Despite only covering 3% of the world’s land area, peatlands store about 30% of the all terrestrial carbon, a function that must be preserved as countries work to lower their greenhouse gas emissions.
Yet doing so has been a sensitive issue at times, given the uses that peat has traditionally had in the horticultural sector and as a fuel for home heating.
As the development of solar, wind and other renewable energy sources for the latter ramps, perhaps so too should ‘paludiculture‘, the productive land use of wet and rewetted peatlands that preserves the peat soil and minimises carbon dioxide (CO2) emissions.
Also known as ‘wet agriculture’, the practice can be “an effective way of avoiding damaging agricultural practices on carbon-rich peatlands”, while simultaneously keeping the land in use, according to the Organic Trust.
“Through cultivating specific crops and maintaining high water levels, paludiculture is a viable and environmentally friendly solution to preserve and grow peat and keep accumulated carbon stored in the soil.
“As the name implies, wet farming also restores a functional wetland, which can clean water and buffer against flooding,” it said in a statement.
Preserving carbon storage is key, but another benefit that this practice can offer is a potential solution to the issues that the horticulture sector is facing in securing peat as a growing medium.
Doing so has become very difficult for many growers as the harvesting of horticultural peat from bogs larger than 30ha now requires a complex, multi-stage licensing system, which was the subject of intense discussions at a meeting of the Joint Oireachtas Committee on Agriculture, Food and the Marine last November.
Two reports on the issue were presented at the meeting, which stated that many growers don’t engage with this process, although many TDs and backbenchers defended this, citing “an over complicated system” as the reason for this.
The government commissioned a working paper on the issue early last year, which showed that the horticulture sector requires approximately 131,000m3 cubic metres of peat for propagation annually.
Due to this high demand, the paper aimed to establish the sector’s requirements and identify viable alternatives to peat as a growing medium.
According to the Organics Trust, paludiculture could play a role in addressing this challenge, as one perennial crop which grows well in wet peatlands is sphagnum moss.
Trials have shown that both dried and green sphagnum moss, more often known as peat mosses, “could be the closest in quality and texture to peat”, it said.
“[It is] an exciting prospect that it could be harvested as biomass and composted to make a renewable growing medium for the horticulture sector to replace peat completely.
“If so, wet farming could prove to a profitable and sustainable innovation for marginal, high-maintenance, agricultural land, future-proofing farming while supporting a matrix of wetlands,” it added.
The final report from the Working Group on the Use of Peat Moss in Horticulture was published in January 2022, and discusses the use of these sphagnum mosses as a growth medium.
It outlines that their use in the horticultural industry has been studied extensively in Europe and that they are viewed as “a renewable and sustainable alternative to extracted peat”.
It mentions a 2015 study which stated that testing on these mosses have shown that they generally perform “at least as well as standard peat-based media”, but a low lignin content may mean they’re unsuitable for long-term use.
Although it states that the cost of farming sphagnum “far exceeds that of peat”, the report also recommends that “this type of farming in cutaway bogs should be encouraged in Ireland”.