Vegetated shingle consists of accumulations of pebbles that are larger in diameter than sand (>2mm diameter) but smaller than boulders (<200mm). Vegetation colonises deposits of shingle lying at or above the mean high-water spring tides.
- Site: Shingle deposition; colonised by vegetation
- Main species: Black-thorn, herb robert, lichen
- UK: 6,203 ha
- NI: 50 ha
- Vegetated shingle banks occur at the upper end of the shore, typically in long strips.
- The most simple & common type of shingle structures is the fringing beach, which forms a narrow strip, usually in contact with the land behind. Shingle spits develop where there is an abrupt change in coast direction. Bars are spits that cross an estuary mouth or bay & barrier islands are formed where there is a large accumulation of shingle offshore. Cuspate forelands develop when shingle builds up against an exisiting spit, fringing beach or relict storm ridges, forming large structures (JNCC, 2004).
- Vegetation that colonises coastal shingle has been well surveyed in Northern Ireland. It is dependent on the habitat. For example, as stability increases more species can colonise the shingle surface.
- Beaches that are stable between spring & autumn are typically dominated by summer annuals such as cleavers Galium aparine & oraches Atriplex spp. Those stable over 3 / 4 years are dominated by short lived perennials such as biting stonecrop Sedum acre & beaches that remain stable over 5-20 years, long-lived perennials such as Priority Species, sea kale Crambe maritime characterise. Longer periods of stability see the colonisation of heath or grass-heath vegetation which includes heather & blackthorn Prunus spinosa.
- Vegetated shingle habitats are harsh environments for plants, with strong winds, salt spray & little soil. Vegetated shingle in NI has not been fully surveyed but Cooper et al. (1992) found that nine coastal sites contained shingle or strandline NVC vegetation communities:
– SDI Rumex crispus – Glaucium flavum shingle community e.g. oysterplant, sea-kale & yellow horned-poppy
– SD2 Honkenya peploides – Cakile maritime strandline community
– SD3 Matricaria maritima – Galium aparine strandline vegetation
- Where shingle beaches are occasionally flooded with sea water, free-draining beds of larger shingle or cobbles may support lichen communities & grasses, such as crested hair-grass Koeleria macrantha, red fescue Festuca rubra & shrubs such as ivy Hedera helix & burnet rose Rosa pimpinellifolia.
- Sheltered coarse shingle banks support rank grasses such as couch Elymus farctus at highest levels, but sea mayweed Tripleurospermum maritimum common saltmarsh grass Puccinellia maritima & annual sea-blite Suaeda maritima near the strandline.
- Sand & fine shingle strandlines support annual species such as sea rocket Cakile maritime & prickly saltwort Salsola kali during summer months.
Current Status in UK & Ireland
- Shingle that supports perennial vegetation is a rare habitat, with an estimated 6,153 ha in Great Britain; 5343 ha in England, 700 ha in Scotland & 110 ha in Wales.
- Vegetated shingle is a scarce habitat in Northern Ireland, with an estimated 50 ha (P.Corbett pers.comm; NIEA, 2005), of which 30 ha is considered stable. Vegetated shingle has declined over the past century in Britain & Ireland. In a seven year period (1991-1998), 32% (29 ha) was lost in NI (Murray et al., 1992; NIEA, 2005).
- Vegetated shingle is threatened by shingle extraction, housing, recreational activities (e.g. walking, sports), removal of grazing, defence works, which may alter the movement of shingle, climate change which may increase the mobility of the shingle due to increased sea levels & storms.
- Rathlin Island Coast
- Giants Causeway & Dunseverick