The Environmental Protection Agency’s (EPA) emissions estimate for grasslands has been slashed by 65% after the agency carried out “significant recalculations” of land use emissions in light of recent scientific findings.

Changes to the national emissions inventory came after two studies on emissions from farmed peatlands were published last year.

These changes were taken on board by the EPA, reducing land use, land use change and forestry (LULUCF) emissions from 2023’s estimate of 7.30Mt of CO2 equivalents to 3.98Mt.

The inventory’s grassland sub-category was adjusted from a net emissions figure of 7.09Mt in 2023 to 2.48Mt in 2024, which represents a drop of almost two-thirds in the emissions accounting report.

This grassland figure has been calculated for 2024’s inventory by taking carbon emissions from peaty soils as a source of approximately 4.5Mt of CO2 equivalents and grasslands on mineral soils as representing a carbon sink of around 2Mt.

Overestimated area

Prompting the changes were a Teagasc study that found the area of drained grasslands on peat soils had been “grossly overestimated” and a separate study published by the International Peatland Society which found greenhouse gas emissions from grazed peatlands to be “significantly overestimated”.

An accurate picture of the drainage status of the country’s 340,000ha of peaty grasslands were unknown up to the publication of Teagasc’s review last June.

This review found that effective drainage systems are only in place over around 100,000ha, as much of the drainage network in place on these grasslands do not effectively drain the peaty soils.

Prior to this, the EPA’s emissions modelling assumed all of this farmland to be drained effectively and emitting an average of 26t/ha of carbon dioxide every year.

Grasslands acting as ‘rewetted’

One of the Teagasc officers who lead the study, Dr Pat Tuohy of Moorepark, discussed the “formal argument” put forward by researchers after 2023’s findings for a relook of peatland emissions in the EPA’s figures.

“I think the recent changes have meant that there’s a view taken that there is a fair proportion of that land category that is already acting as rewetted or somewhat rewetted,” Tuohy told Friday’s Signpost webinar.

“It wasn’t fair to class the drainage status of those soils as unknown, because we had very much a clear idea of what was happening out there from historic work and our own work and we proposed changes for inclusion in future inventory updates.”

The researcher suggested that the drainage situation of much of the country’s peatlands could be understood by many of the attendees.

“You don’t have to do too much driving around this country to find yourself in a wet peatland, particularly in the wintertime and we have had a very long winter as we speak,” he continued.

“It is certainly not fair to prescribe that they are all at the same water table and much of our work heretofore has been trying to introduce some subtlety in how those figures are established and going forward with future projects to estimate as best we can what is the mean water table.

“There is a level of saturation for long periods of the year on a large proportion of these soils and to try [to] come up with a more reasonable water table depth is what our work is predominantly about at the moment.”

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