Coastal Heritage Magazine
Island Science: Special Ecosystems Lure Researchers
South Carolina’s wealth of undeveloped barrier islands and sand banks are hotbeds for research because natural processes occur on those landforms with minimal human intervention.
Joey Holleman
Editor
Island Science: Special Ecosystems Lure Researchers
The view to the south from atop the substantial sand dunes at the northern tip of Waties Island is stunning and educational. Nary a human soul walks the 2.5-mile beach or tromps through the wide dune field of the undeveloped barrier island.
Across a narrow, constantly shifting inlet to the south, the hotels of North Myrtle Beach toss afternoon shadows on flocks of sunbathing vacationers.
Most people experience the South Carolina coast on vacations spent in places like North Myrtle Beach, where they often walk directly off the hot summer sand into a hotel or house. For a small subset of the population, however, late spring and summer marks the time to head to the state’s undeveloped barrier islands. Field season for research scientists means steering boats through winding tidal creeks, bushwhacking through thick maritime forests, and driving all-terrain vehicles (ATVs) up and down beaches marked with more turtle tracks than footprints.
Despite a lack of facilities and an abundance of biting insects, undeveloped barrier islands represent nirvana for researchers. They can study natural ecosystems with little direct impact from humans – gauging wind energy potential without buildings to affect the breeze, tracking sea turtle genetics without curious beachcombers bothering nests, installing trail cameras at alligator nests without fear the expensive equipment might be stolen.
Fortunately, undeveloped barrier islands and beaches are common along the South Carolina coast. Twenty-one of the 34 barrier islands on the South Carolina coast are either undeveloped or have just a handful of structures. The state’s developed sandy beaches stretch out for 98 miles, which is slightly more than the 89 miles of undeveloped beaches, according to a report titled “The Physical Condition of South Carolina Beaches 1980-2010.” As that work in the Journal of Coastal Research indicates, barrier islands are extremely dynamic. In fact, the linear distance of sandy beaches is constantly in flux, not so much because people are constructing new beachfront buildings but because barrier islands naturally move. Meanwhile, similar dynamics can factor into a rise in the actual number of undeveloped barrier islands. For instance, Cape Island in the Cape Romain National Wildlife Refuge split at least temporarily into three separate islands when tropical storms or hurricanes in the past decade created new inlets in the skinny strip of land. Also, just south of Winyah Bay in one of the few regions on the S.C. coast where barrier islands are building up rather than eroding, what once was not much more than a sand bar is now known by its government caretakers as Sand Island. Not on most maps yet, it features the four geographic attributes of a barrier island:
- active sandy beach,
- vegetated high ground,
- water on all four sides, and
- salt marsh attached to the back side.
Like all scientists who spend time on the state’s undeveloped islands, they appreciate the locale as they gather data. “We’re fortunate that we get to spend time on these islands, and it is not something I take lightly,” says Patrick Jodice, a professor in Clemson University’s Forestry and Environmental Conservation Department who heads up the pelican project. “There are few places you can do work like this.”
Islands Have Lured Scientists for Centuries
Documented research on the state’s barrier islands goes back about 250 years. Naturalists William Bartram and Mark Catesby detailed various flora and fauna on islands near Charleston and Savannah, Georgia, in books published in the 1700s. And on November 10, 1831, John J. Audubon spent time on Cole’s Island, which overlooked a sand bank very near where Bird Key Stono meanders today. He focused on long-billed curlews that flocked to the area, and initial sketches that day contributed to the curlew illustration in his landmark work, The Birds of America.
“They flew directly towards their place of rest, called the Bird Banks,” Audubon noted in his Ornithological Biography, “and were seen to alight without performing any of the evolutions which they exhibit at their feeding places, for they had not been disturbed that season.”
Even in 1831, barrier islands and sand banks were ideal for making observations about nature because creatures were undisturbed by humans or other predators. While vacation homes and golf courses have sprouted on many large barrier islands on the S.C. coast since the 1950s, efforts to build on the state’s undeveloped private barrier islands have slowed in recent years. Development plans have been floated for Waties Island, Bay Point Island near Beaufort, and Morris Island along the Charleston Harbor.
Most undeveloped barrier islands in South Carolina are publicly owned and protected from development pressures. The University of South Carolina Beaufort controls Pritchards Island, though erosion has forced the evacuation of a former research facility there. The S.C. Department of Parks, Recreation, and Tourism bought St. Phillips Island in 2018, with plans for only minor park development.
North, Sand, South, Cedar, Murphy, Capers, Pockoy, Pine, Otter, and Turtle islands, as well as various sand banks that blink on and off through the years, are managed by SCDNR. The U.S. Fish and Wildlife Service is caretaker of the Cape Romain National Wildlife Refuge islands — Cape, Lighthouse, and Bulls — as well as Raccoon Key.
Much of the land behind them also is protected, allowing for beach retreat. What follows are snapshots of the work researchers did in these special places along the South Carolina coast in the spring and summer of 2019.
Waties Island: Determining Wind Energy Potential
About one-third of Waties Island, along with high land on the bluff just inland of the island, was bequeathed to the Coastal Education Foundation, a nonprofit organization affiliated with Coastal Carolina University (CCU), in 1995 by Anne Tilghman Boyce. The rest of the northernmost barrier island in South Carolina is privately owned, but none of the island is developed now.
For more than two decades, CCU has utilized the island for class field trips and research on topics such as native archaeology, beach erosion,
and salt marsh ecology. Professors and students unlock the gate and drive over a short bridge into a world dominated by nature.
Waties, with about 520 acres that stays dry during an average high tide, features a wide natural dune field. Paul Gayes, director of CCU’s Burroughs and Chapin Center for Marine and Wetland Studies, likes to take first-time visitors to the dunes at the north end of the island for the dramatic view of an undeveloped barrier island immediately juxtaposed with the tourism-based infrastructure of the rest of the Grand Strand. “I find that backdrop really changes the nature of a range of environmental discussions related to policy and land use,” Gayes says.
While researchers at CCU have been looking into offshore wind energy potential for years, the study of wind potential over land in the region is relatively new. At the height turbine towers were built in the past, the wind over land in the S.C. coastal plain is too weak and inconsistent for efficient power production, Gayes says. But new technology allows for taller turbine towers, and researchers want to determine if the winds are stronger up in the 400 to 525-foot range. The SODAR process measures the effect of atmospheric turbulence on sound waves, and it provides accurate wind-speed readings at much higher elevations than traditional structure-mounted wind gauges.
Over the past three years, the Waties SODAR station collected data which indicate good wind potential up to 650 feet. “This provides a critical vertical profile,” Gayes says. “The measured velocity was better than expected. That means if towers go a little taller, it opens up new possibilities in South Carolina. Two or three years ago, there was no chance; now there is potential.”
North Island: Eradication of a Non-Native Species
North Island in Georgetown County ranks among the most wild of South Carolina’s barrier islands. Northern philanthropist Thomas Yawkey bequeathed the land to what is now the SCDNR in 1976, and his will put strict stipulations on the island’s management as part of the Tom Yawkey Wildlife Center (YWC). Basically, he wanted nature to have its way on North Island with as little human impact as possible. Much of the 4,400-acre island is heavily forested, with dense undergrowth interrupted by majestic live oaks.
Geography has been kind to the island, with replenishing sediment washing down five rivers into Winyah Bay and North Inlet and longshore ocean currents creating minimal erosion. Thus the island’s nine miles of beach have remained relatively stable as time and tide have allowed the buildup of one of the largest dune fields in the state, sometimes more than 110 yards wide.
In recent years, non-native feral hogs trekked down from the dense forests to the wide beaches to find an abundant food source – the eggs of loggerhead sea turtles. A survey in 2010 found 25 of 26 sea turtle nests sampled on the island had been destroyed by feral hogs. Property managers decided to take action against the hogs in favor of turtles that have nested on coastal islands for centuries.
Staff from YWC and the U.S. Department of Agriculture Wildlife Services Division threw every resource at the hogs. Trapping and public hunts removed 243 hogs in six years, and sharpshooters were more effective after the population fell to 11 in 2013. The last remaining hog was killed by a sharpshooter at a sea turtle nest in 2016. No hogs have shown up on trail cameras since then, says Jamie Dozier, the SCDNR wildlife biologist who manages the property.
Research findings give hope they won’t return. Genetic testing of the island and mainland hog populations found they were from distinct lines. In other words, the hogs on the island almost certainly didn’t swim there from the mainland but were brought by boats from other areas, likely as prey for hunters.
As the hog population fell, depredation of turtle nests dropped remarkably: 138 of 158 nests on the island were destroyed by hogs in 2011, but only five were damaged over the next three years. Researchers speculate the hogs conditioned to feeding at turtle nests were among those removed early in the project. When some of the few hogs remaining in 2015 discovered this easy food source, however, nest damage skyrocketed to 75 that year.
The total number of hatchlings lost to hog predation from 2010-2017 was estimated at 19,406. Researchers used a value of $100 per hatchling, based on the minimum civil fine in coastal states for people who take eggs from nests. (Florida’s statute calls for a $100 fine per egg. South Carolina has a minimum fine of $1,000.) Using the more conservative value still adds up to an estimated value of $1,940,600 for hatchlings lost to hog depredation, which makes the $189,880 spent on the hog eradication effort a bargain, according to the research.
As an undeveloped barrier island with no road access, North Island proves both ideal and challenging for the research work. Equipment and people have to arrive by boat, and larger equipment has to be off-loaded onto the beach.
“It could often take an entire day to do a simple task like monitor and rebait a trap,” Dozier says.
But the seclusion also helps. “The risk of impacting people or pets with the removal efforts was minimal,” Dozier says. “The feral hogs also were potentially not as wary of human activity due to having little interaction with people.”
South Island: Studying Alligators Over the Decades
The logistics of research are less difficult on the other islands that make up the YWC. Though researchers have to take a short ferry ride over the Intracoastal Waterway, at least they can drive vehicles on the rutted dirt roads of South Island. Researchers flock to the mostly undeveloped property for projects that in recent years investigated soil chemistry related to prescribed burns, the geological development of spit islands, and breeding or migration patterns of semipalmated sandpipers, Wilson’s plovers, and MacGillivray’s seaside sparrows.
However, the most storied work at YWC deals with alligators. SCDNR biologist Phil Wilkinson began trapping and marking gators on the property 40 years ago. Some of those original marked gators are still around, while new resident gators have moved in and also have been captured and tagged. Wilkinson long ago retired, but he still goes up in a helicopter routinely to spot nests. When not in the air, he joins the research team at YWC to share his wealth of knowledge on the local alligator population. “After 40 years, you get to know each other,” he says, speaking of the alligators, not the people.
Thomas Rainwater, a Clemson University scientist who serves as the YWC’s wildlife research coordinator, has worked alongside Wilkinson on the alligator project since 2010. He says research there debunks theories on alligator growth (it eventually stops when they reach middle age in their 30s or 40s) and female reproductive years (which continue as they reach ages of 60 or more). New projects this year focus on microplastics in alligator scat, the influence of climate (air temperature) on nest temperature and the resulting sex and health of hatchlings, and what factors determine how often and for how long female gators visit their nests after depositing eggs.
To gather nest data, Rainwater heads out five or six days a week from early June through early July, the peak nesting season for alligators. This year, graduate student Randeep Singh and undergraduate intern Maggie Priore join him.
They load up on bug repellant, then hack through maritime forests, wade through marsh grass, or paddle a canoe to islands in freshwater ponds to get to nests Wilkinson spotted earlier from the air. Female alligators thrash about to mash down vegetation – mostly marsh grass – in nest areas about 20 feet in circumference. They look like small crop circles from the air.
This year, the researchers bury thermistors in some of the nests for a temperature study. Also new this year are mounted game cameras that take photos of the nest site once every minute. The images are recorded on memory cards, which have to be replaced every six days. The images help determine not only how often female gators return to their nests, but which potential predators, usually raccoons, show up.
Visits to mount cameras, retrieve eggs, and measure nests can take 30 minutes or more, but camera memory card replacement is as quick as getting to the nest and back. Of course, every trip requires caution. Mother gators typically hang out near their nests. Many of the gators at YWC have been captured and released in the past, making them wary of human encounters. But several times a year, a gator chases researchers away from a nest.
The most dangerous part of gator research involves capturing adults. Rainwater says he had one close call years ago when a gator clamped down on his hand and quickly let go. For 2019, however, none of the research projects require gator captures. Team members joke that their biggest fears involve the pterodactyl-sized mosquitos.
According to Rainwater, the YWC islands are ideal for gator research because the management of former rice fields and other impounded wetlands allows for habitats with varied salinity. It’s also critical that no alligator hunting has been allowed on the property for more than 100 years, and that alligators have been studied there extensively for 40 years. “There’s nowhere else with such long-term data on individual alligators,” Rainwater says. “We catch animals that Phil first caught in the late 1970s and early 1980s when they were already adults. That’s how we can show that they stop growing at some point. And now we can check DNA to see if some of the eggs are connected to females that are 60 to 70 years old.”
Cape Island: Checking on (Lots of) Turtle Returns
Cape Island juts out from the South Carolina coast like a prominent chin, daring bully storm waves to punch it. And they do, so often and with such force during recent hurricanes that what once was one long island is now three, separated by newly created inlets. The middle section is more of a new sand bank than a new barrier island. And the southernmost of the three has latched onto the marsh at the north end of Lighthouse Island, making a mockery of even recent maps.
But no matter how difficult the islands of the Cape Romain National Wildlife Refuge are to pin down, female sea turtles manage to find them and deposit eggs in their sand more often than anyplace else in the state, according to the SCDNR S.C. Marine Turtle Conservation Program. Nest data indicate an average of 1,400 nests were located each year on Cape and Lighthouse islands in the decade from 2009-2018. Then 2019 broke all records, with 3,373 nests on the two islands by the end of August. The vast majority are loggerhead turtle nests.
No wonder Sarah Dawsey, the Cape Romain refuge director, looks exhausted near the end of a day of turtle nest research in late June. Her typical nest-checking day starts at 6 a.m. at a refuge facility in Awendaw, with a short drive to a boat launch in McClellanville, and a gorgeous boat ride through the salt marsh creeks to a dock at a small upland area tacked onto the back of Cape Island’s four-mile stretch of sandy beach.
Dawsey and stalwart volunteer Donnie Lane ride an ATV filled with gear from one end of the beach to the other, stopping every time they spot new sea turtle tracks in the sand. On this day, they find 35 nests and check out many more false crawls, left when the turtles come ashore but decide not to deposit eggs.
At each nest site, Dawsey plunges a metal probe into the sand until she feels the telltale change in density that indicates a nest. Then either Dawsey or Lane digs carefully by hand, down 12 to 18 inches, until they hit eggs. If the nest is in a precarious location, the eggs are removed, counted, placed in a bucket, and relocated to higher ground. If the nest location seems safe from extreme tides, it is left in situ.
Researchers have compiled an inventory of nests and locations since the 1970s. Since 2010, University of Georgia researchers have partnered with natural resource agencies in Georgia, North Carolina, and South Carolina to gather DNA samples from each nest found. By the start of the 2019 season, the genetic database had identified 10,852 individual female loggerheads at more than 68,500 nests.
The goal is to get a better handle on how many different females are nesting in the region each year, how many clutches of eggs each nesting female lays, and if they lay eggs on multiple beaches in the same year.
Most nests have more than 100 eggs, about the size of a pingpong ball, with slightly pliable shells. To obtain a genetic fingerprint, Dawsey and Lane take one egg from each nest. A hole is poked in the shell, the yolk and albumen are squeezed out, and the shell is inserted into a test tube with alcohol to preserve it. Each nest is given a number, which Dawsey marks down in a ledger along with GPS coordinates.
Despite punching the probe into the ground hundreds of times, digging down to dozens of nests, and digging new holes for 11 relocated nests, Dawsey smiles through the exhaustion after more than six hours at the beach on a hot summer day. “The DNA testing shows there are three different generations nesting out here,” she says. “They don’t nest until they’re 30 years old, so there’s a 90-year-old grandma nesting out here!”
Deveaux Bank: Gauging Urban Impact on Pelican Nesting
As a boat carves out of Bohicket Creek into the North Edisto River, Deveaux Bank appears on the horizon as nothing more than a sand bar with minimal green growth. When the boat nears the bank, that assumption proves way off base. The island teems with bird life – on this morning dominated by loud laughing gulls, royal terns, and brown pelicans.
Surrounded by channels of swift-moving water and lacking maritime forest uplands and attached marshes, sand banks remain free of the predatory mammals of classic barrier islands. Birds, probably for that reason, flock to sand banks.
“It’s a special place,” says Clemson University doctoral student Bradley Wilkinson, who rotates his summer 2019 research days among the rich seabird nesting areas on Deveaux Bank, Bird Key Stono, and Castle Pinckney.
Wilkinson works under Clemson’s Patrick Jodice on a S.C. Cooperative Fish and Wildlife Research Unit project. On a stiflingly hot and windless July morning, Wilkinson and his assistant, Wake Forest University undergrad Landis Pujol, set out to tag several brown pelicans on Deveaux Bank.
To start the banding process, Wilkinson creeps up on the nesting site carrying a pole with a loop on the end. He crouches for several minutes, waiting for the best opportunity to slip the loop over an adult pelican. When Wilkinson finally latches onto a bird, Pujol races out with a cloth bag to put over the bird’s head and keep it as calm as possible during the banding and examination.
The bird is weighed, then Wilkinson attaches a metal band to one leg and a plastic band to the other leg. Ribbons wrapped under the wings pass through a miniature GPS tracking device, making it look like the bird is wearing a small backpack. Along the way a feather sample is clipped, a
blood sample taken, wing and tarsal measurements collected, and all of the data written in a notebook.
After less than 15 minutes, the pelican is set free, flapping its wings a few times on land before skimming gracefully over the water. Jodice is one of the authors of a 2016 study that found pelicans captured and fitted with transmitters, after a day or two of adjustment, breed and behave similarly to others in their nesting community that haven’t been captured.
The bird Wilkinson snags is the 52nd pelican to be equipped with a transmitter for this project from 2017-2019. The field season is nearing a close because Wilkinson has only eight more transmitters.
Brown pelicans are a wildlife management success story. Once considered endangered, largely because of the impact of pesticides such as DDT on egg shells, the species rebounded once those pesticides were banned. It was removed from the endangered list in 2009. Jodice assumed such a high-profile species had been thoroughly studied, but he found slim information on its migratory and foraging patterns. Tagged birds are filling those knowledge gaps.
For instance, transmitter data indicate pelicans fly much farther away from their nests to forage than previously suspected. Jodice says that information can help inform questions about development in marine ecosystems.
“We’ve been able to add a lot of detail about migration movements, how they get here and how long it takes,” Jodice says. “You can’t understand potential conservation issues if you don’t understand that trip.”
Barrier Islands Form, AGE in Multiple Ways
The most elemental research on barrier islands focuses on their geography. They form in three ways:
- when a new inlet cuts off a spit at the end of an island, as the south end of Cape Island did before attaching to Lighthouse Island,
- when offshore sandbars build up and vegetation takes hold, as at Sand Island, or
- when former high ground is drowned, either through erosion or rising sea levels.
Pockoy Island at Botany Bay Heritage Preserve provides a modern example of the formation of barrier islands through inundation of higher ground. Fifty years ago, Pockoy was a hummock island waystation on a long, man-made causeway out to a barrier island known as Botany Bay Island. As Botany Bay Island succumbed to erosion, the sand that marked its beach retreated to Pockoy. Digitized maps indicate the shoreline moved 1,640 feet from 1949 through 2016, according to Katie Luciano, a coastal geologist with the SCDNR. That’s 24.5 feet per year, before rising sea levels combined with multiple hurricanes to eat away another 150 feet of the central beach from Pockoy in 2016 and 2017. “This is coastal geology in action,” Luciano says. The recent erosion threatens a shell ring created 4,300 years ago by the region’s early inhabitants. In May 2017, two branches of research combined as archaeologists working on the shell mounds helped Luciano and College of Charleston (CofC) geologist Scott Harris collect a vibracore sample nearby. Vibracoring utilizes high-frequency, low-amplitude vibrations to drive a core tube into the ground. They also collected samples on what might be a dune ridge on the back of Pockoy, and another on a hummock island behind Pockoy.
Harris has been gathering samples throughout the coastal region for decades, and OSL results are fascinating. For instance, OSL dating indicates Folly Island has been front beach for 500 to 2,000 years. The hummock island just behind Folly, Long Island, was front beach about 2,000 years ago. The next ridge of hummock islands that includes Goat Island was front beach 6,000-8,000 years ago. And the ridge just behind Goat Island that includes Sol Legare Road was beach about 82,000 years ago.
These dates drive home the reality that coastal islands in general and barrier islands in particular constantly change. To get a better handle on the how and why, researchers study the current islands’ sediment budget, checking upper level sediment to determine where it came from, how long it stays, and where it goes. They can tell whether the sediment washes down from inland rivers or is dragged along by currents just offshore.
“In order to understand what we’ve done on inhabited barrier islands, we have to go to the uninhabited ones,” Harris says. “They show a true natural system in action.”
Whether studying geology, wind energy, wild hogs, alligators, sea turtles, or brown pelicans, that most natural of environments is what lures scientists to the undeveloped islands.
Reading and Websites
Audubon, John James, Ornithological biography, or an account of the habits of the birds of the United States of America, 1831-39, Edinburgh: Adam Black.
Engeman et al., “Feral swine harming insular sea turtle reproduction: The origin, impacts, behavior and elimination of an invasive species,” Acta Oecologica, June 2019.
Kana, Timothy W., Steven B. Traynum, Dan Gaudiano, Haiqing L. Kaczkowski, and Trey Hair, “The Physical Condition of South Carolina Beaches 1980–2010,” Journal of Coastal Research, September 2013.
Lamb, Juliet S., Yvan G. Satge, Christine V. Fiorello, Patrick G.R. Jodice, “Behavioral and reproductive effects of bird-borne data logger attachment on Brown Pelicans (Pelecanus occidentalis) on three temporal scales,” Journal of Ornithology, April 2017.
Rhodes, J. Edwards, “Optically Stimulated Luminescence Dating of Sediments over the Past 200,000 Years,” Annual Review of Earth and Planetary Sciences, May 2011.
Sea Turtle Nest Monitoring System
Wilkinson, P.M., T.R. Rainwater, A.R. Woodward, E.H. Leone, and C. Carter, “Determinate growth and reproductive lifespan in the American alligator (Alligator mississippiensis): evidence from long-term recaptures,” Copeia, December 2016.