INTRODUCTION TO SEA CLIFFS

Origins and definitions

Sea cliffs originate where erosion takes place as the sea cuts into the base at the base of a landform. Removal of accumulations of debris derived from the cliff through wave action helps to create the typical cliffs so familiar on many coasts. The definition of different types of sea cliff are thus dependent on the nature of the underlying rock type and the processes by which they are formed. Vertical or near vertical cliffs in both 'soft' and 'hard' rocks are present throughout the world. Both are well represented in the UK with 'hard' rock cliffs predominating in the north, 'soft' rocks in the south and east. A range of plants, breeding birds and invertebrate animals inhabit these areas, where they help to form important wildlife sites.

Traditional management

Vertical or near vertical sea cliffs are by their nature difficult to access. As a result they are relatively unaffected by human activity and management in the traditional sense is limited. Cliff tops and more gently sloping cliffs ('hard' and 'soft' rocks) are used for grazing stock, where they provide sheltered grazing for sheep (and less frequently cattle).

Reasons to restore

On more stable cliff slopes and cliff tops, especially in areas of chalk and limestone important calcareous grasslands have disappeared as agriculture intensification has taken place on the cliff tops. Ploughing and the conversion to arable use is often accompanied by a move away from pastoral farming. The development of course grassland and scrub further compromises the diversity of the species-rich grassland and heath as grazing is reduced or abandoned. Where the slopes are also subject to erosion from the sea (as at Beachy Head), then the vegetation can be reduced to a narrow, or even nonexistent fringe on the cliff top.

Cliff-tops, especially those in the warmer south have also been the subject of building the 'house with a sea view'. This has had a two-fold impact, firstly destroying the cliff top habitat and secondly by imposing a requirement for coastal protection. These pressures are especially important where cliffs are composed of unstable softer rocks and may be rapidly eroding. In these areas a variety of protective structures are built. These include sea walls and other structures which protect the toe of eroding cliffs, stabilisation and drainage of cliff slopes and in the most extreme cases (usually along the sea front of coastal towns) complete obliteration of the cliff slope with concrete. This may have had a sometimes unforeseen, knock-on effect further along the coast as the sediment supply to the nearshore zone is reduced.

States and values

Two different series of states have been identified for the purposes of this Guide. Those associated with the first, mostly stable state, are for hard rock cliffs. Here the states are determined by the nature of the vegetation and associated animals:

• State 1 - where the vegetation is open exposure and/or the presence of grazing animals helps to prevent more vigorous species from overwhelming the often species-rich communities;
• State 2 - where a reduction in grazing pressure results in the growth of course grassland and scrub leading to an overgrown vegetation.

On softer rock cliffs erosion is a dominant force. Here the cliff states are divided in relation to the stability of the slopes themselves, four state have been identified:

• State 1 rapidly eroding cliffs, virtually devoid of vegetation;
• State 2 cliffs with some degree of stability supporting vegetation in a mosaic with open bare ground;
• State 3 areas where artificial stabilisation measures to prevent erosion have caused the cliff to become overstable;
• State 4 a stable state where periodic and longer term erosion takes place in cycles and mature vegetation including woodland can develop.

Because of their inaccessibility cliffs have an apparently restricted set of economic values when compared with some other habitats. However, they do provide the most spectacular scenery and are of considerable recreational value and nature conservation interest. Harder rock cliffs may have some economic value for grazing on cliff slopes and cliff tops. Some also provide aggregate for building. Softer rock cliffs also make a contribution to the sediment budget in some areas. Material released from eroding cliffs may be moved along the shore, helping to protect other cliffs and or form new sedimentary habitats such as saltmarsh, sand dune and shingle.

Guidance (routes to restoration)

Because of the great differences between the approach to restoration of 'hard' and 'soft' rock cliffs guidance is included for both. The route to restoration on hard rock cliffs relies on scrub control and grazing management (State 2 to State 1). Grazing management can be a complex issue, especially when restoring rare invertebrate populations. The grazing regime, which is adopted will be critical to success. On soft rocks the re-introduction of instability to over-stable cliffs (State 3 to State 2) may be all that is required. On the face of it, a relatively straight forward process. However, the preoccupation with protecting buildings may make such activities difficult to put in place, especially where coastal protection structures are already in place. The case of Birling Gap provides an illustration of a recent decision not to intervene when property was threatened.

Key publications

• Background documents: There are no books devoted exclusively to sea cliffs. A general appraisal of the ecology of inland and coastal cliffs is available in the Cambridge Studies in Ecology (Larson et al. 2000); earth cliffs (May 1977) and rocky cliffs (Goldsmith 1977) are included in Chapters 11 and 12 respectively; Chapter 3 (Doody 2001)
• Guides: Restoring biodiversity in soft rock cliffs, is dealt with in an English Nature Research Report 398 (Lee et al. 2001) available from the EN library service;
• Web sites: The National Trust http://www.nationaltrust.org.uk/environment/. The nature conservation section provides a useful review of "Grazing for Nature Conservation on National Trust Land" by Matthew Oates, Adviser on Nature Conservation, November 1998.

References

Doody, J.P. 2001. Coastal Conservation and Management: an Ecological Perspective. Kluwer, Academic Publishers, Boston, USA, 306 pp. Conservation Biology Series, 13

Goldsmith, F.B. 1977. Rocky cliffs. In: The Coastline, ed.Barnes, R.S.K.John Wiley & Sons, Chichester, 237-251.

Larson, D.W., Matthes, U. & Kelly, P.E. 2000. Cliff Ecology: Pattern and Process in Cliff Ecosystems. Cambridge University Press, Cambridge , 340 pp. Cambridge Studies in Ecology

Lee, E.M., Brunsden, D., Roberts, H., Jewell, S. & McInnes, R. 2001. Restoring biodiversity to soft cliffs. English Nature Research Report, 398 English Nature.

May, V.J. 1977. Earth Cliffs. In: The Coastline, ed.Barnes, R.S.K.John Wiley & Sons, Chichester, 215-235.