Habitat account - Coastal sand dunes and continental dunes
Background to selection
|Distribution of SACs/SCIs/cSACs with habitat 21A0 Machairs. Click image for enlarged map.|
Description and ecological characteristics
Machair is a distinctive sand dune formation formed by a particular combination of physical factors, including climate and landform. Sand with a high shell content is blown onshore by the westerly winds that prevail in the north and west of Scotland, onto a low-lying coastal plain. Vegetation develops that is typical of calcareous to neutral sandy grassland. In these northern locations the machair grassland has a number of species extending their southern range on the west coast. The most extensive and floristically-rich formations occur as a mosaic of drift-line, foredune, machair plain and transitions to saline lagoons and saltmarsh, or to calcareous lochs, acidic grasslands, fens, heath or bog. These habitats occur within machair, but some may additionally be identified as Annex I types in their own right.
It is believed that machair grassland has been modified by man throughout its development. Traditionally, machair supports extensive grazing regimes and unique forms of cultivation that rely on low-intensity systems of rotational cropping. This traditional agriculture sustains a rich and varied dune and arable weed flora. Some of the arable weed species are now largely restricted in the UK to these traditionally managed areas. The habitat type also supports large breeding bird populations and is particularly important for waders and corncrake Crex crex.
European status and distribution
Machair is found nowhere else in the world but the north and west of Scotland and western Ireland. Machair is a priority habitat in Ireland but not in the UK.
UK status and distribution Click to view UK distribution of this habitat
It is estimated that more than two-thirds of the global machair resource is found in Scotland. Machair complexes occur in the Outer and Inner Hebrides and to a smaller extent on the mainland and the Northern Isles. The Outer Hebrides support the largest and richest examples of cultivated machair and a variety of uncultivated machair types. The Inner Hebrides machair complexes are largely uncultivated, as are those in Ireland. The largest and best-developed area of machair on the mainland is Sheigra – Oldshoremore.
Site selection rationale
Site selection has taken account of the wide range of variation in physical type shown by Scottish machairs and has also been influenced by the UK’s special responsibility for machair conservation. (Machair is a priority habitat in Ireland but not in the UK). The largest sites have been selected, as these demonstrate the best structure and function and include the most diverse examples of transitions to other habitats. Sites have been selected from across the range of machair in the Outer and Inner Hebrides and on the Scottish mainland.
|Coll Machair||Highlands and Islands|
|Coll Machair complex is uncultivated, seasonally grazed in parts and has a high species diversity. The site is a complex of dune, wetland and machair habitats. It has a particularly diverse series of transitions to other habitats because of its complex physical structure. Coll Machair is representative of this habitat type in the Inner Hebrides and is the second-largest area of machair in this part of Scotland. On Totamore Dunes, a foredune ridge is succeeded by a series of erosion and accretion features, dominated by a mosaic of semi-fixed dune and particularly species-rich slack communities. On the landward side, Machair Mhór is the best example of a machair plain on Coll, grading from dry to wet machair and then into swamp communities. In the north the dune system has dammed a valley, resulting in the formation of Loch Ballyhaugh. The Annex II species 1833 Slender naiad Najas flexilis is present, for which the site is also selected. Semi-fixed dune communities dominate Crossapol and Gunna, interspersed with a mosaic of fixed dune communities that are particularly species-rich. On the edge there are transitions from wet machair and dune slacks to wet heath, and a complex of small, species-rich machair lochs.|
|Monach Islands||Extra-Regio, Highlands and Islands|
|Monach Islands complex is representative of machair types found in the Outer Hebrides and is similar to that found on North Uist. These islands consist almost entirely of machair and support some of the best examples of grazed uncultivated machair in the Outer Hebrides. There are rich calcareous grasslands as well as transitions to loch and acidic grassland. The islands are separated from outside human influences by 10 km of sea, and have been uninhabited and uncultivated since 1947. There are few human visitors, and therefore little interference with ecological processes compared with other machair systems. They provide a reference point for measuring the impact of human activities on machair systems.|
|North Uist Machair||Highlands and Islands|
|North Uist contains very extensive areas of both wet and dry machair. The site supports the second-largest extent of machair in the Outer Hebrides. The machair in North Uist is different from that found on South Uist because of local differences in traditional methods of cultivation. A high proportion of the machair on North Uist has been traditionally cultivated or used for rough pasture, although areas of uncultivated machair found at Baleshare and Kirkibost are of interest because of their high species diversity. There is a mosaic of other habitats, with well-developed lochs and fens (e.g. at Balranald Bog) and transition to saltmarsh and sediment flats (e.g. Baleshare and Kirkibost, and Vallay). Machairs Robach and Newton is regarded as the most dynamic system in the Uists. The wet machair supports an unusual population of the southern species sea rush Juncus maritimus, its only occurrence in the Uists.|
|Oldshoremore and Sandwood||Highlands and Islands|
|Oldshoremore and Sandwood complex is one of the largest and least-disturbed examples of machair on mainland Scotland. It is perhaps the most species-rich in the SAC series for the habitat type. The areas of machair grassland within the site are uncultivated and, mostly, grazed. They represent floristic communities not found on any other machair, for example mountain avens Dryas octopetala heath. Mainland plant communities tend to be more varied than those on the islands and the machair flora of this area is particularly species-rich.|
|Oronsay||Highlands and Islands|
|Habitat occurrence account not yet available.|
|South Uist Machair||Highlands and Islands|
|South Uist in the Outer Hebrides has the most extensive cultivated machair system in Scotland, extending the whole length of the island and up to 2 km inland. There is extensive grazing, and rotational cultivation, mainly to provide cattle fodder. The area is very diverse in physical form and is extremely rich in plant species. Extensive areas of wet machair include transitions to machair lochs or wet heath, marshes and peatland. The site is selected for several of these Annex I habitat types in their own right. The standing waters within the site exhibit a wide range of pH and salinity. The Annex II species 1833 Slender naiad Najas flexilis occurs in a number of them, for which the site is also selected.|
|Tiree Machair||Highlands and Islands|
|Tiree is considered to have the most extensive and diverse area of machair outside the Outer Hebrides. 24% of the total area of the island is machair. The machair complex on Tiree is uncultivated and has a long history of seasonal grazing. There is a diverse series of physical machair formations. The Tiree complex is also noteworthy as one of the few examples of rabbit-free machair in Scotland. An Fhaodhail and the Reef is an extensive area of wet machair grading into an extensive marsh and wetland (An Fhaodhail), and is the only site in the Inner Hebrides that is influenced by saline water, although this has recently been restricted by the insertion of a tidal flood-gate. The site is unusual in that it is grazed only by cattle, a traditional management practice that has maintained an extremely rich and varied flora. In contrast, Hough Bay – Balevullin is a complex of dry machair and hummocky dunes forming an intricate mosaic with wet machair and dune slack vegetation.|
|Tràigh na Berie||Highlands and Islands|
|Tràigh na Berie is one of four sites selected for machair in the Western Isles, and is the sole representative on Lewis and Harris, which together form the largest island in this group. The machair grassland within the site is linked to the beach (the source of its sand supply) by marram dune and two types of semi-fixed dune. The inland transitions are atypical and particularly varied, with superb climbing machair-like grassland where sand is blown to considerable heights, enabling plants such as stoneworts to thrive in shallow lochs at 50 metres above sea level. The wetland transitions on lower ground are also rich and varied, and a large hollow in the east of the site supports an area of dune slack vegetation which is rare in the Western Isles. Orchids are varied and numerous, with the frog orchid Coeloglossum viride particularly common. A crimson sub-species of the early marsh orchid Dactylorhiza incarnata coccinea, often known as the ‘dune orchid’, occurs, as well as unusual hybrids between orchid genera. Other noteworthy plants include the northern gentian Gentianella amarella septentrionalis. The machair system as a whole at Tràigh na Berie is particularly notable for its rich botanical diversity, including machair grassland with five types of sand dune vegetation as well as inundation grassland and a range of traditional cultivation types and their fallows.|
SACs/SCIs/cSACs where this Annex I habitat is a qualifying feature, but not a primary reason for site selectionNot applicable.
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