Barrier Island Ecology

Barrier islands are long, narrow, offshore deposits of sand or sediments that parallel the coast line. Some barrier islands can extend for 100 miles (160 km) or more. The islands are separated from the main land by a shallow sound, bay or lagoon. Barrier islands are often found in chains along the coast line and are separated from each other by narrow tidal inlets, such as the Outer Banks of North Carolina.

The current theory is that barrier islands were formed about 18,000 years ago when the last Ice Age ended. As the glaciers melted and receded, the sea levels began to rise, and flooded areas behind the beach ridges at that time. The rising waters carried sediments from those beach ridges and deposited them along shallow areas just off the new coast lines. In addition, rivers washed sediments from the mainland that settled behind the islands and helped build them up. Over time, silt, sand, and sediments carried by the rivers and oceans interacted with the troughs and ridges formed by the action of the glaciers, producing narrow strips of land. Barrier islands eventually emerged from these activities, built on the foundations provided by the continuous introduction of new raw materials.

Barrier islands serve two main functions. First, they protect the coastlines from severe storm damage. Second, they harbor several habitats that are refuges for wildlife.

Barrier Islands have four distinct habitats and the wildlife that inhabit them: Ocean/Beach/Dune, Maritime Forest, Freshwater Lagoons, Salt Marsh/Estuary, click underlined to learn more.