Lowland Fens

Habitat Description

Fens occur on soils that experience at least periodic waterlogging. They can encompass a wide range of plant communities on both peat and mineral soils and can include swamps, mires, springs and flushes. Fens often occur in association with other semi-natural habitats especially wet woodland, wet grassland and open water. In Northamptonshire fens occur solely on mineral soils, in the form of swamps, springs and flushes, and are generally associated with other wetland habitats. The following NVC communities may be present:

S5 Glyceria maxima (reed-sweet-grass) swamp

S6 Carex riparia (greater pond-sedge) swamp

S7 Carex acutiformis (lesser pond-sedge) swamp

S10 Equisetum fluviatile (water horsetail) swamp

S12 Typha latifolia (reedmace) swamp

S14 Sparganium erectum (branched bur-reed) swamp

S22 Glyceria fluvitans (floating sweet-grass) water margin vegetation

S23 Other water margin vegetation

S26 Phragmites australis Urtica dioica (common reed nettle) tall herb fen

S28 Phalaris arundinacea (reed canary-grass) tall herb fen

  Swamps tend to be relatively species-poor wetland habitats dominated by coarse grass or sedge species. They typically form in depressions in the ground, or as fringing vegetation alongside rivers, ponds, reservoirs etc. Springs occur where water wells up from underground aquifers, whilst flushes occur on sloping ground with impeded drainage. Species assemblages are partly determined by the underlying geology of the area.

Current UK Status and Trends

Total UK extent is approximated at 18,050 ha.

Estimated Current Northants Resource

Rare, up to 38 ha occurring in association with other wetland and grassland habitats.

Progress Towards BAP Targets 2002-2007

Previously contained within the 'Reedbeds and Swamps' and 'Springs and Flushes' habitat action plans.

Lead Partner

The Wildlife Trust

Main Issues and Threats

  • Very little remaining in Northamptonshire. Much is isolated in small fragments, dangerously reducing species' population sizes and making it impossible for individuals to move between them.
  • Fragmentation due to drainage and reclamation for agriculture.
  • Degradation in quality and species diversity due to lack of management and drying out of land often leading to scrub encroachment and succession to woodland.
  • Reduction in water quality, an increase in the incidence of pollution, both point source and diffuse, and nutrient enrichment leading.

General Strategy

  • Burrow down into the Green Infrastructure strategy on a field-by-field basis to identify the current resources and highest priorities for linkage by sympathetic management of degraded sites and establishment of new sites.
  • Re-introduction of management and restoration of existing sites, funded primarily through the Countryside Stewardship Scheme (Advice can be provided by The Wildlife Trust, RNRP or FWAG).
  • Monitor and manage water level and quality at the catchment scale to promote rehabilitation of degraded sites and creation of new sites. Bringing land adjacent to fens and wet woodland into a set-aside scheme is important to reduce nutrient enrichment.
  • Ensure that management of flood risk works with and enhances natural systems, for example through the reconnection of watercourses with their floodplains.
  • Increase structural and floristic diversity and prevent dense scrub encroachment.
  • This habitat may occur across the whole of the county, therefore specific target areas occur wherever this habitat is identified.

Associated National Priority Species

  • Blood vein (moth)
  • Double dart (moth)
  • Goat moth
  • Greater water parsnip
  • Marsh stitchwort
  • Oblique carpet (moth)
  • Reed bunting
  • Scarce four-dot pin-palp
  • Shoulder-striped wainscot (moth)
  • The crescent (moth)
  • The concolorous (moth)
  • Tubular water-dropwort

Specific Management Required for Associated Species


Northamptonshire Status

Management Prescriptions

Key Sites

Greater water parsnip


Keep water in ditches open by occasional clearance with a bucket excavator or scythe. Prevent growth of carr and do not allow heavy grazing or frequent cutting.

Wadenhoe Marsh and Achurch Meadow SSSI, Achurch Marsh.


Target Code

Target Type

Target Description

Target Units

Northants Baseline Resource



Unit Cost £

Total Cost £


Maintain Extent

Maintain the current extent and standard of fen-type habitats.



No Loss






Restore 40 ha of floodplain to LWS standard fen-type habitats by 2015.





575/ha + 60/ha/yr

23,000 initial


Action Code

Action Description

Lead Partner

Support Partner(s)

Related Target


Identify the location of habitat that classifies as lowland fen.

Northamptonshire Biodiversity Partnership




Manage the water level at Southfield Farm Marsh SSSI in order to maintain the area of lowland fen.

The Wildlife Trust

Natural England



Manage water level and quality at a catchment scale to promote rehabilitation of existing sites.

Environment Agency

Water Companies (Anglian Water /Severn Trent Water)



Identify where greater water parsnip occurs and promote management for this species on these sites.


The Wildlife Trust



Through management of flood risk create 20 ha of lowland fen on flood plain.

Environment Agency




Restore 20 ha of lowland fen in areas adjacent to existing fen, reedbed and wet woodland through agri-environment schemes. Funding may be targeted to the Nene Valley.

Natural England