General site character

Tidal rivers, Estuaries, Mud flats, Sand flats, Lagoons (including saltwork basins) (1%)

Shingle, Sea cliffs, Islets (54.2%)

Heath, Scrub, Maquis and Garrigue, Phygrana (29.8%)

Dry grassland, Steppes (15%)

Habitats that are a primary reason for selection of this site are:

Vegetated sea cliffs of the Atlantic and Baltic Coasts

Sidmouth to West Bay is separated from the other two cliff cSACs on this part of the south coast of England, Isle of Portland to Studland Cliffs and St Albans Head to Durlston Head, by Chesil and the Fleet, which does not have a cliffed coastline. Sidmouth to West Bay is an example of a highly unstable soft cliff coastline subject to mudslides and landslips. The principal rock types are soft mudstones, clays and silty limestones, with a small chalk outlier in the west. The central part comprises the extensive Axmouth to Lyme Regis landslip, where chalk overlies the unstable rocks mentioned, resulting in slips ranging from frequent minor events to occasional mass movement events when entire blocks of the chalk scarp move seawards. The eastern part has no chalk capping and is subject to frequent mudslides in the waterlogged soft limestones and clays. Vegetation is very varied and includes pioneer communities on recent slips, calcareous grassland and scrub on detached chalk blocks and extensive self-sown woodland dominated by ash or sycamore.

Tilio-Acerion forests of slopes, screes and ravines a Priority feature (tilio  latin for lime and acer latin for syscamore)

This site includes an area of active landslipping between Axmouth and Lyme Regis. These landslips have created, and will continue to shape, the mosaic of Tilio-Acerion, sycamore woodland, mixed scrub, grassland and pioneer communities. This mosaic of habitats makes this site rich in invertebrates, especially bees and wasps, such as Ectemnius ruficornis, Andrena simillima and Nomada fulvicornis. The woodland has a hazel understorey and a ground-flora dominated by ivy (with numerous ivy broomrape) and hart’s-tongue with abundant dog’s mercury and tutsan. The Red Data Book lichen Parmelina carporrhizans  occurs on ash trees.

Habitats present as a qualifying feature, but not a primary reason for selection of this site

Annual vegetation of drift lines:

This habitat type occurs on deposits of shingle lying at or above mean high-water spring tides. The types of deposits involved are generally at the lower end of the size range of shingle (2-200 mm diameter), with varying amounts of sand interspersed in the shingle matrix. These shingle deposits occur as fringing beaches that are subject to periodic displacement or overtopping by high tides and storms. The distinctive vegetation, which may form only sparse cover, is therefore ephemeral and composed of annual or short-lived perennial species.

Approximately one-third of the UK coastline is fringed by a shingle or sand/shingle beach, but much of this is too dynamic to sustain drift-line vegetation. Many of the fringing beaches with drift-line vegetation are small, and annual vegetation may exist in one location in one year but not another. Therefore, although widespread around the UK, sites where this Annex I type is persistent are rare, and even the largest sites probably support less than 10 hectares of this habitat. At most sites the habitat is naturally species-poor, and there is a limited range of ecological variation.

Site selection rationale

The ephemeral nature of this habitat type has been taken into account during site selection. Sites have been selected to reflect the more constant occurrences of drift-line vegetation found in association with larger, more stable areas of shingle structures. The selected sites represent the majority of the more persistent examples of this habitat type in the UK. They all exhibit good conservation of structure and function (i.e. they are relatively unmodified and are less prone to human disturbance) and represent the range of variation in substrate type and physical structure.

For example the site account for Chesil beach:

Chesil and the Fleet, Dorset

Chesil Beach is a large, 28 kilmoetre long, relatively undisturbed shingle bar, and is one of two representatives of Annual vegetation of drift lines on the south coast of England. The inner shore of the beach supports extensive drift-line vegetation dominated by sea beet and orache. This community exists in a dynamic equilibrium with the perennial shrubby sea-blite community typical of Mediterranean and thermo-Atlantic salt loving scrubs (Sarcocornetea fruticosi), for which this site has also been selected.

© Crown copyright. All rights reserved. Natural England [2015].