Biodiversity

Biodiversity Links

Shingle (accumulations of pebbles ranging from 2 to 200mm diameter) is characteristic of high energy environments - Sussex shingle is mainly composed of flint pebbles derived by marine erosion of the Cretaceous chalk and Tertiary deposits, or by erosion of ice during glacial times. In Sussex, shingle is mainly carried eastwards along the coast by longshore drift due to prevailing southwesterly winds - however from Selsey Bill in West Sussex it travels westwards.

The shingle is deposited either as fringing beaches running along the coastline, or as cuspate forelands - the most extensive in this region being at The Crumbles near Eastbourne and at Rye and Dungeness on the East Sussex/Kent border.

The shingle in these sites is aligned in sub-parallel ridges of differing ages, the oldest ridges generally being the furthest from the present shoreline. Communities on shingle range from the pioneer plant communities on fringing shingle beaches through a lichen-rich turf to gorse scrub on disturbed or marginal areas, bramble on damper patches and where grazed to a species-rich turf. Shingle also supports other habitats; in some natural hollows wetland communities include reed swamp, fen and carr. These wetland communities can also develop as a result of damaging excavations.

The full range of communities is seen at Rye Harbour and Dungeness. Also saline lagoons can develop behind shingle barriers, for example at Widewater in Sussex. The shingle vegetation assemblage varies depending upon the distance from the sea, the size of the shingle pebbles and the availability of water.

At Pagham Harbour the shingle has developed a classic shingle spit landform with a series of sub-parallel ridges and recurves, marking different phases of extension and frontal accretion. On the fringing shingle beaches, vegetation typically develops in the shelter of the main bank. In Sussex, both natural and maintained shingle barriers play a very important role in coastal defence.