Coastal sand dunes are dynamic but fragile buffer zones of sand and vegetation that form where the following three characteristics can be found: large quantities of sand persistent wind capable of moving the sand suitable locations for sand to accumulate The process of dune formation begins with a steady on-shore wind capable of moving sand. The wind moves the sand into piles. Eventually the sand pile becomes so steep that the leeward side of the sand pile collapses under its own weight and spills down at an angle that serves to stabilize the dune. Over time, the dune migrates in the direction of the wind, as the wind moves sand up the dune's slope and over the edge. Sand dunes often form around obstructions such as rocks, drift wood, decaying plant matter, and detritus that is washed up during high-tide. This decaying plant matter forms a perfect substrate for plants to set root. Plants the first set root in sand dunes are referred to as pioneer plants and are often grasses that have special adaptations for the harsh environment of the dune (high salt tolerance, waxy leaves that retain water, rolled leaves to reduce surface area and exposure to evaporation). These pioneer plants stabilize the dune. Their roots bind the sand and their leaves decrease wind speed and reduce erosion. After pioneer plants stabilize the dune, it becomes more habitable for other plants to move in. A progression of vegetation types set hold onto the dune, each changing the substrate's characteristics and structure, gradually making the dune suitable for the next vegetation type. Sand dunes, though dynamic, are fragile habitats. The mat of vegetation covering a dune is vital to reducing dune erosion and if this vegetation is disturbed or uprooted, the dune is destroyed.