216 



Terrestrial Ecosystems — Our Li\in,i; Rcsimrces 



Southern 



Forested 



Wetlands 



by 



B.D. Keeland 



James A. Allen 



Virginia V. Burkett 



National Biological Service 



Fig. 1. Approximate distribution 

 of forested wetlands along rivers 

 and streams in the souttieastem 

 United States prior to European 

 colonization (Putnam et al. 1960). 



European settlers in many parts of the south- 

 ern United States encountered a landscape 

 largely comprising forested wetlands. These 

 wetlands were a major feature of river flood- 

 plains and isolated depressions or basins from 

 Virginia to Florida, west to eastern Texas and 

 Oklahoma, and along the Mississippi River to 

 southern Illinois (Fig. 1 1. Based on the accounts 

 of pre-2()th-century naturalists such as 

 Audubon. Banister, John and William Bartram. 

 Brickell. and Darby, the flora and fauna of many 

 wetlands were unusually rich even by precolo- 

 nial standards (Wright and Wright 1932). These 

 early travelers described vast unbroken forests 

 of oaks, ashes, maples (Quercus, Fniximis, 

 Acer), and other tree species, many with an 

 almost impassable understory of saplings, 

 shrubs, vines, switch cane, and palmetto. Low 

 swampy areas with deep, long-term flooding 

 were dominated by baldcypress (Taxodium dis- 

 ticlntm) and tupelo (Nyssa aquatica or N. syl- 

 vcitica var hifloni) and typically had sparse 

 understories. 



Most southern forested wetlands fall in the 

 broad category of bottomland hardwoods, char- 

 acterized and maintained by a natural hydrolog- 

 ic regime of alternating annual wet and dry peri- 

 ods and soils that are saturated or inundated 

 during a portion of the growing season. 

 Variations in elevation, hydroperiod, and soils 

 result in a mosaic of plant communities across a 

 floodplain. Wharton et al. (1982) classified bot- 

 tomland hardwoods into 75 community types, 

 including forested wetland types such as 

 Atlantic white cedar hogs {Chamuecyparis thy- 

 oides). red maple {Acer rubnim var driini- 

 niondii) and cypress-tupelo swamps, pocosins, 

 hydric hammocks, and Carolina bays. 



Realistic estimates of the original extent of 

 forested wetlands are not available because 

 accurate records of wetlands were not main- 

 tained until the early 20th century, and many 

 accounts of wetland size were little more than 

 speculation (Dahl 1990). Klopatek et al. (1979) 

 estimated the precolonial forested wetland area 

 of the United States to be about 27.2 million ha 

 (67.2 million acres), but Abemathy and Turner 

 (1987) suggested that this figure was low 

 because it ignored small isolated wetlands. 



Status 



Estimates of the current forested wetland 

 area vary. Shaw and Fredine (1956) estimated 

 that as of the mid- 1950"s, the United States had 

 about 19.1 million ha (47.2 million acres) of 

 forested wetlands. Frayer et al. ( 1983) reported 

 a similar total. 20.1 million ha (49.7 million 

 acres), as of the mid-1970's. Between 1940 and 

 1960. the area of southern bottomland hard- 



woods increased from about 14.8 to 15.1 mil- 

 lion ha (36.6 to 37.3 million acres) but declined 

 to 12.5 to 13.1 million ha (30.9 to 32.4 million 

 acres) by the mid-197()"s (Hefner and Brown 

 1985; Turner etal. 1988). By the mid-1980's, an 

 additional 1.4 million ha (3.5 million acres) of 

 forested wetlands were lost, mostly from the 

 southeastern United States. 



The Southeast (including Alabama, 

 Arkansas, Florida, Georgia, Kentucky, 

 Louisiana. Mississippi. North Carolina. South 

 Carolina, and Tennessee) makes up only 16% of 

 the surface area of the contemiinous United 

 States yet accounts for about 47% of the total 

 wetland area and 65% of the forested wetland 

 area (Hefner and Brown 1985). Fifteen percent 

 of the land surface of the Southeast can be cat- 

 egorized as wetlands, whereas only 5% of the 

 land surface on a national basis is wetlands. 



Before the mid-l970"s. about 54% of palus- 

 trine wetland losses on a national basis were in 

 forested areas. Palustrine wetlands include all 

 nontidal wetlands dominated by trees, shrubs, 

 persistent emergents. emergent mosses or 

 lichens, and all such wetlands that occur in tidal 

 areas where salinity due to ocean-derived salts 

 is below 0.5 ppt (Cowardin et al. 1979). 

 Between the mid-l950"s and the mid-1970's, 

 more than 2.2 million ha (5.4 million acres) of 

 palustrine forested wetlands were lost within 

 the Southeast, accounting for 92% of the 

 national loss for this wetland type (Hefner and 

 Brown 1985). Since the mid-1970's, loss of 

 forested wetlands has accounted for 95% of all 

 palustrine wetland losses (Dahl et al. 1991 ). 



Despite dramatic losses since the beginning 

 of the colonial period, southern forested wetlands 

 currently account for about 36% of all wetlands 

 and 60% to 65% of all forested wetlands in the 

 contemiinous United States (Hefner and Brown 

 1985; Dahl et al. 1991). Although loss rates 

 have declined recently, most wetland acreage 

 lost every year in the United States is from 

 southern forested wetlands (Alig et al. 1986). 



The most dramatic wetland loss in the entire 

 nation has occurred in the forested wetlands of 

 the Lower Mississippi River Alluvial 

 Floodplain (LMRAF). This vast wetland 

 extends nearly 1.000 km (621 mi) from the con- 

 fluence of the Mississippi and Ohio rivers to the 

 Gulf of Mexico and originally covered more 

 than 10.1 million ha (25.0 million acres; Hefner 

 and Brown 1985). About 8 million ha ( 19.8 mil- 

 lion acres) of this area were forested wetlands in 

 Arkansas, Louisiana, and Mississippi. Recent 

 estimates reveal that fewer than 2 million ha 

 (4.9 million acres) of forested wetlands remain 

 in the LMRAF (The Nature Conservancy 1992). 

 and the remaining portions of the original area 

 are extremely fragmented (Fig. 2) and have lost 



