Palsa mire
Quick facts
| Red List habitat type | code RLD3.1 |
|---|---|
| Threat status | |
| Europe | Critically Endangered |
| EU | Critically Endangered |
| Relation to |
|
| Source | European Red List habitat factsheet |
| European Red List of habitats reports | |
| European Red List of habitats (Excel table) |
Summary
This habitat type is consists of mires in the subarctic region with sporadic permafrost, most characteristically palsa mounds elevated by permafrost lenses. Palsa mires are found in the discontinuous permafrost zone of Iceland, northern Fennoscandia and arctic Russia, in areas with average annual temperature below -1 °C, with climatic optimum between -3 to -5 °C and annual precipitation below 450 mm. Typically, palsa mounds occur in groups in the central, thick-peated areas of palsa mires. Palsa mounds with dome shape are 10-100 m wide and 2-7m high. Other types are longitudinal string-form or extensive plateau- form palsas that reach 1-3 m high. Palsa mound summits are covered by Sphagnum peat that insulates heat so that the active layer of thaw is limited to 30-60 cm. The perennial frozen core of palsa mounds consists of frozen peat and silt material with ice lenses and crystals. Pounikko-type hummock ridges (D3.12) formed by seasonal frost action can be found particularly in marginal areas of palsa mires. Palsas can have different successional stages: young palsa formations have Sphagnum hummock vegetation, while older palsa mounds become dry and their exposed peat surfaces are subject to erosion that may lead to melting and partial collapse. Completely melted palsas result in the formation of thermokarst ponds.
The palsa mound summits provide dry microhabitats in palsa mires. Typical species growing on the palsa mounds include Dicranum elongatum, Polytrichum strictum, Empetrum nigrum and Rubus chamaemorus and many lichens. Sides of palsa mounds often have abundant Betula nana, Ledum palustris and Eriophorum vaginatum. Palsa mires resemble D3.2 Aapa mires in hydrology and vegetation of the wet mire surfaces of areas between the palsa mounds, but regular hummock-string patterning is usually not found. Palsa mires are usually weakly minerotrophic and vegetation types overlap with those of D2.2a Poor fens and D2.3 Quaking mires. In the wet surfaces, Sphagnum lindbergii, S. riparium, Eriophorum angustifolium and Carex rotundata are typical dominant species.
Indicators of good quality:
- Under natural conditions, water table is very close to peat surface in fen areas between palsa mounds and carpets of mosses prevail with abundance of characteristic sedges.
- There are no ditches that drain or disconnect water flow (seepage or overland flow) in the palsa mire complex.
- Only few of the palsa mounds are melting and collapsing, indicating natural dynamics, while most palsa mounds remain frozen with intact peat cover.
- Seasonal thaw of permafrost, the so called active layer, may reach 50-60 cm, while substantially deeper active layer approaching 1-m depth indicates melting and collapse.
Threat status
Synthesis of Red List assessment
However, there are certain comments to the assessment that need to be mentioned. First of all, monitoring of the active layer depth was possibly undertaken on big palsa mounds whose degradation may have occurred as part of their natural cycle. Furthermore, palsa mounds themselves are only components of the palsa mire habitats, while other indicators of habitat quality are poorly known and have not been considered in this assessment. In addition, extrapolation of recent trends to the future is heavily dependent on which precise recent period of climate fluctuation was included in the data. It is also noteworthy that there is no complete information available on area cover and decrease throughout the whole distribution of the habitat type.
| EU | |
| Red List Category | Red List Criteria |
| Critically Endangered | E |
| Europe | |
| Red List Category | Red List Criteria |
| Critically Endangered | E |
Confidence in the assessment
Pressures and threats
- Transportation and service corridors
- Paths, tracks, cycling tracks
- Human intrusions and disturbances
- Off-road motorized driving
- Trampling, overuse
- Natural System modifications
- Human induced changes in hydraulic conditions
- Natural biotic and abiotic processes (without catastrophes)
- Erosion
- Climate change
- Temperature changes (e.g. rise of temperature & extremes)
- Flooding and rising precipitations
Habitat restoration potential
Trends in extent |
|
Average current trend in quantity |
|
Decreasing  |
Decreasing |
| EU28 | EU28+ |
Trends in quality |
|
Average current trend in quality |
|
| Decreasing |
Decreasing |
| EU28 | EU28+ |
Conservation and management needs
List of conservation and management needs
- Measures related to wetland, freshwater and coastal habitats
- Restoring/Improving the hydrological regime
- Measures related to spatial planning
- Establish protected areas/sites
- Establishing wilderness areas/allowing succession
- Legal protection of habitats and species
Distribution
Geographic occurrence and trends
| EU28 | Present or presence uncertain | Current area of habitat (Km2) | Recent trend in quantity (last 50 years) | Recent trend in quality (last 50 years) |
|---|---|---|---|---|
| Finland mainland | Present | 104 | Decreasing | Decreasing |
| Sweden | Present | 137 | Decreasing | Decreasing |
| EU28 + | Present or presence uncertain | Current area of habitat (Km2) | Recent trend in quantity (last 50 years) | Recent trend in quality (last 50 years) |
|---|---|---|---|---|
| Norway Mainland | Present | 150 | Decreasing | Decreasing |
| Iceland | Present | Unknown | Decreasing | Decreasing |
Extent of Occurrence, Area of Occupancy and habitat area
| Extent of Occurrence (EOO) (Km2) | Area of Occupancy (AOO) | Current estimated Total Area | Comment | |
|---|---|---|---|---|
| EU28 | 104750 | 287 | 241 | |
| EU28+ | 417 | 391 | Iceland area missing |
EOO = the area (km2) of the envelope around all occurrences of a habitat (calculated by a minimum convex polygon).
