First-of-its-Kind Study Casts More Shade on Forest Carbon Offsets

Yet another report has cast doubt on the accuracy and reliability of the carbon credits companies and individuals purchase to offset their climate-polluting emissions. 

The first-of-its-kind peer-reviewed study, published in Frontiers in Forests and Global Change Tuesday, looked at almost 300 projects that made up 11 percent of the carbon credits on offer to date. It found that methods for calculating the carbon credits were often in conflict with scientific best-practices, which increased the risk of “significant over-estimation” of the amount of carbon a project might keep from the atmosphere. The report comes around two months after a major investigation found that 94 percent of the forest offset credits verified by top carbon credit certifier Verra did not truly offset any emissions. 

“Offsetting is a misnomer — you can’t ‘offset’ your emissions,” research leader Barbara Haya from the University of Berkeley’s Goldman School of Public Policy told Bloomberg. “We need alternative ways of supporting climate mitigation because the current offset market is deeply not working.”

The new paper looked specifically at credits offered for Improved Forest Management. These are forestry practices that could potentially boost a managed woodland’s ability to store carbon, such as waiting to fell trees until they are older or avoiding the use of high-impact infrastructure like roads. Strategies like these do have the potential to increase carbon storage by carbon stocks by 0.2 to 2.1 gigatonnes of carbon-dioxide equivalent each year worldwide, the study authors noted. However, for this to happen, a funded project must actually remove more carbon from the atmosphere than would have been removed if the project had not been funded, something the researchers found was not always the case. 

That’s because of problems with calculating the baseline against which emissions offsets are calculated, i.e. what would have happened if the project had not taken place. There are many ways of fudging the baseline to exaggerate a project’s carbon storage. For example, most projects will involve stands of trees that store more carbon than the regional average. However, since the regional average is often used as a baseline, projects will pick plots of forest that already deviated from it. According to one study cited in the report, nearly 30 percent of the projects it reviewed that were used by the California Air Resources Board (CARB) for the state’s emissions scheme overestimated their carbon storage for this reason. Another baseline error is for projects to compare their practices to aggressive clear-cutting when this was never likely to occur. 

“The most important area for reducing over-crediting is changing the way baselines are determined,” the study authors wrote. 

The majority of credits reviewed in the study were issued by American Carbon Registry (ACR), Climate Action Reserve (CAR) and Verified Carbon Standard (VCS) and used as registries by CARB. The registries and CARB have all defended their methodology, according to Bloomberg. However, this isn’t the first time forest management credits have been called into question. Last year, Bloomberg reported on a deal between carbon development firm Blue Source, LLC, the State of Michigan and five Wisconsin counties to create forest carbon offset projects on around 800,000 acres from which around 10 million carbon credits were expected to sprout over 10 years. However, forest managers and experts said it was unlikely management practices in the forests would actually change, meaning no additional carbon would be absorbed. 

 “It’s kind of a nothing-burger for the climate,” professor of political science at Edgewood College in Madison, Wisconsin, Steven Davis told Bloomberg at the time. “These forests have been managed the same way for 70 years.”

There are ways to make carbon credits more accurate, which the study authors recommended. These included setting baselines to the history of a particular plot of land as opposed to the regional average or avoiding assuming that the trees would have been cleared otherwise. 

‘Several changes to the protocols could result in more accurate and conservative baselines,” the study authors wrote. 

However, there is a fundamental problem with relying on offsets to reach net zero emissions when the latest Intergovernmental Panel on Climate Change report makes clear that climate pollution must be nearly halved this decade to have a shot at limiting the global temperature rise to 1.5 degrees or two degrees Celsius by 2100. 

“It makes the global community think that we’re doing more than we’re really doing at this brief moment we have to dramatically reduce our emissions to prevent runaway climate change,” Haya told Bloomberg.