MIDA - Marine Irish Digital Atlas

Terrestrial Coastal Habitats

Overview

Terrestrial coastal habitats are categorized for MIDA as environments that are located at the coast but are not under tidal conditions. However, these habitats are influenced by the effect of seawater through spray manoeuvred by wind and waves, which in turn influences the plant communities living here and distinguishes these habitats from inland terrestrial areas. These ecosystems are broadly distinguished as sea cliffs, shingle/gravel banks and sand dune systems. There is a great variation between the habitats and their species composition owing to the variety of different local conditions.

Details

Sea Cliffs

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Shingle and Gravel Banks

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Sand Dune Systems

Sea Cliffs

The rocky cliffs of Moher, Co. Clare, are home to large colonies of seabirds.

Sea cliffs are situated either directly on the coast or are separated from the water by a narrow shore. Cliffs can vary in gradient from gently sloped to vertical. Maritime cliffs can be rocky, referred to as hard cliffs, or they are formed from unconsolidated material containing mud, sand, gravel or a mixture of these sediments and are called soft cliffs. However, there are many intermediate types. Hard cliffs are often steep and in most cases support a smaller amount of flowering and seed-bearing plants than soft cliffs, although the latter are more susceptible to erosion. Hard cliffs consist mostly of weather resistant materials such as granite, sandstone and limestone. Shales and boulder clay in unconsolidated material cause soft cliffs to be less stable and therefore to form less steep gradients. Soft cliffs are more readily colonised by vegetation. Rocky cliffs are often covered in lichens but may sustain many salt tolerant plants in their soil filled cracks and are frequently home to seabird colonies. Large colonies of seabirds can be found on the Cliffs of Moher (Co. Clare), Horn Head (Co. Donegal) and Little Skellig (Co. Kerry).

Armeria maritima– sea pink or thrift growing on cliffs in the southwest.

Plant life on maritime cliffs can differ substantially owing to varying wind and salt spray exposure. The chemistry of the underlying substrate influences the type of plants found here. Other factors determining the variety of vegetation are the water content and stability of the underlying substrate.

Salt tolerant plants that grow on maritime cliffs are:

Thrift (Armeria maritima),

Sea Aster (Aster tripolium),

Sea Plantain (Plantago maritima),

Roseroot (Rhodiola rosea),

Bladder Campion (Silene vulgaris) and

Grasslands containing Red Fescue (Festuca rubra) or even heath.

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Shingle and Gravel Banks

Note the variation in vegetation cover across this shingle bank in Farranamanagh, Co. Cork.

This habitat forms when shingle and gravel mount up above the high tide watermark. These dynamic habitats are also known as storm beaches because they are under irregular impacts from storms. Plants colonising these areas must be able to handle conditions of sparse soil and salt spray winds. Furthermore, owing to the unstable nature of this habitat, vegetation has to face disturbances such as burial or erosion. Consequently, vegetation cover is more prominent on the less exposed landward side. However, the plants that live on shingle and gravel banks support invertebrates and coastal birds. More stable conditions occur when this habitat is located further away from the shore, therefore leading to more mixed plant communities. These communities can range from moss and lichen to mature grassland, lowland heath and sometimes scrub.

Dynamic coastal habitats such as shingle and gravel banks are threatened by coastal squeeze. This happens when wildlife is caught between fixed coastal defences on the landward side and rising sea levels on the seaward side. To escape the rising sea the habitats would naturally move landward but are stopped by fixed defences. However, these habitats themselves are natural coastal defences and should be considered as an alternative to traditional defences such as sea walls. Illegal extraction of gravel is also a threath to these fragile habitats.

Plants that colonise Shingle and Gravel Banks	Rare species
Sea Sandwort (Honkenya peploides), Annual Sea-blite (Suaeda maritima), Sea Beet (Beta vulgaris), Rock Samphire (Crithmum maritimum), Sea Mayweed (Tripleurospermum maritimum), Herb-robert (Geranium robertianum), Cleavers (Galium aparine), Buck's-horn Plantain (Plantago coronopus), Sand Couch (Elymus juncea), Curled Dock (Rumex crispus)	Perennial Plants:
	Sea-kale (Crambe maritima), Oysterplant (Mertensia maritima)
	Bird:
	Little Tern (Sterna albifrons) – nesting sites of this bird on open shingle beaches are exposed to human disturbance and predators.

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Sand Dune Systems

Sand Dunes, Tramore Beach, Co. Waterford

Sand dunes, Tramore, Co. Waterford.

The development of Coastal Sand Dune Systems depends on the sufficient and continual supply of sand and the presence of onshore winds. Dry sand is blown from beaches landwards and placed above the high water mark. The sand is retained by dune building grasses such as Marram grass (Ammophila arenaria). Dune systems are dynamic and complex living systems, which have specialised flora and fauna owing to particular characteristics, for example nutrient poverty. Dunes are often affiliated with habitats such as machair, scrub and wetlands. Sand dune systems are sensitive to human induced changes. Human uses of these habitats range from recreation and over grazing to military training. Many dune systems suffer from extraction of material for the building industry and the dumping of rubbish.

Habitats belonging to sand dune systems:

Embryonic Dunes, Marram Dunes and Fixed Dunes;
Dune Scrub and Woodland;
Dune Slack;
Machair.

Dune habitats that are in succession from unstable first stages of formation to more stable ecosystems
Embryonic Dunes	Marram Dunes	Fixed Dunes
Embryonic Dunes are also referred to as shifting dunes because they are unstable mounds of sand. These hills are up to one metre in height and are characteristic of the first stage of sand dune formation. The sparse vegetation hinders movement of the sand, which is then collected into a mound.	This habitat is more stable than the embryonic dunes and located towards the seaward side of a sand dune system. Dune building plant species such as Marram (Ammophila arenaria) allow the dunes to reach heights of up to 20 meters. However, the dune surface is not completely covered with vegetation and loose sand is blown away in the frequent windy conditions.	Fixed dunes provide the most complete vegetated surface cover and are therefore the most stable of the three habitats. More diverse plant communities can be found including herb rich grasslands or heath. Perennial grasses dominate these dunes, while Marram is present but not as common. Moss and lichen cover are typical for this habitat, often overlying a thin but distinct layer of humus. Orchids such as Dactylorhiza majalis and Anacamptis pyramidalis can be found in this environment. Some fixed dunes are used for grazing and can therefore contain agricultural herbs.
Plants species: Sand Couch (Elymus juncea), Lyme-grass (Leymus arenarius), Sea Rocket (Cakile maritima), Saltwort (Salsola kali), Sea Sandwort (Honkenya peploides)	Plants species: Marram (Ammophila arenaria), Sand Sedge (Carex arenaria), Sea Spurge (Euphorbia paralias), Sea-Holly (Eryngium maritimum), Cat's-ear (Hypochoeris radicata), Ragworts (Senecio spp.)	Plant species: Red Fescue (Festuca rubra), Bents (Agrostis spp.), Marram (Ammophila arenaria), Ling (Calluna vulgaris), Bell Heather (Erica cinerea), Creeping Willow (Salix repens), Lady's Bedstraw (Galium verum), Common Bird's-foot Trefoil (Lotus corniculatus), Kidney Vetch (Anthyllis vulneraria), Ribwort Plantain (Plantago lanceolata), Eyebrights (Euphrasia spp.), Yarrow (Achillea millefolium), Cat's-ear (Hypochoeris radicata), Hawkbits (Leontodon spp.), Wild Thyme (Thymus praecox).

Dune scrub and woodland
Scrub succession in Sand Dune system, Co. Mayo

This habitat can develop when scrub or woodland succeed the herbaceous plant communities on flattened, fixed dunes. However, in most cases scrub and trees are planted to stabilise the dunes. This habitat is not common in Ireland because of persistent disturbances to sand dune systems due to grazing, recreation and agriculture. The majority of the existing dune woodlands are non-native conifer plantations. Scrub species found in this habitat are:

Gorse (Ulex spp.),

Hawthorn (Crataegus monogyna),

Blackthorn (Prunus spinosa),

Juniper (Juniperus communis),

Burnet Rose (Rosa pimpinellifolia),

Bramble (Rubus fruticosus agg.),

Elder (Sambucus nigra),

Non-native Sea-buckthorn (Hippophae rhamnoides)

Dune slacks
This habitat occurs between dune ridges or in hollows on the landward side, where the water table is at or close to the surface of the depression. These areas are more nutrient rich and wet than their surroundings and can support plants that require higher moisture and nutrient content.

Orchid - Dactylorhiza incarnata sp., Co. Clare

Dactylorhiza incarnata sp., County Clare

Orchids like Dactylorhiza incarnata, Gymnadenia conopsea and Epipactis palustris can be found here and if the area stays permanently wet Mare's-tail (Hippuris vulgaris) and Water Horsetail (Equisetum fluviatile) are present. Other plants found in this habitat include:

Creeping Willow (Salix repens),

Creeping Bent (Agrostis stolonifera),

Common Reed (Phragmites australis),

Sedges (Carex spp.),

Rushes (Juncus effusus, J. maritimus),

Common Marsh-bedstraw (Galium palustre),

Water Mint (Mentha aquatica),

Silverweed (Potentilla anserina),

Bog Pimpernel (Anagallis tenella).

Machair

Machair in Maghera, Co. Donegal.

In Europe this rare habitat can only be found on the north and west coasts of Britain and Ireland. In general, Machair translates from Gaelic as ‘extensive, low-lying fertile plain’. These grassy areas are characterised by species-rich, herbaceous vegetation and can contain mosaics of dry and wet areas. They have formed on wind blown calcareous sands and contain plants that are typical for both sand dunes and calcareous grasslands. The development of machair has been influenced by human activities. Historically, these areas would have been associated with agriculture. Nowadays, machair is still grazed. However, these unique habitats are also used for recreational activities such as campsites and sport pitches or other developments, which can affect them adversely. Common plant species on machair include:

Red Fescue (Festuca rubra),

Ribwort Plantain (Plantago lanceolata),

Daisy (Bellis perennis),

Common Bird's-foot Trefoil (Lotus corniculatus),

Lady's Bedstraw (Galium verum)

White Clover (Trifolium repens).

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Spatial Data Sources

The following are suggested sources for geospatial data related to the topic:

If you are aware of any spatial data regarding this theme please contact us.

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