The majority of the shingle in the BAR area forms fringing beaches. Most of the shingle is within reach of the waves and so is very mobile. Where it is thrown beyond the reach of the waves, it begins to build up and some specialised plants can start to get a hold. click here for an example.
Beaches like this are very rare globally. Outside of north-west Europe they are only found in Japan and New Zealand. There are about 5000 hectares of vegetated shingle in England, more than half of which is at just two sites, Rye Harbour and Dungeness. East and West Sussex have about 1000 hectares ie one fifth of the English resource. In France, the majority of the vegetated shingle is found between Ault and le Hourdel in the Somme.
Shingle beaches are harsh environments for plants. There is hardly any soil, very little freshwater, strong winds, salt spray and sometimes inundation by the sea, burial or even the loss of whole ridges during big storms. A few plants have developed special adaptations to survive these conditions. For further details see our shingle plants page.
Shingle is important for animals. Birds like Terns and Ringed Plover nest on shingle, laying their highly camouflaged eggs amongst the pebbles. Some invertebrates are shingle specialists, e.g. the caterpillar of the rare Toadflax Brocade Moth is found almost exclusively on shingle at a few sites in East Sussex and Kent. There are several spiders which are only found on shingle beaches and a completely new species of fly was recently found living deep within the beach at Rye Harbour.
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Sand dunes develop behind wide sandy beaches that dry out at low tide. Strong winds blowing onshore pick up the sand and carry it away, depositing it in small mounds at the back of the shore. These embryonic dunes are liable to be washed away by storm waves and also remodelled with every change in wind direction, but, if they survive long enough, they start to become colonised by plants, e.g. Marram Grass that are specially adapted to the difficult growing conditions. These plants help to stabilise the sand with their extensive root systems and also trap further supplies of sand amongst their leaves and stems. In this way the original mounds of sand grow progressively higher until eventually the dunes become ‘fixed’ and form a rich dune grassland which will eventually support species such as orchids. The plants in turn attract invertebrates providing food for higher animals, for example, the Common Lizard which buries its eggs in the warm sand. .
Sand dunes occur at only a few sites on the Sussex and Kent coasts because the dominant beach material is shingle, rather than sand. The biggest dune areas are at Camber Sands and Sandwich Bay, where particularly wide sandy beaches are uncovered at low water.
The French Channel coast presents a striking contrast. Wide sandy beaches are common, and shingle scarce. Where the beaches are backed by low ground and not chalk cliffs, extensive dune systems have developed. From the Somme estuary north to the Belgian border 53% of the coastline is fringed by sand dunes. Some of these dune areas started forming a thousand or more years ago, and the dunes reach heights of 35 m or more. The older dunes are well wooded, unlike those of Sussex and Kent. Growing in the dune slacks are a great variety of rare and interesting plants.
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There are two types of maritime cliffs in the BAR area, chalk cliffs found for example, between Brighton and Eastbourne and softer sandstone cliffs, found for example between Hastings and Fairlight. There are about 45km of cliffs, largely undefended from erosion by the sea on the UK side of the Channel. These have national and European importance for their biology and geology.
In some areas erosion has created a chalk shelf at the base of the cliff. Deep gullies in the shelf are rich in marine wildlife. Unfortunately many cliffs have been protected or reinforced with concrete. This prevents natural coastal processes and removes natural nesting places for seabirds.
Cliffs can be a hostile area to colonise, but they provide an important niche for several species, e.g. several types of solitary bees and wasps burrow into the sandstone cliffs.
A few hardy species of plants can survive, either on cliff tops or in the small amounts of soil which build up on ledges. Hoary Stock persists in East Sussex despite massive coastal development, and is only found in a few sites on the south coast. Thrift is a typical coastal plant, growing in densely packed cushions to protect itself from the wind.
Our cliffs have significant ornithological interest with breeding populations of Kittiwakes and Fulmars nesting on narrow ledges in the chalk. There are breeding populations of Peregrine Falcons around Peacehaven and the Seven Sisters and Sand Martins nest in the sandstone cliffs.
Saltmarsh and mudflats
Saltmarsh and mudflats are very productive wildlife habitats. They are home to a unique set of plants and animals, including a wide variety of feeding birds. Large areas of these habitats have been and continue to be lost, but almost all that remains is designated as Sites of Special Scientific Interest (SSSIs).
There are about 50 hectares of saltmarsh at Rye Harbour Nature Reserve and at Cuckmere Haven, designated SSSI. Saltmarsh is an effective form of natural coastal defence, absorbing the energy of the waves. About 100 hectares are lost in the UK every year through sea level rise, coastal defence and land reclamation.
Saltmarsh forms a lush silvery greensward with winding creeks. The type of vegetation that grows here depends on how high the land is above sea level and so how often it is covered by the sea. Glasswort is the first plant to colonise low down on the shore, whilst higher up there are species like Sea Purslane and Sea Aster. All these plants are very salt tolerant and are adapted in some way to retain freshwater e.g. Sea Aster has fleshy leaves whilst others may have hairy or waxy leaves.
Saltmarsh has a high conservation value for the communities it supports. It is rich in invertebrates and is especially good for birds. It provides a high tide roost for waders which feed on the adjacent mudflats, ducks and geese graze on the vegetation and passerine (perching) birds feed on the seeds. It also provides a nesting habitat for waders, gulls and terns.
Saline lagoons are very rare. These bodies of water which form behind sand or shingle ridges are fed by salt and fresh water. This means they have a narrow range of salinities, ideal for some highly specialised animals like the rare Lagoon Cockle. These in turn provide food for wading birds and terns.
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Threats to our coastal habitats
Waves are much more effective at causing erosion once beaches have begun to erode, so they represent a more significant threat to coastal properties. Several beaches in the BAR area have been renourished from offshore deposits of shingle and still need careful management.
Our shingle beaches were deposited at the end of the last ice age. Although small amounts of shingle are added from erosion of flints out of the chalk cliffs, coastal defences stop this erosion and so cut off the supply. Piers, marinas and jetties also stop shingle moving along the coast.
Sea levels are rising by about 6mm a year in the south east. This is a combination of the effects of climate change and the fact that the south of England is sinking, and has been since the end of the last ice age. We are also seeing an increase in the number and severity of storms. This has serious implications for shingle beaches for both biodiversity and coastal defence.
Coastal development increases the demand for coastal defence works and constrains the natural movement and development of our coastal habitats. The combination of sea level rise and coastal development leads to a phenomenon called coastal squeeze. This is where coastal habitats are prevented from rolling landwards as they would naturally with sea level rise, because of hard structures behind them, and so the habitats are squeezed out.
Another pressure on our coastal habitats is enrichment, from agriculture, dumping, burning of garden waste and fouling by dogs. These change the natural conditions from the very narrow niches to which coastal plants are adapted. Garden escapes are another problem particularespecially where houses are built right up onto the beach, and specialised native plants are crowded out.
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|Last updated 15/12/05 PF|