Dune Building and Vegetation Sand dunes are mounds or ridges of beach sand deposited by wind. Their shape is determined by the amount of sand available and the prevailing wind direction. Dunes occur when dry sand begins to build at some obstacle, such as plant debris or a shell. If a plant grows on the mound that results, the mound will begin to grow larger. As it blows around vegetation, the wind's speed is reduced, causing sand grains to drop.
Plant roots help to stabilize the sand.
Few plant species are able to thrive in the harsh beach or dune environment. To survive, they must be able to tolerate salt spray, extreme heat, drought, sand blasting and burial, and low nutrient supply. Importance of Dune Protection Dunes are extremely important as barriers to waves or storm surges. They also can serve as a source of sand or sediment for rebuilding the beach and protect low areas behind them. Even minor damage to the dune or dune vegetation can make the dune less stable.