Compromised sinks? Re-evaluating carbon dioxide removal potentials by closing climate impact loops

National Determined Contributions (NDCs) increasingly rely on forest-based mitigation, yet climate-driven risks such as wildfires fundamentally threaten forest carbon sink reliability while shifting CO2 concentrations could strengthen carbon uptake by boosting plant photosynthesis. Therefore, integrated assessment models (IAMs) estimates must account for these global dynamics to provide realistic mitigation potentials from forests. We present an integrated modelling approach using IAM-FIRE alongside the Global Change Analysis Model (GCAM) to evaluate these feedbacks simultaneously across various SSP-RCP scenarios using ESM-driven climate emulations. Our methodology employs a dynamic scalar-based approach to adjust default GCAM forest vegetation carbon density (VCD) based on projected fire carbon emissions and net primary productivity (NPP) from IAM-FIRE. We run 28 scenarios (4 baselines and 24 impact-enabled scenarios) and report global and regional implications. Results indicate that CO2 fertilization is the dominant global driver, with NPP scalars showing a significant upward trend which could reach a +30% growth increase by 2100 in high-forcing scenarios like SSP5-7.6. In contrast, the fire scalar impact is an order of magnitude weaker but dampens the rate of VCD growth in high-emission pathways. At the global level, the scaled scenarios have minor impacts on atmospheric CO2 concentrations, typically varying by less than 0.3% from baseline. However, divergences emerge regarding net terrestrial uptake (NTU) and regional implications. In SSP1, while NPP scalars provide an early NTU gain, forest expansion is reduced by 2100 due to weakening fertilization effect. Conversely, fire scalars cause a reduction in forest expansion in fire-prone regions like Latin America. The model responds to increased disturbance through land re-allocation, reducing the vegetation carbon stocks in some regions. These findings underscore the importance of accounting for several climate impacts and their socioeconomic implications to ensure that land-based mitigation strategies are realistic and resilient to future climatic realities.