Habitat account - Coastal sand dunes and continental dunes
2120 Shifting dunes along the shoreline with Ammophila arenaria (`white dunes`)
Background to selection
|Distribution of SACs/SCIs/cSACs with habitat 2120 Shifting dunes along the shoreline with Ammophila arenaria (`white dunes`). Click image for enlarged map.|
Description and ecological characteristics
Shifting dunes along the shoreline with Ammophila arenaria ("white dunes") encompasses most of the vegetation of unstable dunes where there is active sand movement. Under these conditions sand-binding marram Ammophila arenaria is always a prominent feature of the vegetation and is usually dominant. In the UK the majority of such vegetation falls within NVC type SD6 Ammophila arenaria mobile dune community. This is a dynamic vegetation type maintained only by change. It can occur on both accreting and eroding dunes, but will rapidly change and disappear if stability is imposed. It rarely occurs in isolation because of its dynamic nature and because it is successionally related to other dune habitats. The habitat type excludes the low, embryonic dunes where occasional exposure to saltwater flooding constrains the growth of marram and where plants of the strandline mingle with salt-tolerant, sand-binding grasses; such vegetation is referable to Annex I type 2110 Embryonic shifting dunes.
The species composition of shifting dunes is constrained by the harsh conditions, but the vegetation is by no means uniform. The most marked floristic variation relates to the degree of instability. Where sand accretion is extremely rapid it is possible to find vegetation that consists only of A. arenaria. As rates of sand deposition decline the marram is joined by more species, first by other specialised dune plants, then by less specialised grasses, drought-tolerant annuals and a restricted number of specialised bryophytes such as the moss Tortula ruralis ssp. ruraliformis. This moss plays an important part in completing the stabilisation of the sand surface. Towards the seaward edge of the zone of shifting dunes, salt-tolerant plants such as sea sandwort Honckenya peploides may be prominent, along with the sand-binding sand couch Elytrigia juncea. Further inland these species are rarely prominent.
There is also geographical variation in the floristic composition of the habitat type. A number of typical shifting dune plants such as Portland spurge Euphorbia portlandica and sea-holly Eryngium maritimum are mostly confined to the south of the UK, while lyme-grass Leymus arenarius is much more abundant in the northern half of Britain, where the vegetation may fall within the NVC type SD5 Leymus arenarius mobile dune community.
European status and distribution
Shifting dunes along the shoreline with Ammophila arenaria are found throughout the coastal zone of the EU.
UK status and distribution Click to view UK distribution of this habitat
This habitat type is geographically widespread around the UK coastline, although in many places it is restricted to a narrow strip.
Site selection rationale
Sites have been selected to cover the geographical range of the habitat type and its ecological variation. The selected sites are generally those with the largest expanses of the habitat type, and with active dune processes which maintain the structure and function of the habitat type. Sites that exhibit zonations related to the stability of the dune system have been particularly favoured, as such zonations are seen as indicative of good conservation of structure and function.
The distribution of high-quality shifting dunes is not even, and more than one example has been selected in some parts of the UK to reflect this uneven distribution.
Well-developed shifting dune vegetation is almost always associated with a number of other dune habitats and the sites selected contain a range of such transitions to fixed dune, dune heath and dune slack habitats.
|Barry Links||Eastern Scotland|
|Shifting dunes along the shoreline are found as an identifiable band along the coastal edge of Barry Links on the east coast of Scotland. The site is mostly undisturbed and there are active coastal processes along the undefended seaward edge resulting in areas of dune accretion, particularly along the southern edge of the site. Where dunes are accreting, they are dominated by marram Ammophila arenaria, and there are well-developed transitions to dune grassland and heath.|
|This large site in south-west England contains a substantial area of mobile dune vegetation, including representative examples of most of the main variants found in the south-west of the UK. There are good numbers of characteristic specialist plants typical of this region, such as Portland spurge Euphorbia portlandica, sea spurge Euphorbia paralias and sea-holly Eryngium maritimum. Transitions to dune slack and fixed dune are a prominent feature of this site.|
|Carmarthen Bay Dunes/ Twyni Bae Caerfyrddin||East Wales, West Wales and The Valleys|
|Carmarthen Bay Dunes is representative of mobile dunes in south Wales and contains a very large area of shifting dunes along the shoreline, covering approximately 80 ha in total. In parts of the system (e.g. at Whiteford Burrows) dunes are actively accreting and there are clear zonations of embryonic dunes, shifting dunes and semi-fixed dunes. Uncommon species recorded within the shifting dunes include sea spurge Euphorbia paralias.|
|Coll Machair||Highlands and Islands|
|The dunes at Crossapol and Feall Bay have the greater part of the mobile dune on Coll, maintained not only by high exposure and good sand supply but by a number of significant blowouts including three very large cauldron blowouts, one of which rises to 35 m O.D. As is frequently the case in western Scotland, there is very little foredune, and the dune front is steep with slumped turfs. Marram Ammophila arenaria dominates the dunes to the extent of being the only species present in some areas, and having only scattered creeping thistle Cirsium arvense and sand couch Elytrigia juncea; lyme-grass Leymus arenarius is absent.|
|Dornoch Firth and Morrich More||Extra-Regio, Highlands and Islands|
|This large dune system on the east coast of Scotland is physically diverse, with areas of active accretion, areas of marine erosion and areas of internal instability. There are well-formed parabolic dunes in one area. All of these formations provide opportunities for Shifting dunes along the shoreline with Ammophila arenaria to develop. As a result this habitat type is relatively extensive within the site. The vegetation is representative of northern mobile dune vegetation, with lyme-grass Leymus arenarius prominent in some stands. The site is largely undisturbed, resulting in a natural habitat structure.|
|Dorset Heaths (Purbeck and Wareham) and Studland Dunes||Dorset and Somerset|
|Studland Dunes represents shifting dunes along the shoreline in southern England. Shifting dunes form one part of the very well-marked successional sequences. The seaward dune ridge supports marram Ammophila arenaria vegetation mainly of NVC type SD6e Ammophila arenaria mobile dune, Festuca rubra sub-community, though three other types are represented. There are transitions to embryonic dunes, which are rare on the south coast partly because of intense recreational pressure, and extensive transitions to decalcified fixed dunes and dune heath.|
|Luce Bay and Sands||Extra-Regio, South Western Scotland|
|Torrs Warren – Luce Sands is a very large site in south-west Scotland, with examples of two types of shifting dune vegetation. The foredunes are morphologically less active than other sites in this part of the UK, with less sand accretion and erosion. Nevertheless, there is sufficient sand accretion to support a narrow band of Shifting dunes along the shoreline with Ammophila arenaria, with associated species such as sand sedge Carex arenaria and red fescue Festuca rubra. In addition, shifting dune vegetation with marram is found on blow outs, where active sand movement is occurring in the semi-fixed dunes that form the landward part of the site.|
|Morecambe Bay||Cumbria, Extra-Regio, Lancashire|
|Shifting dune vegetation forms a major component of the active sand dune systems at the entrance to Morecambe Bay on Walney Island and the Duddon Estuary at Sandscale Haws. A small area is also present at the entrance to the Wyre. Sandscale Haws supports a mosaic of shifting communities, which form a continuous block around the seaward edge of this site. There are transitions to 2110 Embryonic shifting dunes. The prograding shingle spits at either end of Walney Island support dune systems at South End and North End Haws. Species associated with these shifting dunes include sea holly Eryngium maritimum, sea spurge Euphorbia paralias, Portland spurge Euphorbia portlandica and sea bindweed Calystegia soldanella.|
|Morfa Harlech a Morfa Dyffryn||West Wales and The Valleys|
|Morfa Harlech a Morfa Dyffryn (Morfa Harlech and Morfa Dyffryn) is one of two sites selected to represent Shifting dunes along the shoreline with Ammophila arenaria in north Wales. It lies at the junction of two major marine sediment transport systems, and as a result provides an excellent example of active accretion. Shifting dunes are therefore extensive, being particularly well-developed at Morfa Dyffryn. Notable species recorded here include hound’s-tongue Cynoglossum officinale and sand cat’s-tail Phleum arenarium.|
|North Norfolk Coast||East Anglia|
|Shifting dunes form a major component of the complex of often linear dune systems that make up the North Norfolk Coast, which is representative of Shifting dunes along the shoreline with Ammophila arenaria in East Anglia. The site supports over 100 ha of shifting dune vegetation, 8% of the estimated total area of this habitat type in Britain. The shifting dune vegetation is also varied, containing examples of all the main variants found in the southern part of the geographical range.|
|North Northumberland Dunes||Northumberland and Tyne and Wear|
|This site consists of a number of dune systems on the north-east coast of England, most of which are accreting and forming suitable conditions for the development of shifting dunes with Ammophila arenaria. Lyme-grass Leymus arenarius is a characteristic species in this habitat type in north-east England, often as an important component. Climbing dunes can occur on steep rocky coasts, as found at Bamburgh. Some of the dune systems support a number of uncommon dune plants, some of which are at the limit of their distribution in the UK.|
|Saltfleetby-Theddlethorpe Dunes and Gibraltar Point||Lincolnshire|
|The dune system on the composite site Saltfleetby–Theddlethorpe Dunes and Gibraltar Point contains good examples of Shifting dunes within a complex site that exhibits a range of dune types. At this site the Ammophila-dominated dunes are associated with lyme-grass Leymus arenarius and sand sedge Carex arenaria. These shifting dunes are part of a successional transition with 2130 Fixed dunes with herbaceous vegetation and 2160 Dunes with Hippophae rhamnoides.|
|Sands of Forvie||North Eastern Scotland|
|The dunes that cover part of Sands of Forvie form one of three sites on the east coast of Scotland selected to represent Shifting dunes along the shoreline with Ammophila arenaria. They are exceptionally mobile, with large areas of bare sand, and there are extensive areas of this habitat type on the site. The site is particularly noted for the substantial areas where sand accretion is so rapid that only marram Ammophila arenaria can survive. However, other types of shifting dune vegetation can be seen, reflecting different degrees of instability. For example, in areas where there is less sand accretion, red fescue Festuca rubra may be found with the marram.|
|Shifting dunes along the shoreline with Ammophila arenaria occurs along the seaward edge of the northern half of this extensive dune system. It is representative of shifting dune vegetation in south-east England, a region where the habitat type is very restricted in its distribution. Although the area of this habitat type is small by comparison with other listed sites, the shifting dune vegetation contains a good range of characteristic foredune species including sea bindweed Calystegia soldanella, sea spurge Euphorbia paralias and sea-holly Eryngium maritimum.|
|A substantial stretch of the Sefton Coast dune system in north-west England is fronted by about 163 ha of shifting dunes. Marram Ammophila arenaria usually dominates the mobile dunes, amidst considerable areas of blown sand. Where rates of sand deposition decline, lyme grass Leymus arenarius, sea-holly Eryngium maritimum and cat’s-ear Hypochaeris radicata occur, with red fescue Festuca rubra and spreading meadow-grass Poa humilis present on the more sheltered ridges. Sea spurge Euphorbia paralias and the nationally scarce dune fescue Vulpia fasciculata are frequent, while sea bindweed Calystegia soldanella is very local. Formby Point is the hinge point between two coastal sub-cells. The zone around the Point has been eroding since 1906 while areas north and south of this zone are accreting (where the nature of the coast allows). The rapid erosion is therefore reducing the area of shifting dunes at Formby, and high, steep eroding dunes abut the beach with extensive areas of blown sand immediately inland.|
|Tiree Machair||Highlands and Islands|
|Mobile dune is scarce on Tiree except on west Tiree, the largest dune system in the Inner Hebrides. The dune front morphology and vegetation closely resemble Crossapol and Feall Bay on Coll Machair but blowouts are less frequent and there is a more rapid transition to semi-fixed dune. As at Coll Machair, the mobile sands contribute to the maintenance of dynamic hindshore 21A0 Machair.|
|Y Twyni o Abermenai i Aberffraw/ Abermenai to Aberffraw Dunes||West Wales and The Valleys|
|Abermenai to Aberffraw Dunes is one of two sites selected in north Wales. It contains one of the largest areas of lyme-grass Leymus arenarius shifting dune community in Wales. The mobile dunes at the southern end of the site support an abundance of sea-holly Eryngium maritimum, and there is well-developed zonation of dune types, including both seaward transitions between mobile dune and foredune, and landward transitions to fixed dune and dune slack.|
SACs/SCIs/cSACs where this Annex I habitat is a qualifying feature, but not a primary reason for site selection
|Bann Estuary||Northern Ireland|
|Dee Estuary/ Aber Dyfrdwy||Cheshire, East Wales, Extra-Regio, Merseyside, West Wales and The Valleys|
|Durness||Highlands and Islands|
|Humber Estuary||East Yorkshire and Northern Lincolnshire, Extra-Regio, Lincolnshire|
|Invernaver||Highlands and Islands|
|Monach Islands||Extra-Regio, Highlands and Islands|
|Murlough||Extra-Regio, Northern Ireland|
|North Antrim Coast||Northern Ireland|
|North Uist Machair||Highlands and Islands|
|Oldshoremore and Sandwood||Highlands and Islands|
|Penhale Dunes||Cornwall and Isles of Scilly|
|Solent Maritime||Extra-Regio, Hampshire and Isle of Wight, Surrey, East and West Sussex|
|South Uist Machair||Highlands and Islands|
|Winterton - Horsey Dunes||East Anglia|
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