Atlantic and Baltic rocky sea cliff and shore

This is a linear, narrow habitat of rocky cliffs and shores along the coasts of the Arctic Sea, the Baltic Sea, the North Sea and the Atlantic Ocean (southwards until Oporto, Portugal). In most cases it is related to eroding coasts, where the bedrock is exposed due to the eroding energy of the sea, but in some cases (like in the upheaval area of the Bothnian Gulf) rocky shores are found on sedimentary coasts. The habitat is restricted to hard cliffs, made of granite (crystalline rocks), sandstone, limestone, marble or schists. Soft, quickly eroding cliffs (for example with a loamy soil) are under habitat B3.4a. Pebble beaches are not included here, but considered part of shingles (habitat B2.1-3a). Littoral caves (HD Annex 1-type 8330) are considered under marine types. Anthropogenic rocky shores (dikes, stone walls) may contain several of the same species as sea cliffs, but are not considered part of this natural habitat. The habitat is dominated by exposed bedrock, while vegetation cover is low. The slopes are in many cases steep. Erosion at sea level causes the fall of higher parts of the cliffs, which conserves the steepness of cliffs, but in hard bedrock erosion rates are insignificant. Near the shoreline sometimes a notch is seen, where waves have eroded the bedrock surface. Elevation ranges from a few to several hundreds of meters. Amongst the highest sea cliffs in Europe are Slieve League in County Donegal, Ireland, reaching about 600 meters above the sea, and the cliffs on the West-coast of Iceland (more than 400 meters). The majority of the bedrock sea shores along the Baltic Sea are low with smoothed and rounded slopes, which are products of glacial abrasion. Cliffs are primary habitats on which no or little succession takes place, due to constant disturbance and ecological constraints by waves, wind and salt spray, combined with a lack of available water in the substrate. There is some influence of grazing, especially on cliff tops. But in many cases this habitat is inaccessible and rather undisturbed, the latter being a rarity on the European continent. Exceptions exist however, like in the Baltic Sea area, where summer houses are built also on sea cliffs. Rocky sea cliffs show gradients in species composition along the climatic gradient from south to north; besides three altitudinal zones are distinguished, from the supralittoral belt to the cliff top. The lowest, supralittoral zone is under the influence of waves, wind and sea spray and has a similar species composition as rocky shores, mainly consisting of lichens and algae. Also the middle cliff zone is very exposed, both wind and salt spray, and almost absent of soil development. Here a mixture of halophytic and chasmophytic vascular plant species is found. A species more-or-less restricted to this zone is the fern Asplenium marinum. The upper cliff and cliff top have a deeper soil, a higher vegetation cover and a vegetation which forms transitions towards grassland, heathland, shrub and forest habitats. In contrast to other regions in the world, hardly any shrub or tree species is found on the Atlantic cliffs, as few salt resistant species exist on the continent. The rocky shores of the Baltic Sea make an exception due to the low salinity of the sea. Also the gradient from south to north shows a shift in species composition in Europe. Common species over most of the latitudinal gradient are Armeria maritima, Crithmum maritimum, Plantago coronopus, Plantago maritima, Silene vulgaris subsp maritima, and on the cliff top Agrostis stolonifera and Festuca rubra. Typical northern cliff species are Cochlearia scotica, Ligusticum scoticum, Puccinellia maritima (on relatively wet sites), Saxifraga oppositifolia, Sedum (=Rhodiola) roseum and Silene acaulis. The lower cliff zone and rocky shores in boreal areas (like in the Baltic) contain few vascular plants, but are mainly occupied by filamentous algae and lichens (Caloplaca sp., Ramalina sp.). The arctic cliffs of Svalbard and Jan Mayen island contain Oxyria digyna and Chrysosplenium tetrandum as typical species, while (further) arctic elements are formed by Alopecurus alpinus, Taraxacum arcticum, Cerastium arcticum and several lichens. Cliff species with a relatively southern distribution are Catapodium marinum, Sagina maritima, Daucus carota subsp. gummifer, Euphorbia portlandica, Inula crithmoides, Spergularia rupicola, Plantago crassifolia, Plantago maritima, Frankenia laevis, Dactylis glomerata subsp. oceanica and several species of Limonium. Examples of Limonium species with a restricted range are Limonium binervosum agg., Limonium dodartii, Limonium dufourei, Limonium girardianum, Limonium normannicum, Limonium ovalifolium and Limonium virgatum. Along the coasts of the Channel, the rare Rumex rupestris (a species of the Annex II of the Habitats Directive) may be found in places where freshwater gathers on the lower part of cliffs, together with Apium graveolens, Samolus valerandi and Agrostis stolonifera. Halimione portulacoides and Salicornia ramosissima can grow in the most wind and salt spray exposed cliffs, like those of the Massif Armoricain. Some cliffs have a high diversity of saxicole lichens. Some rare species are characteristic for some biogeographic zones, like Teloschistes flavicans. The coastal cliffs of Europe are important breeding sites for large colonies of sea birds, amongst which puffins, northern gannets, guillemots and razorbills. Different birds nest in different parts of the cliffs, but in general steep cliffs are preferred (safe against predators) in areas where plenty of sea food is available. Bird colonies may harbour several nitrophilous plant species, due to the guano and trampling, like Tripleurospermum maritimum, Stellaria media, Cochlearia danica, Cochlearia officinalis, Atriplex ssp., Beta vulgaris subsp. maritima, Sonchus oleraceus and Poa annua. In some cliffs of Brittany, the rare Asplenium obovatum subsp. obovatum is found.

Indicators of good quality:

The following characteristics are considered as indicators of good quality:

·     no disturbance by man

·     presence of sea bird colonies

·     presence of characteristic zonation belts

·     high diversity in lichens

Synthesis of Red List assessment

Confidence in the assessment

Pressures and threats