Wetlands & Drained Organic Soils Emission Factors

The IPCC wetlands model

The 2013 Wetlands Supplement treats organic soils by their water status. Drained soils emit CO₂ (peat oxidation), CH₄ (from ditches) and N₂O, plus dissolved organic carbon washed to water. Rewetted soils largely stop the CO₂ loss but emit more CH₄. Coastal wetlands are accounted like forests — a carbon stock in biomass and soil whose change on clearing or restoration is the emission or removal.

Drained organic soils

Draining a peatland exposes its stored carbon to oxidation, turning a natural sink into a large, sustained source. The emission factors give the annual CO₂ (as carbon), CH₄ from ditches, and N₂O per hectare, by land use and climate. CO₂ values are tonnes CO₂–C (multiply by 44/12); CH₄ is kg/ha/yr; N₂O is kg N₂O–N (multiply by 44/28), each then converted with a GWP.

Greenhouse-gas emission factors

Dissolved organic carbon (DOC)

Rewetted organic soils

Rewetting a drained peatland stops the CO₂ loss — the CO₂ factor turns slightly negative (a small removal) — but the returning anaerobic conditions raise methane. These factors give the trade-off by climate and nutrient status.

Coastal wetlands (blue carbon)

Mangroves, tidal marshes and seagrass meadows — “blue carbon” ecosystems — store exceptional amounts of carbon in biomass and waterlogged soil. These parameters give the above-ground biomass stock and growth, carbon fraction, root-to-shoot ratio, dead wood and soil carbon used to estimate the carbon lost when they are cleared or the carbon gained when they are restored.

Application — formula & worked example

Drained cropland on peat. One hectare of boreal/temperate cropland on drained organic soil: CO₂ EF 7.9 t CO₂–C → 7.9 × 44/12 = 29.0 t CO₂; N₂O EF 13 kg N₂O–N → 13 × 44/28 = 20.4 kg N₂O → ×273 = 5.6 t CO₂e; CH₄ negligible. Total ≈ 34.5 t CO₂e per hectare, every year the peat stays drained.

Rewetting the same land. Restoring the water table turns the CO₂ factor slightly negative (a small removal) but raises methane — for a boreal poor fen, CH₄ rises to ~41 kg/ha/yr (×27.9 ≈ 1.1 t CO₂e) against a CO₂ removal of about −1.2 t CO₂. The net lands near zero — a swing of roughly 34 t CO₂e/ha/yr versus leaving it drained, which is why peatland rewetting is such a high-leverage mitigation.

Framework requirements

Wetlands emissions are a Scope 1 emission (or removal) for the operation managing the land, and the Wetlands and organic-soil lines across the Agriculture and Land categories in national inventories.

Common reporting errors

1. Reporting CO₂–C as CO₂. The CO₂ factors are tonnes of carbon — multiply by 44/12 to get CO₂, or you understate by roughly two-thirds.
2. Forgetting the 44/28 on N₂O. N₂O factors are N₂O–N (nitrogen); convert to N₂O before applying the GWP.
3. Treating drained peat as a one-off. Drainage emissions recur every year the water table stays low — multiply by the number of years drained, not once.
4. Ignoring the methane cost of rewetting. Rewetting stops the CO₂ loss but raises CH₄ — net the negative CO₂ factor against the positive CH₄ factor rather than claiming the CO₂ saving alone.
5. Omitting ditch methane and DOC. Drained organic soils also emit CH₄ from drainage ditches and lose dissolved organic carbon to water — include both where the guidance requires.
6. Confusing organic soils with mineral soils. These are peat (organic) soils; the mineral-soil carbon-stock-change factors in the land-use change dataset are a different method — don’t apply one to the other.
7. Treating blue-carbon stocks as emissions. Coastal biomass and soil carbon are stocks; the emission or removal is the change on clearing or restoration.
8. Using the wrong climate or land use. Factors vary strongly with climate zone, nutrient status and land use (cropland, plantation, peat extraction) — match them to the site.

Methodology, boundaries & uncertainty

What this dataset is. The IPCC wetlands parameter set — CO₂, CH₄, N₂O and dissolved-organic-carbon emission factors for drained and rewetted organic soils, and coastal blue-carbon biomass and soil parameters for mangroves, tidal marshes and seagrass — from the 2013 Supplement to the 2006 IPCC Guidelines: Wetlands, as implemented in the GreenCalculus MasterBrain. Part of the IPCC AFOLU Tier-1 dataset.

Boundary. Emissions and removals from organic (peat) soils under drainage and rewetting, and carbon stocks in coastal wetland ecosystems, reported in Scope 1. Mineral-soil carbon change is in the land-use change dataset; forest biomass in the forest-land dataset; managed-soils N₂O from mineral soils in the agricultural-soils dataset.

Rounding policy. Values are reproduced at IPCC precision. CO₂ and DOC factors are tonnes CO₂–C (or C) per hectare per year; CH₄ kg per hectare per year; N₂O kg N₂O–N per hectare per year; biomass stocks t dry matter or t C per hectare; ratios and fractions dimensionless.

Uncertainty. Wetland factors carry wide uncertainty — drainage CO₂ and CH₄ vary strongly with water-table depth, nutrient status and management, and coastal carbon stocks vary by region and species. Tier-1 defaults suit national and screening estimates; measured or region-specific values are expected where organic soils or coastal wetlands are a key category.

Applicability. Climate- and land-use-specific defaults; match the climate zone, nutrient status, land use and ecosystem, and use measured values where available.

Implementation & provenance chain

1. Primary source — 2013 Supplement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories: Wetlands, Chapters 2 (drained inland organic soils), 3 (rewetted organic soils) and 4 (coastal wetlands).
2. MasterBrain — each parameter is curated under a stable afolu.wetlands.* key with its source reference and GHG scope/category; current version v2026.203 (2026-09-22).
3. REST & CSV — the /afolu-wetlands-factors endpoint projects these rows as JSON; the CSV button below serves the identical set.
4. Calculators — GreenCalculus land-sector tools read the same keys, so a published inventory and this page cannot diverge.
5. Update plan — static reference; revalued on a new IPCC refinement to the wetlands method. Logged in the version history and bumps the dataset version.

Data access — REST API & CSV

The full 106-row dataset is available as a machine-readable REST endpoint and as a flat CSV download — the same rows shown above, versioned and citable.

Citation guidance

Cite the IPCC primary source. These factors are a subset of the GreenCalculus IPCC AFOLU Tier-1 dataset, which holds the citable DOI — cite the parent dataset, not a separate wetlands DOI.

IPCC (2014). 2013 Supplement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories: Wetlands (Hiraishi, T., et al., eds). Published by the IPCC, Switzerland.

IPCC 2013 Wetlands Supplement primary citation

Say, Jeremiah (2026). IPCC AFOLU Tier-1 emission factors (machine-readable). GreenCalculus. Zenodo. https://doi.org/10.5281/zenodo.20621658

Parent dataset DOI — includes the wetlands subset

Browse the full IPCC AFOLU Tier-1 emission factors dataset, of which this page is a part.

Frequently asked questions

Version history