What is it?
Fens are peatlands that receive water and nutrients from the soil, rock and groundwater, as well as from rainfall.
Fens can be described as ‘poor-fens’ or ‘rich-fens’.
Poor-fens, where the water is derived from base-poor rock such as sandstones and granites, occur mainly in the uplands or are associated with lowland heaths. They are characterised by short vegetation with a high proportion of bog mosses Sphagnumspp. and acid water (pH5 or less).
Rich-fens are fed by mineral-enriched calcareous waters (pH5 or more) and are mainly confined to the lowlands and where there are localised occurrences of base-rich rocks such as limestone in the uplands.
Lowland fens occur on soils that are at least periodically waterlogged. They range from small to extensive, but are generally circumscribed and limited in extent by agricultural or forestry activity. The category encompasses a range of water supply mechanisms. Variety also arises from differences in the constituents of the water, fluctuation levels and movement.
Fen habitats support a diversity of plant and animal communities. Some can contain up to 550 species of higher plants – a third of our native plant species. They host up to, and occasionally more than, half the UK’s species of dragonflies, several thousand other insect species, as well as being an important habitat for a range of aquatic beetles. In intensively farmed lowland areas, fens occur less frequently, are smaller in size and more isolated than in other parts of the UK.
The situation in the South East
|Extent in England|| 8,000 ha
|Extent in the SE region|| 1,629 ha
|Percentage UK resource in the SE||20%|
|Extent covered by SSSI designation|
Rate of Change
|County||1998 extent (ha)||2008 extent (ha)|
|Isle of Wight||20||12|
Fens are dynamic semi-natural systems and, in general, management is needed to maintain open-fen communities and their associated species richness. Without appropriate management (eg. mowing, grazing, burning, peat cutting, scrub clearance), natural succession will lead to scrub and woodland forming. Current factors affecting this habitat type are:
- Abstraction. Past loss of area by drainage and conversion to intensive agriculture. Excessive water abstraction from aquifers has dried up or reduced spring line flows and generally lowered water tables. Abstractions have also affected the natural balance between the differing water qualities of ground water and surface water
- Small total area of habitat and critically small population sizes of several key species dependent on the habitat
- Lack of or inappropriate management of existing fens, leading to drying, scrub encroachment and succession to woodland
- Valley fens are particularly susceptible to agricultural run-off and afforestation within the catchment
- Enrichment or hyper-trophication resulting in changing plant communities
Vision for Lowland Fen
The South East Biodiversity Forum’s vision for this habitat is that there should be:
- No further loss of existing habitat
- Good management including, where appropriate, scrub control, light grazing and visitor management
- No damage to site integrity from activities arising outside the sites, eg. inadequately managed public access • Re-creation of lowland fen on appropriate sites to restore some past losses, including the linking up of fragmented sites
- Greater public appreciation of lowland fen and their specialist wildlife, including greater awareness of the impacts of human pressures
How we can deliver this vision
- MoD Integrated Land Management Plans (www.defence-estates.mod.uk/conservation/2_biodiversity.php)
- Provision of land management advice by statutory (Natural England) and non-statutory agencies (NGOs)
- Agreements under Higher Level Stewardship
- Project funding (SITA Trust, WREN etc)
- Site management plans
- Land purchase/management agreements by NGOs
- River restoration linked to Water Framework Directive Programme of measures
- Catchment Sensitive Farming tackling diffuse pollution issues