Annex IV protected areas: water dependent habitats and species and high status sites

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3.5. Coastal onshore habitats.

Habitat Code

Habitat Name

Structure and functions (Condition)

Overall Conservation Status


Annual vegetation of drift lines (40)




Perennial vegetation of stony banks (48)




Embryonic shifting dunes (44)




Shifting dunes along the shoreline with Ammophila arenaria (“white dunes”) (55)




*Fixed coastal dunes with herbaceous vegetation (“grey dunes”) (52)




*Decalcified fixed dunes with Empetrum nigrum (7)




*Atlantic decalcified fixed dunes (Calluno-Ulicetea) (12)




Dunes with Salix repens ssp. argentea (Salicion arenariae) (14)




Humid dune slacks (26)




Machairs (*in Ireland) (32)



Note #: The number of SACs in which each habitat occurs as either a qualifying interest, or is present, is given in brackets. * Priority Annex 1 listed habitats are indicated with * and are bold-faced. Colour-coded to represent the 2007 Article 17 Conservation Status assessment: green = favourable, amber = unfavourable-inadequate, red = unfavourable-bad.

Coastal onshore habitats occur as a qualifying interest in 73 SAC sites nationally. Annex 1 listed surface water dependent lake habitats also occur in 11 of these sites, and river habitats occur in a further 4 sites. Coastal onshore habitats include dependency on coastal, transitional, surface water and groundwater source types (see Section 5, Table 5.1).

Coastal onshore habitats depend on coastal geomorphological and sediment transport processes for their formation and continued existence, and are highly vulnerable to climate change impacts including increased storm surges and rising sea levels. They have an important current role in coastal protection, and their immediate hinterland often includes low-lying areas of other water dependent habitats such as coastal lagoons (e.g. Lady’s Island Lake and Tacumshin SACs in Wexford), or saltmarsh and fen (e.g. the Murrough Wetlands SAC in Wicklow). In other locations, these coastal onshore habitats protect low-lying hinterland in agricultural, and/or in residential use (e.g. north Dublin). NPWS has recently completed digital habitat mapping of this group of habitats.
Drift line, stony banks and sand dune systems are widely distributed around the Irish coast. Sand dune systems may include wetland habitats Humid dune slacks 2190, and Dunes with Salix repens ssp. argentea (Salicion arenariae) 2170, which occur in topographic depressions in dune systems and are mainly ground water dependent, generally with a lens of fresh water overlying more saline water.
Machair is a distinct geomorphological and ecological habitat that is unique to the exposed Atlantic north-west coasts of Ireland and Scotland. In Ireland, machair occurs from Co. Galway north to Donegal. It develops in exposed conditions where wind erodes an original sand dune system down to a level just above the water table, where the wet consistency of the sand prevents further erosion. Typically, there is a small escarpment or dune ridge along the shore, with the machair plain in its lee, although machair can also develop over coastal rock platforms in the absence of a dune building phase. Typically, there is a lake on the landward side of the machair plain, at the junction of the sand with the underlying bedrock and its associated soils and subsoils. Lake water chemistry in these situations may be influenced by a combination of acidic bed-rock, wind blown sand of marine origin with a significant proportion of shell giving a calcareous influence, and brackish ground water or wind-blown salt giving a saline influence. Machair is a dynamic habitat; as sand moves across the plain, lakes and other wetland habitats such as marsh and fen tend to become infilled, while new wet areas are exposed by erosion of sand down to the water table. Wetlands are thus an integral part of machair habitat, with ground water, surface water, and in some instances transitional water contributing.
For landscape reasons, coastal onshore habitats attract recreational uses including golf courses, sports pitches, and caravan and car park developments, as well as residential development. These lead to hydrological pressures including water abstraction for golf course irrigation and other purposes, reducing groundwater levels, leading to saline intrusions, and impacting adversely on dune slack and machair habitats and on the water dependent plant and animal species associated with them. Reduced water table levels may also make these landforms more vulnerable to erosion. Water quality pressures associated with agricultural fertiliser use, and with domestic and recreational facility waste water, are likely to arise in dune slacks, wetland areas and lakes associated with dune and machair systems – although this has not been investigated by Article 17 monitoring to date, the findings for lagoon and lake habitats suggest that eutrophication is likely to occur in dune and machair wetlands, and may also constitute a risk to groundwater given the permeable nature of the sandy soils present. Groundwater vulnerability is generally extreme in these areas.
It should be noted that the hinterland of coastal onshore habitats often includes shallow soils over relatively impermeable rock, so that nutrients and other pollutants arising from diffuse sources will tend to flow over the bedrock and find their way to lakes and other wetlands within the coastal onshore habitat complex, giving rise to cumulative impacts.
Agricultural improvement and overgrazing are widespread in dune and machair systems, but while they are the most widespread source of adverse impacts on these habitats reported in the conservation status assessments, they are considered reversible through the agreement and implementation of sustainable grazing levels under NPWS Conservation Plans and REPS schemes.
Water status pressures leading to unfavourable conservation status in individual coastal onshore habitats within SACs arise from ground water abstraction, and eutrophication (see Appendix 8, and the SAC_Water_Dependency database). Pressures on water dependent species associated with coastal onshore habitats are discussed in Section 3.5.1 below.

3.5.1. Water dependent species associated with coastal onshore habitats.

Common name (#)

Scientific name

Main pressures and threats

Petalwort (20)

Petalophyllum ralfsii

Water abstraction

Narrow mouthed whorl snail (18)

Vertigo angustior

Adverse hydrology, eutrophication, pesticides

Petalwort Petalophyllum ralfsii

Petalophyllum ralfsii is a small thalloid liverwort, and is usually found on damp, calcareous sand in dune slacks and machair, where it is wet or even subject to inundation in the winter. In dune slacks it often occurs in a zone around the margins of seasonally flooded basins or depressions. In machair it is usually found around the sides of eroding sand hills on open, flushed sandy plains. P. ralfsii often seems to favour the sides of paths or wheel ruts where the soil receives some disturbance, leading to gaps in the vegetation. It does not grow in slacks that are water-filled for long periods, or which are heavily shaded. It usually disappears from view when the substrate dries out in the summer, surviving as tubers. It can vary in apparent abundance from year to year, depending on weather conditions. P. ralfsii occurs as a Qualifying Interest in 20 SACs in Ireland; the entire national range is protected.
Because of the fragility of its habitat and its specialised ecology, P. ralfsii is potentially threatened by a large number of factors, including holiday developments, recreational activities, under-grazing, over-grazing, erosion and desiccation due to water abstraction. Its conservation status is currently assessed as favourable. The main threat identified arises in relation to groundwater abstraction.
Narrow-mouthed whorl snail Vertigo angustior

The narrow-mouthed whorl snail Vertigo angustior is listed as a qualifying interest in 13 SACs and occurs in 5 further SACs. Most sites for this species are in sand dune systems along the western seaboard, it survives at only two inland sites: Pollardstown Fen and Ryewater Valley/Cartron SACs in Cos. Kildare and Meath, and has been recorded recently for the first time in fen habitat in Curraghchase Woods in Co. Limerick (Site Code 00174).

In Ireland Vertigo angustior is found associated with decaying vegetation in the litter layer, or in damp moss, in association with permanently moist but free-draining (permeable) soil, not subject to inundation. It is the latter requirement that makes seemingly suitable and widespread habitat unable to sustain a population of V. angustior. It can tolerate salt spray and brief submersion by high water spring tides.

Vertigo angustior is sensitive to modification of site hydrology which affects ground-water or surface water, eutrophication including exposure to agricultural run-off giving rise to changes in plant community structure; application of pesticides (including herbicides). Exposure to leisure activities, especially on coastal sites, can have serious negative impact on V. angustior populations e.g. installation of caravan parks, marina development (on estuaries), motor vehicles/sports. Introduction of shrubs, e.g. sea buckthorn Hippophae rhamnoides, can also be a problem on coastal sites.
In Ireland, the main loss of Vertigo angustior sites appears to be a result of loss of riverside and canal-side habitat, exploitation of esker sites and drainage of local wetlands or more extensive areas, and sheep grazing and over exploitation of dune sites. Its conservation status is currently assessed as unfavourable – inadequate. A 3-year monitoring programme for all Vertigo sites is in progress for NPWS, with annual updates on distribution and a final report due in December 2010. The main threat identified arises in relation to groundwater abstraction.

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