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104 Wetland Classific~tion Until recently wetland classification systems were developed and designed as regional systems or designed primarily to evaluate wetlands for use as water fowl habitat (U,S. Fish and Wildlife Service). Although the regional systems and the Fish and Wildlife Service system produced valuable baseline data, it ~s not generally possible to compare wetlands on a national or international scale. Recognized wetland habitat losses prompted the Fish and Wildlife Service to initiate a l\ational we tlands inventory in 1974 to supplement and update the agency's previous inv,entory conducted in 1954. A major outcome of the most recent inventory was the development of a hierarchical taxonomic type system of classification th,at incorporates three fundamental components of wetlands: soil, hydrology and vegetation (Cowardin et al. 1979). The system has gained consider,able support after extensive peer review, comments from state and federal ;ogencies, field testing, and use during the early phases of the 1974 inventory. It has been offiCially adopted by the Fish and Wildlife Service (45 Federal Register 65322, 10-2-80) and more recently by the Soil Conservation Service pending results of field trials, and is rapidly gainIng international recognition. The primary objective of the cl.usific8l:ion system is to impose boundaries on natural and man created wetland ecosystew. for purposes of inventory, evaluation, comparison, mctnagement and llben iapplicable, mitigation of impacts to wetlands caused by Dlan's activHies. l1'1e classification system progresses fr()m SYSTEMS and SUBSYSTEllS, at the most general levels, to CLASSES, SUBCLASSES, and DC>>IINANCE TYPES at the lower levels. Additional descriptive information is given by utilizing terms called OODIFIERS at the class level and. at lower levels in th" classification hierarchy. The classification hierarchical structure for the five SYSTE~S, eight Sl.;llSYSTEHS, and seven CLASSES is illustrated in Figure ;'. Taxono:nic type artificial keys are available to classify wetlands according to sysl:em, subsystem, and class (Cowardin et al. 1979). Systems. All wetlands can be easily grouped into one of the fIve basic types of systems: marine, estuarine, riverine, lacustri.ne and palustrine, based on hydrological, chemical, biological and geomorphologic characteristics (See Figures 8-12). Riverine wetlands occur along the streambanks and shores of streams or in other situations where water is primarily restricted to a stream channel. Lacustrine wetlands are associated with the littoral zone of lakes, while palustrine wetlands are nontidal wetlands that are not associated with stream channels or lclke margins. Palustrine wetlands include a wide variety of wetlands tlu't some workers have categorized according to nutrient: content and source of inflowing water (Whigham and Bayley 1978). Subsystems. Systems are further subdivided into more specific categories called subsystems according to trsditional hydrological