Ashepoo-Combahee-Edisto (ACE) Basin National Estuarine Research Reserve, South Carolina

Source: NOAA


caption Ace Basin Reserve boundary map. (Source: NOAA)

ACE Basin is one of the largest undeveloped estuaries on the East Coast. It is named for the Ashepoo, Combahee and Edisto rivers, which meander past cypress swamps, historic plantation homes, old rice fields and abundant tidal marshes to meet at South Carolina’s biologically rich St. Helena Sound.

The ACE Basin National Estuarine Research Reserve protects the natural beauty, abundant wildlife and unique cultural heritage of the area. In addition, the reserve preserves habitat for many endangered or threatened species, such as shortnose sturgeon, wood storks, loggerhead sea turtles and bald eagles.

Commercial fisherman harvest bountiful supplies of shrimp, crabs, oysters, clams and finfish each year in the ACE Basin. Recreational fishermen ply the mudflats for spottail bass, flounder and shrimp, while paddlers enjoy the natural beauty of a maze of salt marsh creeks and the black waters of the rivers.

Research conducted at the ACE Basin Reserve enhance the protection of these commercial and recreational uses by monitoring water quality, providing information on the abundance and types of important plant and animal species, and evaluating the overall health of the ACE Basin ecosystem.

Through a variety of educational programs, the reserve provides timely information to coastal decision makers, lawmakers, teachers, students and the general public. The reserve sponsors a summer lecture series, develops curriculum materials for teachers, offers a touch tank program for children and conducts educational cruises where students and teachers learn about estuaries and their values to marine life.

The ACE Basin Reserve is within the National Estuarine Research Reserve System (NERRS), a network of estuarine habitats protected and managed for the purposes of long-term research, education, and coastal stewardship. Established by Congress in 1972 as part of the Coastal Zone Management Act (CZMA), the NERRS is administered as a partnership between the National Oceanic and Atmospheric Administration (NOAA) and the coastal states.

Biological Resource

The ACE Basin contains six distinct ecosystem habitat types that range from subtidal areas and vast wetlands to uplands. These habitats are characterized by more than 1500 different plant and animal species that interact with the physical environment to create the ACE Basin ecosystem. Major groups of organisms that occur in the ACE Basin include phytoplankton, plants, decomposers, zooplankton, benthic invertebrates, insects, decapod crustaceans, fish, reptiles and amphibians, birds, and mammals. In addition to groups of organisms, this section describes some of the basic ecological principles that underlie the ACE Basin ecosystem.

An ecosystem is defined as "a set of organisms (community) living in an area, their physical environment, and the interactions between them". Although it has not always been clearly recognized, humans are completely dependent on the ecosystems in which they live. Humans have been dependent on the ACE Basin ecosystem for over 6,000 years. The many processes that integrate energy and nutrients flowing through the ACE Basin ecosystem provide its human inhabitants a variety of services. Besides providing food and shelter, the ecosystem provides waste treatment (by way of carbon dioxide consumption, oxygen production, and breakdown of sewage), a water filtration system (by the soil), recreational opportunities, and a basis for economic development. Some of these services, such as food production, are readily apparent and have a market value. In the ACE Basin, commercial fishing is an important means of food production. Likewise, both agriculture and forestry products are produced in the ACE Basin and have a market value. Less apparent services include biological and chemical processes, such as the transfer of energy through the food chain, that operate in order to produce the fish or agricultural products. These services are generally taken for granted; yet they may be severely impacted by land use and pollution. Remove any one of these "services" and the character and function of the other components can be compromised.

Coastal areas, such as the ACE Basin, located between the open ocean and upland areas, have a high diversity of habitats and microhabitats, supporting diverse and abundant communities of plants and animals. As habitats are modified, ecological processes in these habitats also change and some of these changes may be significant. One of the greatest threats to habitat diversity in the ACE Basin is the conversion of existing habitats to structurally and biologically simpler habitats such as agricultural fields, pine plantations, and urban or residential areas. In addition to the direct loss of habitat, the resulting fragmentation of the remaining forested and wetland areas results in decreased species diversity. As a consequence of fragmentation in the ACE Basin, ecotones where the vegetative communities previously graded slowly from wetland to upland forest have been changed to sharper boundaries between wetland areas and what are now agricultural fields or suburban developments.

Other threats to the ACE Basin ecosystem occur as a result of human disturbance of the natural transfer of energy and trophic structure, which can alter the carrying capacity of the ecosystem. In addition, the current global economy is consuming more energy than is renewable over the long term, and humans are heavily dependent on nonrenewable fossil fuels and nuclear energy. Energy use at the local level of the ACE Basin is no exception. Millions of dollars in fuel, fertilizer, and pesticides are used to increase the production of agricultural products well beyond natural levels. When fossil fuels become expensive and scarce, it will be difficult to maintain the current production levels on ACE Basin farms. In order to limit the impact humans have on the ACE Basin ecosystem, appropriate management decisions must be made at the federal, state, and local government levels as well as by individual property owners and residents of the ACE Basin.


Flora associated with the habitats within the ACE Basin National Estuarine Research Reserve include live oak, slash pine, southern magnolia, red bay and cabbage palmetto, with sub canopy of southern red cedar and shrub layer of wax myrtle and yaupon holly. Shell-mound buckthorn is a rare flora.

Other plant species include bald cypress, Canby’s dropwort, sea oats, smooth cordgrass and wild rice.


Some reptile species found in the ACE are American alligator, diamondback terrapin, eastern diamondback rattlesnake, loggerhead turtle and southeastern five-lined skink. Some mammals are bobcat, bottlenose dolphin, eastern gray squirrel, fox squirrel, gray fox, marsh rabbit, raccoon, river otter and white-tailed deer. Invertebrates include American oyster, blue crab, fiddler crab, grass shrimp, hard clam, horseshoe crab and white shrimp. Some fish species are American shad, Atlantic croaker, bay anchovy, black drum, largemouth bass, red drum, shortnose sturgeon, Southern flounder, spot, spotted seatrout, striped bass and striped mullet. Birds include American oystercatcher, barred owl, clapper rail, Eastern brown pelican, eastern wild turkey, green-winged teal, least turn, osprey, peregrine falcon, red knot, red-cockaded woodpecker, red-railed hawk, red-winged blackbird, southern bald eagle, wood duck and wood stork.

Endangered Species

The ACE Basin Reserve is crucial to the survival of many threatened or endangered species. Nine federally endangered species (peregrine falcon, Canby’s dropwort, chaffseed, hawksbill turtle, leatherback turtle, red-cockaded woodpecker, shortnose sturgeon, West Indian manatee and wood stork) utilize the ACE Basin. Six federally threatened species (bald eagle, Eastern indigo snake, green turtle, American alligator, loggerhead turtle, piping plover) have also been observed in the area. In addition, 30 species are designated as threatened, endangered or species of concern by the state of South Carolina.


caption Aerial photograph of Carolina Bay. Note: Northwest to Southeast orientation. (Source: USGS)

Geomorphology integrates the study of the interactions between physical components of the atmosphere, the Earth (lithosphere), and water (hydrosphere) with the biological communities of plants and animals, and especially humans that modify landforms. The periodic landward and seaward movement of the shore across the coastal plain can be seen in the landforms of the ACE Basin such as relict dune ridges and marsh plains.

The lower coastal plain of South Carolina, including the ACE Basin, has been subjected to repeated cycles of sea-level rise and fall which has resulted in a complex three-dimensional mosaic of Pleistocene-age fluvial and marine sediments. The coastal portion of the ACE Basin is characterized by sea islands, marsh islands, and barrier islands that are interlaced by estuaries, extensive salt marshes, intertidal areas, and oyster reefs. Three major rivers (Ashepoo, Combahee, and Edisto) provide fresh water and influence the character of inland portions of the study area. Additionally, there are approximately 20 Carolina bays in Colleton County that are larger than 0.8 hectares. One bay in Colleton County exceeds 3,000 meters in length.

The primary source of sediments to the Basin is the deposition of terrestrial sediments carried there by rivers, and from the deposition of reworked marine sediments during submerged periods. The major rivers in the ACE Basin, the Ashepoo, Combahee, and Edisto, each have extensive drainage areas. The Edisto River, with its headwaters beginning below the fall line in South Carolina has the largest watershed of the three rivers. The Edisto River is the primary source of materials eroded from upland areas and supplied to the ACE Basin. The smaller Ashepoo and Combahee rivers originate from swamps on the coastal plain and also contribute large amounts of fresh water, and dissolved and suspended materials to St. Helena Sound. During wet weather episodes, the rivers of the ACE Basin, and especially the Edisto River, may expand out into their flood plains carrying thousands of tons of sediment. Fine mud and organic materials settle onto the soil and provide a fresh source of nutrients and minerals to the plant communities, making the flood plains very productive areas.

The ACE Basin has extensive areas of salt marsh formed during periods when sedimentation rates are great enough to keep pace with sea-level rise. The primary salt marsh vegetation type is Spartina spp. with a multispecies community developing at higher elevations not frequently inundated by seawater. Oyster reefs are also found in the Basin's plankton-rich tidal streams and provide habitat (structure) for animals within the intertidal zone, replacing the function which submerged aquatic vegetation (SAV) and coral reefs serve in other regions.

More recent anthropogenic processes shaping the ACE Basin coastal landscape include timber harvesting; agriculture; land use conversion, primarily for development; modifications to beachfronts; and dredging or filling of channels and wetlands. Implementing land use practices that recognize the geomorphic constraints within the ACE Basin will help to reduce anthropogenic impacts to its environment.

Tidal Range and River Flow

The mean range of semi-diurnal tides varies from about 7.2 feet at the mouth of the St. Helena Sound to 6.1 feet in the upper reaches of the estuary. Stream flow in the Edisto River is substantial (74m3/sec or 2,614ft3/sec at Givhan’s Ferry) and fairly constant.

Soil Types

The soils of the mainland, the sea islands and some of the barrier islands, were deposited during the Pleistocene period at least 25,000 to 35,000 years ago. Most barrier island soils are of more recent origin, having been laid down during the Holocene period within the last 4,000 to 5,000 years. These soils vary from sand-clay mixtures with distinct horizon development to soils of predominantly quartz sand with indistinct horizon development.

Socioeconomic Assessment

Our interactions with the environment, including extraction of resources and alteration to the physical landscape, often have far-reaching effects. To manage resources of the ACE Basin effectively, there must be both an understanding of the physical and biological environment and knowledge of socioeconomic conditions. Socioeconomic data provide an important perspective of the individuals and businesses that reside in the ACE Basin. These entities are the primary stakeholders in the region's ecological health and economic development, and ultimately determine what strategies will or will not succeed in the area.

The population of the ACE Basin is centered near the three incorporated municipalities of Walterboro, Cottageville, and Edisto Beach. Presently, Walterboro is the only urban area in Colleton County with public water and sewer facilities that can support an increase in the population. In 1990, educational attainment was low in the ACE Basin and 24% of residents in the five incorporated areas lived in poverty. Low educational attainment represents a potentially significant economic barrier for the region. The average earnings per job were only $19,497 in 1996 for Colleton County, with a racial gap in the earnings. It is misleading to assume that average figures are representative of the whole region. The urban areas, and especially the pocket resort and high-end residential communities, have higher relative wealth and educational backgrounds than is apparent from the county or subdivision averages.

That nearly 27% of Colleton County residents travel to work outside the county, compared to approximately 7% and 2% in Charleston and Beaufort Counties, respectively, highlights the need for more opportunities in the Colleton area. It also highlights the potential for Colleton to become a bedroom community to more prosperous areas and the increased threat of the subdivision of natural areas into residential developments. Land-use planning in the ACE Basin will be an important tool to guide development in a way that does not compromise the potential benefits of the area's natural resources. If the ACE Basin's proximity to the economic resources of neighboring areas is used to support sustainable economic development of the Basin's natural resources, then the outflowing tide of economic benefits can be turned back toward the Basin.

The primary industry-related activities in the ACE Basin include light manufacturing, the service sector, forestry, and agriculture. Three key strategies were established by the ACE Basin Economic Task Force to encourage economic growth while preserving the natural characteristics of the Basin: (1) create a framework for responsible growth; (2) enhance awareness, understanding, and appreciation of the Basin; and (3) promote environmentally compatible business development. In particular, natural resource-based industries such as agriculture, forestry, seafood, and local crafts have played a key role in the ACE Basin's heritage, and recommendations were established for exploring new ways to make these industries develop higher value-added products and operate in a more sustainable fashion. New and increased nature-based tourism development is highly desirable and environmentally compatible, thereby allowing the area to capitalize on and protect the region's character and natural assets.

Resource Use

The ACE Basin Characterization study area is primarily rural with only five incorporated communities. The main land-use types in the ACE Basin are agriculture and silviculture, which together generated $58 million for 1994-95 in Colleton County. In addition to forestry and agriculture, the ACE Basin is utilized for hunting, commercial and recreational fishing, and tourism. Tourism in the ACE Basin is centered on its relatively undeveloped natural environment. One of the factors that makes the ACE Basin a unique area is the large amount of land that has been protected and can never be developed as a result of the efforts of state and federal governments, private landowners, and private organizations. Another aspect which makes the ACE Basin unique is the number of sites which are deemed significant natural areas by the South Carolina Heritage Trust Program.


caption Aerial view of upland forest habitat. (Source: SCDNR)

The forests of the ACE Basin are a vital part of the ecology, economy, and beauty of the region. Forestry is part of the Basin's cultural heritage and is vital to its present economy with 43 million dollars in forestry-related revenue in Colleton County during 1994. Forest survey reports for 1993 indicate that 56 percent of the land cover (1,128,960.4 ha, or 457,069 ac) in Colleton County is classified as timberland. This acreage is dominated by upland planted pine and forested wetlands with evergreen upland forest, mixed upland forest, and deciduous upland forest being less important. Hardwood-dominated forests constitute only 1.4 percent of the total forested area. Westvaco Corporation and Georgia-Pacific are the two largest industrial foresters in the ACE Basin; however, most of the total forested acreage (70%) is owned by nonindustrial private landowners.

Forestry efforts are primarily directed at growing loblolly and shortleaf pines, followed by oak, gum, and cypress trees. In the ACE Basin study area, 457,681.1 ha (185,296 ac) are classified as upland planted pine based on the 1997 National Wetlands Inventory. This constitutes most of the total forested land cover. In addition to directed efforts to grow pines by converting scrub oak and other low-quality hardwood stands, natural reseeding of idle or abandoned agricultural land has also favored establishment of loblolly-shortleaf pine. The overall volume of Colleton's standing timber increased an average of 6-8%. Sawtimber also increased, with pine constituting 74% of the total board feet for all species. These trends reflect an improvement in tree stocking as a result of intensive forest management.

Forestry practices have been associated with a number of negative effects over the years. These include impacts to habitat, water quality, biodiversity, and scenic vistas. Effects of forest conversion to pine monocultures include reduction in diversity of forest-dependent animals and canopy/subcanopy vegetation. Forestry has had a major impact on "natural forests" because of monoculture of loblolly and shortleaf pines as opposed to the native slash pine. A common forest management practice in the southeastern United States and Colleton County is the establishment of loblolly or slash pine plantations. After years of rapid growth, these plantations are harvested to produce fiber, lumber, and wood-based chemicals. The affect of even-aged pine plantations on the quality of wildlife habitat has become an issue in forestry.

Contrary to early forestry practices of clearing and abandoning the land, there is presently a trend toward sustainable forestry through the protection of watersheds and wildlife habitat, conservation of soil, and maintenance of aesthetics while continuing to harvest trees. One approach being used in the southeastern United States involves development of selective harvesting techniques that ultimately produce uneven-aged stands of pine-hardwood as well as understory diversity. Several federal forestry assistance programs and landowner assistance programs are available to foresters in the ACE Basin to help them make sound management decisions based on sustainable forestry. An example of an industrial landowner that is practicing sustainable forestry in the ACE Basin is Westvaco Corporation, the single largest private landowner there.

The outlook for forestry in the ACE Basin reflects advances in science and technology, balanced with conservation. These technological advances will continue to help forest landowners meet increasing needs for renewable wood and paper products for local and global markets. An increasing awareness of forest ecology and protection of soil and water in concert with sustainable forest management will help maintain the integrity of forests and contribute to the quality of life in the ACE Basin.

Resource Management

The 182,115 ha (450,000 ac) making up the ACE Basin Task Force Project area support more than 1,500 plant and animal species (not including insects) within six distinct ecosystem habitats. The ecosystems of the ACE Basin are not untouched considering that some level of anthropogenic impact has occurred for the last 6,000 years; however, the ecological integrity of the ACE Basin has been maintained through conscious management and sustainable use of its resources.

Formal protection of the ACE Basin was initiated in 1988 with the development of the ACE Basin Task Force, a unique partnership of state and federal governmental representatives, nonprofit conservation organizations, and private landowners. This group shared a vision of maintaining the natural character of the Basin by promoting wise resource management and continuing traditional uses with improved public access. This vision has provided a framework for land protection in the ACE Basin that has gained national and international recognition. While encouraging traditional land uses such as agriculture, timber production, hunting, and fishing, the overall management goal is to maintain the area's ambiance while restricting industrial and resort development characteristic of much of the state's coastal zone in the past 30 years. To date, well over 316,160 ha (128,000 ac) in the Basin have been protected through conservation easements, management agreements, and fee title purchases. The private landowner initiative has been fundamental to the overwhelming success of the ACE Basin Project.

Conservation, research/monitoring, education, and cooperation have provided the basic architecture for the ACE Basin Project. Conservation is system-driven and embraces "sustainable growth" as a key factor. The desire of its rural communities to maintain their quality of life without the pressures to develop for immediate gain has been unusual and to a large degree shaped by historical good fortune. Today, the movement toward incorporating the needs of a community while preserving its natural values is a novel concept. A major challenge in the ACE Basin is to strike a balance between the area's socioeconomic needs while protecting the benefits of natural systems. This requires good science and a commitment to responsible growth.

Because of its remoteness and relatively pristine nature, the ACE Basin provides ideal sites for monitoring changes in the physical and biological components of the region. The fact that the National Estuarine Research Reserve, National Wildlife Refuge, Ducks Unlimited, and The Nature Conservancy are represented here make the Basin even more attractive for gathering scientific information. Interdisciplinary research is providing information for conserving biological diversity, assessing the impacts of pollution on the structure and function of ecosystems, and for developing sustainable production systems for altered habitats. In addition, the ACE Basin provides a framework for comparative studies of similar problems in different coastal regions. Local communities are being introduced to the idea that protecting natural watersheds and sustainable development are to their long-term benefit. Education and outreach activities to strengthen the understanding and appreciation of these concepts are pivotal.


Humans have lived and utilized natural resources in the ACE Basin for thousands of years. The first human presence in the Basin occurred approximately 6,000 years ago with the Paleoindians. Like their Asian counterparts, Paleoindians are believed to have lived in mobile hunter-gatherer groups and hunted large animals such as mammoths and mastodons. New ways of hunting and gathering marked the end of the Paleoindian period and the beginning of the Archaic period and the modern-day Indians. Until the arrival of Europeans in the sixteenth century, Paleoindian culture evolved into a more sedentary society that relied on hunting in smaller territories and agriculture. Semipermanent villages of several families were built near the hunting grounds. Villagers tilled and planted crops such as corn, beans, and squash during the spring and harvested in the fall. During the summer months, the entire village moved to the homesteads near the coast, where they subsisted on seafood and wild plants, particularly roots.

Human activities have shaped the history, and the cultural and natural resources of the Basin. Early Carolinians cleared thousands of acres of old-growth hardwood forests and planted a variety of crops including corn, tobacco, and root crops. Tens of thousands of acres of bottomland hardwoods along the navigable rivers and creeks of the ACE Basin study area were converted to rice fields. Lumber companies of the late 1800s to early 1900s logged most of the virgin pine forests and swamplands in Colleton County. The modernization of farming practices after World War II resulted in extreme increases in profit and crop production. Improvements in farming techniques, and the construction of the Intracoastal Waterway, roads, and railways were instrumental in promoting the development of the farming industry during the early twentieth century. Today, the extensive pine plantations and rice field systems established during this period are still evident.

Many of the large plantations that once supplied the mills with timber were converted to hunting preserves. The abandoned rice fields and logged forests attracted a rich abundance of game animals, including migratory waterfowl and deer to the area. The interest in hunting led to the evolution of sophisticated wildlife management techniques that help to preserve the natural quality of the ACE Basin study area that we enjoy today.

Most of the more well-known archaeological sites in the ACE Basin date from the recent historic period, particularly the 18th and 19th centuries when the area flourished as a prosperous agricultural region. Some of the more popular historic attractions around the ACE Basin study area include the Colleton County Courthouse, Hunting Island Lighthouse, and Edisto Beach State Park. It is important to recognize that although hundreds of sites have been formally recognized, hundreds to thousands of sites may never be discovered without careful site planning, inventories, and management during land clearing. The use of appropriate planning, identification, and preservation of these cultural resources will sustain them for tourism and future generations.

Partners and Supporters

The reserve is managed by the South Carolina Department of Natural Resources. A 21-member steering committee, representing local business, education, science, forestry, fisheries, environmental tourism, nonprofit conservation, non-governmental organizations and private landowner communities, guides development of research and educational activities.

A strong partnership with the South Carolina Department of Parks, Recreation and Tourism at Edisto Beach State Park has created opportunities for a friends group for protection of and education in the ACE Basin.

Further Reading

Disclaimer: This article is taken wholly from, or contains information that was originally published by, the National Oceanic and Atmospheric Administration. Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the National Oceanic and Atmospheric Administration should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.



(2006). Ashepoo-Combahee-Edisto (ACE) Basin National Estuarine Research Reserve, South Carolina. Retrieved from


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