The level to which an area of reclaimed peat used for agriculture can be returned to its “undisturbed state” and its potential for restoration depends on a number of factors.
These include its original state, the level of and the time since reclamation, and the intensity of management, Minister for Agriculture, Food and the Marine, Charlie McConalogue said.
Each environmental element of the land’s original state, such as water quality and biodiversity will have “varying degrees” of potential for restoration, according to the minister.
Concerns remain over the proposed EU Nature Restoration Law which seeks to restore drained peatlands under agricultural use. The European Parliament will vote at a full (plenary) sitting next week.
The question if drained, reclaimed and farmed peatland can be returned to its “undrained, un-reclaimed and undisturbed state” was recently raised by Deputy Jackie Cahill.
Drained peat soils
A drained peat soil will have continuous high annual levels of CO2emissions if land is maintained in a dry state, Minister McConalogue said in response to the deputy.
Changing the management and maintaining the high organic matter soil in a permanently moist/wet state, however, will reduce the rate of CO2 emissions, the minister added.
While on these lands – drained peat – the reduction of emissions is the main objective, as carbon sequestration is “limited”, Minister McConalogue said:
“This contrasts with the restoration of bogs where sequestration may occur on a restored site after an extended period, estimated at around 20 years, depending on site conditions.”
Acknowledging that there is “much uncertainty” in the data and knowledge around peat soils used for agriculture, the minister said he continues to fund several initiatives.
These include the National Agricultural Soil Carbon Observatory (NASCO) to produce carbon emission and sequestration values of Irish agricultural grasslands, mineral soils and peatlands.
Further initiatives include the ReWet project led by Teagasc and the University of Galway on the impact of water-table management on carbon-rich soils, and two European Innovation Partnership (EIP) projects on reduced management intensity of farmed peatlands.
“These investments will provide a greater understanding of how to reduce greenhouse gas (GHG) emissions from these soils and manage them more sustainably,” the minister said.
Forest carbon sequestration
The role of carbon sinks in climate policy is “more important now than ever” in helping to achieve Ireland’s pathway towards carbon neutrality, the minister said.
While forestry has a “significant” role to play going forward, he said forest carbon sequestration is influenced by factors including species, soil type, site conditions and management practices.
“The rate of sequestration changes over time. When forests are young the sequestration rate is low but as the trees mature, their ability to sequester CO2 increases,” he explained.
Teagasc’s Farm Carbon Tool shows that afforestation of one hectare of peat soils with 50% conifer and 50% broadleaf has the potential to remove 231t of CO2 per hectare, the minister said.
This is based on a mean annual sequestration rate of 3.3t of CO2 per hectare per year (tCO2/ha/yr) for the conifer species, and 0.5t CO2/ha/yr for the broadleaf species on peat soils.
However, the impact on emissions depends on the depth of the peat, Minister McConalogue added.
Emission values
Emission values for farming activities on drained peat soils by the Intergovernmental Panel on Climate Change (IPCC) for grassland with nutrient rich soil with shallow drainage are 16.7t CO2 equivalents (eq) per hectare.
For cropland with nutrient poor soil the IPCC’s emission value is 37.6t CO2 eq per hectare. These emissions are higher compared to permanent grassland as the soil is being disturbed annually, exposing the soil carbon, the minister added.
He stressed that national specific peatland emission values are required for Ireland, and that NASCO data will enable Ireland to better quantify soil carbon emissions and sinks from agricultural land on peat soils.