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The Foredunes

The foredunes are the first dunes to form in the dune system and the develop above the line of wave-deposited debris (strandline) where only the strongest waves during very high tides will reach.

The strandline may slow the wind-blown sand sufficiently so that fast-growing, pioneering plants can start to grow. At Berrow, Lyme grass is among the first plants to become established. This tall grass is able to keep pace with the sand that accumulates around it by rapidly growing upward and outward, slowing the sand down and forming a narrow line of low dunes. The sand accumulates even more quickly when Marram grass arrives. Like Lyme grass it forms tussocks and grows rapidly in response to being swamped by sand.

At this stage, the dunes are know as "yellow" or "white" dunes, because of the areas of bare, uncolonised sand. There is little water or nutrient in the dunes and they are unstable, so that only a few other plants can survive, such as Sand Sedge, Sand Couch and Sea Spurge. However, the dunes slowly become enriched by decaying plant material and the droppings from the rabbits which feed here. Mosses and lichens cover the bare ground between the plants; the dunes are sometimes called "grey" dunes at this stage.

Marram and Lyme grass thrive when fresh sand is being added to the dune, but they die out if the supply ceases. This can occur when a new line of dunes forms upwind. The loss of these grasses, or excessive trampling, can leave the dune open to wind erosion, which may be so great that a gap (blowout) is punched through the dune. The sand blown out of the foredunes will accumulate downwind and as long as it is fresh it will be recolonised by Marram grass and the dunes will once again become stable. Conservation work is being carried out to stabilise the parts of the foredunes which are most prone to windblow.

Dune stabilisation can be achieved in a number of ways, but the most cost-effective method is that of sand fencing. The fences are built across the blow out, at right angles to the prevailing wind. They may be constructed from wooden posts and wire netting or, as will be the case at Berrow, from cut branches of Sea Buckthorn, woven together. Wind speed is reduced by the fence, allowing the sand grains to drop out and build a replacement dune.

Inland, the dunes rise to a height of about 15 metres and the crests are covered in thickets of Sea Buckthorn, Blackthorn and Hawthorn. In summer, the tall, yellow flowers of the Evening Primrose can be seen all over the foredunes.

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