Abstract: Although climate change has become a significant constraint on sustainable socioeconomic development, there remains a research gap in the planning of ecological carbon sink reserve for urban agglomerations in response to climate change. We proposed an integrated framework coupling the Patch-level Land Use Simulation (PLUS) model, the Carnegie-Ames-Stanford Approach (CASA) model, and the Zonation model. Using the Beijing-Tianjin-Hebei urban agglomeration as a case study, based on three climate change scenarios-SSP126 (low-emission sustainable development pathway), SSP245 (medium-emission pathway), and SSP585 (high-emission and high-carbon development pathway)-provided by CMIP6, we applied this framework to simulate the variations of land use change and ecological carbon sink capacity at the urban agglomeration scale, and identified the spatial extent of core ecological carbon sink reserve. The results showed that: (1) By 2030, the ecologically prioritized SSP126 scenario is not the optimal path. Although the ecological space area is reduced under the highcarbon emission SSP585 scenario, the higher average carbon sink values in certain units make it a comparatively better development pathway in the near term. (2) The optimal development pathways differ between the short-term and long-term. By 2060, the optimal pathway is SSP245, while the total ecological carbon sink under SSP585 decreases to the lowest level, due to sustained high temperatures and intensified fragmentation of ecological space leading to a significant decline in vegetation productivity. (3) The core conservation areas will delineate under the SSP126, SSP245, and SSP585 scenarios cover areas of 85014, 84832, and 84834 km², respectively. The spatial heterogeneity of these conservation areas mainly stems from the interaction between climate change and human activities. For example, warming promotes vegetation growth in the northeastern Yanshan region, whereas high-intensity development leads to ecological degradation in the southern mountainous areas and the northwestern farming-pastoral ecotone. In summary, this framework provides more precise conservation zoning pathways and scientifically grounded dynamic regulatory measures for balancing ecological carbon sink reserve with socio-economic development. It offers a valuable reference for the sustainable development of the Beijing-Tianjin-Hebei region and other similar urban agglomerations in the context of climate change.

Key words: climate change, multi-scenario simulation, multi-model coupling, land use/cover change, net primary production, conservation zone