Peatland restoration is a term describing measures to restore the original form and function of peatlands, or wet peat-rich areas. This landscape globally occupies 400 million hectares or 3% of land surface on Earth.Convention on Wetlands. (2021). Restoring drained peatlands: A necessary step to achieve global climate goals. Ramsar Policy Brief No. 5. Gland, Switzerland: Secretariat of the Convention on Wetlands. Historically, peatlands have been drained for several main reasons; peat extraction, creation of agricultural land, and forestry usage. However, this activity has caused degradation affecting this landscape's structure through damage to habitats, hydrology, nutrients cycle, carbon balance and more.
Due to peat formation, peatlands are carbon-rich and noted as carbon sinks. It has been projected that climate change, such as increased temperature and alterations of precipitation, affecting these landscapes under current status could increase releases of greenhouse gases (GHGs). Climate projections indicate increased probability and intensity of weather events, which can increase risk of fires and additional GHG release. Peatlands home a variety of native flora and fauna put at risk by projected degradation from climatic or anthropogenic alternation, placing emphasis and need for restoration efforts. Policy for restoration is in action. In June 2002, the United Nations Development Programme launched its Wetland and Ecosystem and Tropical Peat Swamp Forest Rehabilitation Project and in November the International Peatland Society formed, which promotes restoration and balance of demands on peatlands.
Peatland restoration emphasises the reduction of GHG emissions to slow the effects of climate change. With discussion circulating on human impacts of damage from draining and clearing the landscape. As a result, restoration would involve balancing usage of peatlands for human needs and needs of the natural ecosystems. Presently, main methods of restoration circulate on re-wetting, restoring forestry, localised paludiculture and adaption of anthropogenic usage of peatlands.
Targets of restoration Climate change mitigation and adaptation
Peatlands store carbon from dead plants and hence help mitigate climate change. However, draining and degrading peatlands release large amounts of greenhouse gases. Rewetting and restoring peatlands can significantly reduce these emissions by raising water tables which slower down the plant decomposition. The resulting anaerobic decomposition produces the greenhouse gas methane, but since methane does not remain in the atmosphere as long as other GHGs, the net effect on the climate is likely cooling if a long time frame is considered (decades). The strength of this effect varies between different kinds of peatland, but it is generally most significant in tropical and agricultural peatlands. A raised water table also results in a local direct cooling effect, moist vegetation and soil has a higher thermal conductivity and therefore solar radiation is rather used for evapotranspiration than warming the surface.
Water The goals of peatland restoration in hydrological terms are primarily to improve the quality and regulate the quantity of water. A peatland as an intact ecosystem is a natural water purifier, it filters and stores organic substances, metals or other toxic matter and retains nutrients. These pollutants are stored in the peat for long periods of time, improving the quality of drinking water. The concept of peatlands regulating water quantity has often been compared to the way of a "sponge" works, in times of high availability of water (periods of rainfall) it is sucked up and stored and afterwards, in times of less precipitation, slowly released to the environment. Furthermore, as the water level rises, the risk of peat fire decreases.
Biodiversity In some instances, peatlands may exhibit a comparatively lower number of species. However, in the same biogeographic zone as dryland ecosystems, peatlands contain a greater percentage of specialized and distinctive species. Due to the isolation and heterogeneity of their habitats, peatlands harbor significant populations of endangered and rare species, many of which are unique to peatland environments, and play a role for the conservation of genetic diversity.Convention on Wetlands. (2021). Global guidelines for peatland rewetting and restoration. Ramsar Technical Report No. 11. Gland, Switzerland: Secretariat of the Convention on Wetlands. Restoration seeks to counteract the process of habitat deterioration, which represents the most significant risk to biodiversity. In drained sites there is a tendency for plant diversity to decrease, with mosses (including Sphagnum) facing difficulties in recolonizing such areas. This could be attributed to the hydrological alterations, as well as the loss of the initial soil characteristics.
Restoration effects on the natural environment
Carbon balance Due to the formation of peat developing from partial decomposition of vegetation material, there is a high quantity of carbon within this landscape. As a result, peatlands can be seen as a carbon storage. Carbon fluctuations are dominantly impacted by local hydrology within a peatland.
However, these processes are interrupted by anthropogenic usage of peatlands. Peat extractions cause destabilisation of local ecosystems through physical landscape damage of digging, draining and isolation through habitat fragmentation. As a result of drainage and temperature increase, peatlands are becoming drier, which increases the likelihood of severe fires and the risk of larger carbon dioxide emissions.
Climate regulation Climatic regulation is key to monitored for peatland restoration. Due to the water-logged nature of this environment, consistent seasonality and fluctuations, are essential to restoring stability and protecting pristine peatlands. Climatic change of variables, such as precipitation and temperature, threaten significant factors mostly namely that of hydrology (due to its immediate effects on microbial decomposition within the soil).
Beyond climatic events on peatlands, their restoration offers climatic benefits also. Peatland restoration is noted for significantly reducing air temperature compared to neighbouring agricultural land. This finding offers peatland restoration as a positive step to combat climate change.
Nutrients Peat in general is poor in nutrients and due to its constantly condition of being waterlogged, it has a limited nutrient cycle. Peatlands that have been degraded and used for agriculture, typically have high nutrient levels. Restoring these areas with surface water, which is also relatively nutrient-rich, leads to nutrient overload. To properly restore these peatlands, excess nutrients must be removed. One expensive but effective way is to remove the top layer before restoration and another option is to use paludiculture to remove nutrients over time. Due to peatlands' special flora and fauna, a failure to remove excess nutrients can result in low biodiversity in affected peatlands. However, a study showed that after the restoration of peatlands, the original concentrations of mineral elements such as potassium and calcium was restored.
Hydrology Recent initiatives on peatland restoration showed, that they help preventing and mitigating floodings in specific areas and under specific conditions. This happens within two particular effects. First by sucking up water and second through temporary surface-storage. When peat sucks up water, the groundwater level elevates and captures the rainwater, this is then only released by evapotranspiration, as the water does not flow down the rivers into the sea, but stays in the peatland, it too reduces the probability of droughts. In the temporary surface-storage effect the vegetation acts as a barrier to the water runoff and thus delays it although the netflow of water stays the same, but the time expands and hence the flow rate is reduced. This is a crucial point in flood prevention.
Soil regulation Peatland as an ecosystem is important for regulating soil quality. When the peat covering Sphagnum layer is degraded, the remaining bare peat soil releases sediment to water streams, which pollutes and reduces biodiversity of rivers and water reservoirs. Additionally through wind and water erosion carbon can be released if the peat is blank. Hence a dense Sphagnum covering is important for soil regulation, as it can improve the physical, chemical, and biological flows and properties that allow soils to buffer, filter, and transform chemical substances.
Biological diversity
Plant life Restoration efforts can cause alterations in the hydrology of the system, resulting in hydrological conditions that are more advantageous for the recolonization of Sphagnum mosses. Restoration can also lead to the successful succession of plant communities towards a targeted peatland vegetation by decreasing the abundance of species benefiting from drainage. However, the restoration process may not always result in the full re-introduction of pristine peatland species.
The rewetting of drained fen peatlands can lead to the growth of tall graminoid wetland plants, such as Common reed (Phragmites australis) and Broadleaf cattail (Typha latifolia), which can become the dominant vegetation for many years to decades. This can cause lasting changes to the biodiversity, ecosystem functioning, and land cover characteristics of the area, particularly in terms of geochemistry and hydrology.
Animal life In restored areas, the recovery of animal species is more likely to be affected by the resulting variation in environmental conditions, compared to plant species. Animal species have different requirements, and many of them need specific combinations of conditions, making them more sensitive to environmental changes. The ability of species to disperse and the proximity of source populations in undamaged peatlands are crucial factors that contribute to the recolonization of animal species in restored areas.
Of insects, Odonata species (dragonflies) are negatively impacted by drainage. However, according to a study in Finland, after the peatland restoration they tend to benefit and can colonize new water pools in just three years. Compared to the pristine sites, the drained sites had fewer Odonata species and lower abundance.
A study in Finland revealed that the composition of bird communities in restored areas is different from those in pristine areas and many bird species found in the restored peatlands are generalist in nature. To assess the recovery of specialized bird species in peatlands and bird communities in general, long-term monitoring is necessary.
A major peatland restoration project took place in Snowdonia (Eryri), Wales, where an upland farm witnessed the return of rare bird species after two decades of absence. During the summer of 2021, European golden plover (Pluvialis apricaria) and Eurasian Curlew (Numenius arquata) successfully bred in the rewetted habitats, and chicks sightings were recorded for both species. This is the first case of successful breeding at this site since the 1990s.
Fungi and others