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Study: Greenhouse gas emissions from cultivated peat soils may be lower than assumed

Current calculation methods may overestimate CO2 emissions.

Aerial view of green peatland research fields by a fjord
Many cultivated peatlands along the west coast of Norway have relatively high water tables due to the wet climate. This photo shows a cultivated peatland experiment site at NIBIO Fureneset station in western Norway.
Kathrine Torday Gulden COMMUNICATIONS ADVISER
Presented by: Presented by: NIBIO - Norwegian Institute of Bioeconomy Research
Published

Organic soil, peat, covers less than nine per cent of Norway’s land are.

Around 65,000 hectares are currently used as agricultural land. That corresponds to an area roughly equal to about 90,000 football pitches.

Emissions from these areas are estimated at over two million tonnes of CO2 equivalents per year. This is equivalent to the emissions from 400,000 fossil-fuel cars.

New research suggests that the current methods for estimating CO2 emissions from cultivated peat soils may overestimate emissions. 

This raises questions about how well the reported emissions reflect actual conditions in different parts of the country, especially where groundwater levels are high. 

“This does not mean that cultivated peat soils do not emit greenhouse gases, but rather that emission levels may be lower than assumed across large parts of the country,” says Junbin Zhao, a researcher at the Norwegian Institute of Bioeconomy Research (NIBIO).

Researcher installing a water table sensor in a grassy field in western Norway.
Miyuru Gunathilake installing instrument for measuring water table depth at one of the study sites in Farstad, western Norway.

Peat soils and greenhouse gas accounting

Peat soils contain large amounts of carbon that have accumulated over long periods of time. 

When peatlands are drained for agricultural use, the soil is exposed to oxygen. The carbon breaks down and is released as CO2.

Emissions of methane and nitrous oxide are also included in Norway's official greenhouse gas inventory.

Emissions from cultivated peat soils are currently estimated using so‑called Tier 1 emission factors developed by the IPCC. These are default values used when countries lack detailed national measurements.

While the method is simple to use, it takes limited account of local conditions such as climate and groundwater levels.

Gas chamber system measuring emissions in a green peatland field at Farstad.
The chamber system for measuring greenhouse gas emissions from the peatland site in Farstad.

Groundwater level is crucial

The researchers used a model that simulates the interaction between soil, plants, water, and climate. The model was first calibrated using measurements from two cultivated peatland sites in Norway: one in western Norway and one in northern Norway. It was then used to calculate emissions at 50 locations across the country in the period 2001–2022.

The results show that groundwater level is by far the most important factor for emissions.

“When groundwater levels are very low, the IPCC default values align well with the model results. However, when groundwater levels are higher, which is common in many parts of Norway, the Tier 1 method produces much higher emission estimates than those suggested by our model,” Zhao explains.

According to the study, emissions in many areas may be 31 to 88 per cent lower than current standard methods indicate.

Dr Junbin Zhao in high-visibility gear beside field soil equipment on wet farmland.
Researcher Junbin Zhao out in the field.

Climate and regional differences also matter

The study also shows that climate affects emissions. In warmer regions with longer growing seasons, carbon uptake by plants can partly compensate for emissions from the soil.

This means that the same type of soil can produce different emission levels depending on where in the country it is located.

“This highlights the limitations of using a single emission factor across a country with highly variable conditions,” says Gunnhild Søgaard, head of research at NIBIO.

Two researchers install instruments on a blue container at a rural Pasvik field site in Norway.
David Kniha and Mikhail Mastepanov installing equipment at the study site in Pasvik in northern Norway.

May affect climate measures

If emissions from cultivated peat soils are overestimated, the potential for emission reductions may also be misrepresented. 

This can make it more difficult to assess which climate measures are most effective.

More detailed calculations, so‑called Tier 2 or Tier 3 methods, can provide more accurate results. These methods are based on national measurements and models that better reflect local conditions. 

However, these methods require more comprehensive data from peatland sites across the country than is currently available.

“More accurate estimates would make it possible to design more targeted climate mitigation policies,” says NIBIO researcher Christian Wilhelm Mohr. “This would allow priority to be given to areas with high emissions, rather than applying the same measures uniformly across regions, including those with low emissions.”

Need for more data

The researchers emphasise that their findings do not imply that the standard methodology is wrong. Instead, they believe it's coarse and involves substantial uncertainty.

“This is particularly the case in countries with highly variable climate and drainage conditions, such as Norway,” Zhao notes.

He points to the need for more field measurements and better knowledge of how groundwater levels and management practices vary between different peat areas.

Increased data collection could provide a more robust basis for future greenhouse gas inventories in Norway. This could in turn contribute to more targeted and effective climate measures.

Reference:

Zhao et al. Potential overestimation of carbon dioxide emissions from croplands on organic soils in cool temperate and boreal regions based on a case study from Norway, Communications Earth & Environment, 2026. DOI: 10.1038/s43247-026-03464-5

IPCC greenhouse gas inventories and methods

The IPCC (UN’s Intergovernmental Panel on Climate Change) classifies methods for estimating greenhouse gas emissions into three tiers. These reflect increasing levels of methodological complexity and data requirements.

Tier 1 

The simplest approach. Uses global default emission factors and limited national data. Intended for countries with scarce measurement data, but often associated with high uncertainty.

Tier 2

Builds on the Tier 1 framework but applies country‑ or region‑specific emission factors. This improves accuracy but requires national measurements.

Tier 3 

The most advanced approach. Uses detailed models and/or extensive measurement datasets that capture local conditions, temporal variability and management practices. Provides the most accurate estimates,but is also the most resource‑intensive.

Tier 2 and Tier 3 methods are generally considered more accurate than Tier 1, particularly for emission sources that vary strongly with climate, land use and management.

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