Credit: Dawn Rain, Kings Canyon National Park, California, United States via photopin (license)

Forest carbon credits may prove to be a useful tool to reduce net carbon emissions from land use and supplement overall emissions reductions. To be effective, however, carbon credits must represent real carbon storage that can be measured and attributed to the crediting system.

One of the hallmarks of a high-integrity carbon credit program is that they ensure “additionality,” meaning that the credited carbon storage or emissions reductions would not have occurred without the sale of carbon credits. Put another way, we need to ensure that landowners aren’t getting credit for conducting business as usual, and instead, all carbon credits represent net emissions reductions that can be attributed to the crediting program. It’s a scenario we’re watching play out in California’s carbon market.

The California carbon market: Opportunities for improvement

Much of the credit additionality critique has focused on forest carbon credited under the California carbon market. Forests can be credited under an “improved forest management” protocol in which forest carbon density is compared to a baseline forest carbon density, which is informed by an average of the carbon densities of the same general forest type in a particular region.

However, recent research has suggested that these general forest types and regions are so broad that improved forest management projects can be compared to forests that are much less carbon-dense for reasons of geography and ecology rather than improved management in the project area. These projects can be credited for carbon that would have existed under a business-as-usual scenario, leading to over-crediting and a lack of additionality.

New research from EDF corroborates these concerns and refines previous research by accounting for more variability in ecological factors that affect carbon sequestration. Our paper published in the journal Ecological Applications integrates tree species composition data to account for variability in forest carbon density that results from environmental factors in one particularly ecologically diverse region. Using this new method to constrain baseline carbon density, we found several credited projects in this region that did not contain significantly more carbon than expected under typical private management when controlling for these environmental factors. The good news: this new method could be used to more accurately calculate additionality to refine California’s carbon market protocol and ensure the integrity of the improved forest management carbon credits in this market.

The broader landscape of credit integrity

This work on additionality is part of a broader portfolio of research EDF is conducting on other aspects of the integrity of carbon credits from natural climate solutions. A March 2022 policy paper by researchers at EDF and Woodwell Climate Research Center published in the journal Science discussed how to ensure that credits issued for agricultural soil carbon represent real, long-lasting, additional carbon stocks and do not simply shift carbon losses from one area to another, as well as the importance of consistency between crediting protocols on these issues. Ongoing work includes a review of monitoring, reporting, and verification of various natural climate solutions across an array of protocols.