A study published in Nature on May 20 assessed the likelihood that U.S. forests will release stored carbon over the next century due to wildfires, drought, and insect infestations. The research concluded that current carbon-credit systems, specifically the buffer pools designed to cover such losses, are insufficient.
Key Findings on Carbon Reversal Risks
The research team used forest plot data, satellite observations, and machine learning to map risks across the continental United States. The study identified significant increases in the area of forest expected to experience a carbon reversal (loss) under climate change projections:
- Wildfire: Projected to expand from 10% to 33% of assessed area.
- Drought: Projected to expand from 19% to 21% of assessed area.
- Insects: Projected to expand from 23% to 25% of assessed area.
Regions including Idaho, Southern California, Arizona, and New Mexico were identified as having an 80% or greater chance of carbon loss due to wildfire within the next century.
Inadequacy of Carbon Credit Buffer Pools
The study examined buffer pools, which are reserves of extra carbon credits intended to compensate for losses from natural disturbances. According to the researchers, for projects within the California Air Resources Board (CARB) program, buffer pools would need to be, on average, six times larger to fully cover expected losses over a 100-year period.
The study also noted that current offset protocols often treat risks as stable over time and space, whereas actual risks vary by location and are increasing due to climate change.
Researcher Statements
Senior author William Anderegg, a biology professor at the University of Utah, stated that forests face increasing durability risks due to climate change, which have been underappreciated in carbon markets. He added that the research provides a method for using better science to guide forest project locations toward low-risk areas.
Co-author Anna Trugman of the University of California, Santa Barbara, said that while achieving net zero emissions will require a portfolio of solutions, escalating disturbances associated with climate change make it riskier to rely on forests for carbon sequestration in many regions.
Co-lead author Chao Wu of Tsinghua University stated that, compared to other natural disturbances, wildfire was found to be the largest climate-sensitive risk to durability for forest-based climate solutions.
Methodology and Implications
The study involved scientists from the University of Utah, University of California Irvine, CarbonPlan, University of California Santa Barbara, University of Leicester, The Nature Conservancy, University of Pennsylvania, Stanford University, and Clark University.
The researchers suggested that policies can be adjusted using better science to account for varying risks, potentially guiding projects to lower-risk areas.