of Water Chemistry Modifiers, adapted from the Venice System, is used to describe the salinity of 

 the water. Fresh waters are further divided on the basis of pH. Use of a hierarchical system of soil 

 modifiers taken directly from U.S. soil taxonomy is also required. Special modifiers are used where 

 appropriate: excavated, impounded, diked, partly drained, farmed, and artificial. 



Regional differences important to wetland ecology are described through a regionalization that com- 

 bines a system developed for inland areas by R. G. Bailey in 1976 with our Marine and Estuarine 

 provinces. 



The structure of the classification allows it to be used at any of several hierarchical levels. Special 

 data required for detailed application of the system are frequently unavailable, and thus data gather- 

 ing may be prerequisite to classification. Development of rules by the user will be required for specific 

 map scales. Dominance Types and relationships of plant and animal communities to environmental 

 characteristics must also be developed by users of the classification. Keys to the Systems and Classes 

 are furnished as a guide, and numerous wetlands and deepwater habitats are illustrated and classified. 

 The classification system is also compared with several other systems currently in use in the United 

 States. 



The U.S. Fish and Wildlife Service conducted an inven- 

 tory of the wetlands of the United States (Shaw and 

 Fredine 1956) in 1954. Since then, wetlands have under- 

 gone considerable change, both natural and man related, 

 and their characteristics and natural values have become 

 better defined and more widely known. During this inter- 

 val, State and Federal legislation has been passed to 

 protect wetlands, and some Statewide wetland surveys 

 have been conducted. 



In 1974, the U.S. Fish and Wildlife Service directed its 

 Office of Biological Services to design and conduct a new 

 National inventory of wetlands. WTiereas the single pur- 

 pose of the 1954 inventory was to assess the amount and 

 types of valuable waterfowl habitat, the scope of the new 

 project is considerably broader (Montanari and Townsend 

 1977). It will provide basic data on the characteristics and 

 extent of the Nation's wetlands and deepwater habitats 

 and should facilitate the management of these areas on 

 a sound, multiple-use basis. 



Before the 1954 inventory was begun, Martin et al. 

 (1953) had devised a wetland classification system to serve 

 as a framework for the National inventory. The results 

 of the inventory and an illustrated description of the 20 

 wetland types were published as U.S. Fish and Wildlife 

 Service Circular 39 (Shaw and Fredine 1956). This cir- 

 cular has been one of the most common and most influen- 

 tial documents used in the continuous battle to preserve 

 a critically valuable but rapidly diminishing National 

 resource (Stegman 1976). However, the shortcomings of 

 this work are well known (e.g., see Leitch 1966; Stewart 

 and Kantrud 1971). 



In attempting to simplify their classification, Martin et 

 al. (1953) not only ignored ecologically critical differences, 

 such as the distinction between fresh and mixosaline in- 

 land wetlands but also placed dissimilar habitats, such as 

 forests of boreal black spruce (Picea mariana) and of 



southern cypress-gum (Taxodium distichum-Nyssa 

 aquatica) in the same category, with no provisions in the 

 system for distinguishing between them. Because of the 

 central emphasis on waterfowl habitat, far greater atten- 

 tion was paid to vegetated areas than to nonvegetated 

 areas. Probably the greatest single disadvantage of the 

 Martin et al. system was the inadequate definition of types, 

 which led to inconsistencies in application. 



Numerous other classifications of wetlands and deep- 

 water habitats have been developed (Stewart and Kan- 

 trud 1971; Golet and Larson 1974; Jeglum et al. 1974; 

 Odum et al. 1974; Zoltai et al. 1975; Millar 1976), but most 

 of these are regional systems and none would fully satisfy 

 National needs. Because of the weaknesses inherent in 

 Circular 39, and because wetland ecology has become 

 significantly better understood since 1954, the U.S. Fish 

 and Wildlife Service elected to construct a new National 

 classification system as the first step toward a new Na- 

 tional inventory. The new classification, presented here, 

 has been designed to meet four long-range objectives: (1) 

 to describe ecological units that have certain homogeneous 

 natural attributes; (2) to arrange these units in a system 

 that will aid decisions about resource management; (3) to 

 furnish units for inventory and mapping; and (4) to pro- 

 vide uniformity in concepts and terminology throughout 

 the United States. 



Scientific and common names of plants (Appendix A) 

 and animals (Appendix B) were taken from various sources 

 cited in the text. No attempt has been made to resolve 

 nomenclatorial problems where there is a taxonomic 

 dispute. Many of the terms used in this classification have 

 various meanings even in the scientific literature and in 

 some instances our use of terms is new. We have provided 

 a glossary (Appendix C) to guide the reader in our usage 

 of terms. 



