Fens
Fens are dynamic, semi-natural systems and management is generally needed to maintain open fen communities and their related species richness. Without appropriate management and water supply, natural processes will lead to scrub and woodland forming.
Norfolk is considered to have the best representation of fen types in England, particularly valley head and floodplain fens. Fen vegetation has declined significantly in the last century, both nationally and across Europe, and fens are now a UK Priority Biodiversity Action Plan habitat. There is also a Biodiversity Action Plan for Fens in Norfolk
Fens can be described as 'poor-fen' or 'rich-fen'. Poor-fen, where the water is derived from base-poor rocks occurs in the lowlands with heathland. Rich-fens are fed by mineral-enriched calcareous waters.
Fen habitats support a particularly diverse array of plants and animals, including:
- Over 250 plant species, some of which cannot be found anywhere else in lowland Britain, such as the fen orchid;
- Birds, such as bittern, bearded tit and marsh harrier;
- Mammals, such as water vole, otter, harvest mouse, vole and water shrew;
- Butterflies such as the swallowtail. The British race of this species occurs only on fens in the Norfolk Broads;
- Moths, including rare species such as reed leopard and fen's wainscot;
- Numerous species of dragonflies and damselflies, such as the scarce chaser and the Norfolk hawker;
- Many other invertebrates, including BAP species such as the reed beetle, a ground beetle, the lesser water measurer, a weevil, and the diving beetle.
Norfolk Status
Norfolk is especially rich in fen habitats, supporting a large proportion of the UK total for certain types. The Broads natural area possesses some 5,000 ha of rich-fen habitat, mostly of the floodplain type, with some examples of valley fen. Rich-fen is also associated with pingo sites such as Thompson Common, East Walton and Adcock's Common and Foulden Common. Elsewhere, numerous rich-fens of the valley head type are found associated with the county's rivers. In north-west Norfolk, some 350 ha of poor-fen is found primarily associated with Roydon Common and Dersingham Bog.
A large proportion of fen habitat in Norfolk has been designated SSSI, with much of this also candidate SAC and Ramsar site. Many fens are managed by conservation bodies, some of which are also managed as NNRs.
Norfolk Fens Assessment Project
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The Fens Assessment Project was undertaken during 2005/6, with funding from the Norfolk Biodiversity Partnership, Breckland District Council and the Environment Agency. The aim of the project was to create a distribution map of all non-SSSI fen sites outside the Broads area; and to assess the management and condition of individual sites to identify those most urgently in need of management or restoration, an action target identified in the Norfolk Fen Biodiversity Action Plan.
Fen vegetation has declined significantly in the last 100 years, mainly as a result of neglect, desiccation, cultivation and enrichment. As a result, fens are now a Priority Biodiversity Action Plan habitat in the UK.
Norfolk is considered to have the best representation of fen types in England, and the highest quality sites in the county are notified as SSSIs/European sites or County Wildlife Sites. Other areas of fen are known to exist, however, but have not been identified or mapped. The mapping element of the project was therefore important in bringing this information together to help protect these sites within the planning and grant scheme processes, as well as in the context of other land management uses.
Using the County Wildlife Site database, aerial photographs and soil maps of Norfolk, the project identified and mapped 678 fen and potential fen sites, of which 174 are wet woodland. The digital map is linked to an Access database which gives 25 fields of key data for each site. The database also identifies sites within 5km of, or adjacent to, wetland/fen SSSI sites, as the condition of these can be a useful indicator of underlying problems, such as drying, to which the SSSI may also be vulnerable.
The condition and management status of approximately 200 of the sites (about 30%) were also assessed by walk-over survey. Almost two-thirds of these were found to be either in decline or unfavourable, with the fen vegetation destroyed in about 3% of cases. Approximately half of the declining and unfavourable sites appeared to be unmanaged. Only one quarter of sites seen appeared to be in favourable condition, with a further 6% in partly favourable and partly unfavourable condition.
18% of sites, with almost two-thirds of these within 5km of a wetland/fen SSSI, and three directly adjacent. Inappropriate management is the main cause of decline at 15% of sites, and over-grazing, including serious poaching, at nearly one-tenth of sites. Other threats noted within the sample included recreational pressure, pollution, enrichment and potential building development.
As a result of this project, a number of sites have been prioritised for restoration, and, in total, 95% of the sites have been recommended for further action. The next phase of this work will be undertaken as part of the Fens Restoration Project commencing in 2008.
Click here for a copy of the Fens Assessment Project summary report.
The Fen Restoration Project
This project (2008-2011) represents the second phase of the Fen Assessment Project, which identified a number of fen sites as urgent priorities for restoration or remedial action, based on site quality and rate of decline. An additional 140 sites were given high priority for further action.
The project has so far received funding from the Norfolk Biodiversity Fund, Plantlife International, the Environment Agency, Anglian Water and Norfolk County Council.
Hilgay Wetland Creation Project
Because of changes to the management of the coastal flood defences on the north Norfolk coast at Norfolk Wildlife Trust’s Cley Marshes nature reserve over the past few years, it is predicted that the site’s vital reedbed habitat will eventually be lost due to an increased influx of saline water into freshwater areas. This will gradually change the area’s characteristics, reduce reedbed habitat and eventually make it unsuitable for breeding bittern.
As a result of these changes the Environment Agency together with Norfolk Wildlife Trust have jointly embarked on a wetland creation project in the Fens near Downham Market to replace the habitat anticipated to be lost at NWT Cley marshes.
The Hilgay Wetland Creation Project will create reedbed habitat on over 60 hectares (154 acres) of former agricultural site in Methwold parish, near to the village of Hilgay in west Norfolk. It is the first part of NWT’s ambitious Wissey Living Landscape project.
The Hilgay project received planning permission in June 2010 and the site will be modified in phases over the next few years through the construction of bunds to retain water and ditches to help water circulation. A large lake will be created to retain water to supply the wetland. Reeds will be planted and encouraged to spread to provide suitable habitat for Bittern. The aim is to have a mixture of open water, wet grassland, wet ditches and reedbed habitats which hopefully will support wetland bird species not currently found on the site including common crane, marsh harrier, water rail, bearded tit and reed warbler.
Why so much effort to protect bitterns?
The bittern became extinct in Britain in 1886 but re-colonised the country in 1911. The population rose to a peak in the 1950s of 80 males (bittern numbers are measured most easily by counting booming males). It then declined as a result of lack of habitat management and quality to a minimum of 11 males in 1997. Since then active conservation work like that planned for Hilgay has allowed the population to recover. In 2009 there were 82 males in the UK with 12 in the Fens, 19 in the Norfolk Broads and 28 on the Suffolk coast.
Many of the sites with breeding bittern on the Suffolk coast and in the Norfolk Broads are threatened by sea level rise. It is therefore important that projects like the Wissey Valley Living Landscape are implemented to provide new habitat for bittern and other reedbed specialist species.
Project diary
Construction work for the new wetland commenced in September 2010, with the work being carried out by Wisbech-based company Fen Ditching. Phase 1 includes the construction of a bund around the outside of the site and involves excavation of material and the creation of a wide perimeter ditch. The ditch will fill with water and become a valuable habitat for wildlife.
Access to the site
Please do not enter the site as construction traffic and excavated trenches are present. Excellent views over the site can be had from the bridleway along the River Wissey.
Contact
For more information contact Nick Carter, Norfolk Wildlife Trust Fens Conservation Officer: nickc [at] norfolkwildlifetrust [dot] org [dot] uk