By Brian Buma, Seb Costedoat, Stephen Crooks, Peter Ellis, Jason Funk, Bronson Griscom, Jennifer Howard, Guy Pinjuv, Jigme Tenzin, Sarah M Walker, and Lahiru Wijedasa

A recent comment piece (Macintosh et al.) in Nature argues that the inclusion of natural carbon credits within emissions trading systems undermines real decarbonisation and weakens carbon pricing. Although we share the authors’ commitment to achieving net zero and ensuring that all carbon credits maintain high integrity, their conclusion rests on critical misunderstandings of the science underpinning natural climate solutions (NCS) and the way carbon markets function.

Causality and Policy Integration

The most fundamental error in Macintosh et al.’s argument lies in their assumption of causality. The authors imply that voluntary and emerging compliance markets that allow credits have delayed stronger government action on carbon pricing. The evidence suggests the opposite.

Carbon pricing instruments are expanding globally, covering roughly 28% of emissions in 2025 – up from 12% a decade ago – and average prices have nearly doubled in that time. Higher prices now go to credits for nature-based removals, while the largest growth in credit retirements in 2024 came from compliance markets.

This expansion has been built upon the experience of voluntary markets, which for over two decades have served as laboratories for innovation. Voluntary carbon markets have evolved into one of the few functioning global systems for quantifying, verifying, and financing NCS. While never intended as the sole funding mechanism for these activities, they have played an essential “sandbox” role in developing methodologies, registries, and monitoring, reporting, and verification (MRV) systems that governments are now integrating into compliance structures under Article 6 of the Paris Agreement.

Far from undermining policy, voluntary markets have shouldered early-stage risks that public systems avoided. Singapore’s recent collaboration with Verra and Gold Standard to align Article 6.2 protocols exemplifies how voluntary market experience strengthens government-led approaches. The evolution in the VCM now complements and strengthens government-led pricing mechanisms.

Economic Efficiency and Political Sustainability

Macintosh et al. interpret lower carbon prices in systems that include nature-based carbon credits as evidence of weakness. In fact, lower prices reflect the relative cost-effectiveness of NCS abatement – a hallmark of efficient climate economics. As Piris-Cabezas et al. (2023) demonstrate, integrating NCS into global markets could double total mitigation outcomes at the same total cost. The same study underscores that carbon pricing is critical to enable developing countries to meet their NDC targets, noting that tropical forest conservation is the largest potential source of enhanced ambition.

Higher carbon prices are not inherently desirable, particularly when they are not politically feasible. Excessively high prices can trigger social and political backlash, as shown by the gilets jaunes movement in France and cost-of-living debates surrounding California’s cap-and-invest program. Fairly priced, high-integrity NCS credits in compliance systems reduce overall costs and enhance public acceptance – key ingredients of durable climate policy.

Beyond economics, NCS credits correct a core market failure by making living ecosystems economically valuable. Properly designed carbon finance programs reverse the destructive incentive that has long made forests “worth more dead than alive.” They channel market value toward geographies with lower governance capacity – where the majority of NCS potential exists (Griscom et al. 2020) – but where top-down regulation remains unlikely in the near term.

Global Equity

High-integrity nature-based carbon credits deliver multiple measurable co-benefits – biodiversity conservation, clean water, and sustainable livelihoods – that align directly with the UN Sustainable Development Goals. These benefits are not incidental but integral to equitable climate action.

Crucially, they channel finance from wealthier, industrialised nations – where most emissions originate – to agricultural and forest communities that hold the world’s greatest opportunities for carbon removals. Despite managing roughly one-quarter of global terrestrial carbon and demonstrating superior protection outcomes, Indigenous peoples and local communities receive less than 1 % of climate finance and of that, only 2.1% makes it directly to communities. Voluntary carbon markets remain one of the few mechanisms capable of directing resources to these front-line stewards. Of course, the opportunity to access carbon market finance for land stewardship should be left with communities themselves, and not precluded based on the perceptions of polluting nations and industries.

Macintosh et al.’s emphasis on mitigation “at source” would concentrate financial flows within wealthy, high-emission countries, exacerbating global inequity and starving the Global South of resources essential for conservation. By contrast, NCS crediting supports a geographically balanced, cost-effective portfolio of actions across both North and South – one that expands, rather than narrows, global participation in climate solutions.

Durability and Additionality

We agree with Macintosh et al. that carbon credits must represent real and durable climate benefits. However, the claim that NCS credits must prove perfect “equivalence” to geological storage ahead of time is unnecessarily restrictive. And it’s important to understand this argument is about policy not science.

Matthews et al. (2023) show that the climate effect of carbon storage depends entirely on the duration of storage, not its physical form. Climate change is driven by greenhouse gas concentrations, which are agnostic to their source: fossil or biospheric. The task for science and policy is therefore to measure and manage reversal risk transparently – through mechanisms such as buffer pools, insurance, third-party guarantees, and continuous monitoring – to ensure that reversals are compensated and net atmospheric benefits maintained over time.

Additionality, likewise, is not a binary attribute. A credit’s validity rests on its capacity to deliver additional mitigation that would not otherwise occur. Uncertainty in additionality is already managed through more conservative approaches to define baselines and a portfolio approach. In terms of the former, conservative baselines ensure credits are issued only for the lower bound of estimated impact, reducing over-crediting risk. And in terms of the latter, rather than relying on a single intervention’s additionality, a portfolio approach leverages complementary strategies to achieve resilience and cost-effectiveness at the system level. In essence, like for an investment strategy, it transforms uncertainty into a manageable risk by spreading exposure, ensuring that aggregate outcomes remain robust even when individual estimates vary.

The science is evolving rapidly, and showing great promise for NCS crediting projects in their ability to demonstrate large amounts of additional climate benefit with high certainty.

A few examples:

• A global analysis by Chloris Geospatial (2024) found that biomass loss inside REDD+ projects and Indigenous territories was roughly two-thirds lower than in surrounding forests, even under intensifying climate stress.
• A 2025 re-analysis of West et al. (2023) using more robust synthetic control estimators in Science found that at least one-third of REDD+ offsets deliver statistically robust climate benefits, suggesting that previous counterfactual studies have underestimated the true impact of voluntary REDD+ credits. Furthermore, as more rigorous carbon credit methodologies replace obsolete ones and the sector incorporates enhanced protocols, we expect that future counterfactual studies will find higher climate mitigation impacts.
• While most counterfactual studies have relied primarily on remote-sensed data, a 2024 Nature Sustainability study combining satellite and household data found REDD+ reduced deforestation by 30% relative to control sites.
• Restoration projects funded by carbon markets are virtually absent from all counterfactual studies and meta-analyses. An exception is this paper (still under peer review), using counterfactual estimates and 3D lidar maps of forests to show that restoration projects across East Africa deliver carbon gains on average nine years after initiation.

Rapidly Evolving Market Integrity

Nevertheless, we agree, and are concerned, that some studies have shown that the additionality of certain projects using older methodologies has been less certain than anticipated. This has accelerated the improvement of accounting systems.

However, Macintosh et al. overlook this rapid evolution of carbon-market science and governance. The latest methodologies directly address many flaws identified in earlier studies. Work on dynamic baselines and jurisdictional performance benchmarks are further strengthening both conservativeness and additionality. Independent governance initiatives and transparency standards, including alignment with ICVCM criteria, are also strengthening trust.

These advances demonstrate a maturing market, not a stagnant one. Demand is increasingly concentrated in high-integrity credits, particularly nature-based projects. According to the Ecosystem Marketplace State of the Voluntary Carbon Market 2025 report, buyers are shifting decisively toward credits meeting recognised integrity standards. This trend reflects the sector’s capacity for continuous scientific and procedural improvement – an essential feature of a functioning market ecosystem.

Conclusion: Integration, Not Exclusion

We share Macintosh et al.’s commitment to high integrity, strong carbon pricing, and rapid decarbonisation. But excluding NCS from emissions trading systems is unnecessary, inefficient, inequitable, and counterproductive. For example, blocking the inclusion of NCS under the Paris Agreement’s Crediting Mechanism (PACM, Article 6.4) would undermine those goals. As 161 scientists recently affirmed, “Do not rule out nature from climate action; the scientific imperative is to incentivise natural climate solutions on the path to net zero.”

Scientific consensus is unequivocal: both fossil fuel phase-out and large-scale natural climate solutions are required to stabilise the climate. Market-based approaches that facilitate trading between and within these sectors accelerate action rather than undermine it. NCS crediting is a powerful opportunity – available now – to mobilise finance where mitigation is most cost-effective and socially beneficial.

Natural carbon credits have already demonstrated measurable success in reducing emissions, safeguarding biodiversity, and directing finance to communities that manage the world’s most critical ecosystems. The voluntary market has matured through iterative learning and increasing alignment with compliance systems.

Now is not the moment to dismantle that foundation. It is the moment to strengthen it, ensuring that voluntary and compliance markets together deliver the just, durable, and scalable climate solutions the world urgently needs.

The 11 authors are scientists and researchers from around the world writing in response to a recent Comment piece in Nature.

Any opinions expressed in this commentary reflect the views of the authors and not of Carbon Pulse.