Forest carbon credits (often in a voluntary market) reflect the savings or sequestration of CO₂ by comparing two scenarios: a baseline and a project scenario. Reference scenario defines what would happen without the project (e.g. continued deforestation), the project scenario describes the intervention (e.g. planting new trees or protecting the forest). The difference between the emissions in these two scenarios represents the “savings” or additional carbon sequestration in the biomass. Carbon is measured using allometric equations (based on trunk thickness and tree height measurements) and area sampling. The obtained living biomass is converted into carbon content (approximately 50 % dry weight) and further into CO₂ equivalent (using the ratio 44/12). The results are often expressed in tCO₂e per hectare (annual increment or total sequestration). Modern approaches use a combination of field measurements with satellite data and LIDAR: it allows mapping of changes in forest cover and aboveground biomass over a wide range. Thanks to this, projects model aboveground biomass and use it to calculate quality factors – baseline, additionality, leakage and permanenceFor example, RMI reports that specialists combine remote sensing with field surveys to more accurately estimate project parameters and baselines.

Calculation examples: In practice, reforestation of tropical forest can be able to sequester ~11 tCO₂/ha/year. In contrast, the loss of one hectare of old-growth rainforest would release on the order of over 400 tCO₂ at once. These estimates demonstrate that protecting existing forests (REDD+) addresses large carbon stocks (old trees), while planting new forests relies on gradual carbon storage over decades. Standards (VCS, GS, etc.) define detailed algorithms for measuring carbon stocks and converting them into CO₂ emissions.

Monitoring, verification and certification of projects

The quality of forest carbon projects depends on credible monitoring and independent verification. Projects are periodically monitor – e.g. crops, number and size of trees, or monitoring forest cover using satellite imagery and aerial surveys. Methodologies such as VCS require projects to analyze the change in deforestation in the surrounding area (“leakage zone”) using satellites. Data records (e.g. monthly images) are combined with local measurements. This is then followed by independent validation and verification accredited institutions (so-called VVB): e.g. public or private auditing firms (DNV, SGS, Bureau Veritas, etc.) authorized by established standards. Without exaggeration, “robust quantification” requires that projects are monitored and the resulting data approved by accredited auditors before credits are issued. This process ensures that the stated reductions actually correspond to the measured data.

Technological developments increase precision: new tools such as AI for image processing, LIDAR and unmanned drones allow for more detailed biomass estimates and early detection of changes. RMI notes that better access to data (open LIDAR, field databases) and machine learning can significantly improve the credibility of alleged carbon stocks. It is worth noting that accuracy also depends on the frequency of monitoring; some standards require annual to quarterly change reports. For a full audit, in addition to GHG amounts, social and environmental impacts, community engagement and compliance with local regulations are also checked.

Main standards and certification systems

There are several recognized certification standards on the market. Verra (VCS) is the most widespread – its VCS program certifies a large number of forest projects, especially REDD+ and plantings (ARR). Verra states that its program has the most certified REDD+ projects in the world. VCS works with a number of detailed methodologies (e.g. VM0047 for ARR projects) and requires demonstration of additionality, project sustainability or the allocation of reserves to cover risks (so-called buffer pools). Gold Standard (GS) (currently under the “Global Goals” program) also offers methodologies for both afforestation and conservation projects with a strong emphasis on social benefits and the SDGs. GS often places strict requirements on community participation and transparency, although its forest methodologies have only emerged in recent years. ART-TREES is a newer standard for country-wide REDD+ (jurisdictional approach). TREES emphasizes accurate accounting, independent monitoring, mitigation of leakage and reversals, prohibition of double counting, and strong environmental/social safeguards. It is developed under the Paris Agreement and is often linked to national programs. Other examples: Plan Vivo focuses on smaller community projects, CCBA gives the title of a certificate of the presence of community and biodiversity benefits.

Project duration, leakages and permanence

Forest projects are long-term in nature – their benefits must be sustained for decades. Typically, standards require that carbon be sequestered for at least 100 years, which is considered a benchmark for permanence. For example, Sylvera states that projects designated as permanent ensure carbon sequestration for at least 100 years. For this reason, in addition to the calculation itself, the methods often also consider the so-called carbon reserves (buffer pools). If CO₂ backflow occurs (forest fire, crustaceans, illegal mining), part of the credits will be withdrawn from these reserves.

Another key factor is leakage. This occurs when a project prevents deforestation in one place, but deforestation is shifted elsewhere (e.g., demanding timber is moved outside the project area). Methodologies calculate such leakages and reduce the credits issued. For example, VCS requires monitoring of changes in deforestation in the surrounding “leakage zone” via satellites. Deforestation outside the project must be included in the calculations, otherwise false credits would be generated. The risk of failure (reversibility) is particularly high in A/R, because young forests are vulnerable to fire, drought, or pests. REDD+ projects are burdened with the risk of political reversal or corruption – e.g., if the government changes its forest protection policy, the “saved” forests may be put at risk again.

Comparison of types of forest carbon projects

• Afforestation/Reforestation (A/R) – planting trees on previously non-forested areas or restoring degraded stands. The advantage is that growing trees actively remove CO₂ from the atmosphere. The typical carbon sequestration rate in the tropics is impressive (~11 tCO₂/ha/year). The disadvantage is the high initial costs and long payback period (trees grow for decades). The project brings credit only later, and the risks include largely unforeseen back-emissions (fires, droughts). Biodiversity depends on the choice of species – natural Afforestation can support ecosystem services, but economically oriented monocultures may have lower diversity. An example is the project Corridors for Life in Brazil: it restores remnants of the Atlantic Forest and is expected to sequester thousands of tons of carbon. A/R is suitable in areas where land is available (empty fields, burned areas) – in both developed and developing countries, in temperate and tropical zones.
• REDD+ (Reducing Emissions from Deforestation and Degradation) – protection of existing forests by ensuring that the project discourages from logging or burning trees. The credits represent emissions that would have been released without the project. The advantage is an immediate large carbon saving: the loss of a hectare of old-growth tropical forest would release more than 400 tCO₂. The biodiversity of old-growth forests is extremely high (e.g. the Amazon contains tens of thousands of species – 70,000 insect species per hectare), so REDD+ projects typically protect key biodiversity. Risks include leakage (e.g. shifting deforestation to another area), uncertainty in additionality (whether the forest would actually be protected even without the project) and corruption pressures. REDD+ projects tend to be large (in jurisdictions or nationally); they are mostly implemented in tropical countries with high deforestation pressure (Amazon, Congo, Indochina).
• Internationally Transferable Outcomes (ITMOs) – originated from the Paris Agreement (Article 6.2) and represent ways in which countries “sell” emissions reduced by projects to each other. Technically, these are credits that are authorized by the government and are paired with a corresponding adjustment to the countries’ carbon accounts. Although methodologically ITMOs are similar to REDD+ outcomes (e.g. countries issue ITMOs from forest conservation projects), the main difference is in their administration: they must be included in the national carbon budget. ITMOs are therefore less project-based and more political in terms of risk – success depends on the credibility of the country, its reporting and compliance with the NDC. ITMOs are not limited to forests or location; they represent a federal framework that can finance projects (including REDD+) in partner countries.

Comparison in points:

• Methodology: A/R projects measure biomass gains from zero (new trees grow) in defined areas; REDD+ uses a historical deforestation reference scenario (which is criticized as overestimated); ITMOs require government verification and adjustment of Article 6 emissions counts, including a national baseline.
• Risks: A/R – reverse emissions (fires, diseases, climate) and growth losses; REDD+ – leakage (deforestation to other regions) and uncertain additionality; ITMO – political/regulatory (sustainability of commitments, NDC changes, possibility of double counting). For example, non-transparent baselines and non-coverage of leakages lead to “fake” credits.
• Biodiversity: A/R can improve biodiversity if native species are planted and mosaic stands are created; the monocultural nature of logging can be a disadvantage. REDD+ protects old, biologically rich forests – thousands of plants and animals grow in them (e.g. the Amazon rainforest with tens of thousands of species). ITMOs (if they come from REDD projects) have the same biodiversity benefits as those projects. Otherwise, if ITMOs finance A/R, their impact on biodiversity depends on the type of project.
• Profitability: A/R projects require more capital and deliver credits gradually (e.g. tropical reforestation ~11 tCO₂/ha/year, but tree growth continues for decades). REDD+ can “sell” more carbon quickly – e.g. 1 ha of old-growth forest prevents the release of ~400 tCO₂ at once, which may be more efficient in the short term. ITMOs are part of national carbon accounts – their price and return depend on political agreements and country demand, not on the microeconomics of the project.
• Geographical suitability: A/R is implemented wherever degraded land is suitable for afforestation (temperate and tropical zones). REDD+ only in countries with forests threatened by deforestation (very often tropics – Latin America, Africa, SE Asia). ITMOs can theoretically connect projects from different regions, but are directly linked to countries with the capacity to manage the Paris Agreement mechanism.

Practical examples, data and challenges

• Examples of projects: As an example of A/R, we can cite the Brazilian project Corridors for Life – is restoring corridors of the Atlantic Forest and expects to sequester thousands of tons of carbon. Well-known REDD+ projects include Rimba Raya (Indonesia) and Kasigau Corridor (Kenya), which protect tropical forests. These projects often also support communities and biodiversity. Under ITMO One can mention mechanisms such as the Japanese JCM or Article 6 Entities, where states recalculate results (e.g. Guyana planned to recalculate its REDD+ results).
• Performance and Controversy: Recent studies warn that many forest credits do not reflect real change. The study, published in Science (2023) examined 26 REDD+ projects across three continents and found that approximately 94% of the % credits issued likely did not correspond to actual emissions reductions. This finding points to overestimation of baselines and underestimation of leakages in practice. Similarly, ProPublica and environmental analysts warn of the risk "greenwashing": without strict verification procedures, companies can use offsets to delay reducing their own emissions. Verra responds that some of the study's methods are questionable, and in the process, it is rewriting its standards (it has temporarily tightened requirements for REDD+).
• Main challenges: In addition to additionality and leakage, this includes ensuring sustainability (e.g. fire management) and social and environmental standards. Experts emphasize the need national frameworks – e.g. The Paris Rules require that all internationally traded forest credits have country-level support mechanisms: a clear national baseline, national monitoring of forest changes, a strategy to prevent leakage, and the involvement of local communities. For example, the California Standard draft stipulates that the baseline must be 10 % lower than the historical average and that projects must hold a reserve of credits to cover increased deforestation.
• Recommendations: Scientists and practitioners recommend combining technological innovations and transparent rules. For example, RMI suggests sharing datasets (LIDAR, field records) and using machine learning for more accurate carbon models. Quality criteria also include guarantees of additionality and permanence – standards often introduce buffer pools or long-term commitments so that sporadic forest losses do not negate the climate benefits. Ultimately, the point is that credits actually mean real and permanent emission reductions – and this has recently been increasingly emphasized in international and voluntary practice.

Sources: In the text, we used not only scientific analyses and market reports (e.g. RMI, Pachama, Mongabay, Conservation Int.), but also official methodologies and standards (Verra VCS, ART-TREES). The information is updated according to current standards and findings through 2024. Spring