COASTAL SAND DUNES Sand_dunes_credit_Amy_Lewis
Dunes develop where windblown sand becomes trapped by specialised dune-building grasses such as marram grass. From windswept ridges to damp hollows (slacks), the range of conditions supports a surprisingly rich variety of wildlife. Sand dunes are consequently of exceptionally high nature conservation interest. The shape, size and position of the dunes may change depending on local wind and wave conditions. Dune stability, acidity and local hydrological conditions are all key factors in determining wildlife diversity.
Where are they found?
Sand dunes develop in the intertidal zone and where onshore winds are prevalent. In total there are some 56,000 ha of sand dunes widely distributed around the UK coast. Some of the most extensive dune systems are found in the Western Isles and Inner Hebrides.
Why are they important?
The bare open sand of highly mobile foredunes which are still actively building is a hostile environment for most plants, but provides ideal habitat for many nationally scarce invertebrates.
Sand lizards can sometimes be found in these habitats. These are one of the UK’s rarest vertebrates, and use bare sand to lay their eggs in. Salt-resistant grasses such as marram and sand couch are amongst the first plants to colonise such areas, binding the loose grains of sand with their creeping underground stems and trapping sand around their shoots, and gradually starting stabilise the sand.
Other plants such as sea holly and sea spurge may also take root on the more sheltered leeward side of the dunes. Orchids are amongst the wetland species which can flourish in wet hollows between the dune ridges.
As the dune system stabilises and the sand is enriched by decaying vegetation and animal manure, the variety of plants and animals increases. The pioneering dune-building species are replaced by species more typical of grassland habitats.
Calcareous dune grassland is particularly species-rich, but if it is not grazed or actively managed, it can be quickly colonised by scrub species such as sea-buckthorn, gorse and blackthorn on dry areas, or birch and willow in the wetter slacks. On dunes which have become acidified by leaching, dune heath develops, invariably containing characteristic species such as sand sedge as well as more typical heathland species such as heather, gorse and crowberry.
Sand dunes attract many birds, particularly shelduck which nest under bushes or in abandoned rabbit holes, moving down the shore at low tide to feed on worms and snails.
Are they threatened?
Trampling, rabbit burrowing, excessive grazing and reduction in the supply of sand can all too easily result in damage to dune systems. Once the thin, stabilising crust or protective plant cover is damaged, erosion quickly follows. Brushwood fences and enclosed pathways can help trap windblown sand and channel public access to combat recreational pressure, but for most of our coastal sand dunes, this is only the tip of the iceberg. Poorly managed attempts to stabilise dunes can also prove equally as damaging as the primary cause of erosion in some cases.
Moreover, controlling pollution and managing grazing density and duration are far more complex issues to address.
Loss of dune habitat to afforestation and as a result of rising sea levels are also important considerations when looking at the vulnerability of sand dune habitats.
How are The Wildlife Trusts helping?
A conservation strategy for sand dunes is set out in the UK Biodiversity Action Plan. The Wildlife Trusts are taking an active part in the implementation of measures included within the strategy to maintain the extent and enhance the habitat quality of sand dune systems, and ensure the continuation of natural processes which create dune systems.
What can I do to help?
Visit wildlifetrusts.org/livingseas to find out how you can help our marine conservation work in the UK.
Depending on where you live, local Wildlife Trust volunteers help out with everything from recording marine wildlife sightings to beach cleans and educational work. Visit our Living Seas pages online or contact your local Trust to find out more.