UK Coastal Habitat Types & Characteristics

 

ShingleBabington's orache growing on a shingle bank © Sue Rees/Natural England

Vegetation of drift lines occurs on deposits of shingle lying at or above mean high-water spring tides. These shingle deposits occur as fringing beaches that are subject to periodic displacement or overtopping by high tides and storms. The distinctive vegetation, which may form only sparse cover, is therefore ephemeral and composed of annual or short-lived perennial species. This type of habitat is found all around the UK coastline.

 

Vegetated shingle consists of sediment with particle sizes in the range of 2–200 mm on which plant communities develop. The vegetation occurring on shingle will depend on the hydrology of a particular site and the amount of finer sediment within the shingle. Typically, the seaward edge harbours pioneer species – more resistant to wind and exposure to sea spray – such as sea kale Crambe maritima. Further from the fringe, conditions allow other plant communities to develop. Where the water table is close to the shingle surface, wetlands plant communities can develop. This habitat can be quite extensive, such as can be seen at Dungeness. Vegetated shingle is very important for some of our breeding birds such as oystercatchers and terns, as well as some gull species. The UK holds a significant part of the European resource of this habitat, which is widespread along our coasts.

 

CliffsMaritime cliff and slope vegetation on the county Antrim coast, Northern Ireland © Paul Corbett

Hard cliffs are rocky slopes fringing hard coasts, created by past or present marine erosion, and supporting a wide diversity of vegetation types with variable maritime influence. Hard cliffs, with vertical or very steep faces, are characteristic of hard igneous, metamorphic and sedimentary rocks and also of chalk, which, although a soft rock, nevertheless forms vertical cliffs.

 

Soft cliffs are slopes fringing soft coasts, created by past or present marine erosion, and supporting a wide diversity of vegetation types with variable maritime influence. Soft cliffs have a sloping or slumped profile, often with a distinct undercliff; they occur on a range of soft rocks, or on hard rocks interspersed with softer deposits. The more mobile soft cliffs occur where there are unstable soft deposits such as mudstones or glacial drift deposits. They may be subject to mudslides or landslips, which create complexes of pioneer and more mature vegetation.

 

SaltmarshSalicornia saltmarsh bed, Strangford Lough, Northern Ireland © Paul Corbett

Pioneer saltmarsh colonises intertidal mud and sandflats in areas protected from strong wave action and is an important precursor to the development of more stable saltmarsh vegetation. It develops at the lower reaches of saltmarshes where the vegetation (mainly pioneer Salicornia species and Spartina maritima) is frequently flooded by the tide, and can also colonise open creek sides, depressions or pans within saltmarshes, as well as disturbed areas of upper saltmarshes.

 

Lower saltmarsh is inundated at least once a day due to tidal action and so supports plant communities that are more salt tolerant that those found in the upper marsh.

 

Upper saltmarsh is found where halophytic vegetation colonises soft intertidal sediments of mud and sand in areas protected from strong wave action. Tidal inundation can still occurs but with decreasing frequency and duration compared to lower areas in the saltmarsh. The vegetation varies with climate and the frequency and duration of tidal inundation. Grazing by domestic livestock is particularly significant in determining the structure and species composition of the habitat type and in determining its relative value for plants, invertebrates and wintering or breeding waterfowl. This habitat occurs all around our coasts, but most of the sites where it is found are in England.

 

Transitional saltmarsh occurs where there is a transition from saltmarsh to dunes or shingle.

 

Dunes Embryo dune in Magilligan SAC, county Londonderry, Northern Ireland © Paul Corbett

Embryo dunes are created by the aggregation of wind-blown sand trapped by debris and vegetation along the strandline. These very unstable dunes are colonised by salt tolerant plants like sea rocket Cakile maritima. As they grow and are less at risk from being washed away by high tides, more plants can colonise and it gradually evolves into a mobile dune.

 

Mobile (‘white’ or ‘yellow’) dunes are unstable dunes where there is active sand movement. They are less salty than the embryo dunes and are constantly replenished with fresh sand. They are colonised by plants like marram grass Ammophila arenaria or Lyme grass Leymus arenarius. They are called ‘white’ or ‘yellow’ dune because there are bare patches of sand visible in between the vegetated areas.

 

Fixed (‘grey’) dunes occur widely around the coasts of the UK and are a major component of many sand dune systems. They are not replenished with fresh sand so that the sand is no longer accumulating. They support a greater diversity of plants that will contribute to stabilising the dunes. They develop landwards of the white dunes.

 

Marram grass sand dunes at Hunstanton, Norfolk, England © JNCC

Dune slacks are low-lying areas within dune systems that are seasonally flooded and where nutrient levels are low. They occur primarily on the larger dune systems in the UK, especially in the west and north, where the wetter climate favours their development when compared with the generally warmer and/or drier dune systems of continental Europe. The range of communities found is considerable and depends on the structure of the dune system, the successional stage of the dune slack, the chemical composition of the dune sand, and the prevailing climatic conditions. Dune slacks are important features for species like the Natterjack toad Epidalea calamita as well as many scarce invertebrates.

 

Dunes with Juniper comprise occurrences of common juniper Juniperus communis scrub on coastal sand dunes in a variety of situations. Both prostrate and erect forms of juniper can be found. Stands are usually very small and are intimately mixed with other habitat types, including dune grassland and heath. There is complete range from discrete stands to more scattered and occasional individuals, which occur within habitat types defined as fixed dunes. In the UK, dunes with Juniper only occur in Scotland.

 

Dunes with sea buckthorn comprise scrub vegetation on more-or-less stable sand dunes in which sea buckthorn Hippophaë rhamnoides is abundant. Sea buckthorn may either form dense thickets, with sparse nitrophilous associates such as common nettle Urtica dioica, or occur as more scattered bushes interspersed with various grasses, typically marram Ammophila arenaria and red fescue Festuca rubra, and associated herbs of dune grassland. This form of dune vegetation is mainly found on Atlantic coasts in the EU. In the UK, the native distribution of Hippophaë is considered to be ranging patchily from Dunbar on the east coast of Scotland down to Dungeness/Camber in Sussex.Harebell flowering on Machair grassland, Berneray, Scotland © Ian Strachan

 

Machair

Machair is a distinctive sand dune formation formed when sand with a high shell content is blown onshore onto a low-lying coastal plain. Vegetation develops that is typical of calcareous to neutral sandy grassland. Traditionally, machair supports extensive grazing regimes and unique forms of cultivation that rely on low-intensity systems of rotational cropping. This habitat type also supports large breeding bird populations and is particularly important for waders and corncrake Crex crex. Machair is found nowhere else in the world but the north and west of Scotland and western Ireland.