A sand dune forms through the movement of sand particles by the wind. The lighter the sand, the more it moves. The heaviest sand particles settle against an object such as a rock or plant and build the dune around it. Onshore winds transport sand from the beach to a more inland area and this is where the sand begins to accumulate. Without vegetation the sand gradually accumulates and drifts can form that change in size and shape. A sand dune begins to stabilize when several pioneer plant species begin to grow. Over time these plants grow extensive roots which anchor the plant and the leaves start to block the sand from the wind.
A sand dune can move or migrate depending upon the size of the particles and the amount of wind. Dunes are fed by wave action that pile up the sand on the beach. As sand builds up it falls forward and creates a slope. Unless the dune is colonized by a plant community it will continue to change shape and size.
The most conspicuous plant on a dune is beach grass (Ammophila breviligulata) which grows up to three feet tall. The leaves form clumps that trap moving sand, holding the small particles in place. It spreads with underground stems called rhizomes that send up shoots for dune stability.
Other plant species that contribute to erosion control include beach heather (Hudsonia tomentosa), dusty miller (Artemisia stelleriana), seaside goldenrod (Solidago sempervirens), beach pea (Lathyrus japonicus), and salt spray rose (Rosa rugosa). Like any ecosystem, a dune with a greater diversity of species is more likely to be stable. A monoculture of any plant becomes susceptible to predation and disease.
Animal life on a sand dune is restricted to those species adapted to harsh conditions, such as extreme temperatures. Camouflaged by the sand and able to adapt to a variety of habitats, the wolf spider (Hogna spp.) is a common predator on the dunes. Insects, birds, and small terrestrial mammals often visit and travel through dune systems. Other species may reside near the toe of dunes such as the threatened piping plover (Charadrius melodus) or exist in the interdunal areas such as the Eastern spadefoot toad (Scaphiopus holbrooki), also classified as threatened.
Copyright Gil Newton 2009 Thanks to Chris Dumas for logo image.