MARITIME CLIFFS Gannets - Credit Lucy-Lush
Maritime cliffs are the vertical slopes on which the coastline formed after many years of slippage and/or coastal erosion. The geology of the cliffs can range from hard to soft cliffs. The hard cliffs will often consist of granite, sandstone or limestone and tend to support fewer plants other than in crevices, on ledges or on a break in the slope where soil is able to accumulate
What are they?
Maritime cliffs are the vertical slopes on which the coastline formed after many years of slippage and/or coastal erosion. The geology of the cliffs can range from hard to soft cliffs. The hard cliffs will often consist of granite, sandstone or limestone and tend to support fewer plants other than in crevices, on ledges or on a break in the slope where soil is able to accumulate.
Softer cliffs consists of less resistant rocks such as shales or boulder clay, the slopes are often less steep allowing for vegetation to easily colonise. Softer cliffs are more prone to erosion or landslides, which is an important factor in the ecology of the community that rely on a large proportion of pioneering plants to quickly re-establish after a landslide.
The composition of plants depends on the soil type, ground stability, water source and the level of exposure to wind and sea-spray.
Lowest on the cliff, closest to the sea, the vegetation is dominated by lichen. Further up the cliff in ledges, crags and crevices common species are rock sea spurrey and rock samphire.
Where are they found?
The UK has about 4000 km of coastal cliffs and over 50% of Europe’s coastal chalk cliffs - of which 75% is designated as Sites of Special Scientific Interest (SSSIs).
The distribution of hard cliffs is higher in the more exposed area such as the coasts of south-west and south-east England, in the north-west and south-west of Wales, in western and northern Scotland and the north coast of Northern Ireland. The distribution of soft cliffs is more restricted and can be found on the east and central south coasts of England, the north coast of Northern Ireland and in north-west Wales.
Why are they important?
Soft cliffs are important breeding sites for several species of seabirds including the razorbill which builds its nests on the soft crevices recently exposed by slippage. Soft cliffs are also ideal habitats for burrow-nesting birds, such as the puffin and the manx shearwater.
70% of the international population of gannets and an important proportion of the European population of shag use cliffs as breeding sites.
Soft cliffs also provide a unique habitat for invertebrates with a combination of friable soils and open conditions maintained by slippage. This offer a habitat for rare species such as the ground beetle (Cicindela germaica), the weevil (Barisanalis), the shore bug (saldula arenicola) and the Glanville fritillary butterfly found on the Isle of Wight. In addition, springs and water seeping from the cliff faces can create pools and wet mud areas providing ideal habitats for solitary bees and wasps for nest building.
Hard cliffs support important species including the snail (Ponentina sub virescens), weevils such as the restricted Cathormiocerus attaphilus and moths like Barrett’s marbled cononet (Hadena luteago). Well established cliffs can also support puffins, gannets and razorbills. The chalk cliffs on the Kent and Sussex coastline on in south England are unique as they support a population of the restricted fiery clearwing (Bembecia chrysidiformis), while the water beetle (Ochthebius poweri) predominantly occurs in the small seepages on red sandstone cliffs faces in South Wales and in south-west England.
Are they threatened?
Erosion is an important factor for the plant community on soft cliffs. The high frequency of pioneer plants allow cliff-dwelling species to retreat along with the cliff line itself, however, high rates of erosion caused by accelerated run-off from agricultural drains, heavy trampling from recreational use and overgrazing can be devastating to the plant community. If a large area is subject to or frequently subject to slippage it can wash away plants reducing the ability for the area to regenerate.
To reduce the effect of damaging human activities on cliffs and to protect activities on overlying land coastal protection systems have been built to slow down or stop the rate of erosion. However, the result of this may be too effective stopping the natural slippage that is part of the ecosystem on cliffs, allowing the early pioneering stages to be progressively overgrown and causing wet flushes to dry out. Using soft netting instead of hard netting to protect against slippage allows more natural slippage to occur.
Intensification of agriculture close to cliffs has caused for introduced species to affect the vegetation composition and reducing the biodiversity. Introducing grazers requires a fine balance as overgrazing can stress the establish vegetation while undergrazing allows scrubs to encroach.
Climate change may have an impact through increased frequency of storms affecting the less resilient plant species.
How are The Wildlife Trusts helping? What can I do to help?
Visit wildlifetrusts.org/livingseas to find out how you can help our marine conservation work in the UK.
Depending on where you live, local Wildlife Trust volunteers help out with everything from recording marine wildlife sightings to beach cleans and educational work. Visit our Living Seas pages online or contact your local Trust to find out more.