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A debate over carbon permanence - how long CO2 must stay stored to count towards offsetting emissions - is reshaping global carbon markets and could determine whether nature remains investable.

At its October 2025 meeting, the UN's Article 6.4 Supervisory Body adopted new 'permanence' rules that will shape how forests, soils, and mangroves are treated as investable climate assets under the Paris Agreement's global carbon market. Article 6.4, which governs international carbon trading, sets the rules for how countries and companies exchange verified emission reductions.

At the center of the debate lies "like-for-like permanence," the idea that carbon emitted from fossil fuels, locked underground for millennia, should only be balanced by carbon storage guaranteed to last just as long. Critics call this a false choice that risks sidelining nature when it is needed most; supporters argue that strict equivalence is vital to preserve market integrity and prevent greenwashing.

The dispute reflects a deeper divide over offsets themselves. Opponents say they let emitters delay real cuts, while advocates argue that, when governed transparently and tied to credible reduction pathways, offsets are a practical bridge for hard-to-abate sectors.

Underlying the permanence debate is an assumption that natural carbon storage is inherently unreliable. Yet more than 200 scientists and climate experts argue that this view is outdated and economically self-defeating. With sound management, verification, and insurance, nature's carbon stores can be made increasingly durable, but only if the new rules are implemented in ways that allow those tools to evolve.

In Do Not Rule Out Nature from Climate Action, the authors warned that "prioritizing theoretical permanence over immediate, scalable, systems-level implementation available through natural climate solutions creates counterproductive delays when rapid action is critical." The letter continues, "Temporary removals can deliver measurable near-term climate value by reducing peak warming and buying crucial time for longer-duration solutions to scale."

This is not abstract. The IPCC Sixth Assessment Report said that 8-13 gigatons of potential annual carbon mitigation could come from natural climate solutions this decade. Engineered removals like direct air capture currently operate at roughly 0.01 megatons per year. "Managing the Earth's climate over the coming decades is as important as managing it over the coming centuries," the authors noted. "Delaying intervention based on permanence criteria alone is therefore scientifically and ethically unjustifiable."

The science of durability challenges the notion that climate benefit only counts if it lasts a thousand years. A tonne of CO₂ stored in a forest for fifty or a hundred years still lowers near-term peak temperatures, slowing feedback loops that could trigger irreversible change.

Lina Barrera, senior vice president of conservation at Conservation International explained in an interview, "Science tells us that reducing emissions, whether by burning fewer fossil fuels or not logging a forest, for some period of time will have a positive impact on the climate. Meeting global climate goals will require every tool in the toolkit. Pursuing perfection rather than utilizing and improving upon immediately available solutions would be a mistake."

To effectively address emissions, Beatriz Granziera, senior climate policy advisor at The Nature Conservancy argues that credibility and practicality must coexist. "Article 6.4 must be a benchmark for quality. But credibility and practicality are not mutually exclusive," she told me. "A mechanism that looks credible on paper but cannot be implemented in practice won't meet the goals of the Paris Agreement."

In practice, the new decision preserves a pathway for nature-based credits while tightening the rules around transparency and accountability. The Supervisory Body's compromise reflects a growing recognition that integrity and inclusion can coexist if risk is clearly defined and priced.

As the Supervisory Body wrapped up negotiations, Beatriz Granziera called the outcome "a much better text than what we had at the start of the week." She noted that strong interventions from countries, scientists, and market actors helped keep nature in the process. "There is still work to be done and challenges ahead for the participation of nature in this mechanism," she said, "but these will be dealt with within the specific context of each activity."

The final text drops the proposal for indefinite post-credit monitoring, which would have required projects to track stored carbon forever. Instead, each methodology will set its own monitoring period, recognizing that sectors face different risks. The decision also clarifies how liability is shared: host countries or third parties may take over monitoring, while project participants remain responsible for reversals through insurance or financial guarantees.

Fixed thresholds for "negligible risk of reversal" have been removed; risk will now be assessed within each methodology using a standardized tool. Projects that fully remediate reversal risk can exit by canceling equivalent credits or transferring liability through insurance. A new call for input from host countries will guide how corresponding adjustments apply to buffer-pool units, the share credit reserves that act as insurance against carbon losses when, for example, a forest burns.

"Flexibility and innovation must remain central," Granziera wrote after the meeting, stressing that nature's participation depends on tools like buffer pools, insurance, and the ability to transfer liability.

Across the economy, risk is quantified, priced, and managed, not treated as disqualifying. "There are many ways that the risk of reversals can be managed, like shared reserves of credits or insurance that spreads the risk," Barrera said. "These are common in financial markets and sectors like energy and infrastructure."

Climate mitigation should be no different, managing risk across systems through insurance, credit reserves, and contingency planning. The challenge is not to eliminate uncertainty but to govern it transparently and design markets that reward sound risk management rather than avoidance.

Lowering atmospheric CO₂, even temporarily, has positive impacts, Barrera adds. It helps reduce the likelihood of crossing irreversible tipping points such as ice-sheet collapse or rainforest die-off. Every tonne kept out of the atmosphere buys time to stabilize the systems that keep the planet livable.

As Barrera notes, "lowering atmospheric CO₂, even temporarily, can have positive climate impacts," she explained. This in turn lessens the likelihood of crossing irreversible tipping points such as ice-sheet collapse or rainforest die-off. In other words, each tonne of avoided CO₂ contributes to moderating near-term warming and reducing systemic risk.

Article 6.4 is not just a technical annex; it defines what counts as a valid emission reduction and will set the standard for voluntary and domestic markets alike. "These decisions will determine how carbon markets evolve, and, ultimately, how countries and companies meet their climate goals," Granziera explained. "This is not just another technical rulebook. It's a mechanism that sits at the center of the entire carbon market ecosystem."

If the Supervisory Body had imposed a strict like-for-like standard, the result could have been a freeze in investment. Projects focused on forest protection, soil carbon, and mangrove restoration, many located in developing economies, would become ineligible for crediting. Analysts estimate that natural climate solutions could mobilize hundreds of billions in private finance annually if treated as credible assets under Article 6.4. A narrow durability rule would have stranded many of those investments, diverting finance from cost-effective, immediately deployable mitigation options.

Recent scandals underscore the stakes. The Kariba REDD project in Zimbabwe, once promoted as a flagship forest-carbon initiative, collapsed after revelations that it had overestimated avoided deforestation and lacked adequate safeguards. The controversy became a touchstone for critics who say voluntary carbon markets exaggerate impact and underestimate reversal risk.

An October 2025 review of the offset market argues that many widely used carbon offset programs systematically overestimate their climate impact, often by a factor of five to ten or more, due to persistent issues around additionality, leakage, verification, double counting, and durability. Those failures demand reform, but simply excluding nature from markets would not solve them.

Barrera notes the imbalance already at play explaining, "Nature holds 30% of the solution for meeting global climate goals but only receives about 3% of global climate funding." Excluding nature projects, she said, "would widen a finance gap that needs to be filled."

For investors and companies setting net-zero strategies, the outcome of this debate will shape which credits count, which don't, and how transition portfolios are priced over the next decade.

Observers say the next test will be how the Supervisory Body operationalizes these rules, whether insurance and buffer mechanisms are scalable enough to attract institutional investors.

"If market rules are designed in a way that excludes nature-based activities on technical grounds," Granziera noted, "the practical outcome is that finance from markets will flow almost exclusively to technology-based mitigation options. These are typically developed in the Global North."

That shift would deprive forest nations of revenue precisely when they need it most to meet their own national climate commitments. Nature-based solutions are immediately available and rich in co-benefits, supporting biodiversity, livelihoods, and resilience - while also providing a financial bridge between mitigation and adaptation.

Rather than treating technology and nature as competing options, climate mitigation will need a mix of solutions across different time horizons and risk profiles: immediate, scalable nature-based projects that act now, and longer-duration technological removals that mature over time. As Granziera put it, "We need solutions that act now and later." Barrera agrees that "meeting global climate goals will require every tool in the toolkit." The real question, then, is not whether to choose nature or technology, but how to integrate both intelligently.

New approaches such as dynamic permanence proposed in the Oxford Principles for Net Zero Aligned Offsetting, and actuarial buffer pools that adjust with real-world data are just examples of the way in which the challenge could be addressed. These tools make it possible to assign value to durability while maintaining transparency and scientific rigor.

Barrera stresses that offsets are not a license to pollute. "Offsets are not a substitute for cutting emissions at the source, they're a complement," she says. "Relying solely on direct cuts, especially in high-cost sectors, risks slowing progress and missing near-term climate targets."

The larger lesson from this debate is that credibility and speed are not opposing values. Climate risk is cumulative, and the next two decades will determine whether humanity stays within planetary boundaries. "We need solutions that act now and later," said Granziera, while Barrera added that "storing carbon today is especially important for delaying climate tipping points, like the die-off of the Amazon Rainforest." The decades immediately ahead matter just as much as the centuries that follow.

For investors and policymakers, the question now is how fast the new permanence rules can be operationalized. With COP30 approaching, these definitions will determine which countries attract finance, and whether the carbon market remains a viable bridge between ambition and action.

New UN Carbon Market Rules Could Reshape How Investors Value Nature