Maritime cliffs & slopes are defined as sloping to vertical faces on the coastline where a break in slope is formed by slippage and/or coastal erosion (NIEA, 2005).
- Site: Vertical cliffs-steep slopes-low cliffs
- Main species: Grassland & maritime heath communities
- UK: 4000 km
- NI: 500 km (1:10,000 scale)
- There is no formal definition of a cliff, in terms of minimum height or slope angle, but the zone defined as cliff-top should extent landward to at least the limit of salt spray deposition (maritime influence) (NIEA, 2005). Sea cliffs are structurally diverse as they range from tall vertical cliff faces, steep slopes with the vertical face restricted to the base, to low cliffs with local slope forms above an intertidal rock platform.
- Cliffs can be classified as ‘hard cliffs’ or ‘soft cliffs’, with some intermediate forms. ‘Hard cliffs’ are vertical or steep slopes that are typically formed of granite, sandstone or limestone (i.e. rocks that are resistant to weathering) but can be formed of softer rocks such as chalk. ‘Soft cliffs’ are formed of friable material such as shales & boulder clay. As a result they tend to be more unstable, have little resistance to erosion & are less sloped than ‘hard cliffs’. In sheltered areas this allows for greater colonisation of vegetation (JNCC, 2004).
- Vegetation along the north Co. Antrim & Causeway coasts is characterised by species rich maritime cliff top & cliff-slope grassland & maritime heath communities.
- In a study of nine cliff sites, Copper et al. (1992) recorded six main NVC community types of vegetation. These included: maritime crevice community MC1 rock samphire Crithmum maritimum – rock sea spurrey Spergularia rupicola, MC5 thrift Armeria maritima & seamouse-ear Cerastium diffusum, MC6 spear-leaved orache Atriplex prostrata & sea beet Beta vulgaris, MC7 common chickweed Stellaria media, MC8 thrift & red fescue Festuca rubra and MC9 red fescue & Yorkshire fog Holcus lanatus.
Current Status in UK & Northern Ireland
- There is an estimated 4000 km of UK coastline that has been classified as cliff.
- In Northern Ireland there is an estimated 1,050 km of coastline (on 1:10,000 mapping scale) (JNCC, 1997), of which 500 km is maritime cliff & slope. The NICS (2000) estimated that there are 528 ha of this habitat.
- ‘Hard cliffs’ are widespread around exposed coasts of Britain & Ireland, including the north coast of NI. ‘Soft cliffs’ are relatively scarce but in NI there are glacial-till cliffs to the north of Larne. There is an estimated 7km of soft cliff in NI but more than 250km in ROI (Howe, 2003; NIEA, 2005).
- The coast of NE Counties L’derry & Antrim is dominated by basalt & chalk cliffs. The Giant’s Causeway is well-known for its basalt cliffs.
- Maritime cliffs & slopes are threatened by agricultural improvement (fertiliser use, changing maritime grassland to improved grassland), overgrazing, urban & industrial development, recreation (e.g. walking, vehicles), introduced species (e.g. garden species), quarrying & erosion.
- Giant’s Causeway & Dunseverick
- Rathlin Island Coast
- White Park Bay