Sand dune systems are naturally dynamic. Sand moves, plant communities change, and whole dune systems migrate in response to various climate factors. The shape and size of dunes depends on the supply of sand and the strength and direction of the prevailing wind.

Dunes first form where blown sand is trapped on the strandline by debris or salt tolerant plants. Trapped sand and vegetation will progress to a more stable and persistent habitat, with more fixed vegetation. As the plant cover increases, and other dunes form in front, the sand supply is gradually cut off, resulting in the development of ‘fixed dunes’ which are naturally stable. However, ‘blow outs’ may still occur if the vegetation cover becomes broken. When this happens the wind can act on the exposed bare sand, moving it elsewhere within the dune system, often re-starting the plant succession process. A typical dune system will have a zonation from mobile, young dunes on the foreshore, leading into more mature dunes with grassland where the dunes are older.

Where human activities cause excessive erosion the whole dune system can degrade. The UK Biodiversity Action Plan for sand dunes has targets to protect existing sand dunes from losses due to human activities, and encouraging new dunes to establish to offset natural losses (expected to be around 2% or 237 ha over the next 20 years). A range of priority BAP species have significant populations on sand dunes, including plants such as the dune gentian, fen orchid, mosses, and insects such as the bright wave moth. Some dune sites are important for reptiles and amphibians. The natterjack toad uses seasonally wet dune slacks for breeding, and is now restricted to a small number of coastal sites. Sand lizards are also associated strongly with dune habitats. For both of theses species, action is underway as part of the UK Biodiversity Action Plan to restore populations to their previous range. In addition, recent studies on the Sefton coast have shown that great crested newts also make use of dune pools and dune grassland. Pilot projects have restored dune areas (previously converted to agriculture) to orchid rich grassland within 10 years, although the current rate of restoration will not offset predicted losses.

In England, much of the 11,897 ha of sand dunes are concentrated into a small number of key locations around Northumberland, Lincolnshire, Norfolk, Kent, Dorset, Devon, Cornwall, Lancashire and Cumbria. There are around 50 sand dune SSSIs, covering over 10,000 ha. Of these, 70% are in favourable condition, whilst the remaining 3,000 ha are in unfavourable condition because of inappropriate management, lack of sediment supply due to coastal defence, and development. Coastal sand dunes can be affected by anything that changes the natural rate of erosion and deposition of sand. The seaward edge of sand dunes can be highly mobile, which is important in the exchange of sediment between the beach and the dune system. The rate of erosion and accretion of sand at the top of the beach can be changed by beach management such as artificial cleaning of the strandline. Sea defence and dune stabilisation work can also affect sediment supply and sediment exchange. Artificial stabilisation of dunes is particularly a problem of developed coastlines, where shifting sand is seen as a threat to urban or holiday developments. Golf courses, for example, can prevent sand dunes from migrating inland, and their ability to respond naturally to environmental change. Although stabilisation can help to counteract severe erosion, man-made defence systems generally result in lower dune diversity by inhibiting the natural mobility of dune systems, and may result in sediment starvation elsewhere. Very few dune systems in England are in a natural equilibrium, where erosion is balanced by deposition. Most are eroding, mainly due to lack of sediment supply through over-stabilisation of the front dune-face, or through loss of beach sediments.

In a natural environment, dunes are free to erode and migrate in response to natural events. However, in most English dune systems, landward movement of mobile shifting dunes, where it occurs, is at the expense of older fixed dunes, which are unable
to re-establish further inland because of development, or improved agricultural land. The dune system becomes squeezed between the eroding coastline and development or agricultural land. In individual sites this loss can be considerable. Of the 121 dune sites in England, 55% are in retreat, 17% are advancing and 28% are stable34. Too much stabilisation prevents a dune system from responding to climatic influences.
Sand dune systems are often close to popular tourist beaches. There is extensive human use of dune systems on foot, by motorcycle and fourwheel drive, and there may also be facilities such as car-parking and golf courses. Limited pressure by pedestrians may actually help increase the diversity of sand dune plant communities. High pedestrian pressure, however, such as on heavily-used beach access paths, or vehicle damage, has caused unacceptable erosion of many dune sites. Beach cleaning on key recreational beaches is important, but mechanical beach cleaning reduces the opportunity for new dunes to develop. The development of new golf courses, car parks and other recreational features also causes fragmentation of dune sites, upsetting the natural equilibrium of erosion and deposition. Such developments within the dune system also artificially stabilise the dunes, causing further loss of biodiversity.

Water extraction or drainage, or inappropriate grazing, lowers the water table and dries out damp dune slacks, causing a loss of the wildlife, and reducing the diversity of the dune system. The loss of sand dune areas is not just a problem for wildlife. Fully functioning dune systems have the capacity to contribute to cost effective coastal defences, absorbing wave energy on the front dune face, and naturally moving, eroding and re-establishing in response to coastal processes.

Shingle accounts for some 30% of the English and Welsh coastline. In its most common form, it occurs as a narrow band of beach material that supports strandline plant communities such as sea kale and Babington’s orache, which are adapted to the harsh salty conditions and limited water supply. Occasionally, shingle builds to form major structures such as the barrier beach at Chesil, the cuspate foreland at Dungeness,
and the spit at Orfordness. Of the 5,130 ha of shingle habitat in the UK, some 4,350 ha occur in England. Around 1,600 ha occur at Dungeness on the Kent coast, the largest English site, whilst only five other sites are larger than 100 ha. The main areas of vegetated shingle are in East Anglia, the English Channel coast, and north-west England. England has a significant proportion of the total amount of vegetated shingle in Europe.