The rapid recovery of sphagnum mosses within 10-20 years can reduce methane emissions from bogs and increase carbon sequestration. Bog restoration is considered important for conserving biodiversity, but its climate impact is contested: do restored bogs increase methane emissions so much that restoration does not justify the benefits?
The results of modelling research by Teemu Tahvanainen (Teemu Tahvanainen), a plant ecology researcher at the University of Eastern Finland, challenge that assumption: “The data obtained indicate that methane emissions have been considerably overestimated in earlier studies.”
Particular attention should be paid to typical Finnish peatlands
A peatland forest is a forest growing on peatland; most commercially managed peatland forests have been drained. When peatlands are restored, ditches are either dammed or filled with peat, which allows water to spread and natural vegetation to recover. The number of trees decreases either naturally or as a result of logging. The European Union's Nature Restoration Regulation provides for a considerable proportion of drained peatlands to be restored to their natural state.
In Finland, every second hectare of bog has been drained, mainly for agricultural and forestry purposes. Teemu Tahvanainen's research concerns nutrient-poor, acidic bogs dominated by sphagnum mosses: the most common bog type in Finland. “These are not special varieties of bog, but typical Finnish bogs,” Tahvanainen notes. In their view, sphagnum mosses are the very foundation of bog restoration. They form a thick layer of moss that “creates” new peat. The sphagnum layer works as a mechanism that binds carbon and slows the decomposition of other plant remains.
Europe's peatlands are a significant factor affecting the climate
In Europe, peatlands cover approximately 59 million hectares, almost half of which are degraded, making Europe's drained peatlands the second largest source of greenhouse gas emissions, producing almost 600 Mt CO₂e of emissions per year. Restoring them could be one of the fastest and most cost-effective forms of “climate action”. The Nature Restoration Regulation identifies peatlands as a priority ecosystem, because restoring them could rapidly reduce emissions while improving biodiversity, water quality and resilience to drought and flooding.
Methane emissions and earlier calculations
Earlier estimates of methane emissions from restored peatlands in Finland were based on measurements taken in natural, wet open peatlands, which are vitally important wetland ecosystems where constant water saturation slows decomposition, allowing a thick, carbon-rich peat layer to be preserved over the long term. According to Tahvanainen, this peatland type does not reflect the conditions found in restored forest peatlands: “Restored peatlands often do not develop into very wet peatlands, but rather into hummocky bogs with a thick moss layer. In such conditions, methane emissions are usually lower.”
The study's modelling results indicate that methane emissions from restored forest peatlands may reach only a quarter or a fifth of the previously estimated level. At the same time, as the sphagnum layer recovers, carbon sequestration increases.
Will we see the climate benefits after ten years
Restoration of approximately 50% of the bogs Tahvanainen studied began to produce the desired effect after just ten years. The climate benefits resulting from restoration proved better than in the alternative scenario, in which forestry practice continued as usual, that is, the bog remained drained and was managed for timber production.
“If we take into account the soil emissions produced by alternative forestry practice, it appears that restoration can deliver considerable climate benefits in less than 20 years,” Tahvanainen emphasises. Within the timeframes of the European Union's and Finland's climate targets, the impact is considerable: over 100 years, a reduction of 2 to 6 tonnes of carbon dioxide equivalent per hectare per year.
Not all bogs can be restored
“Restoration is not the one right solution for all drained land,” Teemu Tahvanainen explains. “If a bog has changed substantially and no longer has bog vegetation, recovery will be slow. Restoration is best suited to low-productivity bogs, of which there are hundreds of thousands of hectares in Finland.” These are often not profitable for forestry, but they have great potential for climate and nature conservation.
Sphagnum mosses – both a climate factor and a surprising export product
Sphagnum brings economic benefits. In Finland, sphagnum moss is regarded as an ordinary bog plant, whereas elsewhere in the world it is recognised as a valuable raw material and an expensive niche product. Sphagnum is used mainly in substrates for orchids, bonsai trees and terrarium plants, where a clean, airy and water-absorbing material is required. “In Japan, garden centres sell sphagnum moss in 150-gram packs. The moss is imported from New Zealand, and one pack costs 10-20 euros,” Tahvanainen explains. On trial plots at abandoned peat extraction sites, sphagnum mosses grow very quickly, which is typically also observed in restored bogs. “In suitable conditions, an area can be completely covered with a thick layer of sphagnum moss within five years.”
The economic potential of sphagnum is considerable: if trade and processing chains were developed to supply a specific market niche, the annual yield per hectare would be worth hundreds of thousands of euros. Sustainable cultivation of Sphagnum moss could deliver some of the ecological advantages of bog restoration – accumulating carbon, improving water regulation and creating habitats for bog-dwelling species.
“Sphagnum mosses show that bog restoration can provide nature-based solutions for climate action, for securing biodiversity and for new economic opportunities,” Teemu Tahvanainen emphasises.
The trend is clear
Tahvanainen notes that measurements of methane emissions from restored bogs are still limited and long-term data is only now “beginning to accumulate”. “This is the best overall assessment available to us at present. The results of my research will soon be out of date, but new data will become available.” One thing is already clear: “When it comes to ‘ordinary’ Finnish bogs, there is no reason to assume the worst-case scenario. The potential of bog restoration should not be underestimated.”