FENS, including LOWLAND RAISED BOG and LIMESTONE MARSH AND VALLEY LOCAL HABITAT ACTION PLAN for CAMBRIDGESHIRE and PETERBOROUGH Last Updated: April 2009 1 CURRENT STATUS 1.1 Context Fen habitats may be described as short to tall herbaceous vegetation formed over peat where the water-table is generally close to soil level and where that water tends to flow laterally through the upper soil horizons. They can be split into base-rich or base-poor fens, and topogenous (catchment-fed) or soligenous (groundwater-fed) fens. Fen systems can have a mosaic of basic and acidic fens, within quite small spatial scales, and a combination of water-sources in addition to rainfall. The emphasis of this plan will be on base-rich, open fens on a peat base because these are the predominant type in Cambridgeshire; it does however also include some acid fen, one remnant Lowland raised-bog at Holme Fen NNR (originally fed by rainfall alone, but now drying out), and a few Limestone Marsh and Valley sites around Peterborough. These latter habitats have many affinities with fens and may grade into true fen vegetation. With this complexity, management decisions must be based on site- specific needs and aims. Fen habitats support a wide variety of animal and plant species: some can hold up to 550 species of higher plants, and several thousand species of insects. Fen vegetation in Cambridgeshire once covered many thousands of hectares and was traditionally cut for fuel as well as mown and grazed; most has now been lost through drainage and cultivation and the peats degraded through subsequent oxidation and wind erosion. The potential for new fens to form or be created is severely reduced because of the highly-managed nature of the drainage systems. However, two of the largest, landscape-scale habitat restoration and creation projects in lowland Britain are in Cambridgeshire, the Great Fen Project, near Peterborough, and the Wicken Fen Vision, north of Cambridge. Both of these projects aim to develop a mosaic of wildlife habitats, including wetland habitats, through careful management of water levels, protection of the peat soils and the use of extensive grazing regimes. The exceptional contribution that these projects make towards the maintenance and restoration of wetland habitats, including fens, is recognised. Cambridgeshire and Peterborough Biodiversity Action Plan Page 1 1.2 Biological Status The surviving resource of fen vegetation is confined mainly to a few large sites, namely Wicken Fen NNR, Chippenham Fen NNR and Woodwalton Fen NNR, all of which are SSSIs, components of SACs and Ramsar sites. However, other important sites include Holme Fen NNR/SSSI, Dernford Fen SSSI, Fulbourn Fen SSSI, Stow-Cum-Quy Fen SSSI, Wilbraham Fen SSSI and Sawston Hall Meadows SSSI. There are also other smaller fragments of fen vegetation in areas such as the Ouse and Nene Washes, and in the open Fenlands, forming strips along ditchsides or patches in field corners. These make an important contribution to biodiversity, although they are often degraded and rather species-poor. The UK is thought to hold a substantial proportion of surviving fen in the EU. It is important not to conflate the word ‘fens’ with ‘The Fenlands’ or ‘Fens’ of East Anglia. These cover an area of 4,100 km 2, have been shaped by centuries of flood, drainage and settlement and have their own NE Natural Area Profile; although they once supported many thousands of hectares of fen vegetation, the Fens are now largely under intensive cultivation. As mentioned above, Cambridgeshire is home also to large scale ‘Fen’ restoration projects at Wicken Fen, at Kingfisher’s Bridge nearby and in the Great Fen Project area near Peterborough. These restoration projects involve the restoration of agricultural land to wetlands with complex mixes of vegetation types but a proportion of the vegetation which results is likely to be true fen vegetation. One important role that these projects fulfil is one of the development of extensive buffer zones around core sites of very high conservation value. 1.3 Species A number of species of conservation interest occur in fen vegetation and to a greater or lesser extent in fen habitats in Cambridgeshire; they are listed in Appendix I. Cambridgeshire and Peterborough Biodiversity Action Plan Page 2 2 CURRENT FACTORS AFFECTING FENS IN CAMBRIDGESHIRE • Fens are a successional habitat and active management is required to maintain them. Without management, the accumulation of organic litter and colonisation by woody plants causes drying and leads to the replacement of fen vegetation with scrub and woodland. • Reduction in the water table as a result of abstraction from aquifers and in particular changes in land drainage can reduce the important lateral movement of water into and through fens. • Eutrophication of incoming waters can alter the plant and animal communities found in fens. • Isolation of fens in the county prevents dispersal of plants and small animals between sites. • Climate change. A substantial change in water supply would alter the balance of hydrological inputs to fens and a significant rise in temperature would produce wide-ranging effects such as changes in water quality, the structure of fen vegetation types and the make-up of invertebrate communities. A long-term decrease in rainfall could alter groundwater regimes and may ultimately depress levels in the underlying aquifers to such an extent that these fens cease to be fed with spring waters. All efforts to remedy the situation may then be ineffective. Warmer winters and milder conditions characteristic for urban habitats alter behaviour of animals (increased activity) that would otherwise hibernate. This can lead to losses of energy and consequently affecting the productivity in the breeding season. This process has been well documented for common toads. 3 CURRENT ACTION Legal Status There is a range of national, regional and local planning policies that, along with other legislation, set out requirements for biodiversity conservation. Planning Policy Statement 9 (PPS9): Biodiversity and Geological Conservation (ODPM, 2005) is the key national planning policy document for biodiversity in England. It sets out the key principles that regional planning bodies and local planning authorities should adhere to in order to ensure that biodiversity is fully considered in the development of planning policy and determination of planning applications. The seven policies within the Environment chapter of the Regional Spatial Strategy for the East of England (GO-East, May 2008) set out the requirements for proper consideration to be given to the potential effects of development on the natural, built and historic environment of the East of England. At the local level, the planning policy documents of local planning authorities should take account of BAP and HAP targets and priorities, setting overarching policies for the protection and enhancement of biodiversity. Cambridgeshire and Peterborough Biodiversity Action Plan Page 3 There are eleven sites in Cambridgeshire which are notified as SSSI on account of the presence, at least in part, of fen vegetation and habitats. Some of these also have European designations (RAMSAR, Special Areas of Conservation, Special Protection Areas) The SSSIs are: Bonemills Hollow* Cam Washes Chippenham Fen Dernford Fen Fowlmere Watercress Beds Fulbourn Fen Holme Fen Stow-cum-Quy Fen Sutton Heath and Bog * Upware north pit Wansford Meadow Wicken Fen Whitewater Valley* Wilbraham Fen Woodwalton Fen * = support habitats including lowland raised bog and limestone marsh and valley The number of County Wildlife Sites that contain fen is difficult to be sure of but there are probably about 16 which contain significant areas of fen vegetation, as opposed to reedmace- or reed-swamp. Management, guidance and research • At Wicken Fen NNR between 2000 and 2006, 55 hectares of scrub has been removed and open fen habitats restored. The fen vegetation is now maintained through a combination of traditional cutting regimes and low density grazing with Konik ponies. The summer water deficit suffered at Wicken Fen has been investigated and a remedy is being implemented in conjunction with Natural England and the Environment Agency. • At Holme Fen NNR the grassy glades and acid grassland/heath are mown, but a non-intervention management policy operates on most of its woodland. Plans to recreate and extend bogs are at the investigation stage. This may include lowering the ground level, putting an impermeable membrane in to isolate the water supply from farmland, diverting arterial drainage ditches and raising water levels in adjoining farmland. • At Woodwalton Fen NNR 30 to 40 ha of scrub was cleared in the latter half of the 20 th Century and these areas are maintained with an ongoing Cambridgeshire and Peterborough Biodiversity Action Plan Page 4 cutting and grazing regime. A further 30ha has been cleared since 2000 and incorporated into the management regime. In a few areas, scrub removal on a 20-year cycle also occurs and there is an extensive programme of 5-10 year coppicing. This creates a diverse habitat, and is also very cost-effective. This fen also acts as flood balancing for the Middle Level and there are concerns about the quality of this water. • At Chippenham Fen NNR the core fen-meadows have been mown for a number of decades. However, in 2001 water buffalo were introduced in an attempt to reduce the increasing management burden generated by the ongoing scrub removal programme. • Large scale recreation of fens is occurring on lands adjacent to Woodwalton and Holme Fens (Great Fen Project), by Wicken Fen (Wicken Vision) and also at Kingfisher Bridge near Wicken Fen. At Wicken 330 ha have been acquired for the creation of nature reserve habitats, 62 ha at Kingfisher’s Bridge and 1700ha at Woodwalton/Holme. Not all of this land will develop into fen vegetation but where topography and availability of water allow, a significant proportion may be expected to, exceeding by a very substantial margin the target for fen re-creation set out in the last Fens LHAP.