Fen
A fen is a type of wetland where peat forms. Fens get their water from rain and also from groundwater that has flowed through soil and rock, which brings them minerals and nutrients.[1] Because they are in contact with groundwater, fens are less acidic than bogs, although they are still slightly acidic environments.[2]
Types
Fens can be divided by how water moves through them. In topogenous fens, such as basin fens and floodplain fens, water moves mostly up and down through the peat. In soligenous fens, which include wet areas around springs and flushes, it moves mostly sideways.[3]
Fens can also be divided by the chemistry of their water. "Poor-fens" are fed by water from rocks such as sandstone and granite and are found mainly in the uplands. "Rich-fens" are fed by water rich in calcium and other minerals and are found mainly in the lowlands.[4] Fens are often a stage in a longer process: if left alone, some lowland fens would slowly turn into wet woodland or raised bog.[5]
Wildlife
Fens can be very rich in wildlife. In the United Kingdom, some fens contain up to 550 species of flowering plants and ferns, about a third of the country's native plants, and up to half or more of its dragonfly species.[6] Animals found in fens include water voles and harvest mice, and birds such as marsh harriers, warblers and bitterns.[7]
Conservation
In the UK, lowland fen is found across the whole of the British Isles, but large remnants survive in places such as the Somerset Levels, South Yorkshire and the Fens of East Anglia.[8] Lowland fens were listed as a priority habitat under the UK Biodiversity Action Plan; a 2008 description published by the Joint Nature Conservation Committee (JNCC) says that fen vegetation, as elsewhere in Europe, "has declined dramatically in the past century", and that the UK is thought to hold a large share of the fen surviving in the EU.[9] The JNCC describes the UK's lowland wetlands as "amongst the rarest and most threatened habitats in the UK".[10]
See also
References
- ↑ Biodiversity Reporting and Information Group (2008). Ant Maddock (ed.). "UK Biodiversity Action Plan Priority Habitat Descriptions: Lowland Fens" (PDF). Joint Nature Conservation Committee. Retrieved 20 October 2026.
Fens are peatlands which receive water and nutrients from the soil, rock and ground water as well as from rainfall: they are minerotrophic.
- ↑ "Fen". IUCN UK Peatland Programme. Retrieved 20 October 2026.
Contact with groundwater makes fens less acidic than bogs; however, fens are still slightly acidic environments.
- ↑ Biodiversity Reporting and Information Group (2008). Ant Maddock (ed.). "UK Biodiversity Action Plan Priority Habitat Descriptions: Lowland Fens" (PDF). Joint Nature Conservation Committee. Retrieved 20 October 2026.
Two types of fen can broadly be distinguished: topogenous and soligenous. Topogenous fens are those where water movements in the peat or soil are generally vertical. They include basin fens and floodplain fen. Soligenous fens, where water movements are predominantly lateral, include mires associated with springs, rills and flushes
- ↑ Biodiversity Reporting and Information Group (2008). Ant Maddock (ed.). "UK Biodiversity Action Plan Priority Habitat Descriptions: Lowland Fens" (PDF). Joint Nature Conservation Committee. Retrieved 20 October 2026.
Poor-fens, where the water is derived from base-poor rock such as sandstones and granites occur mainly in the uplands ... Rich-fens, are fed by mineral-enriched calcareous waters (pH 5 or more) and are mainly confined to the lowlands
- ↑ "Fen". IUCN UK Peatland Programme. Retrieved 20 October 2026.
They are also transitional habitats, and some lowland fens would develop into wet woodlands or raised bogs over time, if left alone.
- ↑ Biodiversity Reporting and Information Group (2008). Ant Maddock (ed.). "UK Biodiversity Action Plan Priority Habitat Descriptions: Lowland Fens" (PDF). Joint Nature Conservation Committee. Retrieved 20 October 2026.
Some can contain up to 550 species of higher plants, a third of our native plant species; up to and occasionally more than half the UK's species of dragonflies
- ↑ "Fen". IUCN UK Peatland Programme. Retrieved 20 October 2026.
voles ( Arvicola amphibius ) and harvest mice ( Micromys minutus ) can also be found in fens, as well as birds such as marsh harriers ( Circus aeruginosus ), warblers and bitterns ( Botaurus stellaris )
- ↑ "Lowland wetland habitat descriptions: UK Terrestrial & Freshwater Habitat Types" (PDF). Joint Nature Conservation Committee. Retrieved 20 October 2026.
for example the Somerset Levels, South Yorkshire and Fens of East Anglia. Lowland fen is found across the whole of the British Isles
- ↑ Biodiversity Reporting and Information Group (2008). Ant Maddock (ed.). "UK Biodiversity Action Plan Priority Habitat Descriptions: Lowland Fens" (PDF). Joint Nature Conservation Committee. Retrieved 20 October 2026.
The UK is thought to host a large proportion of the fen surviving in the EU. As in other parts of Europe fen vegetation has declined dramatically in the past century.
- ↑ "Lowland wetland habitat descriptions: UK Terrestrial & Freshwater Habitat Types" (PDF). Joint Nature Conservation Committee. Retrieved 20 October 2026.
consequently they are amongst the rarest and most threatened habitats in the UK