In August this year, Minister of State for Agriculture Pippa Hackett launched a call seeking locally led proposals for a scheme to rewet peatland that had been used for farming.

The rewetting of peat soils in Ireland is seen by some as an important measure to aid carbon sequestration and this was a key element of the Green Party’s wish list in the Government formation talks back in June.

On the face of it, rewetting peat soils sounds simple – pay farmers to block drains on some of their peatland and allow the water table to rise naturally. The raised water table will then lock carbon in the peat by preventing its degradation and halt its escape to the atmosphere.

Some of the measuring stations at Carrownagappul Bog near Mountbellew, Co Galway.

Yet the complexity involved in properly rewetting peat soils is being overlooked and many well-meaning commentators have oversimplified this extremely complex process as being a very simple solution to climate change.

Carrownagappul Bog

Earlier this summer, the Irish Farmers Journal visited the Carrownagappul Bog just outside Mountbellew in Co Galway to get a better understanding of what is involved in rewetting peat soils.

Carrownagappul Bog, which is designated as a special area of conservation, stretches to almost 487ha (1,200 acres) and is one of the largest raised bogs in Ireland. The site is part of the Living Bog project, which is implemented by the National Parks and Wildlife Service (NPWS) and part of the EU-funded LIFE programme that seeks to restore raised bogs and the associated habitats and biodiversity that come with them.

An example of some of the sphragnum moss growing at Carrownagappul Bog.

In all, the Living Bog project is restoring 12 raised bogs located in seven different counties across Ireland with varying levels of success. In Carrownagappul Bog, restoration works were conducted in February and August 2019, which resulted in almost 3,000 peat dams being installed in order to reduce the rate of water flow and raise the level of the water table in the bog.

Ronan Casey, public awareness manager of the Living Bog programme, says the biggest challenge to successfully rewetting land is understanding what is going to happen to the peat and the surrounding lands once you begin to block drains.

Casey says that carrying out the works to block drains is not overly complicated and is actually very cost-effective. However, he says that long before any machines begin to carry out works, there needs to be an extensive hydrology survey done on each site to assess what will happen as the water table rises.

Assessing land levels, water flow paths, catchment boundaries and rainfall levels are all essential parts of a detailed hydrology survey to determine what works are required and what results can be achieved.

These complex hydrology surveys need to be carried out as part of all rewetting projects to ensure the process doesn’t have a negative impact on neighbouring farms, says Casey.

A good example of rewetting

Carrownagappul Bog in Mountbellew is a wonderful example of a peat bog that has been properly rewetted. It is still early days in the project but when I visited the site in August, there were many examples of sphagnum moss growing on the top of the bog once again.

According to Casey, this growth of sphagnum moss on the top of the bog is the clearest indicator that the rewetting is working.

Additionally, the Living Bog team has installed a number of measuring stations throughout the site to monitor water levels, rainfall and the volume of dissolved peat in the water running off the bog.

One of the biggest issues with drained peat soil is that the peat can move with the drainage water and act as a pollutant in downstream watercourses.

Lower levels of peat in the drainage water indicate a stable peat mass in the bog.

In a drained bog, once the water table drops it allows oxygen into the peat and a return to aerobic conditions. This then enables the breakdown of organic matter which releases C02 back into the atmosphere. By keeping the water table high, this process is halted and the carbon remains locked up in the soil.

Casey says the Living Bog team work closely with adjoining landowners, so neighbouring farmers understand the works they are carrying out on the bog. This cooperation also helps ensure that the rewetting works do not accidentally cause flooding issues on their farmland.

Peat soils

It’s important to note there are major differences between rewetting a raised bog and rewetting peat soils used for agriculture.

If peat soils currently used for agriculture are rewetted as part of an agri-environmental scheme, their usefulness as grazing lands will be vastly reduced if not eliminated entirely due to reduced grass growth and increased poaching by cattle of any weight.

This is not to suggest that rewetting peat soils should not be a climate response objective. However, there is a big difference between funding a properly resourced team of experts to rewet designated Irish bogs compared with just paying farmers to simply block drains.

The Living Bog project was given EU funding of more than €5.4m over a five-year time frame from 2016 to 2020. The project has clearly demonstrated what successful rewetted raised bogs can look like but the process is not as simple as just filling in drains.

If our Government is serious about strategically rewetting a large area of peat soils in Ireland over the coming decade, it needs to be honest with farmers about the complexities of this process. It must also be prepared to invest in proper hydrology assessments for every farm before any works commence to block drains.

If it fails to do this, there could be severe consequences for adjoining landowners, farmers and householders, when water starts to build in places once it has nowhere else to go.