Wetlands

• Innhold
• Description of wetlands
• Assessed Ecosystem Types
• Red-listed ecosystem types
• Impact factors
• Existing knowledge
• Expert Committee
• Acknowledgements
• References

Wetlands are defined in Nature in Norway (NiN 2) as "land with a groundwater table sufficiently close to the surface, or with such a plentiful supply of surface water, that organisms that are adapted to life under waterlogged conditions or that require good and stable access to water are abundant" (Halvorsen et al. 2016). This definition is narrower than that which forms the basis of the Ramsar Convention. In our context, wetlands encompass mires, springs, swamp forest and semi-natural wet meadow in mainland Norway.

Description of wetlands

Wetlands are found across the entire country, with the exception of the high alpine bioclimatic zone, and there is large regional and local variation. Hardly any country in Europe has a greater variation in ecosystem types and flora and fauna in wetlands than Norway. The area statistics for wetland are inadequate but Rekdal et al. (2016) state that the total area of intact mires and swamp forest in Norway is 37 719 km² (approximately 12 % of the land area). Of this, 28 319 km² is mire (approximately 9 % of the land area), and 9400 km² swamp forest (approximately 3 % of the land area). Springs cover small areas, much less than 1 %. This is in addition to considerable areas that were mires prior to being drained (approximately 7000 km²; see Moen et al. 2010), and other types of wetland that have been destroyed or strongly altered due to land conversion, draining or cultivation. Areas considered to have disappeared (Collapsed CO), prior to the assessment period of the last 50 years, have not been included in the Red List assessment.

Open mire

Mire is defined in NiN as an area of land with vegetation that requires moisture, that forms peat. This definition does not state a requirement for peat depth. Classification on the basis of vegetation is used to define natural systems, major types and minor types in NiN, while hydromorphological classification is the basis for categorization into peatland formations (landform). All mire areas can be described as both a natural system and a landform. Forested mire is placed under mire and swamp forest V2 in NiN (see below). Mire can also be classified according to its genesis and hydrology (Moen et al. 2011a).

Spring

Springs have oxygenated groundwater that wells up from below the earth, and usually covers a small area. The chemical compostion of springwater reflects the bedrock and sediment that has been deposited by the water. In some places the groundwater discharges over a large area, and can thus give rise to areas with spring forest and spring fen. The influence of springwater varies, where the centre in a weak (astatic) spring can have an upwelling of water only in periods with high groundwater, such as when snowmelt occurs. The weak springs obtain the water from the upper layer. The strong (eustatic) springs have, unlike the weak springs, even water flow, temperature and chemical composition throughout the year, and the water comes from layers far below the surface. There is a considerable difference in the flora and fauna between springs on mineral soil (mineral spring) and springs on peat (deep spring, spring fen).

Mire and swamp forest

Mire and swamp forest encompasses wooded mire (with peat) and wet forest with little or no peat accumulation. The ground will often be humic "swampy soil". The addition of soil water with minerals is even and abundant, and the groundwater level is high. The vegetation includes species associated with forest, swamp and mire, and there is high biodiversity in lime-rich ecosystem types. The species composition varies strongly from type to type, and partly from place to place. This is usually associated with variation in lime-content, moisture conditions and water supply, tree species dominance, and peat accumulation as well as regional variation (cf. Jansson et al. 2011).

Semi-natural wet meadow

This major type encompasses semi-natural land that satisfies the definition of a wetland but without peat formation (Halvorsen et al. 2016). This major type is most commonly found bordering the edge zones of freshwater. Ecologically comparable areas without traditional agricultural management are likely to be swamp forest in the lowlands and densely thicketed or open, damp meadow at higher altitudes. The herb layer is well developed, while the ground layer is usually sparse.

Assessed Ecosystem Types

In wetlands there are 32 assessment entities: 7 major types, 8 entities defined with variables from the descriptive system, as well as 17 peatland formations (Halvorsen et al. 2016). The remaining 6 major types are not assessed for the Red List either because they represent strongly altered wetlands, do not occur on mainland Norway (Thermal spring V5 and Arctic permafrost wetland V7, see Svalbard), or are assessed under Sparsely vegetated habitats (Wet snowbed and snowbed spring V6).

The eight entities defined using the NiN descriptive system are distinguished from the major type in that they are either more exposed to impacts, or they are exposed to other impact factors. Collectively, the outlook for these entities is more negative than for the major type, and they are assigned to a higher Red List category (Table 1). To define these entities we have used bioclimatic zones, forest layer composition within relative partial species composition, and hay-making characteristics (Halvorsen et al. 2016). The entities represent a selection of minor types within the major type, with the exception of Southern cold spring (within V4) and Southern haymaking fen (within V9), where the criterion is occurrence of the major type in boreo-nemoral and southern nemoral bioclimatic zones.

Unique for wetlands is the possibility of using the landform type peatland formation 3T0 as a basis for defining assessment entities for mires. Peatland formations are mire massif types defined by their hydromorphology (Joosten et al. 2017) and there are 17 peatland formations in NiN (Table 1). All the forms exist on mainland Norway with the exception of Polygon mire 3T0-P0 which is only found on Svalbard.

Red-listed ecosystem types

Of the 32 entities which were assessed, 19 are included in the Red List. Semi-natural fen (V9) is the only ecosystem type that is assessed as Critically Endangered CR, eight ecosystem types are assessed as Endangered EN, five as Vulnerable VU and four as Near Threatened NT.

In general, it is the reduction in total area (criterion A) and deterioration in ecological condition (criteria C and D) that have been the determining criteria in the assessments. Limited distribution and area of occurrence (criterion B) has only been a determining criterion for Concentric domed bog and Lime-rich alluvial swamp forest. A deterioration in ecological condition is often due to drainage (digging channels) for agriculture, afforestation, building roads, and other infrastructure development. When peat comes into contact with the air it decomposes and drier conditions prevent further peat formation. Calcareous  (lime-rich) types become poorer because they lose contact with the lime-rich groundwater. Drainage makes poorer living conditions for wetland species, but better living conditions for terrestrial species. An increase in the amount of shrubs and trees is often a consequence of draining land and natural swamp forest transforms into terrestrial forest. The water level drops immediately after draining, and changes in the soil and vegetation are visible within a short period of time. Gradually, the impact will be visible farther from the drainage channel, and decomposition of peat and changes to vegetation will continue for a long time. Much of the drainage channel (ditch) creation that was undertaken more than 50 years ago has had "delayed impacts" during the assessment period of 50 years. Cessation of traditional agricultural management in semi-natural ecosystem types is another source of deterioration in ecological condition. This results in overgrowth, often with the appearance of shrubs and trees.

Southern haymaking fen is Critically Endangered CR due to an extreme deterioration in the ecological condition (degree of degration > 80 %) as a result of cessation of traditional agricultural management and overgrowth on > 80 % of the area. This applies to the past 50 years and is deemed to apply to the next 50 years as well.

Semi-natural fen V9, Atlantic raised bog, Eccentric domed bog, Concentric domed bog, Plateau bog, Palsa mire, Lime-rich southern fen and Lime-rich spruce swamp forest are all assessed as Endangered EN. With the exception of Semi-natural fen, Palsa mire and Lime-rich spruce swamp forest, these are southern, lowland ecosystem types. A common factor for all eight entities is a very significant deterioration in ecological condition (degree of degradation > 80 %) across > 50 % of the area, either in the past 50 years, or anticipated in the next 50 years.

Blanket bogs, Southern cold spring, Lime-rich alder swamp forest, Lime-rich spring (deciduous) swamp forest and Lime-rich alluvial swamp forest are assessed as Vulnerable VU (Table 2) and have a reduction in area of > 30 %, as well as a very significant deterioration in ecological condition (degree of degradation > 80 %). For Blanket bogs an intensified threat is anticipated for the coming 50 years due to wind power developments and for this reason the entity is assessed as Vulnerable VU. For the other four, it is primarily a reduction in area and a deterioration in ecological condition in the past 50 years that are the determining criteria.

Bog V3, Island mixed mire, Ridge raised bog, as well as Lime-rich alder alluvial swamp forest are assessed as Near Threatened NT. For Ridge raised bog it is a reduction in total area that is the determining criterion, while for the other three entities it is a deterioration in ecological condition.

We have not managed to find relevant data on the occurrence or ecological condition of Semi-natural wet meadow V10 (DD). Based on general ecological knowledge about traditional agricultural management and overgrowth on semi-natural land it is likely that the entity will be allocated to one of the Red List categories Near Threatened NT – Critically Endangered CR. It is nevertheless also possible that a large proportion of the reduction in area and deterioration in ecological condition has already occurred so that the result, given more adequate knowledge, will be Least Concern LC.

Impact factors

For wetlands in general, creating drainage channels with the aim of afforestation or agriculture is clearly the most significant impact factor. Digging drainage channels (ditches) has decreased in recent years, not least because doing so is no longer permitted for forestry purposes. In the meantime, old ditches remain, draining many mires and swamp forests, and these will contribute to considerable degradation and loss of localities in the future. Creating drainage channels for agriculture is common, even if to a lesser degree than a few decades ago. This impacts ecosystem types in the lowland areas in particular. Land conversion for the purpose of cultivation may have less significance in the coming 50 year period but this depends on various factors, including whether a ban on the cultivation of mires is adopted, as has been recommended by the Norwegian Ministry of Agriculture and Food.

Within the last 50 year period large areas of wetlands have been lost through land conversion for industry, housing, roads and other infrastructure. This has particularly influenced ecosystem types in lowland areas (Lime-rich southern fen, Southern cold spring, Concentric domed bog, Eccentric domed bog, Plateau bog, Atlantic raised bog) and swamp forest ecosystem types (Lime-rich spruce swamp forest, Lime-rich alder swamp forest, Lime-rich alder alluvial forest, Lime-rich spring (deciduous) forest). With the exception of the raised bogs, these types will also often be impacted by nutrient seepage from agricultural areas.

Concentric domed bog, Eccentric domed bog, Plateau bog and Atlantic raised bog have deep peat and areas with these ecosystem types are therefore particularly attractive for industrial peat extraction (Øien et al. 2017). The government has in autumn 2018 taken the initiative to phase out use of peat and if this is done, industrial peat extraction will be less influential in the coming 50 year period.

Flooding landscapes to create hydropower dams has led to large reductions in the area and ecological condition of wetlands in the past 50 years, especially in alpine areas. In the next 50 years it is expected that the amount of wetland area lost as a result of hydropower developments will decrease (see Norwegian White Paper: 25 (2015-2016)). In recent years, the advent of wind power developments has seen additional land conversion and changes in hydrology. This has reduced the area and ecological condition of wetlands and it is regions close to the coast that have been most affected to date (Arnesen 2018). There are however concrete plans for large-scale developments in alpine areas and in the next 50 years it is expected that wind power development will be one of the most significant impact factors for wetlands both in alpine and coastal areas.

Holiday cabin construction has changed in character over the past 50 years, and contemporary developments usually encompass both road construction and the connection of electricity and water (Haagensen 2014). This has led to reduced areas of wetland in alpine areas and along the coast, as well as a deterioration in the ecological condition. It is an impact that is predicted to become even greater in the coming 50 years. These types of encroachments influence the majority of peatland formations and major types of natural systems, but windpower development has so far particularly influenced entities with a distribution in the vicinity of the coast, such as Atlantic raised bog and Blanket bog.

Ecosystem types dependent on traditional agricultural management are especially vulnerable to changes in the use of non-cultivated areas, and the cessation of haymaking (in such areas) leads to overgrowth and significant changes in vegetation cover (Moen and Øien 1998, 2012, Moen et al. 2001).

Airborne nitrogen deposition has a negative influence on Bog V3 (Bakken and Flatberg 1995, Aarrestad and Stabbetorp 2010) and it is the south-western parts of Norway that receive the most nitrogen (Austnes et al. 2018). The impact of airborne nitrogen deposition is greatest for assessment entities Bog V3, Atlantic raised bog and Blanket bog.

Climate change will have an impact on the development of mires and other wetlands and the effect will depend partly on the type of wetland and regional variation. Significant precipitation promotes soil moisture and therefore creates an increased opportunity for the formation of mires, whilst higher temperatures will increase evaporation and can lead to drier conditions. An increase in temperature will increase both the production and decomposition of organic matter and it is uncertain how these will combine to influence peat formation. Higher temperatures will have a negative influence on Palsa mire due to the melting of ice cores, and on ecosystem types influenced by traditional agricultural management (Semi-natural fen V9, Southern haymaking fen and Semi-natural wet meadow V10) due to an acceleration in the rate of overgrowth. Extreme weather events will have consequences that we cannot predict.

Existing knowledge

In preparing the Norwegian Red List for Ecosystems and Habitat Types 2011 (Møen and Øien 2011) a considerable amount of work was undertaken to collect and assess existing material. This material was also used in 2018. Important sources include reports developed under the Norwegian Mire Nature Reserve Plan (for example Moen 1983), as well as surveys of vegetation types (Fremstad 1997, Fremstad and Moen 2001). A scientific basis for the management plans for typical raised bogs, coastal bogs, lime-rich bogs, and haymaking fens has been developed (Moen et al. 2011a, b, Øien et al. 2015, Lyngstad et al. 2016b). These plans also contain a summary of the knowledge used to make the Red List assessments. The ongoing mapping of typical raised bogs (eg. Lyngstad and Vold 2015) has provided a better basis for assessment of Eccentric domed bog, Concentric domed bog and Plateau bog in particular. Information on occurrence, ecological condition and development of a series of mire types are included in two Emerald Network reports (Lyngstad 2014, Lyngstad et al. 2016a), a report on peat extraction (Øien et al. 2017), as well as a report on mires in northern Norway (Øien et al. 2016). Many of the above-mentioned resources use information extracted from the Myrbase portal (includes mire localities) run by the Norwegian University of Science and Technology (NTNU) University Museum, and the Naturbase portal run by the Norwegian Environment Agency. Myrbase and Naturbase have also been used as primary sources for the Red List assessments in 2018. Rekdal et al. (2016) have provided an improved basis for assessing the area of mires and swamp forest. In order to identify assessment entities, and provide a Red List assessment of these, the information resources prepared for the project by the Norwegian Biodiversity Information Centre have been important, along with guidelines from the International Union for Conservation of Nature IUCN (Bland et al. 2017).

Expert Committee

The expert committee has consisted of Anders Lyngstad (chair), Dag-Inge Øien, Asbjørn Moen, Tor Erik Brandrud and Marit Mjelde. Lyngstad, Øien and Moen have assessed 25 entities under mire, spring and wet meadow, including all the peatland formations. Brandrud has assessed 7 entities under swamp forest.

Acknowledgements

We have cooperated with other expert groups to ensure sound assessments of nature in the transition between wetland and the other groups of major ecosystem types. This has been particularly important in terms of forest and freshwater and this has been taken care of by Brandrud and Mjelde.

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