Barrier Island Ecology

Barrier islands as protection

Hunting Island is one of the six Beaufort Barrier Islands that include Harbor, Hunting, Fripp, Pritchard’s and Capers Island. These barrier islands protect the inland areas and help create the fertile salt marshes that surround the islands. These islands were used by Native Americans for centuries as hunting and gathering places. The Port Royal Sound area was chosen by early European explorers and settlers because it is so well protected from the sea by the extensive barrier islands. Although settlements from the 16th century are largely gone, Beaufort has many very old houses, some nearly 300 years old. This is only possible because the barrier islands protect the inland areas by absorbing and dissipating energy from hurricanes, storms, winds, and waves.

Barrier islands stretch south from mid-New York all the way to Texas and Mexico. This part of the North American coastline is the longest and most varied barrier island coast in the world. Scholars have estimated that in protection from hurricanes in the US, barrier islands have provided $9,683 per hectare (approximately 2.5 acres) per year in damage protection. As hurricane severity and frequency increase with climate change, that value is expected to become $11,223.

In addition, barrier islands provide the protection needed for the creation of productive salt marshes. These marshes are tidal—experiencing high and low tides like the ocean. At high tide a wide variety of sea creatures live in the nutrient “soup” of the salt marsh that is based on the decomposition of the grasses. These include dolphins, tiger sharks, mullets, shrimp, and crabs. Ospreys soar above hunting these sea creatures. At low tide wading birds like egrets, ibises, and herons are seen fishing here. Raccoons may pad through the pluff mud to dine on shrimp or crab..

Barrier islands also protect inland waters for sailors. The Intracoastal Waterway is a 3000-mile sea route along the Atlantic and Gulf coasts that takes advantage of barrier islands to provide protected water for boaters. Coasts without barrier islands are much more dangerous, especially for small sailing vessels, because they must sail in the unprotected open seas. The prefix “intra” means within, because the Intracoastal Waterway is within the coasts.

In most places, natural bodies of water make up the Waterway, and in other places canals or passages were dredged to accommodate marine traffic. The Intracoastal Waterway passes well to the west of Hunting Island traveling south through the St. Helena Sound to Coosaw River and past Beaufort to the Port Royal Sound. Then it stays landward of Hilton Head and Daufuskie Islands and on toward Savannah.

The formation and evolution of barrier islands

The low-lying, flat shorelines of most of the east coast were created by the rising and lowering of sea levels during glacial periods. At various times, the coastline was much farther inland, creating a seashore that ran through today’s Philadelphia, PA, Washington, DC, Richmond, VA, Raleigh, NC, and Augusta, GA. All of Florida, Mississippi, Louisiana, and most of Alabama were underwater. At other times, the oceans were so low that the shoreline was many miles farther out on the continental shelf than it is today. These variations were all the result of glacial action.

Glaciers are formed by the accumulation of snow in northern areas that doesn’t melt in the warmer months of the year. As the earth’s temperatures cooled, glaciers increased in size and spread down from the arctic, pushing rocks and debris south, carving out valleys and shaping hills. Then they melted and retreated during warmer periods, and they shaped the land and the shorelines of New England as they receded. Although glaciers did not reach South Carolina, they had a profound impact on our shores. Over several million years, the sea levels were rising and falling as the earth’s temperatures fluctuated. Wave action acted like a slow broom, sweeping the sands, rocks, and sediment back and forth and flattening the coastal plain and the shoreline. Sand is kept in motion by the waves, and the sweeping motion occurs three to six miles from the beaches, sometimes 60 feet deep. We can think of barrier islands as the remains of the most recent dunes created by the rising seas.

The sand on the beach at Hunting Island was deposited by ancient rivers that brought sediment far out to sea when the oceans were lower. That sand is drawn up by wave action from where it was deposited on the continental shelf at depths of up to 300 feet. The closer it gets to the beach, the stronger the wave action, and the more sand is pushed up onto the beach. A mineral analysis of sand shows that it is primarily comprised of quartz and feldspar, as well as some heavy minerals that originated in the Piedmont. The farther south the beach is, the more it is made of broken shells, or calcium carbonate. Miami Beach is about 50% ground up shells that are up to 13,000 years old. Some beaches in the Florida Keys and Puerto Rico are 100% calcium carbonate.

Page 2>>    Page 3>>                                                

Site LogoHelp us keep Hunting Island State Park a special place

We need only two things to provide the services and projects you see described on this website: your participation and your tax-deductible membership fees. For one $40 membership contribution, you and your family can join Friends of Hunting Island and have unlimited access to the park for one year. All members are encouraged to participate in any of our on-going projects. If you do not wish to join, but want to donate to our efforts, click here to make a tax-deductible donation to the Friends of Hunting Island.