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Can impermanent carbon credits really offset forever emissions?

Kosnipata Valley in Peru. Image by Rhett A. Butler/Mongabay.

Kosnipata Valley in Peru. Image by Rhett A. Butler/Mongabay.

  • A team of researchers has put forth a method that they say makes it possible to compare credits for carbon from forests projects against more permanent storage solutions.
  • The carbon emissions that these credits are meant to offset can last for hundreds, if not thousands, of years in the atmosphere. Forests, by comparison, are subject to fires, disease and deforestation, meaning that their climate benefits can be more temporary than longer-term solutions, such as direct air carbon capture.
  • By “discounting” the credits from forest carbon projects based on conservative upfront estimates of how long a forest will safeguard or sequester carbon, the authors say that “like-for-like” comparisons would be possible.
  • The team published their work Oct. 30 in the journal Nature Climate Change.

Offsetting the carbon emissions released when we fly in a jet or when a company ships its products is one, albeit increasingly controversial, way to address the climate-warming consequences of our everyday activities. The credits sold for offsetting often come from projects aimed at protecting or restoring forests that siphon carbon from the atmosphere as they grow and become healthier. In theory, those forests take up a similar amount of emissions, or their protection sidesteps the burst of emissions that would have been released if they had been cut down.

The trouble is, the carbon in the air might outlast the forests meant to offset those emissions. What’s more, the life spans of forests make it difficult to directly compare their carbon-sequestering potential in price and climate-mitigating potential with other strategies. For example, a nascent technological tool called direct air capture pulls carbon out of the air for storage in rock or underground and may provide longer-term storage.

Now, a team of researchers has put forth a method that they say makes those comparisons more accurate. Doing so could restore confidence that carbon markets can benefit the climate while also channeling much-need funds to conservation, particularly of carbon-rich tropical rainforests, they write. The team published their work Oct. 30 in the journal Nature Climate Change.

“It’s pretty clear from almost all global modeling that we’re not going to avoid very dangerous climate change without slowing down and ideally reversing the ongoing loss of tropical moist forests,” Andrew Balmford, the study’s lead author and a professor of conservation science at the University of Cambridge in the U.K., told Mongabay. “The only viable option for financing that at the moment is through carbon markets.”

A fire watch tower in Jambi, Indonesia.
A fire watch tower in Jambi, Indonesia. Image by Rhett A. Butler/Mongabay.

A 2017 study found that the CO2-absorbing potential of these types of “natural climate solutions” could account for more than one-third of what’s necessary to cap global warming at 2° Celsius (3.6° Fahrenheit) below pre-industrial levels, which scientists say is necessary to avoid the worst effects of climate change. More recently, scientists found that forests aren’t taking up nearly as much carbon as they could with more investment and better management. They also regulate local and regional climates, host untold species of animals, plants and fungi, and sustain the livelihoods of some 1.6 billion people.

But recent research and media reports have questioned the climate benefits claimed by both carbon project developers and purchasers of those credits. The process has shaken the market and threatened forest conservation funding.

“I think there are very real concerns, and I think there are good reasons for those concerns,” Balmford said, though other studies have shown that forest carbon credit projects can diminish deforestation.

“We’re trying to avoid throwing out the baby with the bathwater,” he added, “but there is a problem with the bathwater.”

To address concerns about the permanence of forest carbon storage, Balmford and his colleagues sought to build projections, into the credits themselves, of how long a given forest is likely to stay standing.

The aim was to estimate the value of those credits stemming from the carbon safeguarded or sequestered as a result of protecting a forest, even if, ultimately, that carbon is released back into the atmosphere — for example, if the forest burns or is cut down. During the time it’s standing, a forest helps hold off global climate change, along with providing resources to forest-dependent communities and habitat for biodiversity, Balmford said. Its persistence also buys time for all life to adapt to a changing climate, as well as for more permanent carbon storage solutions to come online and become more affordable.

Under the team’s proposal, project assessors would come up with a “pessimistic” estimate at the outset of a project for how long the carbon will remain locked away in the project’s trees, Balmford said. From that estimate, they would then calculate the relative value of that temporary carbon storage. If one credit represents the permanent storage of a metric ton of CO2 traded on the voluntary market, developers could “discount” their credits if they expect the storage to be temporary. For example, the developer might determine that their credits are worth 60% of a credit for permanent storage; that would mean a buyer who wanted to offset 3 metric tons of CO2 would have to buy five of those discounted credits.

This relative weighting of forest carbon credits allows for “like-for-like” comparisons with credits from permanent carbon storage, the team writes.

Sitio Paho, Pala’wan Indigenous leader Mami Lapasan, carrying a heavy load of almaciga resin.
In Philippines’ Mt. Mantalingahan, Pala’wan Indigenous leader Mami Lapasan, carries a load of almaciga resin. During the time it’s standing, a forest helps hold off global climate change, along with providing resources to forest-dependent communities and habitat for biodiversity. Image by Keith Anthony Fabro for Mongabay.

Until now, developers have used a strategy called buffer pools, in which they set aside a portion that they can never sell. The pools are a form of insurance in case a project’s forests end up releasing the carbon tied to the credits they sell. But because developers can never sell the credits that are held in the buffer pools, there’s no incentive — at least from the standpoint of selling more carbon credits — to ensure a forest’s carbon stays put over the long term.

Conversely, Balmford said his team’s proposed approach would reward ongoing protection. Their method calls for regular assessments of a project’s performance, which provides an opportunity to recalculate the actual amount of carbon protected.

“Unless things are going really, really badly, then the stakeholders will be safeguarding that carbon better than you thought because you weighted things in a pessimistic direction,” he said, meaning the project sells fewer credits than it generates.

“Then, that better-than-expected performance can be the subject of a fresh credit,” Balmford added. “It provides an ongoing incentive to communities … which we think is both good for the planet and good for equity.”

Matthew Brander, a senior lecturer in carbon accounting at the U.K.’s University of Edinburgh, who was not involved in this study, acknowledged that “good projects” can benefit people, biodiversity and the climate, even if the carbon storage is temporary.

Still, “An offset is effectively a license to emit another ton of CO2,” he said, and offsetting that ton requires storage that lasts as long as the emission does — potentially hundreds, if not thousands, of years.

Temporary solutions put off the release of emissions until later on, Brander said, which makes offsetting long-lasting emissions with the relatively short-lived storage of forests “problematic.”

To address that problem, forest carbon credits could be sold on separate markets from those offering permanent storage credits, he said. Or, a company that wanted to offset its emissions might purchase a forest carbon credit that would expire after a set period of time as a way of accounting for the potentially temporary nature of the storage.

Brander said he doesn’t believe that the two types of credits should be viewed as equivalent, even with the sort of discounting that Balmford and his colleagues propose.

“Conceptually, it’s just an impossibility,” Brander said. “They are fundamentally different things.”

Banner image: Kosnipata Valley in Peru. Image by Rhett A. Butler/Mongabay.

John Cannon is a staff features writer with Mongabay. Find him on 𝕏: @johnccannon.

Forests hold massive carbon storage potential — if we cut emissions


Balmford, A., Keshav, S., Venmans, F., Coomes, D., Groom, B., Madhavapeddy, A., & Swinfield, T. (2023). Realising the social value of impermanent carbon credits. doi:10.33774/coe-2023-5v93l-v5

Guizar-Coutiño, A., Jones, J. P. G., Balmford, A., Carmenta, R., & Coomes, D. A. (2022). A global evaluation of the effectiveness of voluntary REDD+ projects at reducing deforestation and degradation in the moist tropics. Conservation Biology, 36(6), e13970. doi:10.1111/cobi.13970

Griscom, B. W., Adams, J., Ellis, P. W., Houghton, R. A., Lomax, G., Miteva, D. A., … Fargione, J. (2017). Natural climate solutions. Proceedings of the National Academy of Sciences, 114(44), 11645-11650. doi:10.1073/pnas.1710465114

Mo, L., Zohner, C. M., Reich, P. B., Liang, J., de Miguel, S., Nabuurs, G. J., … Ortiz-Malavasi, E. (2023). Integrated global assessment of the natural forest carbon potential. Nature, 1-10. doi:10.1038/s41586-023-06723-z

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