Maritime Cliffs and Slopes
Maritime cliffs and slopes form through land slippage or coastal erosion. Slopes can vary between 15° and vertical, although there is no generally accepted definition of the minimum height or angle of slope. Maritime cliffs can be broadly defined as either ‘hard cliffs’ or ‘soft cliffs’ although in practice there are a number of intermediate types. Hard cliffs are usually vertical or steeply sloping. Soft cliffs are often unstable and are generally prone to slumping and landslips.
Maritime cliffs and slopes support a wide range of plant species and are an important breeding ground for many birds. The vegetation of maritime cliffs varies according to geology, degree of slope, and exposure to sea-spray but typically includes species such as red fescue Festuca rubra, thrift Armeria maritima and sea plantain Plantago maritima. Rock faces may also support a diverse lichen flora.
Ledges on maritime cliffs are important nesting sites for sea birds such as kittiwake, fulmar, shag and cormorant. Puffins may nest in burrows in the turf of cliff-tops or slopes.
Many maritime cliffs are of particular geological interest. Sea caves within cliff faces may support a diverse array of marine species, including mussels, cushion sponges and colonial sea-squirts, depending on the degree of water movement and scour at particular points in the cave system.
The UK coastline contains about 4000 km of cliffs. The North East contains around 112 km of cliff and cliff-top habitat, which represents about 3% of the British resource. Most of the Region’s cliffs are non-vertical and less than 50 m in height, the main exception being Boulby Cliffs which at 200 m rank among some of the highest sea cliffs on the British mainland. A mix of hard and soft cliffs are found, with hard cliffs generally being more prevalent in Northumberland and soft cliffs being more common in County Durham.
The majority of the maritime cliffs in the Region are protected by some form of designation. The North Northumberland coast between Amble and the Scottish border is designated as an Area of Outstanding Natural Beauty (AONB) and as a Heritage Coast. In Redcar and Cleveland, the coast between Saltburn and Staithes forms part of the North Yorkshire and Cleveland Heritage Coast. The Durham Coast has recently been designated a Heritage Coast.
Extensive sections of maritime cliff have been designated as SSSIs in recognition of their geological and/or biological interest. Important colonies of cliff nesting seabirds are found at Cullernose Point and at the Farne Islands in Northumberland, at Marsden in South Tyneside and at Boulby Cliffs in Redcar and Cleveland (although this latter is not designated as a SSSI). The flora supported by the Region’s sea cliffs is very diverse. Of particular note is the flora of the Durham coast, which supports a range of interesting species, such as bird’s-eye primrose Primula farinosa and sea spleenwort Asplenium marinium. The vegetated sea cliffs of the Durham coast are now considered to be of international importance and have been designated as a SAC. Sea caves form one of the interest features of the Berwickshire and North Northumberland Coast SAC.
Erosion is a significant process for soft cliffs. While this is important for renewing geological exposures and for maintaining a full range of cliff-dwelling plant species, it can result in cliff-top vegetation being destroyed through being squeezed between a receding cliff-face and cultivated land. This is a problem on some areas of the Durham coast.
Trampling by the public and by livestock may cause the erosion of cliff-top vegetation and disturbance to birds.
Coastal grasslands can be destroyed by cultivation taking place too close to the cliff edge. Fertilizer run-off and herbicide spray-drift may also affect cliff-top vegetation.
Heavy grazing in some areas may reduce the diversity of coastal grasslands. Alternatively, lack of grazing may lead to invasion by scrub and coarse grasses.
Urban development can lead to a demand for coastal protection works which will impede natural coastal processes, including the erosion and slumping which helps to maintain the vegetation of sea cliffs.
Sea cave communities, including microalgal, lichen and faunal turfs, are sensitive to toxic contaminants. Increases in nutrients and organics may locally alter the physio-chemical environment and lead to a change in structural composition of these communities.
Opportunities for protection and enhancement
Coastal Management Plans and Shoreline Management Plans offer the opportunity to address issues affecting maritime cliffs and slopes.