Habitat account - Coastal sand dunes and continental dunes


2110 Embryonic shifting dunes 

Background to selection

Distribution of SACs/SCIs/cSACs with habitat 2110 Embryonic shifting dunes.  Click image for enlarged map.
Distribution of SACs/SCIs/cSACs with habitat 2110 Embryonic shifting dunes. Click image for enlarged map.

Description and ecological characteristics

 

Embryonic shifting dune vegetation exists in a highly dynamic state and is dependent on the continued operation of physical processes at the dune/beach interface. It is the first type of vegetation to colonise areas of incipient dune formation at the top of a beach. On a prograding dune system this vegetation may be the precursor to the main dune-building vegetation dominated by marram Ammophila arenaria. In most cases Embryonic shifting dunes are transient and will either be displaced by marram-dominated vegetation as the dunes develop (2120 Shifting dunes along the shoreline with Ammophila arenaria ("white dunes")) or will be washed away by storms. The continued supply of new sand from the beach plain into the dune system is therefore vital to the continued existence of this community, even if this sand is derived from within the same system. The habitat type is of exceptional importance as an indicator of the general structural and functional ‘health’ of a dune system. Creation of new dune habitat, and indeed the long-term survival of the dune system at which it occurs, is often dependent upon the survival of this habitat type.

 

Embryonic shifting dunes are inherently species-poor and have a limited range of floristic variation. The predominant plants are strandline species such as sea rocket Cakile maritima and the two salt-tolerant, sand-binding grasses: lyme-grass Leymus arenarius and sand couch Elytrigia juncea. These grasses generally occur slightly higher up the beach profile than the true strandline species. There is some geographical variation, even within this very simple vegetation type. While both dune-binding grasses have a wide geographical range, lyme-grass is more abundant in the north and east of Britain and sand couch is more abundant in the south and west. Marram Ammophila arenaria is a common constituent of the habitat type throughout its range.

 

In the UK the majority of vegetation which conforms to this type belongs to NVC type SD4 Elymus farctus ssp. boreali-atlanticus foredune community, but certain stands of SD2 Honkenya peploides – Cakile maritima strandline community (on sand) and SD5 Leymus arenarius mobile dune community may also be referable to this Annex I type when they occur in close association with the Elymus community.

 

By their very nature Embryonic shifting dunes are restricted in the area they can occupy. They are made even scarcer by the fact that only a relatively small number of dunes are actively prograding, the condition under which this habitat type develops best. Embryonic shifting dunes are also particularly vulnerable to trampling by beach users and to mechanical cleaning of beaches, and this may well be a significant factor in limiting their extent.

 

This habitat type rarely occurs in isolation, because it may initiate dune succession, and it is invariably one of several Annex I habitat types to be found on a dune system.

European status and distribution

 

This habitat type has a wide European distribution, and has been recorded from coasts in the Atlantic, Mediterranean, Continental and Boreal Regions.

UK status and distribution Click to view UK distribution of this habitat

 

Embryonic shifting dunes are a rare habitat type in the UK, covering much less than 1,000 ha.

Site selection rationale

 

Owing to the small total extent of the habitat type in the UK, site selection has ensured that a high proportion of the resource is included within the SAC series. Although very localised, the habitat type has a broad geographical range, and this is reflected in the selected sites. By comparison with many other habitats, ecological variation is limited, but the variation that does occur is covered by the SACs. The habitat type is associated with developing (prograding) dunes, which are generally the largest and most structurally and functionally intact dunes in the UK. The distribution of such dunes is not even, and more than one example has been selected in some parts of the UK to reflect this uneven distribution.


Site accounts

Barry Links Eastern Scotland
At Barry Links (one of three representative sites on the east coast of Scotland), there is an identifiable zone of Embryonic shifting dunes with lyme-grass Leymus arenarius, most frequently found on accreting sand spits. Of additional interest is the regular occurrence of an identifiable zone of sand couch Elytrigia juncea foredune, which may extend in summer as a narrow band in front of the main foredune ridge. There are well-developed gradations to 2120 Shifting dunes along the shoreline with Ammophila arenaria (“white dunes”).
Carmarthen Bay Dunes/ Twyni Bae Caerfyrddin East Wales, West Wales and The Valleys
The three Carmarthen Bay Dunes sites within the Burry Inlet provide a representative example of Embryonic shifting dunes in south Wales. They support areas of Embryonic shifting dune in which sand couch Elytrigia juncea is the dominant sand-binding species. There are well-developed transitions to marram Ammophila arenaria dunes.
Dornoch Firth and Morrich More Extra-Regio, Highlands and Islands
There are well-marked lyme-grass Leymus arenarius-dominated areas of Embryonic shifting dunes fronting the prograding sections of this site. Dornoch Firth and Morrich More is one of three sites representing Embryonic shifting dunes on the east coast of Scotland and is the most northerly example of the habitat type in the SAC series. The process of continued progradation is central to the conservation of this habitat type at this site, which has the largest, most complete area of sand dune in the UK, in part owing to the exceptionally high rate of progradation.
Dorset Heaths (Purbeck and Wareham) and Studland Dunes Dorset and Somerset
Embryonic shifting dunes initiate the very clear successional sequence of dune communities at Studland Dunes, which are representative of the habitat type in southern England. This is a part of the UK where this habitat type is rare, partly owing to intensive recreational use of the coast. The site is also of interest in that there are well-developed examples of both sand couch Elytrigia juncea and lyme-grass Leymus arenarius-dominated communities. The former occurs discontinuously along the whole shoreline, while the latter is locally abundant in disturbed locations at the northern end of the site.
Luce Bay and Sands Extra-Regio, South Western Scotland
Torrs Warren – Luce Sands in south-west Scotland is an example of the northern variant of Embryonic shifting dunes, with lyme-grass Leymus arenarius dominant. The length of the dune front at this site, combined with its comparative inaccessibility, helps to ensure that there is an identifiable zone of embryonic shifting dune vegetation. Lyme-grass is well-represented to the seaward edge of the fixed dune, which shows zonation to marram Ammophila arenaria.
Morfa Harlech a Morfa Dyffryn West Wales and The Valleys
Morfa Harlech a Morfa Dyffryn (Morfa Harlech and Morfa Dyffryn) is one of two north Wales sites selected. Embryonic shifting dunes occur as long narrow zones mainly in the Morfa Harlech part of the complex. Both lyme-grass Leymus arenarius and sand couch Elytrigia juncea shifting dune vegetation have been recorded, but the latter is by far the more extensive of the two.
North Norfolk Coast East Anglia
North Norfolk Coast in East Anglia is one of two sites representing Embryonic shifting dunes in the east of England (the other being Winterton – Horsey Dunes). It is a long, thin dune system, displaying both progradation and erosion. The exceptional length and variety of the dune/beach interface is reflected in the high total area of embryonic dune (over 40 ha or at least 14% of the national total). The process of continued progradation is central to the conservation of this habitat type at this site. Sand couch Elytrigia juncea is the most prominent sand-binding grass.
North Northumberland Dunes Northumberland and Tyne and Wear
North Northumberland Dunes represents Embryonic shifting dunes in north-east England. The embryonic shifting dune vegetation of this long series of dunes is both extensive and varied. There are examples of all the main embryonic dune communities. Lyme-grass Leymus arenarius communities are particularly strongly represented, but sand couch Elytrigia juncea communities and strandline species are also present.
Sands of Forvie North Eastern Scotland
Sands of Forvie is one of three sites on the east coast of Scotland which represent the northern part of the UK range of Embryonic shifting dunes. The Sands of Forvie is one of the most geomorphologically active dune systems in the UK, and as a result, the site contains significant representation of dune types associated with shifting sand. Identifiable zones of both lyme-grass Leymus arenarius and sand couch Elytrigia juncea are present, although, as is common with this habitat type, they may be narrow and discontinuous.
Sandwich Bay Kent
The Embryonic shifting dunes at Sandwich Bay are representative of this habitat type in south-east England. The seaward edge of the north of this site displays a good sequence of embryonic shifting dune communities and there is a clear zonation within the dune habitat, with strandline species on the seaward edge and sand-binding grasses inland. Lyme-grass Leymus arenarius is extremely sparse and sand couch Elytrigia juncea is the dominant sand-binding species.
Sefton Coast Merseyside
The Sefton Coast in north-west England displays both rapid erosion and active progradation. Embryonic shifting dunes are of the northern, lyme-grass Leymus arenarius, type and are mainly associated with the areas of progradation, though vegetation dominated by lyme-grass is also found associated with areas of persistent, heavy disturbance further inland.
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 to represent Embryonic shifting dunes in north Wales. Embryonic dunes form a zone across a broad part of the beach/dune interface, making this site one of the most extensive examples of this habitat type in the UK. It is a site where, in contrast to some others in north Wales, recreational damage is minimal.

SACs/SCIs/cSACs where this Annex I habitat is a qualifying feature, but not a primary reason for site selection

Bann Estuary Northern Ireland
Culbin Bar Highlands and Islands
Dee Estuary/ Aber Dyfrdwy Cheshire, East Wales, Extra-Regio, Merseyside, West Wales and The Valleys
Drigg Coast Cumbria
Humber Estuary East Yorkshire and Northern Lincolnshire, Extra-Regio, Lincolnshire
Magilligan Northern Ireland
Morecambe Bay Cumbria, Extra-Regio, Lancashire
Murlough Extra-Regio, Northern Ireland
North Uist Machair Highlands and Islands
Saltfleetby-Theddlethorpe Dunes and Gibraltar Point Lincolnshire
Tiree Machair Highlands and Islands
Winterton - Horsey Dunes East Anglia
 

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