South Atlantic Coastal Plain Ecoregion
Description & Physiography
The South Atlantic Coastal Plain ecoregion encompasses more than 23 million acres across three states, including the southern portion of South Carolina, southeastern Georgia and northeastern Florida. The ecoregion is bordered to the east by the Atlantic Ocean, and to the northwest by the Fall Line (a geologically distinct zone corresponding to the interface between the relatively flat coastal plain and the topographically varied Piedmont). It is bordered on the northeast by the Mid-Atlantic Coastal Plain, on the west by the East Gulf Coastal Plain, on the south by the Florida Peninsula and on the north by the Piedmont.
Though changes in topography may be slight, the South Atlantic Coastal Plain is extremely rich in both species diversity and ecological community diversity. The many ecological systems found in the South Atlantic Coastal Plain ecoregion range from fall-line sandhills to rolling longleaf pine uplands to wet pine flatwoods; from small streams to large river systems to rich estuaries; from isolated depression wetlands to Carolina bays to the Okefenokee Swamp. Other ecological systems in the ecoregion include maritime forests on barrier islands, pitcher plant seepage bogs and Altamaha grit (sandstone) outcrops.
Plants & Animals
Longleaf pine woodlands and associated ecological communities were once the dominant vegetation type in the Southeast Coastal Plain. Fire-maintained longleaf pine woodlands are found across a wide range of soil moisture regimes, and support a large number of plant and animal species (including many endemics). Due to a drastic decline of longleaf pine woodlands across the Southeast Coastal Plain (less than 5 percent remains), many of these species are imperiled. Many of the associated fire-maintained plant communities (e.g. pitcher plant seepage bogs, seasonally flooded depression ponds) are important habitat for plant and animal species and have declined as well. Freshwater aquatic diversity in the South Atlantic Coastal Plain is very high.
River systems are primarily of two types: brownwater (with headwaters north of the Fall Line, silt-laden) and blackwater (with headwaters in the coastal plain, stained by tannic acids). These river systems are relatively free from impoundments in the SACP and often contain unique biological resources; some ecoregional endemics only occur in one river system. Other dominant features of the South Atlantic Coastal Plain include a large number of freshwater wetlands, including one of the largest freshwater wetland systems in the world (the Okefenokee Swamp system), limesink depression ponds and Carolina bays (unusual wetlands of varying water levels that are elliptical in shape, probably formed by wind).
Humans & History
The primary threats to biological diversity in the South Atlantic Coastal Plain are intensive silvicultural practices, including conversion of natural forests to highly managed pine monocultures and the clear-cutting of bottomland hardwood forests. Changes in water quality and quantity, caused by hydrologic alterations (impoundments, groundwater withdrawal and ditching) and point and nonpoint pollution, are threatening the aquatic systems. Development is a growing threat, especially in coastal areas. Agricultural conversion, fire regime alteration and the introduction of nonnative species are additional threats to the ecoregion’s diversity.
Though much has been lost, there are still great conservation opportunities in the South Atlantic Coastal Plain. Many high-quality natural areas remain as large, functioning landscapes. Many of the rivers and streams in the ecoregion remain relatively intact, but are under threat. TNC has a long history in the ecoregion, and has formed strong governmental and private partnerships, allowing the opportunity to work at large scales to preserve the high biological diversity of this rich ecoregion.