Southern Forested Wetlands

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Southern Forested Wetlands
		by *B.D. Keeland* National Biological Service *James A. Allen* National Biological Service *Virginia V. Burkett* National Biological Service

European settlers in many parts of the southern United States encountered a landscape largely comprising forested wetlands. These wetlands were a major feature of river floodplains 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). Based on the accounts of pre-20th-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 precolonial standards (Wright and Wright 1932). These early travelers described vast unbroken forests of oaks, ashes, maples (Quercus, Fraxinus, 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 distichum) and tupelo (Nyssa aquatica or N. sylvatica var biflora) and typically had sparse understories.

Fig. 1. Approximate distribution of forested wetlands along rivers and streams in the southeastern United States prior to European colonization (Putnam et al. 1960).

Most southern forested wetlands fall in the broad category of bottomland hardwoods, characterized and maintained by a natural hydrologic regime of alternating annual wet and dry periods 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 bottomland hardwoods into 75 community types, including forested wetland types such as Atlantic white cedar bogs (Chamaecyparis thyoides), red maple (Acer rubrum var drummondii) 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 maintained 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 Abernathy 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 hardwoods increased from about 14.8 to 15.1 million 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-1970's (Hefner and Brown 1985; Turner et al. 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 conterminous 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 categorized as wetlands, whereas only 5% of the land surface on a national basis is wetlands.
Before the mid-1970's, about 54% of palustrine 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-1950'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 conterminous 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 confluence 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 million 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 many of their original functions (Mitsch and Gosselink 1993). Also, alterations in hydrology and poor timber management practices have resulted in a degraded condition of many of the remaining forests (Alig et al. 1986).

Fig. 2. Distribution of forested wetlands along the Lower Mississippi River: (a) Precolonial extent based on Putnam et al. (1960); (b) recent extent based on 1982 data (data source: U.S. Fish and Wildlife Service, Vicksburg, Mississippi).

Turner et al. (1988) reported annual loss rates of 3.1% for forested wetlands in Arkansas, 0.9% for Louisiana, and 0.5% for Mississippi from 1960 to 1975. Recent U.S. Forest Service inventories indicate continued annual loss rates of 0.7% and 1.0% for the oak-gum-cypress forest type in the Louisiana and Mississippi portions of the LMRAF (May and Bertelson 1986; Kelly and Sims 1989; Vissage et al. 1992).
Causes of Loss
Since colonial times, wetlands have been regarded as a menace and a hindrance to land development: wastelands that were valuable only if drained. During the mid-19th century, Congress passed the Swamp Lands Acts of 1849, 1850, and 1860, granting swamp and periodically flooded bottomlands to the states. Five southern states received 16.7 million ha (41.3 million acres) for draining. By 1960, over 40 million ha (98 million acres) of former wetland area in the United States were under drainage (Turner et al. 1988). Most wetlands were drained for conversion to agriculture; such conversions account for 87% of our national wetland losses.
Large-scale federal navigation, flood-control, and drainage projects have played a large role in these conversions by making previously flood-prone lands dry enough for planting crops (USDI 1988). Other losses have resulted from construction of flood-control structures and reservoirs, mining and petroleum extraction, and urban development. A 40% increase in the population of the South between 1960 and 1980 (Alig et al. 1986) has accelerated wetland losses.
Future Prospects
A significant future threat is global climate change; in particular, sea-level rise represents a direct threat to thousands of hectares of coastal wetlands (Titus et al. 1984). Although the main effects of sea-level rise would be seen in coastal marshes, extensive areas of bottomland hardwood and swamp forest in Florida and Louisiana could be affected by increased flooding and saltwater intrusion (Titus et al. 1984; Pezeshki et al. 1987; Conner and Brody 1989).
Legislation such as the Clean Water Act and the "Swampbuster" provision of the 1985 Public Law 100-233 "Farm Bill" has slowed, but not completely prevented, the loss of forested wetlands. In the future, however, the amount of new losses of forested wetlands may be of less concern than the fragmentation and degradation of the few remaining large wetland areas.
While the amount of forested wetlands in the South is expected to continue declining, there are good prospects for restoration in some areas. Recognition of the scale and effects of bottomland hardwood losses has resulted in interest in restoration techniques. Serious restoration began in the mid-1980's, when state and federal agencies began reforesting former agricultural lands (Haynes and Moore 1988; Savage et al. 1989; Newling 1990). The pace of reforestation picked up rapidly following the establishment of the Conservation Reserve Program (CRP) and later the Wetland Reserve Program, two federal agricultural programs that provide payment to private landowners who plant trees on a portion of their land. The combined efforts of the agencies and these two agricultural programs have resulted in the planting of about 65,000 ha (160,615 acres) of bottomland hardwood forests in the southern United States since 1985. Most restoration has occurred in the LMRAF.
Prospects for a similar rate of reforestation over the coming decade appear excellent. Federal and state natural resource agencies continue to reforest their lands. In addition, they have become heavily involved in promoting reforestation on private lands through initiatives such as the Wetland Reserve Program, the U.S. Fish and Wildlife Service's Partners for Wildlife Program, and the North American Waterfowl Management Plan.
Partnerships are being sought between the forest industry, individual landowners, universities, and several state and federal agencies. Examples of such partnerships include Scott Paper Company's enrollment of 27,500 ha (67,952 acres) near Mobile, Alabama, in the Gulf Coast Joint Venture of the North American Waterfowl Management Plan, and a reforestation research project being initiated in west-central Mississippi that involves International Paper Company, the National Council of the Pulp and Paper Industry for Air and Stream Improvement, six federal agencies, and two universities.
Although there is growing concern that many reforestation projects have not been fully successful, it is clear that when properly done, reforestation can yield impressive results in the LMRAF region (Allen 1990). The technical feasibility of reforestation, along with the current environment of federal, state, and private cooperation in much of the region, suggests that the LMRAF may be one of the best areas of the country to seriously attempt a net gain of wetlands.
		For further information: B.D. Keeland National Biological Service Southern Science Center 700 Cajundome Blvd. Lafayette, LA 70506

References
Abernathy, Y., and R.E. Turner. 1987. US forested wetlands: 1940-1980. BioScience 37:721-727. Alig, R.J., H.A. Knight, and R.A. Birdsey. 1986. Recent area changes in southern forest ownerships and cover types. U.S. Forest Service, Southern Forest Experiment Station Res. Paper. SE-260. 10 pp. Allen, J.A. 1990. Establishment of bottomland oak plantations on the Yazoo National Wildlife Refuge complex. Southern Journal of Applied Forestry 14:206-210. Conner, W.H., and M. Brody. 1989. Rising water levels and the future of southeastern Louisiana swamp forests. Estuaries 12:318-323. Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deepwater habitats of the United States. U.S. Fish and Wildlife Service FWS/OBS-79/31. 103 pp. Dahl, T.E. 1990. Wetlands losses in the United States 1780's to 1980's. U.S. Fish and Wildlife Service, Washington, DC. 21 pp. Dahl, T.E., C.E. Johnson, and W.E. Frayer. 1991. Status and trends of wetlands in the conterminous United States, mid-1970's to mid-1980's. U.S. Fish and Wildlife Service, Washington, DC. 28 pp. Frayer, W.E., M.J. Monahan, D.C. Bowden, and F.A. Graybill. 1983. Status and trends of wetlands and deepwater habitats in the conterminous United States, 1950's to 1970's. Colorado State University, Fort Collins. 31 pp. Haynes, R.J., and L. Moore. 1988. Reestablishment of bottomland hardwoods within national wildlife refuges in the Southeast. Pages 95-103 in Proceedings of a conference: increasing our wetland resources. National Wildlife Federation--Corporate Conservation Council, Washington, DC. Hefner, J.M., and J.D. Brown. 1985. Wetland trends in the southeastern United States. Wetlands 4:1-11. Kelly, J.F., and M. Sims. 1989. Forest resources of Mississippi. USDA Forest Service, Southern Forest Experiment Station, Res. Bull. SO-147. 63 pp. Klopatek, J.M., R.J. Olson, C.J. Emerson, and J.L. Jones. 1979. Land use conflicts with natural vegetation in the United States. Environmental Conservation 6:192-200. May, D.M., and D.F. Bertelson. 1986. Forest statistics for Louisiana parishes. USDA Forest Service, Southern Forest Experiment Station, Res. Bull. SO-115. 59 pp.	Mitsch, W.J., and J.G. Gosselink. 1993. Wetlands, 2nd ed. Van Nostrand Reinhold, New York. 722 pp. Newling, C.J. 1990. Restoration of bottomland hardwood forests in the Lower Mississippi Valley. Restoration and Management Notes 8:23-28. Pezeshki, S.R., R.D. Delaune, and W.H. Patrick, Jr. 1987. Response of baldcypress (Taxodium distichum L. var. distichum) to increases in flooding salinity in Louisiana's Mississippi River Deltaic Plain. Wetlands 7:1-10. Putnam, J.A., G.M. Furnival, and J.S. McKnight. 1960. Management and inventory of southern hardwoods. U.S. Forest Service, Agriculture Handbook 181. 102 pp. Savage, L., D.W. Pritchett, and C.E. Depoe. 1989. Reforestation of a cleared bottomland hardwood area in northeast Louisiana. Restoration and Management Notes 7:88. Shaw, S.P., and C.G. Fredine. 1956. Wetlands of the United States. Their extent and their value to waterfowl and other wildlife. U.S. Fish and Wildlife Service Circ. 39. 67 pp. The Nature Conservancy. 1992. The forested wetlands of the Mississippi River, an ecosystem in crisis. The Nature Conservancy, Baton Rouge. 24 pp. Titus, J.G., T.R. Henderson, and J.M. Teal. 1984. Sea level rise and wetlands loss in the United States. National Wetlands Newsletter 6(5):3-6. Turner, R.E., S.W. Forsythe, and N.J. Craig. 1988. Bottomland hardwood forest land resources of the southeastern United States. Pages 13-28 in J.R. Clark and J. Benforado, eds. Wetlands of bottomland hardwood forests. Elsevier, Amsterdam, The Netherlands. USDI. 1988. The impact of federal programs on wetlands, Vol. 1. The Lower Mississippi Alluvial Plain and the Prairie Pothole region. U.S. Department of the Interior, Washington, DC. 114 pp. Vissage, J.S., P.E. Miller, and A.J. Hartsell. 1992. Forest statistics for Louisiana parishes1991. U.S. Forest Service, Southern Forest Experiment Station Resour. Bull. SO-168. 65 pp. Wharton, C.H., W.M. Kitchens, and T.W. Sipe. 1982. The ecology of bottomland hardwood swamps of the Southeast: a community profile. U.S. Fish and Wildlife Service. FWS/OBS-81/37. 133 pp. Wright, A.H., and A.A. Wright. 1932. The habitats and composition of the vegetation of Okefinokee Swamp, Georgia. Ecological Monographs 2:109-232.

References

Abernathy, Y., and R.E. Turner. 1987. US forested wetlands: 1940-1980. BioScience 37:721-727.

Alig, R.J., H.A. Knight, and R.A. Birdsey. 1986. Recent area changes in southern forest ownerships and cover types. U.S. Forest Service, Southern Forest Experiment Station Res. Paper. SE-260. 10 pp.

Allen, J.A. 1990. Establishment of bottomland oak plantations on the Yazoo National Wildlife Refuge complex. Southern Journal of Applied Forestry 14:206-210.

Conner, W.H., and M. Brody. 1989. Rising water levels and the future of southeastern Louisiana swamp forests. Estuaries 12:318-323.

Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deepwater habitats of the United States. U.S. Fish and Wildlife Service FWS/OBS-79/31. 103 pp.

Dahl, T.E. 1990. Wetlands losses in the United States 1780's to 1980's. U.S. Fish and Wildlife Service, Washington, DC. 21 pp.

Dahl, T.E., C.E. Johnson, and W.E. Frayer. 1991. Status and trends of wetlands in the conterminous United States, mid-1970's to mid-1980's. U.S. Fish and Wildlife Service, Washington, DC. 28 pp.

Frayer, W.E., M.J. Monahan, D.C. Bowden, and F.A. Graybill. 1983. Status and trends of wetlands and deepwater habitats in the conterminous United States, 1950's to 1970's. Colorado State University, Fort Collins. 31 pp.

Haynes, R.J., and L. Moore. 1988. Reestablishment of bottomland hardwoods within national wildlife refuges in the Southeast. Pages 95-103 in Proceedings of a conference: increasing our wetland resources. National Wildlife Federation--Corporate Conservation Council, Washington, DC.

Hefner, J.M., and J.D. Brown. 1985. Wetland trends in the southeastern United States. Wetlands 4:1-11.

Kelly, J.F., and M. Sims. 1989. Forest resources of Mississippi. USDA Forest Service, Southern Forest Experiment Station, Res. Bull. SO-147. 63 pp.

Klopatek, J.M., R.J. Olson, C.J. Emerson, and J.L. Jones. 1979. Land use conflicts with natural vegetation in the United States. Environmental Conservation 6:192-200.

May, D.M., and D.F. Bertelson. 1986. Forest statistics for Louisiana parishes. USDA Forest Service, Southern Forest Experiment Station, Res. Bull. SO-115. 59 pp.

Mitsch, W.J., and J.G. Gosselink. 1993. Wetlands, 2nd ed. Van Nostrand Reinhold, New York. 722 pp.

Newling, C.J. 1990. Restoration of bottomland hardwood forests in the Lower Mississippi Valley. Restoration and Management Notes 8:23-28.

Pezeshki, S.R., R.D. Delaune, and W.H. Patrick, Jr. 1987. Response of baldcypress (Taxodium distichum L. var. distichum) to increases in flooding salinity in Louisiana's Mississippi River Deltaic Plain. Wetlands 7:1-10.

Putnam, J.A., G.M. Furnival, and J.S. McKnight. 1960. Management and inventory of southern hardwoods. U.S. Forest Service, Agriculture Handbook 181. 102 pp.

Savage, L., D.W. Pritchett, and C.E. Depoe. 1989. Reforestation of a cleared bottomland hardwood area in northeast Louisiana. Restoration and Management Notes 7:88.

Shaw, S.P., and C.G. Fredine. 1956. Wetlands of the United States. Their extent and their value to waterfowl and other wildlife. U.S. Fish and Wildlife Service Circ. 39. 67 pp.

The Nature Conservancy. 1992. The forested wetlands of the Mississippi River, an ecosystem in crisis. The Nature Conservancy, Baton Rouge. 24 pp.

Titus, J.G., T.R. Henderson, and J.M. Teal. 1984. Sea level rise and wetlands loss in the United States. National Wetlands Newsletter 6(5):3-6.

Turner, R.E., S.W. Forsythe, and N.J. Craig. 1988. Bottomland hardwood forest land resources of the southeastern United States. Pages 13-28 in J.R. Clark and J. Benforado, eds. Wetlands of bottomland hardwood forests. Elsevier, Amsterdam, The Netherlands.

USDI. 1988. The impact of federal programs on wetlands, Vol. 1. The Lower Mississippi Alluvial Plain and the Prairie Pothole region. U.S. Department of the Interior, Washington, DC. 114 pp.

Vissage, J.S., P.E. Miller, and A.J. Hartsell. 1992. Forest statistics for Louisiana parishes1991. U.S. Forest Service, Southern Forest Experiment Station Resour. Bull. SO-168. 65 pp.

Wharton, C.H., W.M. Kitchens, and T.W. Sipe. 1982. The ecology of bottomland hardwood swamps of the Southeast: a community profile. U.S. Fish and Wildlife Service. FWS/OBS-81/37. 133 pp.

Wright, A.H., and A.A. Wright. 1932. The habitats and composition of the vegetation of Okefinokee Swamp, Georgia. Ecological Monographs 2:109-232.

Southern Forested Wetlands

Status

Causes of Loss

Future Prospects