Out to sea, stretching from the Mournes to St. John’s Point lighthouse is Dundrum Bay, and the Isle of Man can be seen on a clear day. The bay is an important feeding area for both summer birds and over-wintering wildfowl and waders. The bay also hosts healthy populations of both common and grey seals.
Glacial deposits, left by the retreating ice, were channelled into Dundrum Bay by the surrounding hills. These deposits were then sculpted into an anchor upon which the sand began to build up over many thousand years.
Sand comes from three main sources; rock fragments from eroding cliffs, stone particles from rivers, and fragments from the shells and bones of marine creatures. The actual percentage of each will vary from place to place and the sand at Murlough is an average mix of shells and granite.
The long sand flats at Murlough mean the wave energy is dissipated and sand is gently pushed up into long lines. These sand flats are especially good for sand eels on which both seals and seabirds depend. Sand dunes develop when sand is trapped above the high water mark by salt tolerant plants adapted to grow in this harsh environment of temperature extremes and arid conditions.
Fore dunes or 'yellow dunes' are higher and more stable because of the marram grass. As the wind covers the plants in new layers of sand the marram grass simply grows up through it, sending out a second root system just below the surface.
As the sand keeps building up, the marram grass keeps growing, sending out new root systems thus stabilising the whole structure.
A little further inland are the 'grey dunes' where the sand becomes carpeted by mosses and lichens, their colour giving the dunes their name. Here the marram gradually disappears to be replaced by plants adapted to the more stable soils.
The seashell component of the sand makes it slightly alkaline but over time the calcium carbonate from the shells leaches out leaving the sand more acidic. This process leads to the development of heathland and it is in these fixed dunes where the majority of plants and animals are found.