Nature-Based Solutions: REDD+, ARR, and IFM
Nature-based solutions (NbS) represent the largest share of voluntary carbon credits issued to date. By protecting, restoring, and improving the management of forests and other ecosystems, these projects harness the natural carbon cycle to reduce atmospheric greenhouse gas concentrations. This lesson examines the three dominant NbS project types certified under the Verra VCS Program and similar registries: Reducing Emissions from Deforestation and Forest Degradation (REDD+), Afforestation, Reforestation, and Revegetation (ARR), and Improved Forest Management (IFM).
REDD+: Protecting Forests Under Threat
REDD+ is a framework developed under the United Nations Framework Convention on Climate Change (UNFCCC) to provide financial incentives to developing countries for reducing emissions from deforestation and forest degradation. In the voluntary market, REDD+ projects apply this same principle at the project or jurisdictional level.
The mechanism works by establishing a baseline - a projection of how much forest would have been lost in the absence of the project, typically based on historical deforestation rates in the reference region. Credits are issued for the difference between projected deforestation and actual deforestation as monitored during the crediting period.
Example: The Katingan Peatland Project, Indonesia
One of the largest VCS-registered REDD+ projects, the Katingan Mentaya Peatland Restoration and Conservation Project in Central Kalimantan protects over 149,000 hectares of peat swamp forest from conversion to oil palm plantations. The project has issued millions of VCUs and supports local communities through employment, healthcare, and education. Peatland forests are particularly carbon-rich because they store large volumes of ancient organic matter in waterlogged soils - drainage for agriculture releases this carbon very rapidly.
REDD+ projects have faced significant scrutiny. A 2023 investigation by journalists and academics found that a number of high-profile REDD+ projects had substantially overestimated their baselines, leading to over-crediting. Verra and other registries have responded by tightening baseline methodologies, requiring more frequent revisions, and introducing dynamic baseline approaches that better reflect current deforestation trends.
Afforestation, Reforestation, and Revegetation (ARR)
ARR projects create new forests on land that was previously non-forested (afforestation) or that lost its forest cover (reforestation), or restore vegetation cover more broadly. Unlike REDD+, which generates avoidance credits, ARR generates removal credits because new biomass actively sequesters CO2 from the atmosphere.
The VCS Program applies the Agriculture, Forestry and Other Land Use (AFOLU) module requirements to ARR projects. Key methodology considerations include:
- Baseline scenario: What would have grown on the land without the project? Often degraded grassland or scrubland.
- Carbon pools: Above-ground biomass, below-ground biomass, dead wood, litter, and soil organic carbon all count but must be monitored separately.
- Leakage: If the project displaces agricultural activity to other land, that displaced activity's emissions must be deducted.
- Permanence buffer: A proportion of credits (typically 10-20%) are held in a buffer pool to insure against reversals.
Analogy: A Growing Savings Account
An ARR project is like a savings account that grows over time. In the early years, young trees sequester modest amounts of carbon and projects may issue relatively few credits. As the forest matures over decades, the carbon stock grows and annual sequestration increases. This long time horizon means ARR projects require patient capital and present particular challenges for baseline setting as climate conditions change.
Improved Forest Management (IFM)
IFM projects change how existing managed forests are harvested and maintained to increase their overall carbon stock. Common interventions include extending harvest rotations (waiting longer between logging cycles), reducing harvest intensity, protecting high-carbon stands from logging, and switching to lower-impact logging techniques.
IFM generates a blend of avoidance and removal credits: extending a rotation avoids the emission from an imminent harvest while the standing trees continue to accumulate carbon. The methodological challenge is demonstrating that the management change is additional - that the landowner would not have made the same choices without carbon revenue.
IFM in North America
The Climate Action Reserve (CAR) in the United States has developed widely respected IFM protocols for North American forests. Verra's VM0010 is among the most-used VCS methodologies for IFM globally. These projects are popular with buyers because North American forests are subject to strong legal frameworks and have relatively lower political and governance risk than tropical forests. However, wildfire risk - especially in western North America - creates significant permanence uncertainty that has come into sharp focus in recent years.
Permanence: The Central Risk of Nature-Based Solutions
All three NbS project types face the same fundamental challenge: biological carbon stores can be reversed. Fire, disease, drought, pest outbreaks, and political instability can all release carbon that was credited years or decades earlier. Verra's AFOLU requirements mandate that projects contribute to a pooled buffer account - the AFOLU Pooled Buffer Account - sized according to the project's assessed reversal risk. Projects with higher wildfire exposure or weaker governance must contribute more credits to the buffer, reducing their saleable credit volume.
The buffer mechanism has been tested in practice. When the Bootleg Fire burned through Oregon forest in 2021, credits from several Climate Action Reserve forest projects were cancelled against the buffer pool. This demonstrated both that the mechanism works as designed and that it is finite - a period of sustained wildfire losses could deplete buffer pools.
Market leakage occurs when a REDD+ project protects a forest, but logging or agricultural conversion simply moves to an adjacent unprotected area. If this happens, the project has not reduced deforestation; it has merely relocated it. VCS methodology requires projects to assess and deduct leakage. For projects in isolated landscapes far from deforestation pressures, leakage may be minimal. For projects in active agricultural frontiers, the leakage deduction can be substantial - sometimes 20 to 40% of gross credits. Jurisdictional REDD+ approaches, which operate at the national or subnational level rather than the individual project level, are designed to address leakage more comprehensively by accounting for emissions across an entire jurisdiction.
Methodology Examples
VCS has approved numerous methodologies under each category:
- VM0007 / VM0015: REDD+ methodologies for avoided unplanned deforestation
- VM0010: Methodology for IFM conversion from logged to protected forest
- VM0042: Methodology for improved forest management in temperate and boreal forests
- AR-AM0014: CDM-derived methodology for reforestation of degraded land
Each methodology specifies how to define the project boundary, establish the baseline, monitor carbon stocks (typically through forest inventories), and calculate net emissions reductions and removals. Third-party verification bodies audit project monitoring reports against these requirements before credits are issued.
Key Takeaways
- 1REDD+ generates avoidance credits by protecting forests that would otherwise be deforested; it is the largest single category in the VCM by volume but has faced scrutiny over baseline over-crediting
- 2ARR generates removal credits by establishing new forest cover and is methodologically more straightforward than REDD+ but requires long project timelines
- 3IFM generates a blend of avoidance and removal credits by changing harvest practices in existing managed forests
- 4All NbS projects carry permanence risk; the VCS AFOLU buffer pool provides insurance against reversals, but sustained climate-driven losses (fire, drought) test its limits
- 5Leakage - the displacement of deforestation to unprotected areas - must be quantified and deducted from gross credits under VCS methodology