Deferred Harvest on Smallholder Lands

This Module provides the requirements and procedures for the calculation of net carbon dioxide equivalent (CO₂e) removal from the atmosphere through improved forest management (IFM) practices implemented by small forest landowners.

Small forest landowners represent a significant portion of the United States' forest ownership, controlling approximately 36% of total forestland¹. These landowners can substantially contribute to climate change mitigation through IFM practices. However, small landowners face disproportionate barriers to participating in carbon markets due to high transaction costs, complex verification requirements, and limited technical resources.

This Module addresses these systemic barriers by establishing a comprehensive approach to crediting specifically designed for small landowner participation in carbon markets with a design that incentivizes improved ecological and economic outcomes for small private landowners while leveraging technological innovations to reduce participation barriers. The Module focuses on deferred timber harvest strategies that allow forests to accumulate additional carbon beyond baseline management scenarios while maintaining the economic viability of forest ownership for participating landowners.

Carbon accumulation is quantified through a dynamic matching baseline approach that compares project forests to similar reference forests within the same region, accounting for variations in forest type, management history, and site conditions. This Module ensures accurate quantification of additional carbon benefits while reducing the technical burden on individual landowners through continuous change detection owned by Isometric and the Project Proponent. The Module employs advanced remote sensing technology, including LiDAR-enhanced-enhanced forest inventories, to monitor carbon accumulation with high precision across multiple small properties while maintaining rigorous standards for measurement, reporting, and verification and reduced field-based verification costs.

To ensure ecological integrity and biodiversity conservation, this Module requires a high proportion of native species composition within project areas and prohibits enrollment of plantation forests and monoculture systems. The Module includes provisions for invasive species management to enhance ecosystem function and resilience throughout the Crediting Period.

Further, this Module ensures the economic sustainability of project activities for participating landowners through guaranteed revenue sharing arrangements, with landowners receiving a large share of Credit revenue. Contract durations are established based on the biological rotation ages specific to forest types, with a conservative 50-year net-impact deduction to ensure meaningful carbon storage duration.

This Module accounts for the quantification of the gross amount of CO₂e removed via enhanced carbon storage in forest biomass, as well as all cradle-to-grave life-cycle Greenhouse Gas (GHG) emissions associated with the implementation process. This Module is developed to adhere to the requirements of ISO 14064-2: 2019 – Greenhouse Gasses – Part 2: Specification with guidance at the Project level for quantification, monitoring, and reporting of greenhouse gas emission reductions or removal enhancements.

The Module ensures:

• Consistent, accurate procedures are used to measure and monitor forest carbon accumulation through standardized methodologies appropriate for small landowner implementation;
• All net CO₂e removal claims are verified through robust field work and LiDAR-enhanced monitoring systems and third-party validation;
• Forest management practices maintain ecological integrity through native species requirements and biodiversity conservation measures;
• Removals are additional through the use of dynamic matching baselines that account for regional management practices and other guardrails set forth in the Isometric Standard;
• Dynamic baseline methodologies provide accurate quantification of additional carbon benefits through regional reference comparisons;
• Comprehensive risk management through buffer pools and optional insurance mechanisms protects against potential reversals while ensuring transparent Credit delivery;
• Economic viability for small landowners through guaranteed revenue sharing and appropriate contract terms; and
• Technology-enabled monitoring reduces transaction costs while maintaining high standards for carbon accounting and environmental integrity.

Throughout this Module, the use of "must" indicates a requirement, whereas "should" indicates a recommendation.

This Module relies on and is intended to be compliant with the following standards and protocols:

• The Isometric Standard
• Improved Forest Management v1.0, Isometric
• ISO 14064-2: 2019 - Greenhouse Gases - Part 2: Specification with guidance at the project level for quantification, monitoring, and reporting of greenhouse gas emission reductions or removal enhancements

Additional reference standards that inform the requirements and overall practices incorporated in this Module include:

• ISO 14064-3: 2019 - Greenhouse Gases - Part 3: Specification with Guidance for the verification and validation of greenhouse gas statements
• ISO 14040: 2006 - Environmental Management - Lifecycle Assessment - Principles & Framework
• ISO 14044: 2006 - Environmental Management - Lifecycle Assessment - Requirements & Guidelines

Additional principles that were considered in the development of this Module and aligned with, where feasible, include:

• The Core Carbon Principles of The Integrity Council for the Voluntary Carbon Market, v1.1, ICVCM, 2024
• Criteria for High-Quality Carbon Dioxide Removal, Carbon Direct & Microsoft, 2025

This Module was developed based on the current state of the art, publicly available science regarding IFM activities and long-term monitoring of forest carbon projects. This Module aims to be scientifically stringent and robust. We recognize that some requirements may exceed the status quo in the market and that there are numerous opportunities to improve the rigor of this Module as new approaches and techniques enter the Voluntary Carbon Market.

Additionally, this Module will be reviewed when there is an update to published scientific literature, government policies, or legal requirements which would affect net CO₂e removal quantification or the monitoring guidelines outlined in this Module, or at a minimum of every 2 years.

In addition to the requirements outlined in Section 4 of the Improved Forest Management Protocol, Projects are subject to the following applicability requirements, which must be demonstrated in the Project Design Document.

In order to maintain ecological integrity and ecosystem function, demonstrate additionality, and ensure trust and transparency, it is incumbent upon Projects to adhere to the requirements below, which must be demonstrated and reported in the Project Design Document.

Given the nature of this Module, it is anticipated that a Project, facilitated by the Project Proponent, may enroll many smallholder landowners within a Project. To ensure accurate carbon sequestration claims and facilitate Validation and Verification, this Module requires that a Project be registered for a singular or grouped site(s) — sets of land parcels subject to similar bioclimatic, regulatory, and geographic conditions.

Sites must consist of land parcels — discrete areas of land as defined by town, county, or regional tax maps. Contiguous sites or sites within 10 kilometers of each other may be grouped into a single site. Large, discontinuous sites more than 10 kilometers apart from one another must be enrolled as separate sites. Each site within a Project must independently meet all eligibility criteria. Carbon quantification, as set out in Section 8.1, will be calculated at the site level. The Project Proponent(s) and landowner(s) must adhere to the following additional requirements for parcel and site enrollment:

• All sites must be greater than 10 hectares.
• All parcels must have road access.
  • Exceptions to this rule apply under extenuating circumstances — such as the presence of an easement or prior commercial harvest history — and can only be claimed after consultation with Isometric.

To ensure the credibility of the climate impact of the Project activities — and Credits — non-additional areas of the Project must be excluded, as set out by various requirements in Section 4.1 of the Improved Forest Management Protocol and Sections 4.1.2 of this Module.

It is vital to the integrity of the Project that no other areas within each parcel may be excluded from project activities. Landowners participating in the Project must enroll all eligible areas of a parcel. This requirement prevents the selective enrollment of areas that are less desirable for harvest. Land can only be excluded for reasons stated within this Module or the Improved Forest Management Protocol, and these excluded areas must meet be documented within the Project Design Document with sufficient justification of the legal, financial, or operational restrictions on harvest and spatially mapped.

For the purposes of this Module, Parcel Classes will be used for dynamic baselining and carbon quantification — i.e., distributed reference regions used as a point of comparison between behaviors observed in a site and those observed in areas with similar landowners (Figure 1).

Figure 1. Example parcel class distribution within a Project site.

The Project Proponent must generate between 10 and 50 Parcel Classes for the Project by clustering parcels in the ecoregion(s) of the country of the site(s) into groupings with shared socio-economic, topographic, bioclimatic, historical, and structural attributes in relation to the forest. The Project Proponent, where possible, must incorporate the attributes found in Table 1 into its clustering approach.

Table 1. Parcel Classification Clustering Attributes

Project activities must demonstrate additionality by accounting for site-specific constraints that limit harvesting feasibility under baseline conditions. If ecological and site conditions would render harvesting unlikely under baseline conditions, these areas within the Project Boundary cannot be claimed as additional and must be excluded from the Project Boundary. Soil saturation, permanent water bodies, slope gradients, and proximity to dwellings and other structures create natural and regulatory limitations on small landholder deferred harvesting activities that must be evaluated when determining eligible project areas.

Project Proponents must identify and exclude from Crediting any areas within the Project Boundary where physical or regulatory constraints make harvesting highly unlikely under baseline management scenarios.

Historically, harvesting operations in waterlogged soils occurred primarily during periods of prolonged freezing temperatures, which provided ground stability for heavy timber equipment. Climate change has reduced the predictability and duration of these freezing periods, particularly in temperate and polar regions, making winter harvesting increasingly unreliable. Consequently, harvest avoidance in these soil types does not constitute additional management activity beyond what would occur under baseline conditions.

Project Proponents must identify and exclude from Crediting any areas within the Project Boundary with soils classified as "very poorly drained" or "inundated" according to the U.S. Soil Taxonomy classification system, or similarly classified soils in equivalent authoritative sources if a Project occurs outside of the United States of America.

• Exceptions to this rule can be made if the Project Proponent demonstrates all requirements in Section 4.1.2.1.1 below.

Project Proponents may include areas with soils classified as "very poorly drained" or "inundated" within the Project Boundary where evidence demonstrates that baseline harvesting operations remain economically viable despite soil drainage limitations.

Areas with waterlogged soils may be included when the Project Proponent demonstrates:

• Baseline harvesting activities in the region commonly occur during predictable seasonal windows when soil conditions permit equipment access, as evidenced by regional timber market data, harvesting permits, or forestry operation records covering a minimum of the prior 10 years;
• Specialized harvesting equipment or techniques (such as winter harvesting, low ground-pressure machinery, or helicopter logging) are established practice in the region for similar soil conditions, demonstrated through equipment rental availability, contractor specialization, or documented use in comparable forest stands; and
• The proposed IFM activities constitute a measurable departure from baseline management that would otherwise occur despite drainage constraints.

To include these areas, the Project must demonstrate additionality of these waterlogged soils through financial analysis showing that baseline harvesting remains economically feasible despite drainage-related operational constraints, and that the carbon revenue represents a necessary incentive for the proposed management changes.

Project Proponents must identify and exclude from Crediting any areas within the Project Boundary that fall within management buffers around permanent water bodies as defined by applicable governmental regulations or voluntary Best Management Practices (see Appendix C of the Improved Forest Management Protocol).

• Project Proponents must provide documentation of applicable governmental regulations and BMPs governing management buffers around water bodies, along with mapping of permanent water bodies and associated buffer zones within the Project Boundary.

Project Proponents must provide evidence of common harvesting practices and equipment availability within the relevant wood basket to demonstrate whether steep-slope operations are feasible under baseline management scenarios. This evidence must include a spatially-explicit topographic analysis of slope gradients within the Project Boundary and a regional assessment of harvesting capabilities on steep terrain.

• Project Proponents must document the selection of the relevant wood basket, and should ascertain the relevant wood basket by examining governmental, regulatory, or industry databases or identifying the regional catchment of the timber product(s) of their harvest.

Project Proponents must exclude from crediting calculations areas with sustained slopes exceeding 30% over 30 meters in regions where specialized steep-slope harvesting equipment is not commonly deployed.

• The U.S. Forest Service has found that harvest equipment encounters significant limitations on slopes of 25% to 35%, with severe constraints on slopes exceeding 35%. Areas with sustained slopes above these thresholds represent natural barriers to conventional harvesting operations.

Research on non-industrial private forest owner preferences demonstrates that the majority of forest owners will not permit harvesting activities in the immediate vicinity of residential dwellings and other permanent structures². Additionally, regulations or BMPs may prohibit harvesting within a certain proximity of built structures.

Project Proponents must exclude from crediting calculations any areas within 50 feet of permanent structures, or within larger buffers if required by applicable regulations or BMPs (see Appendix C of the Improved Forest Management Protocol).

• To meet this requirement, Project Proponents must include a spatially-explicit vector-based map of all permanent structures within and adjacent to the Project Boundary, along with documentation of any applicable governmental buffer requirements which would prohibit harvesting around dwellings and structures.

Project Proponents must demonstrate that landowners — who have owned the land for more than 5 years — enrolling into the Project do not possess merchantable stocking significantly above the regional average of the Parcel Class. Such stocks of merchantable carbon would indicate a pre-existing intent to conserve or defer harvest in violation of the requirements set out in Section 7.7 Additionality of the Improved Forest Management Protocol.

The Project Proponent must report the initial carbon stock, $M_{AGB}(t_0)$, of each parcel eligible for enrollment — e.g., initial standing carbon stock value — through a field inventory or with LiDAR according to one of the following Capture & Conversion Modules:

The Project Proponent must then develop and report growth curves for each Parcel Class, which describe the average forest growth trajectory.

Using historical disturbance history over the past 10 years, the Project Proponent must then determine and report the average age (and standard deviation) of harvest within each Parcel Class.

• To meet this requirement, the Project Proponent should use the Hansen Global Forest Change Product

The Project Proponent must then document and plot the reported volume or carbon stock of each parcel against the appropriate Parcel Class growth curve, thereby deriving the current stand age of the parcel (Figure 2). If a parcel’s volume or carbon stocking exceeds one standard deviation of that of the average harvest date plus 10 years — to allow for growth into later size-classes — it shall be deemed ineligible for Credits under this Module and removed from the Project.

Figure 2. A growth trajectory of properties within the site’s Parcel Class. (a) The average date and stocking level at harvest within the Parcel Class. (b) Bars surrounding point (a) refer to one standard deviation above and below the average harvest date. (c) The volume-limit at which sites are not eligible for enrollment, determined by taking one standard deviation above the mean, plus 10 years.

Under deferred harvest, the planting of new trees cannot be the primary method to achieve forest cover. Project Proponents must limit new planting only to fill in gaps in existing patches of degraded forests or to regenerate small areas — less than 0.5 hectares — of otherwise forested land.

• The Project Proponent must disclose this planting, as well as the justification for it, within the PDD for initial Validation and subsequent Verifications if any new planting has occurred, and follow all biodiversity requirements as set forth in Section 6.4 of the Improved Forest Management Protocol.

The length of the Crediting Period of the Project shall be determined by the cumulative temporal maximum of the contract lengths of the enrolled landowner(s) and their site(s) or 20 years, whichever is longer. The contract length for parcels enrolled in the Project is determined by the biological and economic trajectory of the forest stand, and set by an assessment of key forest characteristics measured using this Module’s approved remote sensing technologies, ideally LiDAR. These contracts must meet the requirements set forth in Section 5.1 of the Improved Forest Management Protocol.

Project Proponents must assess three critical parameters — current forest size, estimated biological rotation age, and current stand age — to determine contract lengths for enrolled landowners.

The initial contract length for each enrolled landowner, Contract Lengthlandowner, must be calculated using the following equation that takes these parameters into account:

$$Contract\ Length_{landowner} = (\bar{RA} + RA_{SD} + EP) - CSA$$

(Equation 1)

Where:

• $\bar{RA}$ is the mean rotation age of the parcel as determined in Section 4.1.3.1
• $RA_{SD}$ is the standard deviation of the rotation age of the parcel as determined in Section Section 4.1.3.1 Quantification of Merchantable Stock
• $EP$ is the extension period, which is set at $\frac{1}{6}$ of $\bar{RA}$
• $CSA$ is the current stand age of the parcel, as determined in Section 4.1.3.1

The Crediting Period will commence either when the Project Proponent commences activities on a site or on the date of the first enrolled landowner contract signature within the Project, with project activities required to commence immediately. No Credits shall be issued for activities that occurred prior to the contract signature date.

Projects seeking to extend the initial Crediting period must demonstrate continued additionality in line with all requirements set forth in this Module, the Improved Forest Management Protocol, and the Isometric Standard.

The first Reporting Period shall end at a date set by the Project Proponent and approved by Isometric. This first Reporting Period must occur within 5 years of the initiation of the Crediting Period.

As Projects enroll any additional landowner(s), the parcel(s) from the newly enrolled contract(s), i, must take a deduction of Credits based on the time between the date of enrollment and the end of the Reporting Period according to the following Equation 2:

$$ARPF_i= \frac{Days\space to\space end\space of\space Reporting\space Period}{Total\space Days\space of\space Reporting\space Period}$$

(Equation 2)

Where $ARPF_i$ is the Adjusted Reporting Period Factor discount rate applied in Equation 7 to the calculation of CO₂e stored for the parcel(s) under each individual contract, $i$, weighted to ensure only growth since contract initiation is included in the Credit issuance for the Reporting Period (see Section 8.1).

In addition to the requirements set forth in Section 6.4 of the Improved Forest Management Protocol, Projects must not resemble commercial or monoculture plantations.

• In cases where a species naturally grows in monoculture within the Project region or there is scientific evidence for a single dominant species during natural succession, Project Proponents may proceed with monoculture cultivation of this species in consultation with Isometric as outlined in Section 6.4: Safeguarding of Biodiversity.

While a forest management plan is not required for landowner enrollment into the Project, Project Proponents should work with enrolled landowner(s) to develop parcel- and site-specific plans. Project Proponents should facilitate expert forester consultation with enrolled landowners as part of enrollment into the Project, and disclose any such past or planned activity in the Project Design Document.

Certain forest management activities must be disclosed by the Project Proponent, such as Stand Improvement Activities and Harvesting Plans. These activities are subject to the requirements set forth by Isometric in this Module, the Improved Forest Management Protocol (see Section 6.5), and the Isometric Standard.

Enrolled landowners may engage in Isometric-approved stand-improving activities in consultation with the Project Proponent. These activities must follow specific restrictions set initially by the Project Proponent and approved in consultation with Isometric to ensure that the volume of harvested wood does not exceed the volume of issued Credits.

• The Project Proponent must disclose all planned stand-improvement activities in the Project Design Document prior to Validation and at each subsequent Verification, and must inform Isometric of any changes to these plans immediately.

Stand-improving activities in the first three years of each enrolled site within the Project may reduce initial standing carbon stock value by no more than 15% within the enrolled site. Credits will not be issued until the forest biomass within each site recovers above the Project’s baseline following any stand-improving activities.

To ensure that the Project’s carbon stock does not dip below the levels at which Credits were previously issued — which would trigger a reversal — Project Proponents should work closely with enrolled landowners to plan all non-intervention (i.e., deferred harvest) harvest activities.

Project Proponents must work with enrolled landowners and certified foresters to determine any such anticipated selective harvesting schedule and pre-emptively plan reporting and Verification to ensure Credit issuance occurs when enough carbon has been sequestered to prevent the triggering of an avoidable reversal. This selective harvesting is additionally subject to the following requirements:

• Selective harvesting after the first three years must not reduce the Project’s carbon stock more than 15% below the initial standing carbon stock value (see Section 4.1.3.1).
• Project Proponents should provide guidance on minimum stocking and volume requirements.
• Approved activities include fire fuel load management, pre-commercial thinning, and invasive species control — including pest and disease management.

By providing advanced notice of intended forest management activities, enrolled landowners can assist the Project Proponent in managing the expected issuance of Credits, enabling a greater flexibility in forest management activities and harvesting. Enrolled landowners who intend to harvest or actively manage their forest should disclose these plans with the Project Proponent with enough advance notice to ensure compliance with this Module, the Improved Forest Management Protocol, and the Isometric Standard.

To ensure this compliance, the Project Proponent must describe all harvesting plans for the enrolled site(s) in the PDD. It is anticipated that these will be informed by the forest management plan of each enrolled landowner.

Credits will not be issued until the forest biomass within each site recovers above the Project’s baseline following any selective harvesting.

In addition to any Indigenous Peoples stakeholder engagement and Free, Prior, and Informed Consent (FPIC) process that may be required for the Project as proscribed in Section 6.6 of the Improved Forest Management Protocol, Project Proponents must follow the same stakeholder engagement plan and principles of FPIC described in Section 6.6.1 of the Improved Forest Management Protocol for all enrolled landowners.

It is vital that enrolled landowners understand the contracts they are entering into as part of the Project. As part of this stakeholder engagement and FPIC process, Project Proponents must make publicly available and disclose to enrolled landowner(s), and ensure that these landowner(s) understand the following, during the process:

• Financials, including: revenue sharing arrangement, the anticipated value of the carbon Credits, and the anticipated earnings of the Project.
• Carbon Markets, including: the volatility of the carbon market and understand that the sale of carbon Credits is not guaranteed.
• Project Baselines, including: the concept of dynamic baselines, and the unpredictability of forest growth and loss overtime — Credits may be less than anticipated under ex-ante projections.
• Monitoring, including: that their land is being monitored via satellite imagery, airborne manned flights, and/or unmanned aerial systems (UAS) on as frequent a basis as is required by the Improved Forest Management Protocol and this Module, and that this satellite, manned flight, or UAS derived data — as well as geospatial information related to their parcel and site(s) — will be shared with the public through the Isometric Registry.
  • Geospatial information and other data that must be publicly shared by enrolled landowners includes remote-sensing maps and imagery that document the Project’s forest carbon stocks, structure, and ecological benefits.

Given the inherent economic nature of forest management activities, the impacts of the Project extend beyond enrolled landowner(s) to local economies. Giving these stakeholders early notice of planned changes in timber harvest enables market adaptation and prevents job losses in any local timber-based economy.

Project Proponents must provide enrolled landowners an estimate of the likely change in the volume of their future harvest and, in applicable, any quality changes in their forests during the Project that should also be disclosed to loggers and local resource management agencies to inform broader resource and timber planning.

Project Proponents should also provide similar information to any and all requesting entities/individuals — e.g., municipal authorities, research groups, or reporters.

The Project Proponent or enrolled landowners must notify local authorities and loggers, mills, or other parties with whom the enrolled landowner(s) has existing formal or informal offtake agreements of the contracted change in harvest volume and/or schedule of timber upon enrollment into the Project.

In addition to the requirements set forth in Section 6.6.2 of the Improved Forest Management Protocol, the Project Proponent must disburse a minimum of 40% of the revenues generated from Credits issued under the Project to enrolled landowners.

Revenue sharing percentages should be made public, including percent revenue or Credits divided among each party (e.g., Project Proponent, enrolled landowner(s), insurance provider(s), and other documented parties listed in the PDD).

In order to ensure additionality, the Project Proponent must demonstrate a pre-existing intent to harvest trees within the Project Boundary and prove a demonstrable history of commercial harvesting within the property. These requirements must be robustly evidenced by data of the following types.

• A written attestation that the Project Proponent and/or enrolled landowner(s) intended to harvest or would accept harvest offers during the Crediting Period.
  • All pre-existing forest management plans disclosed in the PDD in accordance with Section 8.1 of this Protocol and, if applicable, those in the IFM intervention Module(s) the Project Proponent is crediting against, must specify a likely or planned harvest during the Crediting Period.
• Historical satellite imagery that clearly shows evidence of large-scale commercial harvesting during the Project Proponent’s and/or landowner’s tenure.
  • This evidence should prioritize high-resolution historical imagery with clear sourcing information and acquisition dates. Preferred sources include:
    • Google Earth Engine,
    • The USDA's NAIP or NHAP programs, and private data providers.
  • In cases where high-resolution imagery is unavailable, Sentinel-2 or Landsat imagery may be used as an alternative, which must be accompanied by spectral analysis showing patterns consistent with harvest activities and a detailed explanation for why high-resolution imagery could not be obtained.

In addition to the requirements set forth in the Improved Forest Management Protocol and the Isometric Standard, Projects which contain parcels and/or sites held in trust or under multiple ownership must provide in the PDD spatial boundary documentation accompanied by appropriate ownership verification and written consent from all parties with legal interest in the property.

The carbon pools within the scope of this Module are aboveground and belowground woody biomass, since they can be quantified with the highest level of accuracy and are able to be effectively monitored over time. Soil carbon is excluded from the calculation of $CO_2e_{Stored, RP}$ due to large uncertainties in quantification approaches and/or relatively small contributions to the total forest carbon pool. For the remainder of the Module, the use of AGB and BGB refers to only the living aboveground and belowground woody biomass, respectively, unless otherwise noted.

This Module requires Projects to account for leakage through the Global Timber Model (GTM), which captures both direct landowner behavioral responses (activity-shifting) and broader market-mediated effects (market leakage) within a unified economic modeling approach. This integration reflects the reality that in improved forest management, activity-shifting behaviors are often driven by the same market signals and economic incentives that drive broader market leakage in response to timber supply restrictions. In this Module, leakage is calculated for distinct species groups for each regional wood basket, which vary by geographic location and forest composition.

Recent scientific literature has highlighted significant challenges in accurately quantifying leakage from forest carbon projects. Studies by Badgley et al. (2021)³, Haya et al. (2023)⁴, and others have found systematic over-crediting in forest carbon offset programs, largely due to inadequate accounting for leakage impacts⁵. Research indicates that traditional approaches to leakage assessment often underestimate both the magnitude and geographic scope of displacement effects.

The complexity of global timber markets means that reduced harvest in one location can trigger responses across multiple regions and through various economic pathways. Market-mediated leakage can occur through price signals that incentivize increased harvesting in distant locations, while activity-shifting often occurs through landowner responses that extend to other land owned by the Project Proponent or enrolled landowners, but not included in the Carbon-crediting project.

This methodology adopts a conservative modeling approach with a minimum 15% leakage deduction, using the Global Timber Model (GTM) to prevent well-documented overcrediting that has resulted from other improved forest management methodologies.

The Global Timber Model (GTM) was conceptualized by Sohngen et al. (1999)⁶, and it seeks to re-balance supply and demand in response to market shocks over decadal time periods for forest-type regions.

The GTM has been adopted for carbon projects through an update led by the University of Maine, in collaboration with The Nature Conservancy and the Global Forest Lab at The Ohio State University 2023 leakage assessment version. This updated GTM estimates how forest carbon projects in aggregate change trade balances regionally and globally, as a result of both direct and indirect leakage.

Isometric will quantify the leakage deduction for each Reporting Period for Projects based on global runs of leakage rates (Equation 3) for forest-type regions using the Global Timber Model (GTM), annualized and weighted by the Project’s basal area. As changes to timber harvest through project activities directly and indirectly impact the balance of supply and demand for decades, and the GTM initiates this predicted response within the same decadal time period as the start of the Crediting Period, the leakage deduction schedule for the percent deduction of a Reporting Period, $L_{project, RP}$ will be set at project initiation, and updated as needed by Isometric with the inclusion of any new site(s).

Further information on how Isometric implements the GTM and determines leakage is set forth in Appendix D, which contains additional information on the technical requirements of model implementation and the data sources used for modeling.

The average leakage rate, LR, for each forest type-region (see Appendix D3) in 10-year time periods is calculated as:

$$LR_{f,r,t} = \rho_t \left[ \frac{(PCS_{project,f,r,t} - PCS_{counterfactual,f,r,t}) - (GCS_{project,f,r,t} - GCS_{counterfactual,f,r,t})}{(PCS_{project,f,r,t} - PCS_{counterfactual,f,r,t})} \right]$$

(Equation 3)

Where:

• $LR_{f,r,t}$ is the average leakage rate per given decade in a forest type-region
• $PCS$ indicates the carbon stock within the Project boundaries
• $GCS$ indicates global forest carbon stock
• $f$ is the forest type
• $r$ is the region
• $t$ is the time period (in decades)
• $\rho$ is the discount rate, conservatively set at 5%

The Project’s leakage for each Reporting Period, $CO_2e_{leakage, RP}$ is then calculated using the following equations:

$$L_{project,t} = \frac{\sum B_{f,r,t} \times LR_{f,r,t}}{B_{project,t}}$$

(Equation 4)

Where:

• $L_{project,t}$ is the Project leakage for a given decade
• $LR_{f,r,t}$ is the average leakage rate per given decade in a forest type-region
• $B_{f,r,t}$ is the basal area in each forest type-region in the Project area
• $B_{project,t}$ is the basal area in the Project area
• $f$ is the forest type
• $r$ is the region
• $t$ is the time period (in decades)

And, $B_{project,t}$ must equal $B_{f,r,t}$

As the GTM outputs leakage estimates on decadal timesteps, Isometric will then annualize the Project leakage, applying a linear interpolation between decadal estimates to derive the leakage deduction for each year within a decade:

$$L_{project, RP} = L_{project, 0} + \frac{t}{10}\left( L_{10}-L_0 \right)$$

(Equation 5)

Where:

• $L_{project, RP}$ is the Project leakage rate for a given Reporting Period, RP
• $L_{project, 0}$ is the Project leakage rate for the first year within a decadal time-step
• $L_0$ is the Project leakage rate for the first year within a decadal time-step
• $L_{10}$ is the Project leakage rate for the last year within a decadal time-step
• $t$ is the year into the decadal time step for the Reporting Period, $RP$

The final leakage deduction for each Reporting Period, $CO_2e_{leakage, RP}$ can then be calculated as a percentage of the sequestered carbon in a Reporting Period, $CO_2e_{Stored, RP}$ (see Section 9.1).

$$CO_2e_{leakage, RP} = L_{project, RP} \times CO_2e_{Stored, RP}$$

(Equation 6)

If the leakage rate, $L_{project, RP}$, is <15%, the minimum annual leakage deduction of 15% will be applied by Isometric. When positive leakage is predicted by a negative leakage rate ($L_{project, RP} < 0$%), it will be subject to the minimum annual leakage deduction of 15%. Positive leakage indicates a model which predicts that restricting supply in the region could increase timber prices, and incentives land to be converted to forest or more considered forest management.

Given the distributed nature of improved forest management projects under this Module, the Project Proponent may have project sites with variable contract lengths for the intervention of deferred harvest and forest management practices, often with multiple enrolled landowners. As described in Section 10.1 Durability, this creates challenges for the permanence claim and issuance of Credits with verifiable additionality.

Projects crediting under this Module must apply the permanence factor, $PF$, calculated in Section 10.1.1 to the stored carbon for each Reporting Period, $RP$, to derive the proper value of $CO_2e_{Stored, RP}$ for Credit issuance under the Improved Forest Management Protocol following Equation 7.

$$CO_2e_{stored,RP} = \sum_{i=1}^{n} ARPF_i \times PF_i \times \left( CO_2 e_{AGB,RP,i} + CO_2 e_{BGB,RP,i} \right)$$

(Equation 7)

Where:

• $CO_2 e_{stored,RP}$ is the total $CO_2$ removed from the atmosphere and stored as organic carbon in living trees for the $RP$, in tonnes of $CO_2e$.
• $CO_2 e_{AGB,RP,i}$ is the total carbon stored in living aboveground woody biomass (AGB) over the $RP$, in tonnes $CO_2e$, for the parcel(s) under each individual contract, $i$.
• $CO_2 e_{BGB,RP,i}$ is the total carbon stored in living belowground woody biomass (BGB) over the $RP$, in tonnes $CO_2e$, for the parcel(s) under each individual contract, $i$.
• $ARPF_i$ is the discount rate applied to the calculation of $CO_2e$ stored for the parcel(s) under each individual contract, $i$ (see Section 5.2).
• $PF_i$ is the discount rate applied to the calculation of $CO_2e$ stored for the parcel(s) under each individual contract, $i$ (see Section 10.1.1).
• $n$ is the number of individual contracts $i$.

To derive $CO_2e_{AGB, RP, i}$ and $CO_2e_{BGB, RP, i}$, Project Proponents must calculate $CO_2e_{AGB, RP}$ and $CO_2e_{BGB, RP}$ for the parcel(s) under each individual contract, $i$, according to the guidance and requirements found in Sections 9.3.2 and 9.3.4 of the Improved Forest Management Protocol, respectively.

Isometric encourages Project Proponents to quantify the total above-ground biomass, $M_{AGB}$, in the project area at time point, $t$, through one of the Capture & Conversion Modules listed in Section 9.3.3 of the Improved Forest Management Protocol.

Alternatively, subject to meeting all the requirements set forth in Section 9.2.1, Projects may elect to quantify $M_{AGB}(t)$ through an alternative growth-disturbance model. Projects electing to use a growth-disturbance model must obtain approval from Isometric prior to use; Isometric will conduct a comprehensive evaluation of the methodology to ensure robust and conservative quantification of biomass. This will include assessing the data sources, model development, validation procedures, and uncertainty analyses. Further details of requirements relevant to particular aspects of the method are discussed in the following corresponding sections.

The total aboveground woody biomass, $M_{AGB}$, at the current timepoint, t, can be derived from LiDAR-enhanced forest inventories that rely on high-resolution environmental, bioclimatic, topographic, and geographical covariates to produce growth and disturbance (loss) models based on forest structural characteristics derived from inventory plots.

To apply the growth-disturbance model described in Equation 8, Projects must meet all of the applicability requirements in Sections 9.2.1.1 and 9.2.1.2.

Under this approach, the Project’s total aboveground woody biomass, $M_{AGB}$, at the current time point, $t$, can be calculated as:

$$M_{AGB,i}(t) = M_{AGB,i}(t_m) + \int_{t_m}^t G_i \, dt + \int_{t_m}^t D_i \, dt$$

(Equation 8)

Where:

• $M_{AGB,i}(t)$ is the total aboveground woody biomass at timepoint $t$ in pixel $i$, removed from the atmosphere and stored as organic carbon in living trees, in tonnes of C.
• $M_{AGB,i}(t_m)$ is the carbon stock of pixel $i$ at year $t_m$, where $t_m$ is the time of the most recent assessment of pixel-level carbon using field surveys or LiDAR (see Section 9.2.1.3).
• $t$ is the current year.
• $G_i$ is the rate of carbon accumulation in pixel $i$, derived from the modeling approach, in tonnes C yr$^{-1}$.
• $D_i$ is the rate of carbon loss associated with disturbance in pixel $i$, derived from the modeling approach, in tonnes C yr$^{-1}$.

LiDAR-enhanced growth models may be used to forecast increases in carbon stocks since the last field survey or LiDAR acquisition, according to Equation 8. Project Proponents must meet all of the following requirements to use any LiDAR-enhanced growth model(s):

• The model(s) must be developed using a national or sub-national forest inventory (NFI) plots with repeat measurements spanning at least 10 years;
• The size of pixel i must be equal to the plot area of the NFI plots;
• Pixel i must be matched once to the most similar NFI plot; and,
• Current pixel i must be matched to a historical NFI plot, with plot re-measurements occurring over a period of time equal to or greater than the number of imputation years.

Absolute change is then imputed on an annual basis for each pixel-plot matches, and those annualized growth estimates are added to the latest LiDAR-derived estimate of the pixel (Equation 8).

Disturbance models may be used to estimate forest carbon loss stocks since the last field survey or LiDAR acquisition, according to Equation 8. Project Proponents must meet all of the following requirements to use any disturbance model(s):

• The model(s) must directly forecast absolute or relative decreases in carbon stock following a disturbance; and
• The model(s) must be parametrized with NFI plot re-measurements or repeat LiDAR acquisitions which capture a sufficiently large sample of disturbance events.

Project Proponents are encouraged to leverage commercial high-resolution imagery, spaceborne multi-spectral imagery (e.g., Sentinel-2), and synthetic-aperture radar, SAR (e.g., ALOS or NISAR) in the development of their disturbance model(s).

In the event of a disturbance, the corresponding carbon stock must then be subtracted from the pixel-value and pixel-plot matches must be remapped for subsequent years (Equation 8).

At the initial enrollment of a parcel, and at various timepoints throughout the Crediting Period, the Project Proponent will collect field-based or LiDAR-derived estimates of carbon stock on the parcel to establish $M_{AGB,i}(t_m)$. Project Proponents must quantify this carbon stock through one of the following two approved Capture & Conversion Modules:

The following section outlines the workflow that Isometric will take for the calculation of $CO_2e_{Counterfactual, RP}$ via a dynamic baseline approach; the Project Proponent is not responsible for carrying out the steps in this section. Project Proponents may suggest areas that could constitute suitable control pixels or features for matching based on their expert knowledge of their unique system. However, the ultimate determination of control pixels will be done by Isometric following the procedure and criteria below.

At Validation, the control plot zone must meet the following eligibility criteria:

• Located in the same country and ecoregion as the Project area;
• Does not lie within protected areas, or within other carbon projects;
• Be subject to the same relevant regulations, government incentives, and programs as the Project area; and
• Biomass, e.g., carbon stock values, and productivity values must be within 10% of those of the Project plots.

If possible, other features should also be matched between the control plot zone and project area, such as:

• Within State/Province boundaries
• Species
• Productivity
• Stocking (i.e., tree size)
• Bioclimatic variables (e.g., temperature and precipitation)
• Topography
• Accessibility
• Wealth/Land value
• Millsheds

Initially, the zone for eligible control plots should be limited to the same state or province, or a 100 km band around the Project area — whichever is smaller. However, if suitable matches (see Section 8.2.3 for matching step) are not found in this zone, additional step-outs in 10 km increments may occur to find appropriate control plots, assuming they meet the criteria above. The final area determined for suitable control plots is hereafter referred to as the Donor Zone.

Once the boundaries of the Donor Zone are determined, Isometric will generate high-resolution (≤30 m) pixel maps representing forest carbon stocks or a suitable proxy for forest carbon stocks. These layers must cover the entire project area and Donor Zone at the same resolution for at least five historical time points relative to the start of the Project. Each historical time point must be separated by at least 1 year.

Isometric will select a suitable proxy that meets the following criteria:

• The proxy must be correlated with AGB throughout the Crediting Period.
• If the proxy saturates in the Project area or Donor Zone during the Crediting Period and becomes insensitive to further carbon gain (e.g., as is the case for many simple optical indices), it will be excluded⁷. Proxies such as canopy height from models which use datasets from multiple types of earth observation (particularly 2D satellite imagery, LiDAR and SAR) are preferred⁸.
• The proxy map product should exclude cloud occlusion, saturation, and other contamination. This may lead to seasonal composite images.
• The proxy should be insensitive to seasonal variability, which may be addressed through taking an annual average to remove the seasonal cycle.
• The proxy should be stable, so that in the absence of carbon change, the proxy value stays the same.
• If an AGB map itself is used instead of a proxy map, then the AGB map product used to generate the dynamic baseline must meet the quality requirements in Section 9.3.3 Calculation of MAGB of the Improved Forest Management Protocol.

Project and control plot pixels will be matched by Isometric at Validation, and these matches will be retained and tracked over the Crediting Period. Project pixels are matched to control plot pixels based on a mix of current and historical time series of environmental, socioeconomic, management, and forest structure data — including the selected forest carbon proxy, $C_{proxy}$, of each pixel — using k-nearest neighbors with replacement, or an alternative justified algorithm. Isometric shall use, at minimum and where possible, the datasets in Table 2 for matching.

Table 2. Dynamic baseline pixel matching Criteria and clustering.

All dynamic remotely sensed variables must be captured within 18 months of each Verification.

Project and control plot pixels will be matched within the same parcel classes (see Section 4.1.1.2). To reduce spatial autocorrelation, a maximum of five control plot pixels are permitted within individual non-project parcels. Additionally, a minimum of one interior plot will be selected for each hectare of project area.

This matching will use, at a minimum, five historical time points capturing at least the five years prior to project initiation. Each project pixel must be matched to a minimum of 5 different control pixels, and the mean of each dataset over the group of control pixels is used — with the mean forest carbon proxy over the group of control pixels derived from the map product created using the procedure described in Section 8.2.2. Multiple project pixels may be matched to the same control pixels.

The baseline correction is calculated using the equation below. The difference between forest carbon stock change is assessed per project-control pixel set. Then, the differences are summed across the Project to determine the cumulative baseline.

$$CO_2e_{Counterfactual, RP} = CO_2e_{Stored, RP}\times \frac{\sum_{i=1}^{n}\frac{\Delta C_{proxy,control,i}}{\Delta C_{proxy,control,i}}}{n}$$

(Equation 8)

Where:

• $CO_2e_{Counterfactual, RP}$ is the total counterfactual CO₂ removed from the atmosphere and stored as organic carbon in living trees in the absence of Project activities for the Reporting Period, in tonnes of CO₂e.
• $i$ denotes each of $n$ total project pixels
• $CO_2e_{Stored, RP}$ is the CO₂e stored for the Reporting Period, as calculated in Section 9.1.
• $\Delta C_{proxy, control, i}$ is the average change in forest carbon proxy over the Reporting Period in the group of control pixels matched to project pixel $i$.
• $\Delta C_{proxy, project, i}$ is the change in forest carbon proxy over the Reporting Period in project pixel $i$.

The $\Delta$ represents the change over a Reporting Period, e.g.,

$$\Delta C_{proxy}=C_{proxy}(t_2)- C_{proxy}(t_1)$$

(Equation 9)

where $t_1$ and $t_2$ are the start and end of the Reporting Period, respectively.

At each Verification, the control pixels are reviewed to determine continued eligibility around similar regulatory regimes within control plots as outlined in Section 8.2.1. In the event that control pixel matches are no longer suitable, replacements will be selected for the impacted project pixels. For example, a change in regulations around IFM projects which leads to variance in the legality of such projects between control and project pixels would lead to rematching of control and project pixels.

The counterfactual carbon storage is then used to calculate a performance benchmark for the Project area, $PB_{RP}$:

$$PB_{RP}= \frac{CO_2e_{Removed, RP}}{CO_2e_{Counterfactual, RP}}$$

(Equation 10)

The performance benchmark, $PB_{RP}$, must be demonstrated to be statistically greater than 1 (inclusive of uncertainty with p < 0.05) to meet the additionality requirement, indicating that there is greater carbon removal with the Project than for the counterfactual scenario.

Isometric will account for uncertainty in the dynamic baseline to obtain a conservative estimate of $CO_2e_{Counterfactual, RP}$ in Equation 8. This will include an evaluation of at least the following sources of uncertainty:

• Uncertainty in the forest carbon proxy maps, due to the uncertainty in data and models used to generate the proxy map;
• Uncertainty in how well the forest carbon proxy represents relative changes in carbon stock between the control and project pixels;
• Variation in the ensemble of control pixel values matched to each project pixel, representing the uncertainty across the ensemble of baseline scenarios therein; and
• Uncertainty in the control pixels matched and if they adequately represent the likely Counterfactual scenario.

$CO_2e_{Emissions, RP}$ is the total GHG emissions associated with a given Reporting Period, RP.

Equations and emissions calculation requirements for $CO_2e_{Emissions, RP}$ are set out in the relevant Protocol and are not repeated in this Module.

As part of $CO_2e_{Emissions, RP}$, $CO_2e_{Leakage, RP}$ must be quantified for the Reporting Period. $CO_2e_{Leakage, RP}$ is quantified following the approach described in Section 8.2.

Any models used under this Protocol which contribute to the quantification of net CDR must be well-validated and skillful for the purpose that they were used for. Proof of model validation can be achieved through either:

• A track record of use in science, industry, or government applications, which is demonstrated through multiple peer-reviewed papers, or proof of usage in a number of previous applications. Furthermore, the model must be relevant to the Project area and tree species (e.g., covers similar ecoregions); or
• Newly developed models without a track record of usage must be validated against reputable data sources, which include quality-controlled in situ measurements and public datasets adhering to FAIR (Findable, Accessible, Interoperable and Reusable) principles⁹). Sufficient model validation data must be provided with the PDD.
• Any models developed or used for the purpose of AGB quantification using the methodology described in Section 9.2.1 must be evaluated and approved by Isometric as part of the required comprehensive assessment of the approach prior to use.

Harvest deferral activities require customized contract commitments to achieve additionality. Contract durations must be calibrated to avoid the issuance of Credits for Projects where similar forest growth would have occurred under baseline conditions. Often, short-term harvest deferrals result in the crediting of young forest growth that would have occurred within the existing forest management practice.

• For example, take the case where a 10-year-old forest operating on a 40-year rotation cycle enters a 30-year deferral contract, no additional carbon storage occurs beyond baseline projections, as the trees were already expected to grow for this duration under existing management practices.

Conversely, contract periods that significantly exceed the original harvest timeline may fail to demonstrate financial additionality. Extended commitments may only attract landowners who have already incorporated conservation objectives independent of carbon market incentives into their financial and forest management plans.

• For example, take the case where a 30-year-old forest on a 40-year rotation enters a 30-year deferral contract, this suggests the Project Proponent may have pursued conservation activities regardless of carbon credit revenue — as the new extended harvest would require either additional outside revenue beyond carbon finance or belies pre-meditated agenda of conservation.

This Module’s additionality framework therefore requires customized contract durations that defer planned harvest activities and incentivize enhanced forest management practices in line with the additionality requirements set forth in the Isometric Standard and Improved Forest Management Protocol.

Within aggregated smallholder sites, individual parcels must demonstrate varying deferral periods aligned with their specific baseline management scenarios. This variability in contract lengths, ranging from 20 to 50 years within a single Project, presents challenges for the application of a uniform durability claim and for Credit standardization for IFM through deferred harvest.

To ensure consistent durability across all Credits issued under this Module, a conservative discount factor will be applied to normalize permanence to a standardized 50-year time horizon. Credits issued from contracts with durations shorter than 50 years will receive proportional deductions through this approach to meet a 50-year durability claim.

• For example, a 25-year contract will receive a permanence factor, PF, of 0.5, meaning 50% of calculated removals will be Credited. This approach establishes uniform 50-year durability across all parcels within the Project while maintaining minimum contract length requirements to ensure additionality.

The permanence factor, PF, is calculated as the contract length divided by 50 years.

$$PF_i = \frac{contract\ length_i}{50}$$

(Equation 11)

Where:

• $PF$ is the discount rate applied to the calculation of CO₂e stored in Section 9.3.1 of the Improved Forest Management Protocol for the parcel(s) under each individual contract, $i$.
• $contract\ length_i$ is the length of each individual contract, $i$, in years.

This durability framework ensures that all Credits achieve equivalent permanence regardless of individual contract variations, while maintaining scientific rigor and conservative assessment consistent with the Isometric Standard and Improved Forest Management Protocol requirements for additionality and long-term carbon removal and storage.

The Risk Assessment is used to assess the overall delivery and storage risk associated with improved forest management through deferred harvest and may inform the Buffer Pool contribution during Credit delivery (see Section 10.4 of the Improved Forest Management Protocol). The assessment must first be filled in by the Project Proponent and must be validated by a VVB. During project Validation, discrepancies between the Project Proponent’s self reported score and VVB may result in monitoring or risk mitigation activities, or project ineligibility. Eligible projects must have an initial risk score ≤ 16 and initial risk category scores at or below the following thresholds:

• Project Proponent Capacity Risk ≤ 7
• Financial Viability Risk ≤ 7
• Social Governance Risk ≤ 9
• Disturbance Risk ≤ 14

All risk categories shall have a minimum score of 0, regardless of the outcome of the Risk Assessment.

If Project Proponents choose to forgo a flat 20% Buffer Pool contribution (see Section 10.4.1 of the Improved Forest Management Protocol), this Risk Assessment will inform Buffer Pool contributions for the Project according to the process outlined in Appendix C for each Reporting Period and in accordance with the requirements in Section 10.4.1 of the Improved Forest Management Protocol.

• After each new Risk Assessment evaluation, Isometric will update the required percentage of newly issued Credits that must be contributed to the Buffer Pool by the Project. Isometric encourages Project Proponents to continuously monitor, mitigate, and reduce risks.

Table A1. Risk Assessment for Improved Forest Management projects applying deferred harvest on smallholder land, with the score to be filled out for each question.

The following section outlines how Isometric calculates the indicator scores for climate-related extreme weather disturbance risks to carbon permanence within a project’s region (Figure B1). Project Proponents should use Table B1 to lookup the Isometric-calculated values for their project's region and include those scores in their Risk Assessment (see Appendix A).

Extreme weather risks are assessed via two indicators: a temperature indicator (extreme heat and/or cold) and a hydrologic indicator (flooding and/or drought). Each indicator includes both historical data (1961-2015) and projected future extreme events. Historical data indicate the likelihood of extreme events based on past climate patterns, e.g., projects in regions with extended dry periods are expected to experience increased water stress as part of their typical climate. Climate model projections describe how changing climate conditions, relative to historical patterns, might present an increased risk of disturbances. Areas where there is a larger shift towards extreme conditions under future climate relative to their historical baseline have a greater disturbance risk (e.g., drier conditions relative to historical averages increases risk for drought-driven mortality).

To calculate the scores in Table B1, Isometric uses values from the Intergovernmental Panel on Climate Change AR6 report¹⁰. The temperature indicator, IndicatorTemperature, is calculated using data describing the annual number of frost days (FD, minimum temperature below 0°C) and annual number of days with a maximum temperature above 40°C (TX40) to capture extreme cold and extreme heat risks, respectively. The hydrologic indicator, IndicatorHydrological, is calculated using data describing the maximum 5-day precipitation (RX5Day) and annual maximum number of consecutive dry days (CDD) to capture risks of flooding and drought, respectively. All values come from the CMIP6 climate models. Future projections use the SSP2-4.5 medium term (2041-2060) scenario and are assessed as the change in value relative to a historical baseline (1961-1990).

For each indicator subcomponent, the region’s terrestrial median value is compared with the global terrestrial distribution of the same variable (Table B2). To convert the regional value into a subscore, regional values below the global 75th percentile are considered Low Risk, regional values equal to or greater than the global 75th percentile but below the 90th percentile are Medium Risk, and any regional values equal to or greater than the global 90th percentile are High Risk. Low Risks are given a subscore of 0, Medium Risks are 0.25, and High Risks are 0.5. The overall score for each of the indicators is calculated by summing the corresponding subscores, as described below:

Projected change in the number of frost days is not included as a subcomponent since it is projected that they will decline under future climate across the globe, representing a low risk of future extreme cold events.

Figure B1. Map and lookup table for IPCC regional codes

Table B1. Regional Lookup Table of Disturbance Risk (This table currently displays a subset of regions as an example and will be comprehensive after public review)

Table B2. Global Benchmark Values for Extreme Weather Risks.

By default, Projects are subject to a flat 20% Buffer Pool contribution as outlined in Section 10.4.1 of the Improved Forest Management Protocol. Project Proponents may opt to calculate a project-specific Buffer Pool contribution based on the outputs of their Risk Assessment (Appendix A) for each Reporting Period.

The following steps are used to convert the outputs of the Risk Assessment into a Buffer Pool contribution:

1. Sum the total score for each risk category in Table A1.
2. Map the risk score for each risk category into a Buffer Pool contribution using Table C1.
3. Sum the Buffer Pool contribution for each risk category to obtain the total Buffer Pool contribution.

Table C1. Risk score to Buffer Pool contribution conversion for each risk category.

The Buffer Pool contribution for each risk category is determined using a sigmoid function described by Equation C1. The Buffer Pool contribution for each risk category ranges from 2% to 8%.

$$BP_{risk}=\frac{L}{1+e^{-k(x-x_0)}}+2$$

(Equation C1)

Where:

• $BP_{risk}$ is the Buffer Pool contribution for a given risk category.
• $L=6$ is the range of Buffer Pool contributions within each risk category (2% to 8%).
• $k = \frac{10}{cutoff -1}$ is the steepness parameter of the sigmoid curve and determines how quickly the function transitions between its minimum and maximum values.
• $x_0 = \frac{cutoff}{2}$ is the midpoint of the sigmoid curve.
• $x$ is the risk score for a given risk category.
• $cutoff$ is the value at which the Project fails the Risk Assessment, noted in Appendix A.

The sigmoid function, Equation C1, applied to each risk category can also be visualized in Figure C1.

Figure C1. Buffer Pool contribution based on risk score for each risk category.

The Project has completed the Risk Assessment and obtained the following risk scores in a Reporting Period:

• Project Proponent Capacity Risk = 2
• Financial Viability Risk = 4
• Social Governance Risk = 3
• Disturbance Risk = 3

Mapping these risk scores to Table C1, the total Buffer Pool contribution for the Project is:

2.7% + 6.0% + 3.1% + 2.5% = 14.3%

This appendix provides detailed information on how Isometric implements the Global Timber Model (GTM) for leakage assessment in this Module, including technical requirements, scalar values, and forest type-regional classifications used in the modeling process.

Isometric implements the Global Timber Model (GTM) to quantify leakage deductions for each Reporting Period based on global runs of leakage rates for forest-type regions, annualized and weighted by the Project's basal area (see Section 7.2). Currently, Isometric uses a 2023 version of the GTM published by Dr. Adam Daigneault at the University of Maine and collaborators from The Nature Conservancy.

Isometric currently applies the scalar values and parameters found below in Table D1 in its GTM implementation.

Table D1. Summary Table of Key Scalars in GTM for Protocol Leakage Assessment

To date, the GTM uses a global implementation rate representing the proportion of all forest land globally available for harvest that is enrolled in forest carbon projects. Isometric determines harvest eligibility by accessibility, i.e., all accessible forests are eligible. However, Isometric has excluded forest area reported in the FAO Forest Resources Assessment as "protected".

As of the certification of this Module, the total global area of land enrolled in forest carbon projects is 77.599 Mha, based on an analysis of all forest-based carbon projects recorded by Renoster as of June 3, 2024. This represents approximately 8% of the total available forest area, which is 982.5 Mha as of the certification of this Module.

Research by Haya et al. (2023)^{4, 11}, Stapp et al. (2023)¹², and others suggests that the majority of forest carbon projects greatly overestimate emission reductions and that enrollment in carbon projects has historically been unlikely to result in near-term reductions in harvesting or deforestation. Thus, Isometric applies a conservative estimate that the actual amount of carbon project land on which all harvest is prevented is 50% of the calculated implementation rate of 8%. Thus, Isometric applies a global carbon project implementation rate of 4% (Table D1).

Isometric will match the species present in the Project area to a GTM forest type and region (Tables D2, D3). The forest types are based on the 2010 United Nations Food and Agriculture Organization (UN FAO) Global Ecological Zones (GEZs), with enhanced resolution for United States forest types based on USFS FIA Regional Groupings. If species or genus are not explicitly listed in the GTM forest types, consult authoritative sources including local foresters and wood-database.com to determine similar commercial use and ecological characteristics for matching.

Table D2. Forest type and region classification table for the United States

Table D3. Forest type and region classification table for Countries and regions excluding the United States.

Isometric would like to thank Renoster, for their extensive feedback during this Module's development.

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7. Gao, S., Zhong, R., Yan, K., Ma, X., Chen, X., Pu, J., ... & Myneni, R. B. (2023). Evaluating the saturation effect of vegetation indices in forests using 3D radiative transfer simulations and satellite observations. Remote Sensing of Environment, 295, 113665. https://doi.org/10.1016/j.rse.2023.113665 ↩

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