Market Correction

Measure for (Re)Measure

Global estimates for the climate mitigation potential of soil carbon sequestration, which is achieved primarily through regenerative agricultural practices, vary. They range from a high of offsetting 30% of anthropogenic emissions to other lower estimates. The U.N. Intergovernmental Panel on Climate Change estimates the potential for soil carbon sequestration in croplands and grasslands to be 0.4 to 8.6 gigatons of CO2 equivalent per year — a range that at its lowest end represents as little as 1% of total annual global fossil fuel emissions to as much as 1.5 times the annual emissions of the United States at the highest end. This very broad range reflects the variety of approaches used to estimate the mitigation potential of soil carbon sequestration as well as the significant measurement and verification challenges.

“A general theme is that a lot of underlying data that inform these approaches come from small plot research trials that are largely concentrated in the Global North and represent a limited range of cropping systems and climate types,” says Emily Oldfield ’05, ’11 MESc, ’19 PhD, senior scientist at the Environmental Defense Fund and YSE associate research scientist.

Such limited data is part of what undermines confidence that these estimates represent realistic mitigation opportunities for soil carbon sequestration and why soil carbon credits have faced scrutiny in voluntary markets, the YASSP team emphasizes.

In agricultural soils, CO2 removal through soil carbon sequestration occurs only when management interventions lead to a net increase in soil carbon stocks over time, whereas avoided emissions occur when practices slow or prevent ongoing soil carbon losses relative to “business-as-usual” practices. Many global estimates implicitly assume removal because they rely on point-in-time comparisons that do not capture the trajectory of change in soil organic carbon stocks.

“Both scenarios mean less carbon dioxide in the atmosphere, and hence climate mitigation when compared to business-as-usual practices,” Bradford says. “But if you likened the situation to your retirement account, the difference should really matter to you. It would be beneficial to slow the rate of losses that are bringing your balance down, but you’d much rather be building that balance up.”

This distinction, far from being theoretical, directly affects estimates of mitigation potential and expectations about whether agricultural soils can contribute to atmospheric CO2 drawdown, with implications for the role of soil carbon in carbon dioxide removal (CDR) targets, negative emissions frameworks, and the voluntary carbon market.

The YASSP team has been working to bridge this evidence gap by detailing the implications of agricultural soil carbon removals versus avoided emissions for climate mitigation and by defining ways to expand and improve soil Measurement, Monitoring, Reporting and Verification (MMRV) approaches and datasets. They have co-authored several studies and reports on soil MMRV in which they detail their findings that a “measure and remeasure” approach using soil samples collected across hundreds of fields at the scale of commercial agriculture can provide more reliable evidence of how much carbon is being stored.

In one recent study, co-authors Bradford, Oldfield, Kuebbing, and lead author Alexander Polussa ’24 PhD, YSE research project manager, sampled and resampled soils from 80 dairy farm fields in the Hudson Valley, New York, at densities and scales that are largely unprecedented, and were able to directly prove the power of measure and remeasure designs to precisely and accurately quantify soil carbon change.

Although sampling at this scale — up to tens of thousands of soil samples over longer time periods — is rare, the YASSP team sees opportunity to further implement the measure and remeasure approach as developers and buyers in the carbon markets demand more stringent modeling.

“There is a plethora of emerging approaches to estimate how much soil carbon has been gained by implementing regenerative practices — such as those that use AI and remote sensing,” Bradford says. “As folks begin to ask whether these technologies are fit for purpose, I’m hopeful that they appreciate that the only way to test and prove these technologies is to help set up and run the causal measure and remeasure designs that we know from health, economic, and other disciplines are the only proven way to generate reliable data of intervention effectiveness.”

Shifting the Paradigm

By 2024, two key signals of market demand—carbon market purchases and retirements — had declined fairly dramatically from their 2022 peak. Confidence was shaken, at least in part, by a series of high-profile journal articles and journalism exposés that raised questions about the validity of carbon credits, particularly forest carbon credits. Partly in response to this growing skepticism, YASSP and YCNCC hosted a workshop in April 2024 on carbon crediting. The workshop was successful in demonstrating that market actors wanted to get together to effect change, Kuebbing notes.

It was at a second workshop several months later that the SHIFT-CM (Science for High Integrity Frameworks to Transform Carbon Markets) initiative was born. Led by YASSP and The Nature Conservancy, the initiative brings together research scientists and applied practitioners who directly work in the voluntary carbon markets to develop good practice guidance and determine research priorities to support the emergence of the next generation of carbon markets.

“These practitioners are key to the initiative’s success because they are the people who design and implement projects that are conserving, restoring, or managing nature — and they are the people who want to purchase carbon credits as part of their own organization’s climate mitigation strategy,” Kuebbing says.

Each of SHIFT-CM’s six working groups will produce one or more deliverables to fill their respective research gaps, with a provisional deadline of December 2026. YASSP is leading the Buffer Pools & Beyond working group. Buffer pools are the primary risk management tool used in carbon crediting for all nature-based projects to account for the possibility that carbon stored in a project might be released back into the atmosphere before the end of the project’s credited lifetime. However, there is concern that the amount of credits reserved in buffer pools is not enough to cover potential future losses, especially if the climate continues to warm and create higher probability disturbances. In one notable example, wildfires depleted nearly one-fifth of California’s total buffer pool in less than a decade — equivalent to at least 95% of the contributions set aside to protect against all fire risks over 100 years. So, the market is actively seeking to develop ways to manage such risk and ensure the durability and longevity of carbon credits.

The YASSP-led group is cataloging and organizing these ideas so that market actors can share a common lexicon on the potential approaches to non-permanence risk and better understand the challenges and risks in deploying them. The Buffer Pools & Beyond group includes representatives of standards bodies, groups that create protocols, project developers, other market actors, and research scientists from other institutions, Kuebbing notes.

“The goal of these hybrid working groups is not only to generate new data, models, and tools, but to also bolster collaboration among a bunch of people who all want to see these climate mitigation actions scale — and scale quickly,” she says. “I think when people work together to find solutions, it’s more likely that the ideas will be applied, and that people will have confidence that the proposed solutions are good ones.”