Report 307
Guidance on the interpretation of the Biodiversity Broad Habitat Classification (terrestrial and freshwater types): Definitions and the relationship with other classifications
(2000)
Jackson D.L.
This report contains the definitions for each of the terrestrial and freshwater types of the biodiversity Broad Habitat Classification

Summary

 
This report contains the definitions for each of the terrestrial and freshwater types of the biodiversity Broad Habitat Classification. The definitions given are based upon the descriptions agreed by the UK Biodiversity Group and published in volume two of the second tranche of action plans (UK Biodiversity Group 1998b). In addition to the definitions, annex 1 of this report contains tables which show the correspondence between these broad habitat types and a number of other standard habitat classifications and select lists of habitats of conservation interest commonly used in the UK for collecting and reporting data.
 
The information presented in this report will form the basis of a manual of interpretation for the Broad Habitat Classification which will be published by the Joint Nature Conservation Committee at a later date. In addition to the definitions and correspondence tables, the full manual will contain detailed descriptions including information on the structure, characteristic species, distribution and extent of each broad habitat type.
 
Content

 

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Acknowledgements

Many people have assisted during the review of the biodiversity Broad Habitat Classification. In particular the following people have assisted in drafting the definitions of the terrestrial and freshwater broad habitat types: Colin Barr (Centre for Ecology and Hydrology), Tim Blackstock (CCW), David Stevens (CCW), Jeanette Hall (EN), Richard Jefferson (EN), Keith Kirby (EN), David Horsfield (SNH) and Des Thompson (SNH). In addition the following people have supplied detailed comments on the definitions and the relationships with other habitat classifications: Helen Armstrong (SNH), Phil Boon (SNH), Bob Bunce (CEH), Bill Butcher (Somerset Environmental Records Centre), Andrew Coupar (SNH), Catherine Duigan (CCW), Tristan Hatton-Ellis (CCW), Liz Howe (CCW), David Howell (SNH), Jeff Kirby (on behalf of the Department of the Environment, Transport and the Regions), Jim Latham (CCW), Angus MacDonald (SNH), Roger Meade (EN), Carrie Rimes (CCW), Ian Strachan (JNCC) and Marcus Yeo (JNCC).
 

1Introduction
1.1 This report
This report contains the definitions for each of the terrestrial and freshwater types of the biodiversity Broad Habitat Classification. The definitions given are based upon the descriptions agreed by the UK Biodiversity Group and published in volume two of the second tranche of action plans (UK Biodiversity Group 1998b). In addition to the definitions, annex 1 of this report contains tables which show the correspondence between these broad habitat types and a number of other standard habitat classifications and select lists of habitats of conservation interest commonly used in the UK for collecting and reporting data.
 
The information presented in this report will form the basis of a manual of interpretation for the Broad Habitat Classification which will be published by the Joint Nature Conservation Committee at a later date. In addition to the definitions and correspondence tables, the full manual will contain detailed descriptions including information on the structure, characteristic species, distribution and extent of each broad habitat type.
 
1.2 Biodiversity Action Plan
The Convention on Biological Diversity was one of the major initiatives arising from the Earth Summit held in Rio de Janeiro in 1992. The Convention, which has been signed by 150 countries including the United Kingdom, and European Union, requires each contracting party:
 
"...to develop national strategies, plans or programmes for the conservation and sustainable use of biological diversity, or adapt for this purpose existing strategies, plans or programmes which shall reflect, inter alia, the measures set out in this Convention relevant to the Contracting Party concerned".
The UK Government response to the Convention was set out in Biodiversity: The UK Action Plan published in January 1994 which sets out the overall goal for biodiversity as:
 
"To conserve and enhance biological diversity within the UK and to contribute to the conservation of global biodiversity through all appropriate mechanisms".
 
One of the main outcomes of the UK Action Plan was the setting up of the UK Biodiversity Steering Group (now called the UK Biodiversity Group), who were given the task of preparing a detailed programme of action to achieve this objective. This group has co-ordinated the preparation of action plans for our most threatened species and wildlife habitats. Costed action plans which have set quantifiable targets have been produced for 391 species and 45 habitats of highest priority for conservation. These plans have been published in Biodiversity: The UK Steering Group report in 1995 (UK Steering Group, 1995) and five volumes of UK Biodiversity group: Tranche two action plans during 1998 and 1999 (UK Biodiversity Group 1998; 1998b; 1999b; 1999c).
 
In addition to identifying a suite of 'priority' habitats and species requiring action it was also considered important to understand how these are set within the context of the whole land surface and surrounding sea of the UK. A classification of broad habitat types has therefore been developed. 
 
 
1.3 Biodiversity Broad Habitat Classification
A framework classification for 37 habitat types across the whole of the UK was published in the UK steering group report (UK Steering Group 1995). A brief habitat statement was also published for each of these to inform national and local policy and action. Whilst this provided useful contextual information for the initial action planning process, there were gaps in the classification and the Biodiversity Steering Group recommended that these and some of the ambiguity in the habitat descriptions should be revisited.
 
The terrestrial and freshwater elements of the classification were therefore re-examined in 1997 by a cross-sectoral group led by the JNCC. The findings of this group were published in the second volume of tranche two action plans along with brief descriptions of each type (UK Biodiversity Group 1998b). Changes to the marine and coastal habitat types were reviewed separately by the Marine Targets Sub-Group and the revised classification and habitat statements for the coastal and marine types have been published in the fifth volume of tranche two action plans along with the costed action plans UK Biodiversity Group 1999c).
 
In addition to providing the framework for the biodiversity action plan process, the revised Broad Habitat Classification will also be used for UK reporting on the condition of protected sites. The Broad Habitat Classification is also the framework through which the Government is committed to meet its obligations for monitoring in the wider countryside. The Countryside Survey 2000 undertaken by the Department of the Environment, Transport and the Regions (DETR) and the Natural Environment Research Council (NERC) will provide information on the extent and quality of some of the more widespread broad habitat types.
 
 
1.4 The review of the terrestrial and freshwater broad habitat types
In reviewing the terrestrial and freshwater broad habitat types the group gave due regard to the original basis for the selection of broad habitats types, namely that (i) there should be a limited number of habitat types and (ii) the definitions should be simple and easily understood by a broad range of people. In addition the working group concluded that the biodiversity Broad Habitat Classification should aim to be provide:
 
  • a comprehensive framework for surveillance of the UK countryside and surrounding seas which is compatible with other widely-used habitat and land-cover classifications, particularly Phase 1 and the Countryside Survey 2000:
  • a means of setting priority habitats in context and a system for identifying gaps and emerging new priorities in the list of priority habitats; and
  • a means of characterising patterns and mosaics upon which wide-ranging species are dependent.

 

The working group used the following six criteria to re-examine the biodiversity Broad Habitat Classification:
 
  1. Comprehensive - All of the habitat types of the UK should be described within the classification.
  2. Exclusive - The habitat types should be discrete to ensure that there is a "once-only fit" in the classification for each habitat encountered in the field.
  3. Structured - The classification should provide a framework for organising and presenting the priority habitats that are the focus of action plans.
  4. Nested - Priority habitats should fit into only one broad habitat type.
  5. Measurable - Broad habitats should be easily recognisable, have a measurable surface area and physical or biological features that are clearly characterised and wherever possible can be selected from existing systems for data collection.
  6. Consistent - There should be consistency in the division of the broad habitats. The classification should not sub-divide some ecological units more finely that others.

 

The changes made to the terrestrial and freshwater elements of the biodiversity Broad Habitat Classification are presented in Box 1 below.
 
Box 1: Revisions to the terrestrial and freshwater elements of the Broad Habitat Classification
*Original broad habitat type Change made New broad habitat type
1 Broadleaved and yew redefined to include mixed woodland 1 Broadleaved, mixed and yew woodland
2 Planted coniferous woodland redefined to include native and semi-natural coniferous woodland 2 Coniferous woodland
3 Native pine woodland now only recognised as a Priority habitat type  
4 Lowland wood pastures and parkland now only recognised as a Priority habitat type  
5 Boundary features redefined to include linear features 3 Boundary and linear features
6 Arable redefined to include horticulture and woody crops 4 Arable and horticulture
7 Improved grassland unchanged 5 Improved grassland
8 Unimproved neutral grassland redefined to include semi-improved neutral grassland 6 Neutral grassland
10 Calcareous grassland unchanged 7 Calcareous grassland
9 Acid grassland unchanged 8 Acid grassland
  added 9 Bracken
11 Lowland heathland redefined to include upland heathland 10 Dwarf shrub heath
12 Grazing marsh Priority habitat  
13 Fens, carr, marsh, swamp and reedbed redefined to remove carr and include flushes 11 Fen, marsh and swamp
14 Lowland raised bog redefined to include blanket bogs 12 Bogs
15 Standing open water redefined to include canals 13 Standing open water and canals
16 Rivers and streams unchanged 14 Rivers and streams
17 Canals deleted and incorporated into standing open water  
18 Montane restricted to only habitats which occur exclusively in the montane zone 15 Montane habitats
19 Upland heathland deleted and incorporated into Dwarf shrub heath  
20 Blanket bog deleted and incorporated into Bogs  
36 Limestone pavements now only recognised as a Priority habitat type  
  added 16 Inland rock
37 Urban redefined to include all built-up areas 17 Built-up areas and gardens
The numbers for the broad habitat types listed in column 1 are taken from the original biodiversity Broad Habitat Classification published in Biodiversity: the UK Steering Group Report (UK Biodiversity Steering Group 1995).
 
 

2 Definitions of the terrestrial and freshwater biodiversity broad habitat types

The following definitions are based upon the descriptions of the revised broad habitat types agreed by the UK Biodiversity Group.
 
2.1 Broadleaved, mixed and yew woodland
This broad habitat type is characterised by vegetation dominated by trees that are more than 5 m high when mature, which form a distinct, although sometimes open canopy with a canopy cover of greater than 20%. It includes stands of both native and non-native broadleaved tree species and yew Taxus baccata, where the percentage cover of these trees in the stand exceeds 20% of the total cover of the trees present. Woodlands that are dominated by conifer trees with less than 20% of the total cover provided by broadleaved or yew trees are included in the 'Coniferous woodland' broad habitat type. Stands of broadleaved, mixed and yew woodland may be either ancient or recent woodland and either semi-natural arising from natural regeneration of trees, or planted. Recently felled broadleaved, mixed and yew woodland is also included in this broad habitat type where there is a clear indication that it will return to woodland. Otherwise it is classified according to the field layer composition.
 
Scrub vegetation, where the woody component tends to be mainly shrubs usually less than 5 m high, and carr (woody vegetation on fens and bog margins) is included in this broad habitat type if the woody species form a canopy cover of greater than 30% and the patch size of scrub is greater than 0.25ha. Exceptions to this include dwarf gorse Ulex minor and western gorse Ulex gallii which are included in the 'Dwarf shrub heath' broad habitat type, montane willow scrub which is included in the 'Montane habitats' broad habitat type, and scrub on sand dunes and shingle which is included in 'Supralittoral sediment' broad habitat type. Stands of bog-myrtle Myrica gale are included in this broad habitat type as scrub if they are more than 1.5 m tall. This habitat type does not include hedges (woody vegetation that has been managed as a linear feature) as these are included in the 'Boundary and linear features' broad habitat type.
 
 
2.2 Coniferous woodland
This broad habitat type is characterised by vegetation dominated by trees that are more than 5 m high when mature, which form a distinct, although sometimes open canopy which has a cover of greater than 20%1. It includes stands of both native and non-native coniferous trees species (with the exception of yew Taxus baccata) where the percentage cover of these trees in the stand exceeds 80% of the total cover of the trees present2. Woodlands that are made up of broadleaved, yew and conifer trees with less than 80% of the total cover provided by conifer trees are included in the 'Broadleaved, mixed and yew woodland' broad habitat type. Recently felled coniferous woodland is included in this broad habitat type where there is a clear indication that it will return to woodland. Otherwise it is classified according to the field layer composition.
Scots pine Pinus sylvestris is the only pine tree that is native to the UK, and forms native woodland only in Scotland. Semi-natural woods of Scots pine are normally called native pinewoods. The majority of coniferous woodlands in the UK are plantations of species that are either not native to the UK or to the sites on which they occur.
 
2.3 Boundary and linear features
This broad habitat type covers a diverse range of linearly arranged landscape features such as hedgerows, lines of trees (whether constituting part of a hedgerow or not), walls, stone and earth banks, grass strips and dry ditches. These features may occur separately or in combinations forming multi-element boundaries. This habitat type also includes some of the built components of the rural landscape including roads, tracks and railways and their associated narrow verges of semi-natural habitat.
 
This habitat type does not include roads, tracks and railways in urban areas as these are included in the 'Built-up areas and gardens' broad habitat type. It also does not include canals and ditches that are water-filled for the majority of the year, which are included in the 'Standing open water and canals' broad habitat type, rivers and streams which are in the 'Rivers and streams' broad habitat type, and linear features in woodland such as rides and fire breaks which are included in either the 'Broadleaved, mixed and yew woodland' or 'Coniferous woodland' broad habitat types. Cereal field margins managed for nature conservation are included in the 'Arable and horticultural' broad habitat type.
 
 
2.4 Arable and horticultural
This broad habitat type covers arable cropland (including perennial, woody crops, and intensively managed, commercial orchards), commercial horticultural land (such as nurseries, commercial vegetable plots and commercial flower growing areas), freshly-ploughed land, annual leys, rotational set-aside and fallow. This habitat type includes cereal field margins but not field boundaries as these are included in the 'Boundary and linear features' broad habitat type. This habitat type also does not include domestic gardens and allotments as these are included in the 'Built-up areas and gardens' broad habitat type.
 
2.5 Improved grassland
This broad habitat type is characterised by vegetation dominated by a few fast-growing grasses on fertile, neutral soils. It is frequently characterised by an abundance of rye-grass Lolium spp. and white clover Trifolium repens. Improved grasslands are typically either managed as pasture or mown regularly for silage production or in non-agricultural contexts for recreation and amenity purposes; they are often periodically resown and are maintained by fertiliser treatment and weed control. They may also be temporary and sown as part of the rotation of arable crops but they are only included in this broad habitat type if they are more than one year old. Sown grasslands which are less than one year old are included in the 'Arable and horticultural' broad habitat type.
 
2.6 Neutral grassland
This broad habitat type is characterised by vegetation dominated by grasses and herbs on a range of neutral soils usually with a pH of between 4.5 and 6.5. It includes enclosed dry hay meadows and pastures, together with a range of grasslands which are periodically inundated with water or permanently moist.
Neutral grasslands are sometimes referred to as mesotrophic grasslands. The plant species assemblages that develop on neutral soils are different from those that develop on acid soils (acid or calcifugous grassland) and calcareous soils (calcareous or calcicolous grassland). For the most part neutral grassland communities have few diagnostic indicator species but lack strong calcicoles or calcifuges characteristic of base-rich and acid soils respectively. The National Vegetation Classification describes 12 types of unimproved and semi-improved neutral grassland (Rodwell 1992).
 
These types are listed in Box 2 below.
 
Box 2: NVC types included in the 'Neutral grassland' broad habitat type
MG1 Arrhenatherum elatius grassland
MG2 Arrhenatherum elatius-Filipendula ulmaria tall-herb grassland
MG3 Anthoxanthum odoratum-Geranium sylvaticum grassland
MG4 Alopecurus pratensis-Sanguisorba officinalis grassland
MG5 Cynosurus cristatus-Centaurea nigra grassland
MG6 Lolium perenne-Cynosurus cristatus grassland (part only)
MG8 Cynosurus cristatus-Caltha palustris grassland
MG9 Holcus lanatus-Deschampsia cespitosa grassland
MG10 Holcus lanatus-Juncus effusus rush pasture
MG11 Festuca rubra-Agrostis stolonifera-Potentilla anserina grassland
MG12 Festuca arundinacea grassland
MG13 Agrostis stolonifera-Alopecurus geniculatus grassland
 
Unimproved or species-rich neutral grasslands are usually managed traditionally as hay-meadows and pastures. Semi-improved neutral grasslands are also included in this broad habitat type and these grasslands are usually managed for pasture or for silage or hay. Neutral grassland differs from improved grasslands by having a less lush sward, a greater range and higher cover of herbs, and usually less than 25% cover of perennial rye-grass Lolium perenne.
 
 
 
2.7 Calcareous grassland
This broad habitat type is characterised by vegetation dominated by grasses and herbs on shallow, well-drained soils which are rich in bases (principally calcium carbonate) formed by the weathering of chalk and other types of limestone or base-rich rock. Although the base status of such soils is usually high, with a pH of above 6, it may also be more moderate and calcareous grassland communities can occur on soils with a pH as low as 5.
 
Calcareous grasslands are also called calcicolous grasslands and are sometimes referred to as chalk or limestone grasslands. The plant species assemblages that develop on calcareous soils are different from those that occur on neutral soils (neutral or mesotrophic grassland) and acid soils (acid or calcifugous grassland), and characteristically include a range of strict calcicoles. The National Vegetation Classification describes 14 types of calcareous grassland (Rodwell 1992). These types are listed in Box 3 below.
 
Box 3: NVC types included in the 'Calcareous grassland' broad habitat type
CG1 Festuca ovina-Carlina vulgaris grassland
CG2 Festuca ovina-Avenula pratensis grassland
CG3 Bromus erectus grassland
CG4 Brachypodium pinnatum grassland
CG5 Bromus erectus-Brachypodium pinnatum grassland
CG6 Avenula pubescens grassland
CG7 Festuca ovina-Hieracium pilosella-Thymus praecox/pulegioides grassland
CG8 Sesleria albicans-Scabiosa columbaria grassland
CG9 Sesleria albicans-Galium sterneri grassland
CG10 Festuca ovina-Agrostis capillaris-Thymus praecox grassland
CG11 Festuca ovina-Agrostis capillaris-Alchemilla alpina grass-heath
CG12 Festuca ovina-Alchemilla alpina-Silene acaulis dwarf-herb community
CG13 Dryas octopetala-Carex flacca heath
CG14 Dryas octopetala-Silene acaulis ledge community
 
2.8 Acid grassland
This broad habitat type is characterised by vegetation dominated by grasses and herbs on a range of lime-deficient soils which have been derived from acidic bedrock or from superficial deposits such as sands and gravels. Such soils usually have a low base status, with a pH of less than 5.5. This habitat type includes a range of types from open communities of very dry sandy soils in the lowlands, which may contain many annual species, through closed pastures on red brown earths, to damp acidic grasslands typically found on gleys and shallow peats.
 
Acid grasslands are also referred to as calcifugous swards. The plant species assemblages that develop on acid soils are different from those that develop on neutral soils (neutral or mesotrophic grassland) and calcareous soils (calcareous or calcicolous grassland) and are characterised by the presence of a combination of calcifuge species. The National Vegetation Classification describes six types of acid grassland (Rodwell 1992). These types are listed in Box 4 below. This habitat type also includes inland sand dune communities (Rodwell 2000). Acid grassland types and snow-bed communities which occur exclusively in the montane (Alpine) zone are included in the 'Montane habitats' broad habitat type and acid grassland types found on shingle habitats are included in the 'Supralittoral sediment' broad habitat type.
 
Box 4 NVC types included in the 'Acid grassland' broad habitat type
U1 Festuca ovina-Agrostis capillaris-Rumex acetosella grassland
U2 Deschampsia flexuosa grassland
U3 Agrostis curtisii grassland
U4 Festuca ovina-Agrostis capillaris-Galium saxatile grassland
U5 Nardus stricta-Galium saxatile grassland
U6 Juncus squarrosus-Festuca ovina grassland
SD10 Carex arenaria dune (inland sub-communities only)
SD11 Carex arenaria-Cornicularia aculeata dune (inland sub-communities only)
 
 
2.9 Bracken
This broad habitat type covers areas dominated by a continuous canopy cover of bracken Pteridium aquilinum at the height of the growing season. It does not include areas with scattered patches of bracken or areas of bracken which are less than 0.25 ha which are included in the broad habitat type with which they are associated. It also does not include areas of bracken under forest or woodland canopy which are included in either the 'Broadleaved, mixed and yew woodland' or the 'Coniferous woodland' broad habitat types.
 
2.10 Dwarf shrub heath
This broad habitat type is characterised by vegetation that has a greater than 25% cover of plant species from the heath family (ericoids) or dwarf gorse Ulex minor. It generally occurs on well-drained, nutrient-poor, acid soils. Heaths do occur on more basic soils but these are more limited in extent and can be recognised by the presence of herbs characteristic of calcareous grassland. Dwarf shrub heath includes both dry and wet heath types and occurs in the lowlands and the uplands.
 
This habitat type does not include dwarf shrub dominated vegetation in which species characteristic of peat-forming vegetation such as cotton-grass Eriophorum spp. and peat-building sphagna are abundant, or that occurs on deep peat (greater than 0.5 m) as these are included in the 'Bog' broad habitat type. It also does not include heath types which are exclusively alpine in distribution as these are included in the 'Montane habitats' broad habitat type. Heath types on sand dunes or shingle are included in the 'Supralittoral sediment' broad habitat type and heath types on maritime cliffs and slopes that are influenced by salt spray are included in the "Supralittoral rock" broad habitat type.
 
 
 
2.11 Fen, marsh and swamp
This broad habitat type is characterised by a variety of vegetation types that are found on minerotrophic (groundwater-fed), permanently, seasonally or periodically waterlogged peat, peaty soils, or mineral soils. Fens are peatlands which receive water and nutrients from groundwater and surface run-off, as well as from rainfall. Flushes are associated with lateral water movement, and springs with localised upwelling of water. Marsh is a general term usually used to imply waterlogged soil; it is used more specifically here to refer to fen meadows and rush-pasture communities on mineral soils and shallow peats. Swamps are characterised by tall emergent vegetation. Reedbeds (i.e. swamps dominated by stands of common reed Phragmites australis) are also included in this type.
 
This habitat type does not include neutral and improved grasslands on floodplains and grazing marshes which are included in the 'Neutral grassland' and 'Improved grassland' broad habitat types respectively, nor ombrotrophic mires (blanket, raised and intermediate bogs) as these are included in the 'Bogs' broad habitat type. It also does not include areas of carr (fen woodland dominated by species such as willow Salix spp., alder Alnus glutinosa or birch Betula spp.) as these are covered in the 'Broadleaved, mixed and yew woodland' broad habitat type unless cover is less than 30%.
 
2.12 Bog
This broad habitat type covers wetlands that support vegetation that is usually peat-forming and which receive mineral nutrients principally from precipitation rather than ground water. This is referred to as ombrotrophic (rain-fed) mire. Two major bog types are identified, namely raised bog and blanket bog. These two types are for the most part fairly distinctive but they are extremes of what can be considered an ecological continuum and intermediate (or mixed) types occur.
 
The vegetation of bogs which have not been modified by surface drying and aeration or heavy grazing is dominated by acidophilous species such as bog-mosses Sphagnum spp., cotton-grass Eriophorum spp. and cross-leaved heath Erica tetralix. The water-table on these types of bogs is usually at or just below the surface.
 
This habitat type also includes modified bog vegetation that essentially resembles wet or dry dwarf shrub heath but occurs on deep acid peat which would have once supported peat-forming vegetation. Modified bog also includes impoverished vegetation dominated by purple moor-grass Molinia caerulea or hare's-tail cotton-grass Eriophorum vaginatum. Although there is no agreed minimum depth of peat that can support ombrotrophic vegetation, unmodified bog can be identified floristically by the presence of characteristic species such as cotton-grass Eriophorum spp. and peat-forming sphagna. Peat depth, although somewhat arbitrary, is used as the primary criterion to separate types of modified bog vegetation from the 'Dwarf shrub heath' broad habitat type and certain types of 'Fen, marsh and swamp' broad habitat type. Therefore vegetation dominated by dwarf-shrubs, cotton-grass Eriophorum spp., or purple moor-grass Molinia caerulea vegetation on peat greater than 0.5 m deep is classified as bog for the purposes of the Broad Habitat Classification.
 
In lowland areas with predominantly acid substrata there are examples of valley and basin mires that receive acid surface seepage, which gives rise to vegetation similar to that of bogs. However, these types are covered in the 'Fen, marsh and swamp' broad habitat type.
 
 
 
2.13 Standing water and canals
This broad habitat type includes natural systems such as lakes, meres and pools, as well as man-made waters such as reservoirs, canals, ponds and gravel pits. It includes the open water zone (which may contain submerged, free-floating or floating-leaved vegetation) and water fringe vegetation. Ditches with open water for at least the majority of the year are also included in this habitat type.
 
Standing waters are usually classified according to their nutrient status and this can change naturally over time or as a result of pollution. There are three main types of standing waters, namely: oligotrophic (nutrient-poor), eutrophic (nutrient-rich), and mesotrophic (intermediate). These lake types exist along an environmental gradient and intermediate types occur. Other types of standing water include dystrophic (highly acidic, peat-stained water), marl lakes, brackish-water lakes, turloughs and other temporary water bodies. Coastal saline lagoons are not included in this habitat type but are covered by the 'Inshore sublittoral sediment' broad habitat type.
 
The transition between open water and land is often occupied by tall emergent vegetation called swamp or reedbed, or wet woodland called carr. In practice this vegetation often forms a continuum but for the purposes of the Broad Habitat Classification marginal emergent vegetation that is greater than 5 m wide, or areas of wetland habitat adjacent to the waterbody that are greater than 0.25 ha, are included in the 'Fen, marsh and swamp' broad habitat type. Areas of wet woodland greater than 0.25ha are included in the 'Broadleaved, mixed and yew woodland' broad habitat type unless the cover of the canopy is less than 30%.
 
 2.14 Rivers and streams
The 'Rivers and streams' broad habitat type covers rivers and streams from bank top to bank top, or where there are no distinctive banks or banks are never overtopped, it includes the extent of the mean annual flood. This includes the open channel (which may contain submerged, free-floating or floating-leaved vegetation) water fringe vegetation and exposed sediments and shingle banks. Adjacent semi-natural wetland habitats such as unimproved floodplain grasslands, marshy grassland, wet heath, fens, bogs, flushes, swamps and wet woodland, although intimately linked with the river, are covered in other broad habitat types.
 
2.15 Montane habitats
This broad habitat type includes a range of vegetation types that occur exclusively in the montane zone such as prostrate dwarf shrub heath, snow-bed communities, sedge and rush heaths, and moss heaths. The distinction between the sub-montane and montane zone is often blurred and the two usually merge through a band of transitional vegetation. Exclusively montane habitat types can be recognised by their floristic composition and their physiognomy (prostrate vegetation). Widespread arctic-alpine species such as stiff sedge Carex bigelowii, crowberry Empetrum nigrum hermaphroditum, trailing azalea Loiseleuria procumbens, dwarf willow Salix herbacea, and alpine clubmoss Diphasium alpinum, in association with frequent to abundant woolly fringe-moss Racomitrium lanuginosum or cladonia lichens Cladonia spp., and other macro-lichens such as Cetraria islandica, are useful indicators of montane communities.
 
Calcareous grasslands including those dominated by mountain avens Dryas octopetala, fens and springs, blanket bog and rock habitats which also occur in the montane zone are not included in this habitat type but in the 'Calcareous grassland', 'Fen, marsh and swamp', 'Bog', and 'Inland rock' broad habitat types respectively. This type also does not include dwarf shrub heaths and grasslands that straddle the notional boundary of the former tree-line with little change in floristics and physiognomy and these should be treated as components of other broad habitat types.
 
 
2.16 Inland rock
This broad habitat type covers both natural and artificial exposed rock surfaces which are greater than 0.25ha, such as inland cliffs, caves, and screes and limestone pavements, as well as various forms of excavations and waste tips such as quarries and quarry waste.
 
A number of vegetation types associated with rock habitats are also included in this broad habitat type. These are: chasmophytic vegetation (plant communities that colonise the cracks and fissures of rock faces); calaminarian grassland (a grassland type which is found on soils which have levels of heavy metals, such as lead, chromium and copper, that are toxic to most plant species); and certain types of tall herb and fern vegetation, which as a result of grazing pressure are much reduced in extent and confined to areas inaccessible to grazing animals such as cliff faces and ledges, and to a lesser extent, on lightly-grazed steep rocky slopes and boulder fields.
 
2.17 Built-up areas and gardens
This broad habitat type covers urban and rural settlements, farm buildings, caravan parks and other man-made built structures such as industrial estates, retail parks, waste and derelict ground, urban parkland and urban transport infrastructure. It also includes domestic gardens and allotments. This type does not include amenity grassland which should be included in the 'Improved grassland' broad habitat type.
 
 

 

3 Relationships with other standard UK habitat classifications

Correspondence tables which show the relationship between the broad habitat types and a number of standard habitat classifications and select lists of habitats of conservation interest commonly used in the UK are presented in Annex 1 of this report. Correspondence tables have been produced for the following classifications and select lists:
 
  • Phase 1 habitat classification (JNCC 1993);
  • Countryside Survey 1990 reporting categories (Barr et al. 1993);
  • Biodiversity Priority habitat types (UK Biodiversity Steering Group 1995);
  • EC Habitats Directive Annex I habitat types(Commission of the European Communities 1997); and
  • National Vegetation Classification plant communities (Rodwell 1991a,b; 1992; 1995; 2000).

 

Differences in the rationale behind the methodologies for the different habitat classifications mean that most of these classifications do not bear a consistent or simple relationship to each other. They use a range of parameters for classification, so that they are not strictly comparable. For example, the National Vegetation Classification uses only floristics to define the different community types, whereas classifications like the Phase 1 habitat classification and the biodiversity broad habitat types use a mixture of criteria including environmental factors, species composition and vegetation physiognomy. Commentary is provided where one-to-one relationships between the categories in the different systems do not exist. However, it is not always possible to provide explicit rules on how the categories should be separated.
 
The correspondence tables presented in the annex also include the coastal and marine broad habitat types.
 

4 References

Barr CJ, Bunce RGH, Clarke RT, Fuller RM, Furse MT, Gillespie MK, Groom GB, Hallam CJ, Hornung MJ, Howard DC & Ness MJ 1993 Countryside survey 1990 Main report London, Department of the Environment. (Countryside 1990 Series volume 2)
 
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Rodwell JS ed 1991a British plant communities, volume 1: woodlands and scrub. Cambridge, Cambridge University Press
 
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Rodwell JS ed 1995 British plant communities, volume 4: aquatic communities, swamp and tall herb fens. Cambridge, Cambridge University Press
 
Rodwell JS ed 2000 British plant communities, volume 5: maritime communities and vegetation of open habitats. Cambridge, Cambridge University Press
 
UK Biodiversity Steering Group 1995 Biodiversity: The UK Steering Group Report. Volume 1: Meeting the Rio challenge. London, HMSO
 
UK Biodiversity Group 1998a Tranche two action plans. Volume I: Invertebrates and vascular plants. Peterborough, published by English Nature on behalf of the UK Biodiversity Group
 
UK Biodiversity Group 1998b Tranche two action plans. Volume II: Terrestrial and freshwater habitats. Peterborough, published by English Nature on behalf of the UK Biodiversity Group
 
UK Biodiversity Group 1999a Tranche two action plans. Volume III: Plants and fungi. Peterborough, published by English Nature on behalf of the UK Biodiversity Group
 
UK Biodiversity Group 1999b Tranche two action plans. Volume VI: Terrestrial and freshwater species and habitats. Peterborough, published by English Nature on behalf of the UK Biodiversity Group
 
UK Biodiversity Group 1999c Tranche two action plans: Volume V Maritime species and habitats. Peterborough, published by English Nature on behalf of the UK Biodiversity Group
73 pages
ISSN 0963 8091
 
Please cite as: Jackson D.L., (2000), Guidance on the interpretation of the Biodiversity Broad Habitat Classification (terrestrial and freshwater types): Definitions and the relationship with other classifications, JNCC Report 307, 73 pages, ISSN 0963 8091