Forest methane science
How Forest Methane Uptake Affects the Climate
Trees remove methane, a potent greenhouse gas, from the air through their bark. Researchers measured this uptake only recently. Current forest-carbon methods do not credit it. This page explains how uptake works, how we measure it, and how we estimate its effect on the climate.
How the uptake works
How Microbes Remove Methane Through Tree Bark
Our 2024 Nature study found evidence consistent with microbes consuming atmospheric methane on and within tree woody surfaces. Aerobic methane oxidation uses oxygen and produces carbon dioxide. Researchers are still studying where the organisms responsible for atmospheric uptake live in the tree and how they use methane. Oxygen availability varies within the stem. Soil-derived methane can also travel up trees and leave through the bark. These figures illustrate the atmospheric uptake process that SelvaFlux measures.
The next figure shows a stem in cross-section.
The next figure shows a common pathway for bacterial methane oxidation.
Oxidizing methane to carbon dioxide is a net climate benefit. Methane traps far more heat than carbon dioxide while it is in the air, on the order of 30 times as much over 100 years and roughly 80 times over the first 20, mass for mass. Converting a methane molecule to carbon dioxide leaves a much weaker greenhouse gas, so the net effect is to reduce warming.
Methanotrophs differ in their affinity for methane. Low-affinity types are active only where methane is abundant, as in wetlands and landfills. High-affinity types oxidize methane at its atmospheric concentration, about 2 parts per million, and are the ones responsible for the atmospheric sink.
Across the world’s well-drained soils, methane-oxidizing microbes remove on the order of 30 million tonnes of methane a year. Our Nature 2024 study found that tree bark adds a sink of the same order of magnitude. Genome sequencing in bark has identified organisms with methane-metabolism genes, but their activity depends on the organism and its setting.
Leung and colleagues (2026) also observed hydrogen uptake in Australian wetland tree bark. Scaling their field rates to global woody surface area gave an estimated net hydrogen uptake of 0.6 to 1.6 million tonnes a year. The study’s larger gross estimate of 35 to 55 million tonnes came from laboratory rates. Bark incubations also consumed carbon monoxide; the methane-consumption experiments used elevated methane concentrations.
Stoichiometry, step by step
[H] is a reducing equivalent, carried by NAD(P)H and similar cofactors. The first step uses two. The next three oxidation steps produce six, leaving four for respiration. At the formaldehyde step, some carbon can be used to build cell biomass.
The final figure shows the estimated global distribution.
CH₄ uptake: A. Shenkin (SelvaFlux). Basemap: Google.
To estimate methane uptake for a forest, we need to measure its woody surface area. How we measure that →
Published bark measurements
Forests Remove Methane From the Air
Most efforts to reduce methane warming focus on cutting emissions. Forests also remove methane already in the air. In , we measured uptake at four upland forest sites and scaled the observations to estimate a global sink.
Direct measurements let us estimate the climate effect of this uptake. Forest projects would need an approved methodology before the uptake could be credited.
Methane and near-term warming
Methane Causes Strong Warming Over a Short Period
Methane remains in the atmosphere for about a decade. Removing it reduces warming over the following decades. GWP20 compares the heat-trapping effect of a methane pulse with the same mass of carbon dioxide over 20 years. GWP100 makes that comparison over 100 years.
Why We Use GWP20
Our main calculation estimates methane payments using GWP20. We also show GWP100 for comparison. Google’s September 2026 methane purchase from Terradot uses GWP20 for rice-methane elimination. That agreement is an example of a buyer using GWP20. Tree-methane credits still require an approved method and verified projects. Our GWP20 Q&A explains the agreement and its limits.
Methane accounting
How Three Metrics Describe the Same Methane Uptake
Our warm-tropical reference is 16.8 kg CH₄/ha/year. Each metric expresses the climate effect of that uptake differently. Our payment calculations keep the price per reported unit the same, so the choice of metric changes the estimated income. The trees remove the same amount of methane in each comparison.
Methane removal is expressed in tCO₂e GWP20 per hectare per year. This excludes project deductions and the climate effect of carbon from the removed methane, which we have not estimated.
The same methane uptake is expressed in tCO₂e GWP100 per hectare per year, before project deductions.
The reference calculation uses a rounded warm-tropical uptake rate:
- Physical methane uptake46.7 µg/m²/h × 41,200 m²/ha × 8,760 h/year ≈ 16.85 kg CH₄/ha/yearWe measured uptake of 46.7 µg CH₄/m²/h near 2 m height at Gigante, Panama, in . The woody surface area is the rounded tropical estimate from that study. The model uses 16.8 kg CH₄/ha/year for planning; the displayed inputs give about 16.85 kg.
- Methane uptake expressed with GWP200.0168 t CH₄ × 81.2 = 1.36416 tCO₂e GWP20/ha/yearUsing GWP100 gives 0.0168 × 27 = 0.4536 tCO₂e/ha/year. Using the supplementary table’s factor of 27.9 gives 0.46872.
- GWP* when uptake starts in year 1Years 1 to 20: 1.8144 tCO₂-we/ha/year; after year 20: 0.1134 tCO₂-we/ha/yearThe calculation uses 27 × (4qₜ − 3.75qₜ₋₂₀), where q is annual methane uptake in tonnes, t is the current year and t−20 is 20 years earlier. It assumes zero uptake before the project and full mature-forest uptake from year 1. Cain et al. 2019 describes this approach.
GWP* depends on how uptake changes over time. We use it to describe a possible climate effect. We also test what would happen if buyers paid for GWP* units from the start of a project. Those payments would require buyer and registry acceptance.
The reforestation calculation assumes the woody surface area and methane uptake of a mature forest from year 1. We have not yet measured how uptake develops as restored forests grow. A slower increase would reduce early payments and change the GWP* result over time. SelvaFlux is working to measure that change.
Payment Assumptions Determine the Financial Result
The main calculation assumes the same price per tonne of biomass CO₂ and per tonne of CO₂-equivalent methane removal using GWP20. These are assumed prices; they do not come from tree-methane purchase contracts. A different methane price changes the estimated income. GWP20, GWP100 and GWP* each describe methane differently, so we report them separately and do not add them.
Independent methane studies
Results From Other Research Groups
Our 2024 Nature study measured methane uptake by woody surfaces across upland forests, with stronger uptake in the warm tropics. Independent groups have measured uptake at other sites. Laboratory studies have found methane-oxidizing microbes in bark and wood. Some field studies find that stems release more methane than their surfaces take up. The studies below cover different species, tissues and settings. Wetland experiments provide evidence about microbial processes; they do not establish an upland forest uptake rate.
Methane Uptake Through Tree Stems
These studies measured atmospheric methane uptake by tree stems at individual sites. They do not test a global temperature relationship.
- Jardine et al. 2025, Trees. Three days of chamber measurements on one California cherry tree detected net uptake of atmospheric methane.
- Machacová et al. 2021, New Phytologist. In a well-drained tropical rainforest on Réunion, on volcanic substrate, the stems of six species and their bark cryptogams were net methane sinks during sampling at the start of the rainy season.
Methane Uptake by Tree Foliage
Studies have also measured atmospheric methane uptake by leaves. SelvaFlux does not include foliage in its bark-uptake estimates.
- Sundqvist et al. 2012, Geophysical Research Letters. Branch chambers on four boreal species in central Sweden measured net uptake of atmospheric methane by their shoots and foliage.
- Gorgolewski et al. 2023, Ecosystems. In an upland temperate forest in Ontario, tree foliage was a net daytime methane sink.
The Mechanism: Microbes in Bark and Wood
Independent studies have identified methane-oxidizing microbes in bark and wood.
- Jeffrey et al. 2021, Nature Communications. Methanotrophic bacteria in the bark of paperbark trees cut the methane the trees emit by about 36%, with uptake rising where more of these bacteria live.
- Jeffrey et al. 2021, New Phytologist. Carbon-isotope measurements up the trunk showed about a third of the methane moving through the stem is oxidized on the way.
- Leung et al. 2026, Science. Sequencing across eight Australian tree species found genes for gas metabolism. Incubations of bark from two wetland species confirmed hydrogen and carbon-monoxide consumption, and methane consumption at elevated methane concentrations.
- Putkinen et al. 2021, New Phytologist. Metagenomic sequencing of boreal Norway spruce needles found monooxygenase genes potentially able to consume methane.
Studies That Found Net Methane Emissions
Whether trees take up or emit more methane varies by species and setting. Stem measurements do not by themselves establish the methane balance of the whole tree or forest.
- Epron et al. 2026 (online 2025), Tree Physiology. In a cool-temperate mountain forest, average potential bark methane oxidation was about ten times smaller than measured trunk emissions in the same trees. The authors concluded that the sampled trees were likely a net source.
- Hettwer et al. 2025, Biogeochemistry. In a Maine conifer forest, living stems of spruce, hemlock, and red maple were net methane emitters across the moisture gradient.
- Kasak et al. 2026, Agricultural and Forest Meteorology. In a California blue oak savanna, oak stems were a weak but persistent methane source year-round at all three measured heights, and the ecosystem was a net methane source even though its soils took up methane. Chambers reached 2.7 m up the trunk. The reported mean trunk area was about 6% of mean whole-tree woody surface area. The study did not measure upper stems or branches.
- Gewirtzman et al., bioRxiv (preprint, version 3, 28 February 2026). In upland forests, tree stems were net methane emitters at the chamber scale, though the sapwood just beneath the bark, and the heartwood, carried methane-oxidizing genes alongside the methane-producing ones.
At the scale of a country
National Forest Methane Inventories
We propose field campaigns with national forest institutions and climate funders to measure uptake and test satellite estimates. A national annual estimate would require suitable geographic and seasonal coverage, plus a tested method for scaling the field data. That estimate could give governments additional information for national forest accounts.
The IPCC Guidelines contain no method for bark methane uptake, and the Common Reporting Tables have no line for it. No country reports it today. A country can describe measurements of the flux in its national inventory document. It can state that the inventory does not yet estimate the flux and set out a method it plans to develop. A future national total could include changes caused by forest clearing or restoration. This accounting creates no carbon credit, offset, or NDC target credit. It does not license continued emissions.
For governments and jurisdictionsOther forest benefits
Methane Is One Benefit of Standing Forests
Standing forests store carbon, support biodiversity, recycle rainfall, and protect soil. SelvaFlux measures methane uptake. These other benefits are not included in the methane credit.
Other benefits of standing forestsSelvaFlux is discussing candidate sites with developers while it prepares the field system and pilot terms. No pilot agreement has been signed, and no registry credits bark methane today. SelvaFlux plans for a first issued credit in 2030 or later. Approval is not guaranteed, and registry timelines can slip.
The homepage explains the projected revenue for forest-project developers.
References
Where the Numbers Come From
- Forest methane uptakeGauci, V. et al. (2024). Global atmospheric methane uptake by upland tree woody surfaces. Nature.DOI
- Methane rate-based accounting (GWP*)Lynch, J., Cain, M., Pierrehumbert, R. & Allen, M. (2020). Demonstrating GWP*: a means of reporting warming-equivalent emissions that captures the contrasting impacts of short- and long-lived climate pollutants. Environmental Research Letters 15(4), 044023.DOI
- Methane conversion factorsSmith, C., Nicholls, Z. et al. (2021). The Earth’s Energy Budget, Climate Feedbacks, and Climate Sensitivity Supplementary Material. Table 7.SM.7, page 16, gives 81.2 and 27.9 with methane-carbon accounting excluded. Forster, P. et al. (2021), Chapter 7, Table 7.15, page 1017, gives the non-fossil GWP100 value of 27.0 used in our comparison, under a different methane-carbon convention.Table 7.SM.7Table 7.15
- Forest biomass growthCook-Patton, S. C. et al. (2020). Mapping carbon accumulation potential from global natural forest regrowth. Nature 585, 545-550.DOI
Methane Accounting Rules
See how GHG Protocol, SBTi, registries and national reporting treat methane, and which rules are changing.