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Machair (geography)
Encyclopedia
Plain
In geography, a plain is land with relatively low relief, that is flat or gently rolling. Prairies and steppes are types of plains, and the archetype for a plain is often thought of as a grassland, but plains in their natural state may also be covered in shrublands, woodland and forest, or...
found on some of the north-west coastlines of Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
and Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
, in particular the Outer Hebrides
Outer Hebrides
The Outer Hebrides also known as the Western Isles and the Long Island, is an island chain off the west coast of Scotland. The islands are geographically contiguous with Comhairle nan Eilean Siar, one of the 32 unitary council areas of Scotland...
. Two distinct types exist:
- A type of sand-duneDuneIn physical geography, a dune is a hill of sand built by wind. Dunes occur in different forms and sizes, formed by interaction with the wind. Most kinds of dunes are longer on the windward side where the sand is pushed up the dune and have a shorter "slip face" in the lee of the wind...
pasturePasturePasture is land used for grazing. Pasture lands in the narrow sense are enclosed tracts of farmland, grazed by domesticated livestock, such as horses, cattle, sheep or swine. The vegetation of tended pasture, forage, consists mainly of grasses, with an interspersion of legumes and other forbs...
, subject to agricultural cultivation, which prevails in wet and windy conditions; - The land between a beachBeachA beach is a geological landform along the shoreline of an ocean, sea, lake or river. It usually consists of loose particles which are often composed of rock, such as sand, gravel, shingle, pebbles or cobblestones...
and the area where sand encroaches on peat bogBogA bog, quagmire or mire is a wetland that accumulates acidic peat, a deposit of dead plant material—often mosses or, in Arctic climates, lichens....
s further inland.
Geology
In both cases, a machair is a former beachBeach
A beach is a geological landform along the shoreline of an ocean, sea, lake or river. It usually consists of loose particles which are often composed of rock, such as sand, gravel, shingle, pebbles or cobblestones...
, left higher in elevation than the current adjacent beach following a drop in sea level
Sea level
Mean sea level is a measure of the average height of the ocean's surface ; used as a standard in reckoning land elevation...
or isostasy
Isostasy
Isostasy is a term used in geology to refer to the state of gravitational equilibrium between the earth's lithosphere and asthenosphere such that the tectonic plates "float" at an elevation which depends on their thickness and density. This concept is invoked to explain how different topographic...
.
Machairs largely owe their fertility to the fact their sand has a high seashell content- sometimes as high as 90%. This sand is blown inland, acts to neutralize the acidity of the peatbogs and results in the fertility of the grassland.
Ecology
Machairs have received considerable ecological and conservationalConservation biology
Conservation biology is the scientific study of the nature and status of Earth's biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction...
attention, chiefly because of their unique ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
s. They can house rare
Rare species
A rare species is a group of organisms that are very uncommon or scarce. This designation may be applied to either a plant or animal taxon, and may be distinct from the term "endangered" or "threatened species" but not "extinct"....
carpet flowers, such as Irish Lady's Tresses
Spiranthes
Spiranthes, commonly called Ladies'-tresses, is a genus of orchids Spiranthes, commonly called Ladies'-tresses, is a genus of orchids Spiranthes, commonly called Ladies'-tresses, is a genus of orchids (family (Orchidaceae) belonging to the subfamily Orchidoideae.It has a very wide, almost...
, orchids
Orchidaceae
The Orchidaceae, commonly referred to as the orchid family, is a morphologically diverse and widespread family of monocots in the order Asparagales. Along with the Asteraceae, it is one of the two largest families of flowering plants, with between 21,950 and 26,049 currently accepted species,...
and Yellow Rattle
Yellow rattle
Yellow Rattle or Cockscomb, Rhinanthus minor, is a flowering plant in the genus Rhinanthus in the family Orobanchaceae, native to Europe and Western Asia....
, along with a diverse array of bird species including the Corn Crake
Corn Crake
The Corn Crake, Corncrake or Landrail is a bird in the rail family. It breeds in Europe and Asia as far east as western China, and migrates to Africa for the winter...
, Twite
Twite
The Twite is a small passerine bird in the finch family Fringillidae.The Twite is a small finch, similar in size and shape to a Linnet. Birds of the subspecies flavirostris are long, and those of the subspecies altaica are long. It lacks the red head patch and breast shown by the Linnet and the...
, Dunlin
Dunlin
The Dunlin, Calidris alpina, is a small wader, sometimes separated with the other "stints" in Erolia. It is a circumpolar breeder in Arctic or subarctic regions. Birds that breed in northern Europe and Asia are long-distance migrants, wintering south to Africa, southeast Asia and the Middle East...
, Common Redshank
Common Redshank
The Common Redshank or simply Redshank is an Eurasian wader in the large family Scolopacidae.- Description and systematics :...
and Ringed Plover
Ringed Plover
The Common Ringed Plover or Ringed Plover is a small plover.Adults are 17-19.5 cm in length with a 35–41 cm wingspan. They have a grey-brown back and wings, a white belly, and a white breast with one black neckband. They have a brown cap, a white forehead, a black mask around the eyes...
, as well as rare insects such as the northern colletes
Northern Colletes
The Northern Colletes is a species of bee within the genus Colletes. Northern Colletes are solitary bees, though females may nest in what are termed aggregations – sites where the bees nest close together, but do not form colonies as social bees do...
bee. Some machairs are threatened by erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
caused by rising sea levels as well as by recreational use of vicinity beaches.