space were put forward in terms of degraded forests, untreated mines, demolished illegal land use, wetlands, urban green spaces and farmlands, and the policy implications of territorial ecological space planning and governance in the capital Beijing was proposed to replace increment with spatial optimization and multi-objective coordination.