Around 1,200 km (20%) of England’s coastline consists of cliff 19, widely distributed from Northumberland to Land’s End and up the west coast to St Bees Head. Although hard cliffs of rocks such as granite, limestone or sandstone are important for wildlife, the cliffs consisting of softer rocks make the greatest contribution to coastal processes through the ease with which they are eroded, thus supplying sediment to beaches and estuaries. Coastal geology and geomorphology: diversity and value.

The English coast has a diverse and spectacular geology. Many localities are known across the world as places where geological features or successions of rock were first defined. Coastal areas such as those around Kimmeridge Bay in Dorset have given their name to globally recognised periods of geological time; rocks deposited anywhere in the world between 145 and 154 million years ago are said to be of Kimmeridgian age20. And there are proposals that the coast between St Audrie’s Bay and Doniford Bay in Somerset should be considered as the internationally agreed reference section for the base of the Jurassic System. The conservation of such coastal sites is a key priority.

The diversity and splendour of our coastal landscape derives from the complex range and variation in rock formations. Whether they are hard or soft, tilted or horizontal, folded or faulted determines the variety of vertical cliffs, embayments and coastal landslips that we see today. These rock exposures provide a window into the past, and an opportunity to explore (through fossils) a past world of giant and unusual animals, and long-extinct life forms such as dinosaurs and ammonites. The recent declaration of the coast of Dorset and East Devon as a World Heritage Site for its geology and geomorphology recognises the scientific and cultural history and importance of this classic area.

For over 200 years, important and exciting fossil discoveries have been made in our coastal cliffs and foreshores. These finds, such as the ichthyosaurs and plesiosaurs (marine reptiles), from the cliffs of Lyme Regis and Charmouth in Dorset, and from the North Yorkshire coast, help us understand how life on our planet evolved through time. The Isle of Wight cliffs regularly yield dinosaur fossils such as Iguanodon, one of
the first dinosaurs to be described, and the soft cliffs of London Clay in Essex and Kent are a rich source of fossil shark’s teeth. These would not come to light without natural, undefended cliffs, subject to gradual processes of cliff erosion that
continually reveal new material.

England’s coasts also contain a rich suite of geomorphological (landform) features, including extensive lengths of coast with landforms that have developed in the recent past, and which continue to evolve. Particularly important are the processes that form and mould the coast, and the need for these processes to continue to operate. These affect the form and evolution of cliffs, spits, estuaries, salt marshes, dunes and landslips, and many other features. Well known sites include the 28 km long barrier beach at Chesil in Dorset, the extensive sand dunes of the Sefton Coast near Liverpool, and the undulating chalk cliffs of the Seven Sisters in Sussex. All these places are of intrinsic scientific and educational importance, and are also much-appreciated features of England’s coastline. The dynamic evolution of these processes and landforms provides the foundations for coastal ecosystems and habitats, and underpins the now accepted need to accommodate dynamism in the conservation of coastal systems.

Away from the heavily populated centres of the coast, most geological and geomorphological sites are maintained by natural processes. This is the preferred and sustainable option. In the vicinity of developed areas, coastal protection works often impact upon these sites, by obscuring rock sequences seen in cliffs, and modifying coastal processes so that some coastal landforms can no longer evolve naturally.

The scientific, educational and historical importance of the geology and geomorphology of England is reflected in the number of Sites of Special Scientific Interest that are designated for their geological interest. All of these sites were selected through a systematic site assessment exercise known as the Geological Conservation Review, carried out in consultation with acknowledged experts over a period of many years. The outcome is a series of 1,300 SSSIs120 which are notified for their geological or geomorphological interest. Approximately 170 of these are at the coast, where they comprise some 60% by number of coastal SSSIs.

The features in these sites range from intrusions of igneous rocks such as granite, folds and faults produced during past mountain building events, sequences of rocks representative of the long and relatively complete geological record of England, to particularly important fossil sites. These are valuable resources for geological research, and many of the sites are regularly used by schools and universities for this purpose. These sites are also valuable for the story they have to tell. They can enthuse and inspire people, both through these stories, and through the aesthetic qualities that many sites possess. The rich variety of rock type, landform and processes of our coasts are fundamental factors in determining the type of plant and animal communities that colonise these areas, emphasising how important it is for coastal managers to understand the interaction of geological and biological processes.Hard rocks form vertical or near-vertical cliffs that are relatively inaccessible to people, enabling seabirds to nest undisturbed and maritime plants to gain a foothold. Ledges and crevices that accumulate soil and humus are the main places where plants such as rock samphire and rock sea-spurrey will grow. The range of plants that occur is often determined as much by the degree of salt spray to which they are exposed, as it is by the nature of the rocks and soils. As a result, vegetation communities exhibit distinct zonation as the influence of salt spray declines. Elsewhere on the rock face, plant communities are dominated by a specialist group of lichens that can survive the effects of salt spray. Hard rock cliffs are important for their populations of breeding seabirds such as razorbill, guillemot and shag. This importance is recognised in the number of cliff sites that are protected for their bird populations. Flamborough Head and Bempton Cliffs Special Protection Area supports England’s only, and Britain’s largest, mainland gannet colony as well as one of the largest kittiwake colonies in the North Atlantic.

Soft cliffs are formed of poorly consolidated material such as shale or boulder clay, which may be inter-bedded with harder rock layers. They slump as they erode and are easily colonised by vegetation, forming slopes rather than vertical cliffs, often with areas of seepage and standing water. Recently exposed soils, following landslips, develop pioneer plant communities. Longer-lived plant communities dominate older surfaces and eventually lead to scrub and woodland on the most stable slopes. The mosaic of habitat types on soft cliffs provides a range of conditions for plants, such as shore dock, and animals, such as solitary bees, wasps and beetles. These include rare plant species such as the slender centaury, which occurs on limestone cliff slopes and grassland. There are 36 UK Biodiversity Action Plan (BAP) priority species which are primarily associated with cliff slopes, with 59 species in total recorded as using the habitat.

The scarce blackneck moth is an example of a nationally rare species that relies on eroding maritime cliffs. Its food plant (wood vetch) is widespread throughout Britain, but the moth also needs the microclimate afforded by bare ground in a maritime climate.