Feature written by Amanda Kellerhals, S.C. Sea Grant Consortium
What is a Barrier Island?
Barrier islands are one of the most fascinating features of the United States coastline. In fact, the U.S. has more barrier islands than any other country, with their footprint stretching along the Atlantic and Gulf coasts. South Carolina has the second-highest number of these islands, just behind Florida, and millions of people visit them each year.
When a barrier island forms, it separates the mainland and ocean. This separation creates a barrier to form other bodies of water like bays, sounds, creeks, and lagoons between the new barrier island and mainland.
Barrier islands are dynamic because they are constantly changing in response to the waves, tides, and erosion. Some low-elevation and unvegetated barrier islands can even disappear completely and reappear years later. Barrier islands can vary in length, from a mile to more than 60 miles!
Many well-known South Carolina destinations are actually barrier islands, including Isle of Palms, Sullivan’s Island, Folly Island, Kiawah Island, and Hilton Head Island.
Hilton Head lighthouse
Why are Barrier Islands Important?
Barrier islands help keep mainland communities safe by serving as a first line of defense (or barrier) for these communities. Beach dunes, grasses, and other vegetation on barrier islands absorb the wave energy that is created by major weather events, and they decrease flooding for residents of these islands. Flooding is reduced by blocking storm surge and the wave energy before they reach the mainland.
Visitation to barrier island beaches supports a wide variety of economic activity, including industries such as recreation, ecotourism, and fishing. Why are barrier islands important to wildlife?
The calm waters that exist between barrier islands and the mainland also protect coastal wildlife. These bodies of water created are the perfect nursery and shelter for fish and shellfish. Other coastal animals like seabirds, sea turtles, and coastal plants use barrier islands for habitat and refuge. Barrier islands help maintain South Carolina’s biodiversity and support many keystone species—animals that play an important role in the health of their ecosystem. Barrier islands are especially crucial for threatened or endangered birds that rely on quiet beaches and dunes for nesting and feeding.
Dolphins strand feeding on Morris Island
Some of the seabirds that can be spotted nesting during breeding season include:
- Laughing Gull (Leucophaeus atricilla)
- Least Tern (Sternula antillarum)
- Gull-billed Tern (Gelochelidon nilotica)
- Forster’s Tern (Sterna forsteri)
- Common Tern (Sterna hirundo)
- Black Skimmer (Rynchops niger)
- Sandwich Tern (Thalasseus sandvicensis)
- Royal Tern (Thalasseus maximus)
- Brown Pelican (Pelecanus occidentalis)
Migratory birds needing rest and food also use the barrier islands as a stopover. The Cape Romain National Wildlife Refuge, a group of barrier islands north of Charleston, S.C., is the rest stop for 100,000 birds each year! Species found include:
- American Oystercatchers (Haematopus palliatus)
- Short-billed Dowitchers (Limnodromus griseus)
- Semipalmated Plovers (Charadrius semipalmatus)
- Rufa Red Knots (Calidris canutus rufa)
Brown pelican rookery on barrier island
Maintaining the health of barrier islands also leads to successful sea turtle nesting, as they heavily rely on this ecosystem.
What is Happening to Barrier Islands?
Barrier islands are being impacted by various human activities. Older shoreline hardening projects, like sea walls that are now prohibited by current regulations, can disrupt the natural sand movement processes that barrier islands rely on. These sea walls were originally intended to mitigate storm surges, but they lock the shoreline in place and prevent sand from rebuilding dunes and moving the way it needs to.
Beach and marsh habitat loss is also occurring on barrier islands because of a “coastal squeeze”, where increasing development and rising sea levels pressure these habitats on both sides. This traps these habitats between development and rising seas, resulting in reduced opportunities for habitat migration or expansion.
Researchers and conservation groups help balance the need for coastal restoration with human activity. Some efforts include:
- Building oyster reefs (a group of oysters forming a colony) which reduce wave energy and help stabilize shorelines
- Volunteers restoring native vegetation, strengthening dunes and improving habitat
- Monitoring island health through community science
Volunteers building an oyster reef
Photo Credit: Noah Stillman, S.C. Sea Grant Consortium
Barrier island visitors can help conserve these unique ecosystems by following local rules: stay on designated trails, avoid nesting areas, keep off the dunes, and respect wildlife zones.
