Guidelines for the Selection of Biological Heritage Sites
6. Section 1: Habitat Guidelines
6.4 SWAMP AND FEN
Application (all swamp and fen guidelines)
This category includes a variety of wetland habitats which receive their water not only from rainfall but also from groundwater sources. They include open water transitions, flood-plain and basin mires, valley mires and flushes and fen-meadows as defined in NCC (1989).
Fe1 Swamp and fen sites over 0.5 hectare and in excess of 20m wide. Species-poor examples of the following NVC(1) types may, however, be excluded:
S10 Equisetum fluviatile swamp
S12 Typha latifolia swamp (sites less than 1 hectare only)
S22 Glyceria fluitans swamp
S28 Phalaris arundinacea fen
M23 Juncus effusus/acutiflorus - Galium palustre pasture
M25 Molinia caerulea - Potentilla erecta mire
Application
This guideline should be applied to all swamp and fen sites which fall in those categories listed after the main title, and which are defined in NCC (1989).
Justification
With a few exceptions, swamp and fen habitats in Lancashire are small and highly fragmented. Any sites meeting the criteria given are of significant nature conservation value, with the possible exceptions of those NVC types listed. The latter are generally of lower nature conservation interest, and in some cases, at least, may be readily re-created. Whilst particular sites may be more valuable, they cannot in general be considered to be automatically part of the Countys critical environmental capital (see Introduction, para. 2.1).
Fe2 Swamp and fen sites (flushes) with 4 or more of the species listed in Table 2.
Application
This guideline is to be applied to flushes or flush-systems less than 0.5 hectare in extent.
Justification
Provided that they remain unaffected by inorganic nitrogenous fertilisers, small areas which are flushed by ground water emerging at seepages or springs often contain a high proportion of the botanical diversity of the upland or upland fringe environments in which they are found. They are an important refuge for decreasing species which were formerly found in bogs (see following section) before widespread drainage, burning and heavy grazing eliminated them. The plant species listed in Table 2 are characteristic of flushes which remain largely unaffected by agricultural improvement.
| Scientific Name | Common Name |
| Anagallis tenella | Bog Pimpernel |
| Andromeda polifolia | Bog Rosemary |
| Carex curta | White Sedge |
| Carex dioica | Dioecious Sedge |
| Carex disticha | Brown Sedge |
| Carex hostiana | Tawny Sedge |
| Carex viridula | Yellow Sedge |
| Carex pulicaris | Flea Sedge |
| Carex rostrata | Bottle Sedge |
| Dactylorhiza maculata | Heath Spotted-orchid |
| Drosera rotundifolia | Round-leaved Sundew |
| Eleocharis quinqueflora | Few-flowered Spike-rush |
| Galium uliginosum | Fen Bedstraw |
| Hydrocotyle vulgaris | Marsh Pennywort |
| Menyanthes trifoliata | Bogbean |
| Narthecium ossifragum | Bog Asphodel |
| Parnassia palustris | Grass-of-Parnassus |
| Pedicularis sylvatica | Lousewort |
| Pinguicula vulgaris | Common Butterwort |
| Potamogeton polygonifolius | Bog Pondweed |
| Potentilla palustris | Marsh Cinquefoil |
| Selaginella selaginoides | Lesser Clubmoss |
| Salix repens | Creeping Willow |
| Trichophorum cespitosum | Deergrass |
| Triglochin palustris | Marsh Arrowgrass |
| Trollius europaeus | Globeflower |
| Vaccinium oxycoccus | Cranberry |
| Valeriana dioica | Marsh Valerian |
Fe3 The best examples of each of the following topographical or hydrological types of swamp and fen remaining in each of the Landscape Zones(3) where they occur, should these fail to meet guidelines Fe1 and Fe2.
Floodplain fen
Springs and flushes
Basin fen
Fen meadow
Open water transitions
Shelf or spur mire
Valley mire
Application
The best examples are identified on the basis of the relevant NCR criteria, and more particularly on the detailed guidance given for each of the listed topographical/hydrological types in NCC (1989) (pp138-148).
Some mire systems are mosaics of swamp and fen, and bog habitats (see Guideline Bo5), or are intermediate in character. Such sites may be considered for inclusion under guidelines Fe3 or Bo5, whichever is the more appropriate.
Justification
In view of the rarity and vulnerability of many swamps and fens, it is considered important that the guidelines should identify the best remaining examples of all major types of swamp and fen in Lancashire, even if the only surviving examples of a particular type fail to meet Guidelines Fe1 or Fe2.
(1) National Vegetation Classification, published as Rodwell
(1995).
(2) Scientific and common names are taken from Stace
2nd Ed. (1997)
(3) See Appendix 1.