Biological Services Prograii 



Classification of 



Wetlands and 



Deepwater Habitats 



of the United States 



Fish and Wildlife Service 



U.S. Department of ttie Interior 



Fig. 2. The Fish and Wildhfe Service's official wetland classification 

 report . 



In developing an ecologically sound definition of wet- 

 land, it was acknowledged that "there is no single, cor- 

 rect, indisputable, ecologically sound definition for 

 wetlands, primarily because of the diversity of wetlands 

 and because the demarcation between dry and wet envi- 

 ronments lies along a continuum" (Cowardin. et al. 

 1979). Previous wetland definitions grew out of different 

 needs for defining wetlands among various disciplines, 

 e.g., wetland regulators, waterfowl managers, hydrolo- 

 gists, flood control engineers and water quality experts. 

 The Service needed a definition that would allow accurate 

 identification and delineation of the Nation's wetlands for 

 resource management purposes. 



The Service specifically defines wetlands as follows: 



"Wetlands are lands transitional between terrestrial 

 and aquatic systems where the water table is usually 

 at or near the surface or the land is covered by 

 shallow water. For purposes of this classification 

 wetlands must have one or more of the following 

 three attributes: 1) at least periodically, the land 

 supports predominantly hydrophytes; 2) the sub- 

 strate is predominantly undrained hydric soil; and 

 3) the substrate is nonsoil and is saturated with 

 water or covered by shallow water at some time 

 during the growing season of each year." 

 (Cowardin, et al. 1979). 



In defining wetland from an ecological standpoint, the 

 Service emphasizes three key attributes of wetland: I) 



hydrology — the degree of flooding or soil saturation, 2) 

 wetland vegetation (hydrophytes), and 3) hydric soils. 

 All areas considered wetland must have enough water at 

 some time during the growing season to stress plants and 

 animals not adapted for life in water or saturated soils. 

 Most wetlands also have hydrophytes and hydric soils 

 present. The Service is preparing a list of hydrophytes 

 and the Soil Conservation Service is developing a list of 

 hydric soils to help further define wetland. 



It is interesting to note that a similar approach to wet- 

 land definition was recently used in a Federal court case 

 in Louisiana to make a legal wetland determination (Scott 

 1979). In his ruling, the judge decided that the area in 

 dispute constituted wetland according to Section 404 of 

 the Clean Water Act because: 1) records showed that 

 virtually all of the tract was flooded every other year 

 (hydrology criterion), 2) the soil types were classified as 

 wetland soils, with two exceptions where information 

 was inadequate (hydric soil criterion), and 3) vegetation 

 capable of surviving and reproducing in wetlands pre- 

 dominated the site (hydrophyte criterion). Thus, the ratio- 

 nale for using these three key attributes now has legal 

 precedent. 



Particular attention should be paid to the reference to 

 flooding or soil saturation during the growing season in 

 the Service's definition. When soils are covered by water 

 or saturated to the surface, free oxygen is usually not 

 available to plant roots. Most plant roots must have ac- 

 cess to free oxygen for respiration and growth; flooding 

 during the growing season presents problems for the 

 growth and survival of most plants. In a wetland situa- 

 tion, plants must be adapted to cope with these stressful 

 conditions. If flooding occurs only in winter when the 

 plants are donnant, there is little or no effect on them. 



It is important to note that the Service does not include 

 permanently flooded deepwater areas as wetland. In- 

 stead, these waterbodies (generally deeper than six feet) 

 are defined as deepwater habitats, since water and not air 

 is the principal medium in which dominant organisms 

 must live. 



In summary, the Service has developed a scientifically 

 sound definition of wetland based on the degree of flood- 

 ing or soil saturation and the presence of wetland plants 

 and/or hydric soils. It is the product of four years of field 

 testing and review by the scientific community. Conse- 

 quently, the Service's concept of wetland is being widely 

 accepted as the national and international standard for 

 identifying wetland. 



References 



Cowardin, L.M.. V. Carter, F C. Goiet, and E.T. LaRoe. 1979. Classi- 

 fication of Wetlands and Deepwater Habitats of the United States. 

 U.S. Fish and Wildlife Service. FWS/OBS-79/31. 103 pp. 



Scott, N.S. 1979. Opinion. Civil Action No. 78-1428. The Avoyelles 

 Sportsmen's League. Inc.. et. al. v. Clifford L. Alexander, et. al. 

 U.S. District Court. Western District of Louisiana, Alexandria Divi- 

 sion. 20 pp. 



