Coastal dunes are accumulations of sand blown by the wind and deposited against a solid obstacle. This is a slow process and, without the help of stabilising plants, the dune disappears in the same way it formed.
For complex dune systems to form, there are some essential conditions: beaches with a shallow slope, strong sea winds, little humidity, moderate precipitation and an abundant supply of sand.
The sandy medium of the dunes means that only a few well adapted species of flora and fauna can survive there. The principal species of stabilising plants are European beachgrass (Ammophilia arenaria) and sand couch grass (Elymus fractus), with an underground stalk (rhizome) which enables them to fix themselves in the sand.