Wetlands represent an important component of the southeastern landscape, comprising 16 percent of the study area. By comparison, wetlands cover only about 5 percent of the lower 48 states (Dahl and Johnson 1991).

Nearly half (47 percent) of all wetlands and more than three-quarters (78 percent) of all estuarine wetlands occur in the Southeast (Fig. 10 & 11), even though the region is only 16 percent of the conterminous United States. Nearly half of the estimated wetland acreage in the Southeast is located in the Gulf-Atlantic Coastal Flats and Coastal Zone physical subdivisions. These two subdivisions account for less than a quarter of the region's total area.

Figure 10.
Wetlands of the conterminous United States

Figure 11.
Estuarine wetlands of the conterminous United States

Wetland loss in the Southeast strongly influences overall wetland trend estimates for the conterminous United States. The region's wetland losses represented 89 percent of the net national loss (Fig. 12). For example, 84 percent of the net losses/conversions of saltmarshes and mangroves (estuarine vegetated wetlands) (Fig.13) and 91 percent of all losses/conversions of freshwater (palustrine) forested wetlands occurred in the Southeast Region (Fig. 14).

Just as wetlands are not evenly distributed across the landscape, neither were sites of significant wetland losses. Over 62 percent of the region's wetland loss took place in the Gulf-Atlantic Coastal Flats and Coastal Zone. Wetland loss in this portion of the region was five times greater than the combined total losses for the 38 conterminous states outside the Southeast Region (Fig.15). Almost 69 percent of the region's palustrine forested wetland loss was recorded within the Gulf-Atlantic Coastal Flats and Lower Mississippi Alluvial Plain.

Specific locations within these physical subdivisions stood out as exceptionally vulnerable to wetland conversion. Large acreages of palustrine forested wetlands were lost in the Gulf-Atlantic Coastal Flats of North Carolina and the Lower Mississippi Alluvial Plain in Louisiana. Nearly 1.2 million acres of wetlands were lost in North Carolina, presumably by a combination of silvicultural and agricultural activities. In the Lower Mississippi Alluvial Plain, nearly one million acres of bottomland hardwood wetlands were destroyed, mostly converted to farm land. Over half of this change took place within the Louisiana portion of the plain.

Figure 12.
Wetland losses in the conterminous United States

Figure 13.
Estuarine vegetated wetland losses in the conterminous United States

Figure 14.
Palustrine forested wetland losses and conversions in the conterminous United States

Figure 15.
Wetland losses in the Gulf-Atlantic Coastal Flats compared to the rest of the United States

Peninsular Florida and coastal Louisiana also experienced notable losses. Nearly all of the 110,000 acres of freshwater marshes lost in Florida were altered for agricultural purposes. Along coastal Louisiana, about 42,000 acres of estuarine marsh were changed to nonvegetated bay bottom due to a variety of causes including erosion, saltwater intrusion, subsidence, sea-level rise, sediment deprivation and physical alteration.

Eastern Tennessee
RIVERINE
JOHN HEFNER

Annual wetland loss rates were variable due to economic conditions, demographic patterns, land values, and farm and timber prices, among other factors. From the 1950's to the 1970's, wetlands of the Southeast were lost at an average net rate of 386,000 acres per year (Hefner and Brown 1984). During the study period from 1974 to 1983, the net rate of regional wetland losses declined to 259,000 acres annually. This is a one-third reduction compared to the rate of the previous two decades (Fig. 16). The loss rate for estuarine wetlands showed particular improvement. And the rate of gains in small open-water bodies accelerated.

Although the overall wetland loss rate declined, the rate at which freshwater forested wetlands were lost or converted accelerated (Fig. 17). Forested wetlands of the region were lost or converted to other wetland types at an average rate of 276,000 acres per year from the mid-1950's to the mid-1970's (Hefner and Brown 1984). However, this rate increased to 345,000 acres per year from the mid-1970's to the mid-1980's.

Figure 16.
All wetlands in the Southeast: Average annual loss

Figure 17.
Palustrine forested wetlands in the Southeast: Average annual loss/conversion

Great Egret
© LARRY R. DITTO