New UMaine Study Reveals Significant Differences in Forest Carbon Models, Calls for Standardization
Premer, M., Simons-Legaard, E., Daigneault, A., Hayes, D., Solarik, K., & Weiskittel, A. Some Models are Useful… for Estimating Standing Aboveground Carbon in US Forests. J. For. (2025). https://doi.org/10.1007/s44392-025-00056-7
ORONO, Maine — As forests play an increasingly critical role in climate change mitigation strategies, a comprehensive new study from faculty affiliated with the University of Maine’s Center for Research on Sustainable Forests (CRSF) reveals that the choice of modeling approach can dramatically affect estimates of forest carbon storage—with implications for carbon markets, climate policy, and land management decisions. Published in the Journal of Forestry, the research provides the first systematic national assessment of forest carbon modeling systems in the United States, evaluating their strengths, limitations, and suitability for different applications.
“We found that commonly used modeling approaches can produce carbon estimates that differ by as much as two-fold over a 100-year projection period,” said lead author Mike Premer, Assistant Professor of Forest Management in UMaine’s School of Forest Resources. “Given the growing importance of forest carbon in voluntary and regulatory climate programs, understanding these differences is critical.”
The study authors reviewed growth and yield systems, landscape frameworks, and process-based models used across U.S. forests. Using a case study in Maine with publicly available Forest Inventory and Analysis data, the team demonstrated substantial variation in carbon projections depending on which modeling approach was employed.
Key Findings
- The USDA Forest Service’s Forest Vegetation Simulator (FVS) received the highest overall rating (0.81 out of 1.0) across six evaluation criteria: usability, complexity, analytical capability, support, validation, and transferability.
- Landscape-level models LANDIS-II and CBM-CFS3 also scored well (0.76 and 0.74 respectively) for their specific applications.
- In the Maine case study, different modeling approaches projected carbon stocks ranging from approximately 700 to over 1,300 million metric tons by 2120.
- No single model is appropriate for all scales or purposes—from individual trees to global biomes.
“These models were originally developed for different purposes—predicting timber yields, simulating disturbance patterns, or estimating global carbon fluxes,” explained co-author Aaron Weiskittel, director of the Center for Research on Sustainable Forests. “They weren’t designed with carbon accounting in mind, yet they’re now being used extensively for carbon offset projects and climate policy decisions.”
Implications for Carbon Markets and Policy
The findings have significant implications for the rapidly growing voluntary carbon offset market and regulatory compliance programs. With forests representing a major natural climate solution, accurate carbon accounting is essential for project verification, land valuation, and policy development.
“Greater investment in model development, refinement, and standardization is urgently needed,” said co-author Adam Daigneault, an assistant professor of forest policy and economics at UMaine. “As carbon markets expand and climate policies evolve, we need confidence that our estimates reflect real-world forest dynamics.”
The study recommends:
- Standardizing initialization datasets for model comparisons
- Validating model outputs with independent field data
- Quantifying uncertainties in long-term projections
- Continuing investment in model development and refinement
Establishing clear guidance on model selection for different applications The research was funded by the National Council for Air and Stream Improvement (NCASI) and the USDA National Institute of Food and Agriculture’s PERSEUS program (Promoting Economic Resilience and Sustainability of the Eastern US Forests).
About the Center for Research on Sustainable Forests
The Center for Research on Sustainable Forests at the University of Maine conducts research to improve the sustainability of forest management in the northeastern United States and beyond, focusing on forest ecology, silviculture, economics, and policy.