A new study suggests that the proportion of grassland peat soils that have been drained in Ireland “is much lower than the current estimate”.
These estimates have assumed that all of these soils – 335,000 ha – are drained and as a result it was also assumed that they were responsible for a significant proportion of emissions, in the region of between 8–9 million tonnes CO2 equivalent annually.
But the results of a new Teagasc study – which has been published in the Journal of Environmental Management this week – provides “reliable evidence” for the first time on the proportion of grassland peat soils that have been “actually drained”.
According to one of the authors of the study, Professor Owen Fenton from Teagasc, the study has “uncovered data in national scientific literature and reports, which enabled a more accurate national figure for drainage status to be proposed.”
The study detailed: “From a drainage design perspective, evidence suggests that relatively small proportions of the grassland peat area was drained effectively using optimal in-field drain spacings required to control the water table at 0.4–0.5 m”.
Peat soils
According to the authors of the study they established a range of likely scenarios to the actual drainage status of peat soils.
These estimate emissions in the range of “3.6 – 4.7 M T CO2 equivalent, a saving of up to 60% on current inventory estimates”.
The authors of the study said these values “correspond to a drained area in the range of 90,000 to 120,000 hectares”.
They also considered the potential of organic soils and the scope for rewetting as a climate change mitigation tool as part of the alternative estimate of the assumed emissions.
One of the authors, Dr Pat Tuohy from Teagasc, said that although large areas of peatland “have been transformed from their natural state to grassland agriculture” there is no evidence to support that “effective drainage ever occurred on as much land as previously assumed”.
Dr Tuohy added: “The drainage status of all grassland peat soils requires further investigation.”
LULUCF
According to the authors of the study the results of the study could “impact significantly on the estimated emissions from grassland peat soils and more broadly on the land use, land use change and forestry sector (LULUCF).
“By accurately quantifying the impact of drainage status on these soils, Ireland can adopt targeted strategies to mitigate CO2 emissions and make informed policy decisions that contribute to a greener future,” they have advised.
The authors of the Teagasc have said that “a refinement of the greenhouse gas (GHG) emissions associated with this land use is required”.