A New Riparian Classification

The aforementioned FWS classification system for wetlands and deep-water habitats (Cowardin etal . 1979) represents the current state of the art in official federal attempts to classify these habitat-types for inventory (in the National Wetlands Inventory), mapping, and protection of the systems. The coauthors of that important publication are eastern investigators and therefore used terms such as "bottomland hardwoods," "wooded swamps," and other regional terms, but riparian was never used. This, in effect, excluded many of the riparian wetlands in the vast region from the Great Plains westward (more than half the United States), with the possible exception of the lush Pacific Northwest. By the standards of some investigators in the wetter, more humid East, many of these areas are not considered wetlands. However, when compared to the surrounding drylands they are unquestionably wetlands, possessing inordinately high wildlife and recreational values and providing premium "living sites" for humans as well as plants and animals.

There are some obvious visual differences between most eastern and western wetlands, but there are also strikingly far-ranging similarities (Johnson etal . in press b). For example, western riparian wetlands are commonly highly visible, more heavily vegetated areas, contrasting sharply with the surrounding dry uplands. This is due largely to the fact that a high percentage of the woody species occurring in these western wetlands show different growth forms from those of surrounding dryland (upland) communities. By contrast, eastern riparian wetlands, along the bottoms of deciduous woodlands, are often not readily apparent because the vegetation growth forms of both habitats are very similar. Eastern investigators, however, have pointed out that the species composition in these eastern riparian woodlands is different from that of the surrounding upland communities (Shelford 1963).

A plethora of other publications have compared species richness and productivity of riparian with upland zones (Johnson and Jones 1977; Johnson and McCormick 1978). Although comparative differences between riparian wetlands and adjacent uplands may not be as extreme for the East as the West, reference to published papers quickly demonstrates that eastern and western riparian systems share a common factor of greater wildlife and recreational importance than surrounding uplands. In addition to the two aforementioned riparian symposia, other publications demonstrating the importance of eastern as well as western riparian systems include a series of national and regional nongame bird symposia conducted by the USDA Forest Service (FS) and bird censuses published quarterly in "American Birds." Johnson (1978b) has shown a differential dependency of avifaunas on riparian zones that is related to regional and local aridity in the Southwest.

Swift and Barclay (1980) demonstrate comparable riparian destruction for both the East and the West (commonly from 70 to 90%). For example, the Sacramento River drainage has an estimated riparian vegetation loss in excess of 98%, while that for southeastern Missouri is approximately 96%. The East apparently still has larger tracts of riparian vegetation left because there were more there originally.

Herein lies the crux of the matter, for in deleting western riparian wetlands from a national inventory, one of the main objectives of the inventory is not met. That objective is to provide practical and legal protection for these wetlands and their attendant ecosystems. Although other programs, such as floodplain zoning and policies of various agencies (see the position papers in Johnson and McCormick 1978), are providing some protection for riparian wetlands, all possible attempts must be made to properly manage these endangered riparian ecosystems.

The "riparian movement" to conserve riparian wetlands is often considered a western concern. However, we have just demonstrated why there is good reason for the East to be equally, or perhaps even more, concerned. Therefore, we present a classification scheme for riparian wetlands which is compatible with the FWS wetlands classification system (figs. 1 and 2). The palustrine system would be the point at which our riparian subsystems would be interfaced with that system (fig. 1). The complexity of these riparian ecosystems has previously defied assignment of subsystems. Table 3 provides our definitions for "riparian" and the subsystems, "hydroriparian," "mesoriparian," and "xeroriparian."

Previous to the 1970s, concerns were largely with clearing riparian zones to allow for "better utility." "Phreatophyte" was the word commonly used instead of riparian to describe vegetation (Johnson and Carothers 1982) for channelization, flood control, water and power projects, and other "water salvage" operations. Today,

Figure l.
Riparian subsystems superimposed on the National Wetlands
Classification System (modified from Cowardin  et al . 1979). * In
more than 25 references checked (standard dictionaries; ecological,
geological, and hydrological dictionaries; and scholarly works on
aquatic ecosystems, the following consensus is established.
Riverine: a) of or pertaining to a river (including the banks); b)
located on or inhabiting the banks of a river. Fluvial: of, pertaining
to, or inhabiting a river or stream. (See Reid and Wood 1976.)

Figure 2.
Riparian subsystems and classes
(modified after Cowardin et al . 1979).

however, the importance of riparian areas to regional ecosystem maintenance, complexity, and diversity has become evident. While there are still riparian areas to be protected from the insidious destruction that has already reduced this habitat-type to but a small portion of its original coverage, any classification system must consider the entire breadth of the riparian continuum. Our proposed system considers this breadth, extending from dry desert arroyos, and those plants and animals dependent upon their ephemeral water sources, to permanent bodies of water, and perennial marshes and streams.