Sand dunes are special landscape phenomenon, usually closely connected with a sea coast or desert. Sand dunes are considered to be a special unstabil ecosystem. Most of plants and animals living there are equipped by some special adaptations to survive. Sand dunes are attractive targets from ecological and ecotouristic points of view.
In physical geography, a dune is a hill of sand built by aeolian processes. Dunes are subject to different forms and sizes based on their interaction with the wind. Most kinds of dune are longer on the windward side where the sand is pushed up the dune, and a shorter "slip face" in the lee of the wind. The "valley" or trough between dunes is called a slack. A "dune field" is an area covered by extensive sand dunes. Large dune fields are known as ergs.
Some coastal areas have one or more sets of dunes running parallel to the shoreline directly inland from the beach. In most cases the dunes are important in protecting the land against potential ravages by storm waves from the sea. Although the most widely distributed dunes are those associated with coastal regions, the largest complexes of dunes are found inland in dry regions, deserts and associated with ancient lake or sea beds.
Dunes form where constructive waves encourage the accumulation of sand, and where prevailing onshore winds blow this sand inland. There need to be obstacles e.g. vegetation, pebbles etc. to trap the moving sand grains. As the sand grains get trapped they start to accumulate, this is the start of dune formation. The wind then starts to affect the mound of sand by eroding sand particles from the windward side and depositing them on the leeward side. Gradually this action causes the dune to “migrate” inland, as it does so it accumulates more and more sand. Dunes provide privacy and shelter from the wind.
As a dune forms, plant succession occurs. The conditions on an embryo dune are harsh, with salt spray from the sea carried on strong winds. The dune is well drained and often dry, and composed of calcium carbonate from seashells. Rotting seaweed, brought in by storm waves adds nutrients to allow pioneer species to colonize the dune. These pioneer species are marram grass, sea wort grass and other sea grasses in the UK. These plants are well adapted to the harsh conditions of the fore-dune typically having deep roots which reach the water table, root nodules that produce nitrogen compounds, and protected stoma, reducing transpiration. Also, the deep roots bind the sand together, and the dune grows into a fore dune as more sand is blown over the grasses. The grasses add nitrogen to the soil, meaning other, less hardy plants can then colonize the dunes. Typically these are heather, heaths and gorses. These too are adapted to the low soil water content and have small, prickly leaves which reduce transpiration. Heather adds humus to the soil and is usually replaced by coniferous trees, which can tolerate low soil pH, caused by the accumulation and decomposition of organic matter with nitrate leaching. Coniferous forests and heathland are common climax communities for sand dune systems.
Young dunes are called yellow dunes, dunes which have high humus content are called grey dunes. Leaching occurs on the dunes, washing humus into the slacks, and the slacks may be much more developed than the exposed tops of the dunes. It is usually in the slacks that more rare species are developed and there is a tendency for the dune slacks soil to be waterlogged and where only marsh plants can survive. These plants would include: creeping willow, cotton grass, yellow ins, reeds, and rushes. As for the species, there is a tendency for natterjack toads to breed here.
Albatros Travel and Expeditions can provide you trips directed into areas with the most remarkable sand dunes ecosystems worldwide. These trips are usually very easy. Even not trained people can take part in such journeys. There is a list of countries where sand dunes can be visited:
Indonesia - coastal parks of several islands
Sri Lanka - three national parks on the southeast coast
Tanzania - two national parks on the eastern coast
New Zealand - the only locality in Stewart Island
Chile - only three national parks - two in the north and one in the south