Terrestrial Carbon Dynamics through 2100: Projections with OSCAR Highlighting Climate and Land Management Impacts

Terrestrial ecosystem carbon dynamics play a critical role in regulating the Earth system's carbon cycle, strongly influenced by atmospheric processes and land management policies. Climate change is transforming carbon cycling within ecosystems and their exchange with the atmosphere, while forest management policies are increasingly recognized as essential nature-based climate solutions. However, the long-term impacts of climate processes and forest management on carbon cycling—spanning historical, present, and future periods—remain poorly understood due to limitations in current modeling frameworks. This uncertainty hinders efforts to optimize forest management strategies and implement effective climate change mitigation measures.

To address these challenges, we employ the state-of-the-art compact Earth system model OSCAR to integrate carbon dynamics predictions from Dynamic Global Vegetation Models (DGVMs) and bookkeeping models. Using the GCB2023 dataset as a historical baseline, we drive the OSCAR model under a range of climate scenarios (i.e., SSP126 and SSP370) and land-use and land-cover change (LULCC) trajectories. Our analysis provides multi-scenario projections of terrestrial carbon fluxes, including regional and biome-specific annual carbon flux estimates through 2100. Additionally, we quantify the inertia of LULCC impacts and evaluate emissions from land-use changes under diverse socio-economic and forest policy pathways, and disentangle the relative contributions of environmental conditions and land-use policies to future carbon dynamics.

Our projections indicate that CO₂ concentrations drive long-term carbon sink trends, while climate variability predominately influences interannual fluctuations. In mid- to high-latitude regions, LULCC carbon balance exhibits minimal sensitivity to forest policies, acting as a modest carbon source or sink. Conversely, in low-latitude regions, robust forest policies are crucial to reversing the carbon source status associated with LULCC. Cumulative emissions from land use can be offset by carbon sinks arising from ecosystem restoration. These findings offer critical insights into the future trajectories of terrestrial carbon cycles and provide a foundation for developing targeted climate change mitigation strategies. Our dataset, which will be updated annually with the latest GCB assessments, serves as a valuable resource for global monitoring, policy evaluation, and strategy optimization.