COS 188-3 - Uncertainty in US forest carbon storage potential due to climate risks

Abstract: Forests have considerable potential to mitigate anthropogenic climate change and provide society with substantial co-benefits. However, climate change risks may fundamentally compromise long-term forest carbon storage and the future forest carbon storage potential remains elusive. Several major approaches are available to project this potential, but these methods have not been systematically compared. Here, we conduct a rigorous, multi-method synthesis of contiguous US (CONUS) forest aboveground carbon storage potential, at both regional and species levels, through a fusion of climate data, extensive forest inventory plots observations, machine learning/niche models, and Earth system model ensembles. We find diverging signs and magnitudes of projected future forest aboveground carbon storage potential across contrasting approaches, ranging from an average total gain of 6.7 Pg C to a loss of 0.9 Pg C, in a moderate emissions scenario. Notably, The Great Lakes region and the northeastern US showed consistent signs of carbon gains across approaches and future scenarios. Substantial risks of carbon losses were found in regions where forest carbon offset projects are currently located. This multi-method assessment highlights the current striking uncertainty in US forest carbon storage potential estimates and provides a critical foundation to guide forest conservation, restoration, and nature-based climate solutions.