8th Jun 2016 - Environment
Sand Dune Daydreams
A romantic and dynamic environment, sand dunes are not only an important part of our coastal daydreams but also incredibly important for the health of the coastline itself. Nothing more than piles of windblown sand which have been stabilised by salt-resistant grasses such as marram and sand couch (that trap further sand and allow the dune to grow), what initially appears to be an inhospitable environment for plants and animals is actually an important but fragile ecosystem.
Over time dunes can grow, shrink and move depending upon the prevailing wind and also the amount of sand available and the size of the grains of sand; they are also heavily impacted by the activity of humans and animals. Dunes often develop in the lee of a pile of seaweed washed ashore, which provides a wind break and traps sand blown up the beach by onshore winds, and as this seaweed rots it provides nutrients for early coloniser species such as marram grass. The salt-resistant grasses have creeping underground stems that trap and bind sand, stabilizing the growing dune. The ever-present wind that gave birth to the dune in the first place shapes it, carving ridges along the foredune (the closest to the sea) and leaving damp hollows (called “slacks”) behind them, out of the wind. In these hollows plants such as sea holly and sea spurge can take root, as well as some species of orchid. One of the UK’s rarest vertebrates, the sand lizard, lays its eggs on bare sand and so dunes provide an ideal habitat for them. As dunes mature and migrate “inland”, being replaced by new foredunes, the sand is enriched by the decaying vegetation of early colonisers and by animal manure (rabbit droppings, for instance) and this allows even more species to establish themselves and a sandy grassland habitat can develop. The grasslands must be grazed or actively managed so that scrub species such as gorse do not over-run them, instead allowing sand hedge and typical heathland species such as heather to establish themselves. Sand dunes and the grass and heathland habitats behind them provide incredibly valuable habitats for many birds, reptiles and invertebrates, however they are also very vulnerable. Natural impacts such as a reduction in the availability of sand feeding a dune system or storm scouring can have both immediate and slow-burning effects, however erosion caused by humans and animals is incredibly damaging. Once stabilizing plants are removed, or the thin crust of sand on the surface of a dune damaged, wind and water quickly scour away the exposed loose sand. Rabbits burrowing into the dunes are one problem, but a major one, and one that we can all do something about, is the impact of humans trampling dunes and collapsing ridges in their hurry to get to the beach, or trying to find a spot sheltered from the wind in which to lie and enjoy the sun. So, in the interests of a fragile coastal ecosystem, next time you visit the beach please be sure to stick to the fenced or way-marked paths if you have to walk through the dunes and please don’t “set up camp” in the dunes or on the fragile slope at the base of a foredune where you might contribute to dune erosion.
Sand dunes are fragile ecosystems, and are an important form of defense for our coasts against the impacts of winter storms. When our recreational activities put pressure on them, it becomes our responsibility to take steps to protect them so that they can flourish rather than falter, and continue to play a part in our memories of the coast.