The insurance mechanism underpinning the largest forest carbon offset program in the United States is dramatically undersized relative to the climate-driven risks facing American forests, according to a study published May 20 in renown scientific journal Nature.
The paper, titled “Forest carbon protocols underestimate climate-driven carbon loss risks,” is co-authored by researchers from the University of Utah, UC Irvine, and several other institutions.
It uses forest inventory data, satellite observations, disturbance modeling, and machine learning to map the risk of carbon reversals—situations where stored carbon is released back into the atmosphere through wildfire, drought, or insect damage—across forests in the contiguous United States.
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The findings are stark. The current buffer pool of the largest U.S. forest carbon mitigation program is likely too small by an average factor of 6.3, and could be anywhere from 2.2 to 8.0 times too small depending on assumptions about future climate scenarios, disturbance severity, and which carbon pools are included in the analysis.
Climate change is projected to increase the 100-year risk of carbon losses from natural disturbance across U.S. forests, with California and the Intermountain West facing the sharpest increases in wildfire risk.
Buffer pools function as a reserve of carbon credits set aside to compensate buyers if a forest project suffers unexpected losses, which functions essentially as an insurance policy for the permanence of forest offsets.
If the pool is too small, carbon released by wildfires or drought cannot be fully compensated, meaning credits already sold to corporate buyers may no longer represent genuine, durable climate benefits.
The study finds that climate change increases the 100-year likelihood of disturbance-driven reversals from wildfire by a factor of 3.3, with smaller but still meaningful increases from drought and insect damage.
The authors conclude that current methodologies used to size carbon offset buffer pools require fundamental revision to remain credible under future climate conditions.
These findings have direct implications for regulators, standard-setters, and the corporate buyers who rely on forest credits to meet emissions targets.
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