Barrier islands have more than one habitat type available for plants and animals. They're comprised of beaches, dunes, barrier flats and salt marshes.
Beaches are an intertidal, or between-tides, zone that is covered with water twice a day. Plants living there consist of algae. Animals calling the beach home include bacteria and burrowing animals such as crabs, clams, shore birds and fish.
Dunes are salty and sandy, boasting root systems of sea oats and bitter pancum to stabilize their structure. Animal life found there is similar to that found on the beach.
Barrier flats are stabilized by growth of cordgrass and sawgrass. There's plenty of life happening there: anaerobic bacteria in the mud decompose organic material; mud-dwelling clams and worms feed on plankton and bacteria; and birds -- such as pelicans, gulls and egrets -- feed on crabs, fish and invertebrates.
Salt marshes experience the tidal flooding of seawater. Plant and animal life there is similar to the barrier flats. The ecosystems of salt marshes aid in purifying runoff from streams and rivers on the mainland.
One problem that all that plant and animal life faces is natural erosion from offshore currents. While we may be able to spot the erosion, our efforts to correct or forestall it are sometimes successful and sometimes not.
A success took place on Cape Hatteras Island, a barrier island on the coast of North Carolina. For almost 200 years, offshore currents had been carrying sand from one end of the island to the other. As a consequence, the Cape Hatteras Lighthouse faced the possibility of falling into the Atlantic due to erosion of the beach nearby. But in 1999, the lighthouse was moved about half of a mile (.8 kilometers) to an inland site. The move successfully preserved the lighthouse.
Efforts in Upham Beach, Fla., however, were not successful. An expensive method called beach nourishment required replenishing the eroded beach with dredged sand. But it took less than one year for currents to erode the replenished sand.
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