Habitat Action Plans - Maritime Cliff and Slopes
(Photo Credit: John Hiskett) |
Click to view the Maritime Cliff and Slopes Action Plan |
Current Status
National Status
- Maritime cliffs and slopes comprise sloping to vertical faces on the coastline where a break in slope is formed by slippage and/or coastal erosion. There appears to be no generally accepted definition of the minimum height or angle of slope which constitutes a cliff, but the zone defined as cliff-top (also covered in this plan) should extend landward to at least the limit of maritime influence (ie limit of salt spray deposition), which in some exposed situations may continue for up to 500 m inland. This plan may therefore encompass entire islands or headlands, depending on their size. On the seaward side, the plan extends to the limit of the supralittoral zone and so includes the splash zone lichens and other species occupying this habitat.
- Approximately 4,000km of the UK coastline has been classified as maritime cliff. Cliffs can be broadly classified as 'hard cliffs' or 'soft cliffs', though in practice there are a number of intermediate types. Hard cliffs are vertical or steeply sloping; they are inclined to support few higher plants other than on ledges and in crevices or where a break in slope allows soil to accumulate. They tend to be formed of rocks resistant to weathering, such as granite, sandstone and limestone, but can be formed of softer rocks, such as chalk, which erode to a vertical profile. Soft cliffs are formed in less resistant rocks such as shales or in unconsolidated materials such as boulder clay; being unstable they often form less steep slopes and are therefore more easily colonised by vegetation. Soft cliffs are subject to frequent slumping and landslips, particularly where water percolates into the rock and reduces its effective shear strength.
- Cliff profiles vary with the nature of the rocks forming them and with the geomorphology of the adjoining land. While most maritime cliffs have been formed by coastal erosion, steep slopes falling to the sea in mountainous districts may have been formed long before the sea level reached its present position; in such cases only the lower part of the slope will have been steepened by the sea.
- The vegetation of maritime cliff and slopes varies according to several factors: the extent of exposure to wind and salt spray; the chemistry of the underlying rock; the water content and stability of the substrate; and, on soft cliffs, the time elapsed since the last movement event. Cliff-top habitats can also be transformed by soil erosion processes.
- Hard cliffs are widely distributed around the more exposed coasts of the UK, occurring principally in south-west and south-east England (the latter area having the bulk of the 'hard' chalk cliffs), in north-west and south-west Wales, in western and northern Scotland and on the north coast of Northern Ireland. Soft cliffs are more restricted, occurring mainly on the east and central south coasts of England and in Cardigan Bay and north-west Wales. There are also examples on the coasts of Fife and Skye in Scotland and Antrim in Northern Ireland.
- Soft cliffs provide important breeding sites for sand martins Riparia riparia, which burrow into soft faces exposed by recent slippages, but they are particularly important for invertebrates as they provide a suite of conditions which are rarely found together in other habitats. The combination of friable soils, hot substrates and open conditions maintained by cliff slippages offer a continuity of otherwise very restricted microhabitats and these support many rare invertebrates which are confined to such sites. These include the ground beetle Cicindela germanica, the weevil Baris analis, the shore bug Saldula arenicola, and the Glanville fritillary Melitaea cinxia.
- Seepages, springs and pools are a feature of many soft cliff sites and these provide the wet muds required by many species of solitary bees and wasps for nest building. They also support rich assemblages of other invertebrates including many rare species which are confined to this habitat. These include the craneflies Gonomyia bradleyi and Helius hispanicus, and the water beetle Sphaerius acaroides.
Links with Other Action Plans
- The Lowland Heathland and Littoral and Sublittoral Chalk Habitat Action Plans have objectives and actions which are relevant to this plan.
Norfolk Status
- The total length of cliff in Norfolk is c24km. The cliffs can be divided
into two main types:
- Hard vertical cliffs composed of chalk and carstone (a ferruginous sandstone) occur for 1.3km at Hunstanton;
- Soft cliffs composed of glacial sands and clays with rafts of chalk occur for most of the coastline between Weybourne and Happisburgh with an estimated length of 22.7km. A few short sections also occur further south. They tend to separate into those with predominately vertical cliffs as at Weybourne and Happisburgh and those with extensive areas of slumping as between Cromer and Mundesley. Extensive areas of grassland are associated with the slumping cliffs covering an estimated 129ha. Seepages are an important feature of the cliffs between Cromer and Mundesley and to a lesser extent between Sheringham and Cromer. Cliff top grassland is present at Hunstanton and between Weybourne and Mundesley sometimes as golf courses or caravan sites. Eastwards the land is generally cultivated to the cliff edge. The habitat is important for a range of species or groups including purple broomrape (Orobanche purpurea), bryophytes, lichens, invertebrates (particularly woodlice, Diptera and Coleoptera), fulmar and barbastelle bat.
- The main cliff areas in Norfolk are summarised in Table 1 below:
Table 1: Distribution and Status of Maritime Cliffs in Norfolk
Site |
Status |
Interest |
Type |
| Hunstanton | SSSI | Geological | Hard rock |
| Weybourne to Sheringham | SSSI | Geological | Soft vertical |
| Sheringham to Cromer | Part SSSI | Geological | Soft slumping |
| Cromer to Overstrand | cSAC and SSSI | Biological and Geological | Soft slumping, many seepages |
| Overstrand to Mundesley | SSSI | Geological | Soft slumping, many seepages |
| Mundesley to Bacton | Part SSSI | Geological | Soft slumping |
| Ostend to Happisburgh | Part SSSI | Geological | Soft vertical |
| Scratby | Soft? vertical |
Current factors causing loss or decline in Norfolk
- Sea defence works are present along many stretches either in the form of a concrete apron or revetments set forward of the base of the cliffs. These were mostly constructed in the period between 1950 and 1980. In many instances, these are gradually deteriorating.
- Arable cultivation continues to the edge, particularly between Overstrand and Mundesley.
- Declines in quality of cliff top grassland through lack of management including increase in Alexanders (Smyrnium olusastrum). Management by cutting in spring or spot spraying may be required to reduce the vigour of this long established alien.
Current Action in Norfolk
- A biodiversity document has been produced for the Shoreline Management Plan area between Kelling and Lowestoft.
- Information board placed at West Runton.
- Consultation underway for the review of the Shoreline Management Plan between Kelling and Lowestoft.
Action Plan Objectives and Targets
National
- Seek to maintain the existing maritime cliff resource of cliff-top and slope habitat, of about 4,000 km.
- Maintain wherever possible free functioning of coastal physical processes acting on maritime cliff and slope habitats.
- Retain the amount of maritime cliff and slope habitats unaffected by coastal defence and other engineering works.
- Where possible increase the amount of maritime cliff and slope habitats unaffected by coastal defence and other engineering works.
- Increase the area of cliff-top semi-natural habitats by at least 500 ha over the next 20 years.
- Improve by appropriate management the quality of at least 30% of the maritime cliff and slope habitats, including cliff-top vegetation, by 2010.
- Improve by appropriate management the quality of as much as possible of the remaining maritime cliff and slope habitats, including cliff-top vegetation, by 2015.
Norfolk
- Maintain and where possible enhance the maritime cliff and slope in Norfolk.
- Increase the area of cliff top grassland by arable reversion. (Quantitative target to be set following further research and survey.)
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