Vegetated sea cliffs are steep slopes fringing hard or soft
coasts, created by past or present marine erosion, and supporting a
wide diversity of vegetation types with variable maritime
influence. Exposure to the sea (wave splash and sea spray) is
a key determinant of the type of sea cliff vegetation, although the
amount of rainfall is also a contributing factor. The most
exposed areas support maritime vegetation dominated by a range of
salt-tolerant plants. More sheltered cliffs support
communities closely related to those found on similar substrates
inland, such as grassland and heath, with only a minor maritime
element in the flora.
There is considerable geographical variation in sea cliff
vegetation types across the UK. Southern sites are rich in
Atlantic-Mediterranean species, while northern sites support boreal
species such as the endemic Scottish primrose Primula
scotica.
Exposure is greatest on the south-west and northern
coasts. The long fetch associated with these coasts generates
high waves and swell, and the prevailing winds help deliver salt
spray to the cliff face and cliff tops. The plant communities
of the vertical hard rock cliffs in the north, which are exposed to
the extreme exposure of the north Atlantic, are characterised by
roseroot Sedum rosea and Scots lovage Ligusticum
scoticum. Cliffs may also support sea campion Silene
maritima and thrift Armeria maritima and, in some
rich areas, Arctic species such as purple saxifrage Saxifraga
oppositifolia and moss campion Silene acaulis.
Cliffs are also important breeding grounds for seabirds like the
kittiwake Rissa tridactyla, razorbill Alca torda,
and guillemot Uria aalge.
In southern Britain the vegetation of hard rock cliffs tends
to be formed by communities of thrift Armeria maritima,
rock samphire Crithmum maritimum, and buck's-horn plantain
Plantago coronopus. The rare curved hard-grass
Parapholis incurva, and the sea lavender Limonium
recurvum may also be present. The relatively sheltered,
dry, calcareous cliffs on the south coast, are sites for the wild
cabbage Brassica oleracea that grows on crumbling edges
and sloping ledges. This species is rare in Britain and is
found in association with other rare species such as early
spider-orchid Ophrys sphegodes and Nottingham catchfly
Silene nutans.