Habitats
Sand dunes
Sandy beaches occur all around the coast but are especially common in Aberdeenshire, Orkney and the Inner and Outer Hebrides, where they can appear to stretch endlessly into the distance. Wherever there are strong onshore winds and a low-lying coastal plain where sand can accumulate, dunes may develop.
Initially, dunes begin to form where wind-blown sand collects around the debris cast from the sea at the top of the beach. Dune-building grasses soon appear; in particular the tall tussocky marram grass, which characterises dunes in this country. These grasses themselves act as a buffer to the wind, trapping more sand, so that the dune grows in height and width. Exceptionally, as at Balnakiel in Sutherland and Crossapol on Coll, dunes may reach 35m or more in height! The grasses also stabilise the sand surface, making it more hospitable for other plants and animals to colonise.
Moving inland the mobile dunes change to more stable ‘fixed’ dunes as the amount of blown sand reduces. As conditions become easier in which to live, many other grasses and herbs become established to form a grassland or heathland.
Machair
In the north-west of Scotland, the strength of the winds produces a distinctive coastal landscape which is found hardly anywhere else in the world. On many exposed coastlines, the extreme winds blow sand inland which smothers the land and forms a broad, flat plain between the beaches and the hills. The name given by the Gaelic speaking people of such areas to this unique and important landform is ‘mhachair’ (or ‘machair’ as it is known in English), and it characterises most of the length of the Western Isles, as well as other islands on the north-west coast.
Machair sand is largely made up of tiny shell fragments. Being calcareous (calcium-rich), these provide an ideal soil which encourages a very rich grassland to develop; in summer months the flowering plants form a dazzling mosaic of colour stretching into the distance. Closely linked with the machair grassland are salty lagoons, freshwater lochs and fens, providing a wealth of different habitats for plants, birds and other animals.
Saltmarsh
Saltmarsh is a relatively rare habitat in Scotland. It is found in river estuaries, deeply indented sea lochs and behind sand or shingle bars, where there is little or no exposure to wave action. In Scotland, the most extensive saltmarsh areas occur in the sheltered upstream areas of the Tay, Forth and Solway Firths and within bays and sea lochs on the west coast. In such places, fine sediment settles out onto the shore and forms mudflats, sometimes many hundreds of metres wide. Certain flowering plants such as glasswort, a succulent plant often harvested for food on the continent, and saltmarsh grass, may then establish in the mud at the top of the shore.
Moving inland, away from the sea, the saltmarsh is flooded less often and so other plants, less tolerant of sea water, become established. Sea thrift, for instance, can be so common that, in early summer, the saltmarsh turns into a vast pink carpet of flowers. This process of succession continues inland until the influence of the sea disappears and there is a change to terrestrial or freshwater habitats.
In winter, estuaries are extremely important roosting and feeding sites for hundreds of thousands of over-wintering waders and wildfowl such as dunlin, widgeon and brent geese. These birds travel from as far away as the Arctic to feed on the mud flats, slatmarsh and surrounding areas. In summer, they are replaced by breeding birds such as redshank and ringed plover.
Sea cliffs
High, rocky cliffs dominate the Scottish coastline, providing some of Britain’s most spectacular coastal scenery. The highest cliffs in Britain, soaring to 430m, are found on the remote islands of St Kilda where they withstand the full force of the Atlantic Ocean.
In summer months the cliffs belong to the seabirds. Tens of thousands of guillemots, kittiwakes, fulmars, razorbills and many more crowd onto the the steep cliffs to lay their eggs and rear their young. Others, such as puffins and manx shearwaters choose to burrow into the steep slopes to nest.
Due to their inaccessibility, to all but the seabirds, cliffs are one of the least modified habitats in Scotland. The hard, near vertical rock faces, broken only by a few ledges and cracks and battered by the wind and waves do not, at first sight, appear a very hospitable environment for life. However, even here, lichens and salt-tolerant plants, such as sea thrift and Scot’s lovage, are able to set root wherever a thin soil can build up in crevices and on ledges. Higher up the cliffs and on the cliff tops, out of reach of the waves but still influenced by saltspray, a richer maritime grassland or heathland develops.
Shingle
Shingle beaches occur all around Scotland but particularly in the Moray Firth, the Hebrides and the Northern Isles. Most of the stones which make up such beaches were formed by erosion of the land during the Ice Age, and were carried to the coast by the glaciers and rivers. Since then they have been reworked and rounded by the constant action of the waves.
Shingle beaches are widespread but ‘stabilised’ shingle with vegetation is relatively rare because few plants are able to colonise this mobile and often exposed substrate. Those that do are typically annual species, such as orache, which die back every year during the winter storms. A more complete plant cover is only available to develop further inland, where the surface has become more stable and a soil layer has developed.
The top of shingle beaches above the spring tide level, especially on exposed coastlines, is often marked by a distinctive ridge of pebbles, known as a storm beach. In places, whole series or ‘staircases’ of these storm beaches have been formed and stranded inland as the high-water mark has retreated seaward. Elsewhere, shingle may accumulate as distinctive spits, extending hundreds of metres along the coast, or as bars linking separate islands.