In the carbon ecosystem, people often refer to “MRV” without paying much attention to the final V, even though this is the stage where everything is decided. Verification is not a bureaucratic formality: it is an independent, methodical examination designed to test the solidity of a project, the credibility of its data, the rigor of its assumptions, and the integrity of its final results. For reforestation projects and, more broadly, for nature-based solutions, verification acts as a revealer: it determines whether the claimed carbon actually exists.
Why do we verify?
The first reason lies in environmental integrity. Too many historical projects have relied on overly generous reference scenarios, optimistic assumptions about mortality or growth, or imprecise assessments of leakage. Verification introduces an essential safeguard. It is what transforms a theoretical model into a measured outcome, and a projection into a documented reality. In reforestation, where sequestration accumulates slowly over many years, this stage becomes the keystone of the entire carbon mechanism: without it, there is no credible credit, nor a durable market.
There is also a legal dimension. Project developers and buyers both face significant risks if credits are issued on weak foundations. Several public cases have shown that, when excessive volumes are later uncovered, the consequences affect not only the project developers but also the companies that purchased the credits. A well-conducted verification protects everyone, including the most serious developers.
Finally, verification is a strict requirement of the standards. Verra, Gold Standard and the French Label Bas-Carbone leave no room for ambiguity: without independent verification, no units can be issued. Verification is therefore embedded not just in the logic of integrity, but also in the regulatory framework that structures the market.
How does verification unfold for an NBS project?
In NBS projects, verification almost always begins with a careful review of the monitoring report, the document where the project team explains what actually happened: areas effectively planted, mortality rates, inventory results, biomass evolution, disturbance events, any leakage observed, and the overall coherence between planned and actual activities. The verifier is not trying to validate what the project claims, but to understand how it was measured.
The next step is the methodological review. Each standard defines a precise framework: how sampling plots are selected — those measurement points used to extrapolate the project’s total biomass — the statistical treatment of the data, the allometric equations applied, the management of uncertainties, and the application of conservative deductions, meaning reductions applied by the method to avoid any overestimation when uncertainty is present. The verifier ensures that the method has been correctly implemented, but above all, that it has been followed with enough discipline to produce robust data. Two reports may both be “compliant” while showing very different levels of scientific maturity; this is where the experience of the verifier becomes decisive.
On the ground, verification becomes very tangible. Permanent plots are revisited, sometimes remeasured to ensure that procedures were correctly applied. The verifier examines the coherence of plantings, the health of young trees, the growth dynamics, and the presence or absence of unexpected activities. A project that looks impeccable on a GIS map may reveal, in the field, unexpected mortality or density issues. The verifier is not there to redo the inventory, but to evaluate whether the measurements underlying the model are credible.
Then comes the most sensitive part: recalculation. The verifier goes through the equations, the emission factors, the construction of the baseline scenario, and checks that the reported volumes are truly those allowed by the method, within the acceptable uncertainty range. This is often where discrepancies appear: poorly documented data, parameters applied outside their valid range, or statistical adjustments that lean too far toward optimism.
Tools used for verification
Verifiers no longer rely solely on field notebooks. Remote sensing has become a cornerstone of modern verification: optical imagery to track land-cover evolution, radar to detect clearing in tropical conditions, and LiDAR to estimate canopy structure. The combination of physical data and field observations now forms the backbone of any serious audit.
The other pillar is statistics. Plot sizing, sampling design, uncertainty management — these elements, if poorly controlled, can shift a project from the “robust” category into the “at-risk” category. A good verifier reads data the way a statistician reads clinical trials: searching for internal coherence, weak signals and potential biases.
Who conducts verification?
Audits are carried out by accredited bodies — VVBs — which themselves are supervised. Today, key actors include Bureau Veritas, DNV, TÜV SÜD, TÜV Rheinland, SGS, Intertek, SCS Global Services and Control Union, each with its own areas of expertise. They are not consultants, but independent third parties that engage their responsibility. Their role is not to improve the project but to determine whether what was done complies — or not — with the reference standard.
Alongside these bodies, a wide ecosystem of specialists supports developers in building solid MRV frameworks: foresters, agronomists, remote-sensing experts, and carbon engineers. Their contribution is to prepare the ground for the audit, reduce the risk of non-conformities, and ensure that the data can genuinely be used.
When verification reveals failures
Underperformance and credit adjustment
The most common situation is underperformance. Plantations may experience higher-than-expected mortality, slower growth, or greater leakage. In such cases, the volume of credits is simply revised downward. The market accepts this: it is inherent to NBS projects, which are exposed to climatic, biological and operational variability.
Methodological non-conformities
The second case is more delicate: methodological non-conformity. When an essential dataset is missing, or when a key element of the protocol has been incorrectly implemented, the verifier issues a corrective action request. This is the moment when the developer’s discipline becomes visible. A well-structured project can correct the issue; a poorly managed one may see its crediting period suspended altogether.
Systemic failures and market corrections
A rarer but much more serious situation is the emergence of systemic failure. The Kariba REDD+ project in Zimbabwe is a prominent example: a reassessment of the baseline scenario revealed that a significant share of issued credits had been based on overly favorable assumptions. The result was the cancellation of credits, compensation requirements, and reputational damage.
A similar pattern appeared in Australia with the HIR method, where several analyses highlighted a significant gap between actual regeneration and that used to justify issued credits. In such cases, verification becomes a market-correction mechanism — sometimes abrupt, but necessary.
There are also more ambiguous cases, where the method itself is questioned. The recent debate around the French Label Bas-Carbone forestry methodology is illustrative: the controversy over the assumed spontaneous growth rate of abandoned land (considered too low by several researchers) shows that even a well-structured system can produce questionable credits if the methodological foundation is biased. No verifier can compensate for a flawed method: verification is only one link in the chain of integrity.
What this means for NBS project developers
A “verifiable” reforestation project is not one that merely follows a protocol; it is a project designed from the outset to be transparent. Data must be well structured, inventories reproducible, assumptions justified, satellite imagery archived, and local teams capable of following the protocol for twenty or thirty years. It also requires accepting conservativeness: any upstream optimism inevitably resurfaces at verification time.
The best strategy is to integrate the verification logic into the very design of the project. This means documenting what is measured — and what is not yet — planning for contingencies, and being ready to answer a verifier’s questions as one would respond to a demanding investor. Only then can reforestation-based NBS credits aspire to the category of high-integrity carbon assets.
In practice: how to prepare an NBS project for verification?
A reforestation project is verified all the more easily when it has been designed to be auditable from day one. The essential point is not to accumulate data but to ensure that it is traceable, coherent, and intelligible to an independent third party. When a verifier arrives, what matters most is neither the size of the project nor the scale of operations, but the discipline with which the teams have applied their protocol.
The solidity of a project rests on three pillars. The first is methodological clarity: a well-documented model, justified assumptions, and a defensible baseline. The second is operational rigor: reproducible inventories, systematic data archiving, and proof of the areas actually planted or restored. The third is transparency: the ability to explain what happened, including when unforeseen events altered the planned sequence.
When these three pillars are in place, verification becomes less a source of stress than a natural step that strengthens the project’s credibility and secures the credit volumes. Project developers should not fear verification: it is, in fact, the moment when solid work is recognised.