Rewetting drained grassland poses ‘a great opportunity’ to reduce greenhouse gas emissions
The Department of Agriculture has identified “at least 40,000ha” of drained grasslands for rewetting, the Joint Oireachtas Committee on Agriculture has heard.
Addressing yesterday’s committee hearing on bog rewetting, Dr David Wilson of Earthy Matters Environmental Consultants outlined that rewetting drained grassland sites “offers the opportunity to target a reduction in greenhouse gas emissions”.
Meanwhile, the expert also warned about the impact of Bord na Móna’s bog rewetting plans on farmland around the River Shannon.
Dr Wilson said: “Under the Department of Agriculture’s Ag Climatise Roadmap, released in December 2020, at least 40,000ha of drained grasslands on peat soils have been targetted for rewetting – referred to as ‘reduced management intensity’ in the report.
"Rewetting of these soils is interesting as it has not been widely implemented in this country, although it has been carried out in other jurisdictions.
"In contrast to cutover and cutaway sites, where there is an emphasis on restoration to a functioning peatland ecosystem with a desire to bring back characteristic peatland flora and fauna, rewetting of drained grassland sites offers the opportunity to solely target a reduction in greenhouse gas (GHG) emissions.
“To date, only one study in Ireland has evaluated the potential for GHG emission reductions in this land use category, and show that carbon dioxide (CO2) sequestration and minimal methane emissions could be achieved even at water levels down to 25cm depths.”
Independent TD Michael Fitzmaurice asked the expert for further clarity on the 40,000ha of grassland identified by the Department for rewetting pointing to Listowel, Co. Kerry, as an example, whereby dairy farms operate on reclaimed boglands that grow grass. Sinn Féin TD Matt Carthy also sought additional clarity on the “other jurisdictions” where grassland rewetting has been carried out.
Dr Wilson responded: "They have identified at least 40,000ha of grassland on organic soils – the point being that, because it is on organic soils, it isn’t sequestering carbon, it is releasing carbon – and that has been recognised in our submissions to the National Inventory Report.
“If it was mineral soil or mineral grassland, there might be a small amount of carbon sequestered, but not on organic (peat) soils.
"Rewetting grasslands is new for us, it’s something we haven’t engaged in in Ireland; but the Germans and Dutch have been working on it.
“Their sites were extraordinary GHG emitters because of the amount of nutrients that had gone into those sites before rewetting, so there was an impetus on them to rewet. The benefits of rewetting in Germany and the Netherlands was very high because the emissions were so high beforehand,” he said.
Based on Ireland’s National Inventory Report for 2020, GHG emissions from the country’s estimated 330,000ha of drained grassland on organic (peat) soils under the Land Use, Land-Use Change and Forestry (LULUCF) sector was reported at 8.3 million tonnes of CO2 per year.
However, recent work by Teagasc indicates that the area of grassland on drained peat soils could be 450,000ha which, according to Dr Wilson, would suggest that emissions from this land use category may be currently “underestimated by 3 million tonnes of CO2”.
It was also outlined to the committee – chaired by Fianna Fáil TD Jackie Cahill – that a new Teagasc project will address some of the “uncertainties” associated with the rewetting of grasslands and subsequently enable Ireland to benefit from the 2018 EU Effort Sharing Regulation.
Meanwhile, on the issue of Bord na Móna’s peatland rewetting project and its potential impact on adjacent farmlands, Dr Wilson warned of possible consequences for lands along the River Shannon.
"My experience of working on Bord na Móna rewetted cutaway bogs over the last 20 years has been that for the majority of these sites, flooding of adjacent lands has not been an issue – an experience in agreement with the community living around Abbeyleix bog for example.
"However, issues might exist for those areas around the Shannon where industrial extraction was previously facilitated by active pumping of drainage water, and where flooding (as opposed to rewetting) may be a problem when the pumps are switched off.”
In closing, and pointing “the momentum” that is “clearly increasing” in Government for peatland rewetting, Dr Wilson highlighted the new European Innovation Partnerships (EIPs) announced by the Department of Agriculture last month – which, he said, will build on the work of ongoing projects such as Burren Life and the Pearl Mussel and Hen Harrier projects.
"These new EIPs will provide an important platform to evaluate the potential of transitioning from current conventional practices to new ‘carbon farming’ models,” he concluded.