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Southern Coastal Plain

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NameColor on MapEPA Code‡
Gulf Coast Flatwoods75a
Southwestern Florida Flatwoods75b
Central Florida Ridges and Uplands75c
Eastern Florida Flatwoods75d
Okefenokee Plains75e
Sea Island Flatwoods75f
Okefenokee Swamp75g
Bacon Terraces75h
Floodplains and Low Terraces75i
Sea Islands/Coastal Marsh75j
Gulf Barrier Islands and Coastal Marshes75k
Big Bend Coastal Marsh75l

† Status: ✓ = Complete ○ = Needs Image … = Incomplete ∅ = Stub Only

This code refers to the US EPA's Level 4 ecoregion codes for the continental U.S., see here.


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About the Southern Coastal Plain

The Southern Coastal Plain is a region in the southeastern US, encompassing the flat, outermost portions of the coastal plain. It encompasses most of Florida, excepting the southernmost portion of the state and the more inland parts of the panhandle, and also covers much of coastal Georgia and narrower regions into South Carolina, Alabama, Mississippi, and Alabama.

Most of this region is very flat, with only subtle changes in topography. The coastline is marked by barrier islands, marshes, and lagoons. The most inland portion of this region, in Florida, also contains numerous lakes. There are streams and rivers throughout, which tend to be slow-moving; wetlands are abundant throughout. Soils here tend to be highly leached and acidic; soils vary in texture, but in much of the region, coarse, excessively-drained sands create drought-prone environments.

The climate here is humid and subtropical. Most of the region has a strong seasonality of precipitation, with hot, wet summers and mild, relatively drier winters. Hot temperatures tend to arrive in May, before the rainy season hits. Summer rains usually arrive in the form of daily thunderstorms, which can ignite fires. The juxtaposition of hot, dry conditions with lightning strikes tends to make the wildfire season here peak from March to June. This region thus has some of the most predictable. The combination of this region being farther south, low, flat, and surrounded by ocean, has led this region's climate to remain largely unchanged by the cycles of glacial and interglacial periods during the ice age. This region has thus been a refuge of climate stability with a history extending farther back than any of the other areas in the eastern US. Areas farther north, even those beyond the limit of glaciation, have experienced dramatic warming and cooling periods, along with shifts in other aspects of climate, during the ice age.

The seasonality of rainfall becomes more pronounced moving southward. However, the western portions of this region have a much wetter winter and thus more constant precipitation year-round. Temperatures are moderated by the low elevation and proximity to the ocean, and winters tend to be mild, but the influence of continental air masses can occasionally bring brief spells of more severe cold. Frost becomes less frequent and severe moving south, but most of this region experiences some frost in most years. This region is subjected to frequent hurricanes, with the south and west of this region being most vulnerable; the northeast is relatively more protected by the concave curvature of the coastline.

This region has some of the longest history of stable vegetation cover in the eastern US, owing to its stable climate through glacial and interglacial periods. Prior to European settlement, this region was mostly covered in longleaf pine (Pinus palustris) flatwoods and savannas, but there were numerous other cover types. Areas with richer forest cover often included slash pine (Pinus elliottii), pond pine (Pinus serotina), pond cypress (Taxodium ascendens), American sweetgum (Liquidambar styraciflua), southern magnolia (Magnolia grandiflora), and laurel oak (Quercus laurifolia). White oak (Quercus alba) and American beech (Fagus grandifolia) are important in the north of this region but reach their southern range limits here and are absent from much of the region. Along major waterways, southern floodplain forests featured bald cypress (Taxodium distichum), pond cypress, water tupelo (Nyssa aquatica), sweetgum, green ash (Fraxinus pennsylvanica), water hickory (Carya aquatica), and a high diversity of bottomland oaks, which have greater species richness here than in areas farther north. The driest sites, especially in the south, featured a variety of open scrubland communities referred to as "Florida scrub".

Land use in this region is intensive but often not particularly intelligent or efficient. Especially in the north, there is extensive forestry, mostly in the form of large, monoculture pine plantations that lack the diversity of natural pine forests. There is also extensive agriculture, especially pastureland for beef cattle, citrus groves, and fish and shellfish farming. This area is also a major destination for tourism and recreation, both to coastal areas, and with Disney World. There are a large number of cities here, including Charleston, SC, Savannah, GA, and in Florida, Jacksonville, Tampa, Orlando, and many other smaller cities. In addition, there is extensive suburban development, both along the coast and inland around the major cities but often extending quite far from them. Much of the coastal development has been carried out without regard to hurricane safety.

Although there are some areas of protected wild lands, including both public and private land, this region has a disturbingly low portion of protected lands relative to its importance as a reservoir of biodiversity. Suburban development in this region has also been particularly inefficient, with a great deal of low-density car-oriented development, thus leading to a disproportionate environmental impact relative to its population and economic scale. Remaining wild habitats here are highly fragmented, especially in the south of this region.

Humans have carried out extensive fire suppression, leading to the decline both of scrublands and of fire-dependent pine forests, especially that of longleaf pine. However, the fragmentation and isolation (including both natural fragmentation and further human-induced fragmentation) of richer, more forested habitats, has led to a lack of more moisture-loving hardwood tree species colonizing these habitats following fire exclusion.

This region is bordered inland by the Southeastern Plains, which constitutes the relatively hillier portion of the coastal plain; that area is less populous and has a relatively higher portion of closed-canopy forests and a greater portion of hardwoods, although it still has a large portion of pine forests. At the west of this region, at the Mississippi River Delta near New Orleans, it is also bordered to the west and south by the Mississippi Alluvial Plain. At the northeast end of this region, it is bordered by the Middle Atlantic Coastal Plain; this border is more subjective and represents a gradual transition to a cooler climate, rather than a well-defined shift in geology or hydrology.

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