Recent discussions at New York Climate Week and new decisions under Article 6.4 of the Paris Agreement highlight growing momentum toward a more scientific, practical, and adaptable approach to managing the durability of nature-based carbon credits.
As carbon markets evolve, so too must the science underpinning confidence in their climate impact. Nowhere is this more evident than durability: understanding how long carbon will remain stored, what could cause it to be released back into the atmosphere, and how those risks can be managed.
For nature-based climate solutions, these are significant questions. Forests and other ecosystems face changing threats from wildfires, droughts, pests and human activities. Robust carbon markets must account for these risks, while recognizing that they vary considerably between locations and can be reduced through effective management.
The good news is that progress is being made on this front, as evidenced by a couple recent developments.
First off, at New York Climate Week in September, the Science for High Integrity Frameworks to Transform Carbon Markets (SHIFT-CM) initiative convened a roundtable bringing together scientists, policy experts and carbon market practitioners to explore how better spatial data and risk modeling could strengthen durability assessments.
Then, just weeks later, the Supervisory Body overseeing the Paris Agreement’s Article 6.4 carbon crediting mechanism adopted a new reversal risk assessment tool, which sets out rules for determining how projects should account for the possibility that stored carbon could be released. While initially focused on non-renewable biomass (e.g. clean cookstoves), this modular tool will likely be adapted to forestry, biochar, and geologic storage methodologies. Although important questions remain about how the tool will work in practice, the final tool included several changes that reflect the broader scientific priorities discussed in New York.
Together, these developments point toward an important opportunity: building carbon markets that assess durability more accurately, respond to emerging science and actively support the management of long-term risks. However, again, more work is needed to ensure the tool actually enables this opportunity.
A common foundation, informed by local realities
One of the clearest messages from the SHIFT-CM roundtable was the need to balance consistency with flexibility. Standardized global or regional data can provide a valuable starting point for understanding durability risk, helping ensure that projects are assessed consistently, giving investors, standard setters and policymakers a shared foundation for decision-making.
But global models cannot capture every local reality. Two forests facing apparently similar climate conditions may have very different exposure to fire, different ecological characteristics or different capacities to withstand and recover from disturbances. Locally available scientific evidence may therefore provide a more accurate picture than global averages alone. Roundtable participants emphasized the importance of establishing transparent criteria for incorporating reliable local information without encouraging selective use of data or undermining consistency.
The recent Article 6.4 decision represents a potentially important step in this direction. The Supervisory Body agreed to allow proposals for alternative natural risk values to be submitted to the UNFCCC Secretariat for consideration. While this does not resolve every concern about the tool’s underlying methodology, it creates an opening for more locally relevant evidence to inform future assessments. The Supervisory Body has also asked the expert panel to recommend revisions to both the natural and human-induced risk values should credible new evidence arise, and that panel is expecting new peer-reviewed studies on natural risks within two to three years.
The challenge now is to develop clear, credible processes that ensure this flexibility improves scientific accuracy while remaining accessible to projects across different regions and levels of technical capacity.
Durability is about more than natural hazards
A second important theme was that durability cannot be understood through environmental hazards alone. Wildfire, drought and other natural disturbances are important risk factors, but the long-term protection of stored carbon also depends on human behavior, governance, socioeconomic conditions and the design and management of individual projects. This is an area where the evidence base needs to be built and where new research from SHIFT-CM will focus, since effective land management, community engagement and interventions that reduce exposure to threats can all influence whether carbon remains stored over time. This distinction matters because durability assessments should recognize not only the risks facing a project, but also the actions being taken to reduce them.
The Article 6.4 Supervisory Body’s recent deliberations illustrate the complexity of this challenge. Discussions over how to quantify human-induced reversal risk and recognize mitigation measures were particularly challenging. The resulting tool sets aside 20% of credits to cover human-induced risks, but also allows projects to reduce this human-induced risk value by up to 65% if the host country has the relevant national frameworks (e.g., NDCs, REDD+) in place.
These decisions reflect an effort to account for both human-related risks and the potential to manage them. But they also highlighted the need to build a robust evidence base, as well as further research to better understand how risks vary across activities and circumstances, and to inform future refinements to the tool.
For SHIFT-CM, this is an important direction for further research. Building on our work mapping natural durability risks, the initiative’s next phase will explore how human factors can be incorporated into more comprehensive assessments.
Importantly, the roundtable also highlighted that better risk assessments should not simply discourage investment in challenging landscapes. In many cases, these are precisely the places where well-designed projects, stronger governance and sustained financing can make the greatest difference. The goal should be to understand risk well enough to manage and reduce it, rather than treating every identified threat as a reason to withdraw support.
Keeping pace with science while providing certainty
A third area of agreement during the roundtable concerned the need for durability assessments to evolve over time.
Our understanding of climate risks is constantly improving. New datasets, advances in satellite monitoring and better modeling techniques offer opportunities to make assessments increasingly accurate and relevant. Yet carbon projects require long-term investment, and constantly changing risk assessments could create uncertainty for developers and buyers.
At the roundtable, participants explored ways to reconcile these competing needs, including scheduled reviews, transparent model updates, transition periods that protect credits already issued under earlier risk maps, and clear rules for incorporating new evidence. The underlying principle is straightforward: scientific progress should inform risk assessments without creating unnecessary instability.
This is especially relevant as the Article 6.4 framework moves into implementation. Although the adopted tool establishes an initial approach, its assumptions, datasets and methodologies should not be treated as permanently settled. Continued scientific scrutiny, opportunities to incorporate new evidence and predictable processes for future revisions will be essential to ensuring the framework remains both credible and workable.
From measuring risk to managing it
Taken together, the Climate Week discussions and recent Article 6.4 developments point toward a broader shift in how carbon markets can approach durability. The question is no longer simply whether nature-based carbon storage is permanent or impermanent. It is how different risks can be understood, quantified, reduced and managed over time.
That requires robust scientific foundations, but also practical frameworks that reward effective risk management and avoid unnecessarily restricting climate finance. The recent Article 6.4 decision points to where the market is headed, but it is not the end of this process. Important details need to be hammered out, and the opportunity now is to continue strengthening these approaches as the evidence develops.
Better durability science should ultimately do more than identify where carbon is at risk. It should help us understand how to protect it, strengthen confidence in credible climate solutions and direct more investment toward the landscapes where effective risk management can deliver lasting climate benefits.
This article was written by:
Susan Cook-Patton, Acting Global Director of Global Natural Climate Solutions Team at The Nature Conservancy
Carl Kish, Senior Policy Lead at the Beyond Alliance
Danae Maniatis, independent adviser on sovereign climate and forest finance and member of SHIFT-CM