ACR IFM Methodology for Small Non-Industrial Private Forestlands
This is a new issue of newsletter from Deloitte Tohmatsu Sustainacraft.
Methodology Updates is a series covering carbon and biodiversity credit methodologies. This article examines American Carbon Registry's Improved Forest Management Methodology for Small Non-Industrial Private Forestlands, which recently issued its first credits to a project that oversees an aggregation of private forests in the Southeastern United States.
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Author: Nick Lau (Applied Scientist)
Summary
On August 27, 2026, American Carbon Registry (ACR) issued the first credits under its Improved Forest Management (IFM) methodology for Small Non-Industrial Private Forestlands. The issuance came from LandYield Small Scale IFM Project I, an aggregation of private forests in the Southeastern United States. The registry record reports 39153 issued credits, bringing attention to how this ACR methodology credits harvest deferral across many small ownerships.
Small non-industrial forests pose a practical scale challenge for IFM crediting. Inventory, validation and monitoring costs can be difficult to support at the individual-property level, while crediting still depends on credible estimates of the carbon on enrolled land. ACR addresses this through a shared project structure for enrollment and administration, combined with plot- and strata-based accounting for quantification. Initial stocks are estimated from either project plots or regional U.S. Forest Service Forest Inventory and Analysis (FIA) plots, then projected through a growth-and-yield model under deferred harvest and a financially feasible baseline harvest schedule. Crediting starts from the difference between those trajectories, after adjustments for leakage and uncertainty.
The methodology therefore reduces some of the transaction costs of working with many small forest owners without replacing project-specific carbon accounting. Its distinctive feature is the combination of shared administration and regional inventory options with a modeled economic harvest baseline. This differs from approaches such as Verra VM0045 and Isometric’s smallholder IFM module, which rely more heavily on matched non-project forests to establish the counterfactual.
1. Inrtoduction: ACR Small Non-Industrial Private Forestlands Methodology
The first issuance under ACR’s Small Non-Industrial Private Forestlands methodology provides a useful entry point for examining the methodology itself. Rather than reviewing the LandYield project in detail, this article focuses on the accounting framework behind it: how small forest ownerships are organized, how starting carbon stocks are estimated, how the no-project harvest baseline is modeled, and how credited carbon is monitored over time.
1.1 Scope and Project Structure
The ACR methodology applies to U.S. non-industrial private forest sites with 40 to 5000 forested acres (16 to 2023 hectares). The credited activity is harvest deferral, retaining timber and its carbon in the forest while further growth accumulates. Owners must hold or control the relevant timber and carbon rights, and the land must be legally available for harvest at enrollment.
The methodology is specific to aggregation or the Programmatic Development Approach (PDA), allowing multiple eligible sites to be administered under a shared project framework. Participating sites must enroll within five years of the project start date. Carbon accounting still distinguishes materially different forest conditions through inventory design, stratification and baseline modeling. Allowed removals remain possible under specified conditions, with their carbon effects reflected in the accounting.
1.2 Additionality and the Project Term
Harvest deferral must exceed what the law already requires. ACR's practice-based performance standard then treats deferral over the crediting period as additional for eligible owners without requiring a separate financial-additionality analysis for each property.
The initial crediting period lasts 20 years, whereas the overarching project's minimum term is 40 years from its start date. The 40-year requirement is an MRV and stock-maintenance commitment. A site may renew crediting under updated rules and a reassessed baseline; otherwise it stops earning credits and remains part of the monitored stock supporting previous issuance.
2. Forest Inventory and Baseline Modeling
The overall carbon accounting framework can be described in 3 main steps: 1) plots estimate starting carbon stocks; 2) stratification assigns those estimates to mapped project acres; 3) the growth model carries the same forest forward under project management and a no-project harvest schedule.
2.1 Estimation of initial carbon stock: Two Sources of Forest Plots
Forest plots provide the measured tree data behind the carbon estimate. Species, diameter and related attributes are converted into carbon stocks and initialize the growth model. ACR allows two routes for obtaining those plot data, namely project-level inventory and regional inventory, with a clear trade-off between project-specific measurement and regional representativeness.
Under a project-level inventory, statistically unbiased plots are established within the enrolled boundary. Their measurements directly sample the participating forest, and the resulting tree lists or stand summaries become inputs to the growth model. This route gives project-specific evidence of initial stocking but requires field inventory work across the enrolled area.
Alternatively, the regional inventory route uses plots from the U.S. Forest Service Forest Inventory and Analysis (FIA) program. These plots sample the wider region and may not fall on enrolled properties, so their tree data represent comparable forest conditions within the project. At least 30 FIA plots overall and four per stratum are required. This reduces fieldwork across small owners, while placing greater importance on whether the FIA sample and stratification are representative of the enrolled forest.
The main carbon pools are live-tree biomass and harvested wood products. Dead wood can matter depending on the selected pool treatment, while litter and soil organic carbon are excluded as de minimis changes. Harvested wood products matter because baseline harvesting would move part of the carbon into products and landfills; standing live trees alone would miss part of the comparison.
2.2 Stratification
Stratification is the link between sampled trees and project acres. ACR groups mapped areas into strata using features such as forest type, age or size class, density, site productivity and management regime. For the regional route, FIA plots must be assigned through an unbiased, spatially explicit stratification with at least 30 plots overall and four plots per stratum. Project-level inventories may also use strata where forest conditions vary enough that a pooled estimate would reduce precision.
2.3 Projecting Growth and Harvest
The same starting forest is then projected forward under different management assumptions. A growth-and-yield model uses the plot-derived stand condition, along with site and regional parameters, to simulate forest growth, mortality, regeneration and harvest. This is the step where inventory becomes a time series rather than a one-time stock estimate.
The same model and stock equations are used for the project and baseline paths. This keeps the growth assumptions consistent, so the credited difference comes from forest management. The baseline applies an economically selected harvest schedule, while the project path reflects deferred harvest and any allowed removals. Projected volumes or biomass are converted into carbon and CO2 equivalent for each stratum, weighted across the mapped area, and updated through monitoring.
The model must be peer reviewed, appropriate to the region or ecosystem, parameterized for its forest conditions, and approved by ACR. Same pre-approved models include Forest Vegetation Simulator and FIBER developed by USDA Forest Service. The specific model can vary, but the proponent must document the plot inputs, model variant, calibration, management settings and outputs so that the projected growth and harvest can be examined.
2.4 NPV-Maximizing Baseline
ACR's baseline is a legally permissible, regionally appropriate harvest schedule that seeks to maximize the net present value (NPV) of timber production over 100 years. NPV converts expected future timber revenues and management costs into present-value terms, allowing the model to compare whether harvesting earlier or waiting for additional growth produces the stronger financial outcome. With ACR's specified 5% discount rate for forest owners, the model weighs earlier receipts against the value of letting stands grow into larger or more valuable timber.
For each feasible schedule, the starting inventory and growth model estimate how much merchantable timber could be harvested. Expected prices by wood-product grade are compared with logging, reforestation, silvicultural, carrying and relevant infrastructure costs. The proponent evaluates a reasonable range of plausible assumptions and selects a conservative, financially feasible schedule with the highest modeled NPV within legal and silvicultural constraints.