Wetland Definitions: History and Scientific Basis
HISTORY OF TERMINOLOGY
The term "wetland" was not commonly used in the American vernacular until quite recently. It appears to have been adopted as a euphemistic substitute for the term "swamp" (Wright, 1907). Nineteenth-century scientists used terms such as mire, bog, and fen to describe the lands that are now called wetlands, and these terms are still used by scientists to describe specific kinds of wetland (Mitsch and Gosselink, 1986; Dennison and Berry, 1993). The term wetland has come gradually into common scientific usage only in the second half of the twentieth century.
Scientists have not agreed on a single commonly used definition of wetland in the past because they have had no scientific motivation to do so. Now, however, they are being asked to help interpret regulatory definitions of wetlands. The application of scientific principles to the definition of wetlands and to the determination of wetland boundaries could help stabilize and rationalize the application of regulations, but it does not ensure that any resultant definition will be precise in its ability to distinguish Wetlands from all other kinds of ecosystems, or in its ability to Specify the exact boundary of a wetland. Judgment and convention will continue play a role, even following full application of scientific principles. In addition, the concept of wetland has a long history in Anglo-American law and carries with it important legal implications that need to be considered in the application of any wetland definition.
Nineteenth-Century American Legislation
From the middle of the nineteenth century to recent times, Congress has passed legislation dealing with the lands now called wetlands, and in doing so has described these lands in a variety of ways.
Swamp and Overflowed Lands Acts
The U.S. Congress granted to Louisiana in 1849 certain wetlands, which were described as "those swamp and overflowed lands, which may be or are found unfit for cultivation...." (Chapter 87, An Act to aid the State of Louisiana in draining the Swamp Lands therein, 9 Stat. 352, 1849). The purpose of the statute was to "aid the State of Louisiana in constructing the necessary levees and drains to reclaim the swamp and overflowed land therein...." This statute was the prototype of a series of swampland acts by which Congress granted wetlands to the states, usually by means of a definition no more precise than the one quoted above. The statutes are codified in 43 U.S.C. §§ 981 et seq. (1988).
States with large amounts of wetland, such as Illinois, Michigan, and Florida, where only half the land was considered suitable for farming, joined a general move to have federal swamplands ceded to them (Gates, 1968). This led Congress to pass the Swamp Land Act of 1850, the intent of which was to enable Arkansas, Alabama, California, Florida, Illinois, Indiana, Iowa, Michigan, Mississippi, Missouri, Ohio, and Wisconsin to reclaim the swamplands within their boundaries (9 Stat. 519, 1850).
Before enacting the Swamp Land Act of 1850, Congress discussed the procedure for selection of swamplands. Advocates of the grants tried to assure opponents that descriptions on surveyors' plats could be the basis for selection, and that the states could finance drainage and development of the lands (Gates, 1968). The 1850 act stated that land should be transferred only when the greater part of a legal subdivision was wet and unfit for cultivation. The Land Office found many such lands, as evidenced by the ultimate transfer of 64 million acres under the act. The act's vague definition—"wet and unfit for cultivation"—led to substantial litigation. Almost 200 swampland cases reached the Supreme Court by 1888 (Gates, 1968). The confused state of the law led to a remedial act in 1855 (Hibbard, 1965).
The swampland acts largely failed to achieve their intended purpose. "In few instances in land history have the results deviated so widely from the plans. ... The Swamp Act provided a means of getting rid of land but to a trifling extent of effecting drainage. The amount of money realized by the state out of the swamp land was small" (Hibbard, 1965).
Wildlife Refuge System
Beginning late in the nineteenth century, federal and state governments and private organizations started to acquire wetlands as waterfowl sanctuaries, including The National Wildlife Refuge System, which contains extensive wetlands acquired as waterfowl habitat through legislation to protect migratory birds (Bean, 1977; Fink, 1994). The federal acquisition of wetlands was important in stemming losses of waterfowl in the 1930s (Greenwalt, 1978), but acquisition did not follow any consistent policy, nor have any definitional criteria been used regularly in determining which wetlands should be purchased. Because much of the money for purchase of wetlands was derived from the sale of duck stamps to hunters, the protection of wetlands especially important to migratory waterfowl has received priority (Bean, 1977).
Rivers and Harbors Act
From the early days of the country's history, Congress gave the U.S. Army Corps of Engineers (USACE) the task of maintaining navigation throughout the United States. This authority was codified under the Rivers and Harbors Act of 1899, which gave USACE the responsibility to regulate dredging and filling of ''navigable waters.'' This phrase, which was at one time interpreted narrowly (Silverberg and Dennison, 1993), was subsequently expanded by the courts to give USACE power to deny permits for the falling of submerged land on the basis of potential ecological damage (Want, 1989). This judicial interpretation was then extended to the water pollution legislation adopted by Congress in the 1970s, and it formed the foundation for a new legal status for wetlands.
New Legal Status
Federal authority for the general protection of wetlands developed only as recently as 1975. The source of this authority was somewhat convoluted, as described below.
Water Pollution Control Act Amendments of 1972
Even as late as 1972, Congress passed major water pollution control legislation without ever using the term "wetland." In the 1972 amendments to the Federal Water Pollution Control Act (FWPCA, later retitled the Clean Water Act), Congress gave USACE and the Environmental Protection Agency (EPA) authority to regulate water pollution in the "waters of the United States," but Congress failed to consider the application of that phrase to wetlands. The term "wetlands" was not used in the act, nor did the legislation use synonymous terms.
The legislative history did not discuss the concept of wetlands, but Congress did indicate that it would interpret the term "navigable waters" broadly.
The Senate's version of the 1972 FWPCA amendments was given by S. 2770. The Senate Committee on Public Works discussed the background of dredge-and-fill activity (FWPCA, Legislative History, Vol. 2: p. 1488). Historically, USACE had authority to regulate the discharge of "refuse" by issuance of permits under Section 13 of the Refuse Act of 1899 (33 U.S.C. § 407). This authority was largely ignored, however, until Executive Order 11574 of President Nixon directed the institution of a permit program under the terms of Section 13 of the Refuse Act "to regulate the discharge of pollutants and other refuse matter into the navigable waters of the United States or their tributaries and the placing of such matter upon the banks" (35 Fed. Reg. 19,627; 1970), which was then implemented by USACE regulation (35 Fed. Reg. 20,005; 1970).
The Senate Committee on Public Works considered integrating the permit program under Section 13 of the Refuse Act of 1899 with Section 402 of the FWPCA amendments of 1972 (FWPCA, Legislative History, Vol. 2: p. 1488). Section 402(m) of the Senate bill, S. 2770, would have transferred the 1899 Refuse Act permit program from USACE to EPA and would have treated the disposal of dredged soil like the disposal of any other pollutant. Sen. Allan Ellender's (D-Louisiana) proposed amendment, which would have retained the USACE's sole authority to issue dredge and fill permits, was successfully opposed by Sen. Edmund Muskie (D-Maine), who stated that the amendment would shift the environmental evaluation authority from EPA to USACE and that "the mission of [USACE] is to protect navigation. Its mission is not to protect the environment" (FWPCA, Legislative History, Vol. 2: p. 1389).
During the debate on S. 2770, the concept of wetlands was not mentioned explicitly, but "restoring the integrity of the nation's waters" was addressed in broad terms (FWPCA, Legislative History, Vol. 2: p. 1254). Sen. Muskie stated that "water moves in hydrologic cycles and it is essential that discharge of pollutants be controlled at the source" (FWPCA, Legislative History, Vol. 2: p. 1495).
The House amendment, H.R. 11896, established a separate USACE-administered permit program in Section 404 for the discharge of dredged or fill material into navigable waters (FWPCA, Legislative History, Vol. 1: p. 816). The House amendment said that "a determination is required that the discharge would not unreasonably degrade or endanger human health, welfare, or amenities of the marine environment, ecological systems, or economic potentialities" (FWPCA Legislative History, Vol. 1: p. 1063).
In the conference committee, the House prevailed in establishing a separate dredge-and-fill program under Section 404, but the disposal site had to be specified through the application of guidelines developed by EPA in conjunction with USACE (FWPCA, Legislative History, Vol. 1: pp. 324-25). Section 404(c) provided that EPA could prohibit disposal at a site if the discharge "will have an unacceptable adverse effect on municipal water supplies, shellfish beds, and
fisheries areas (including spawning and breeding areas), wildlife, or recreational areas" (FWPCA, Legislative History, Vol. 1: pp. 324-25). In support of the compromise, it was argued that USACE and EPA had a responsibility to "identify land-based sites for the disposal of dredged spoil and where land-based disposal was not feasible, to establish diked areas for disposal" (FWPCA, Legislative History, Vol. 2: pp. 177-78).
The conference bill amended the term "navigable waters" to "waters of the United States, including the territorial seas" (FWPCA, Legislative History, Vol. 2: p. 327). During the House debate on the conference report in October, 1972, the House stated that the new and broader definition was in line with more recent judicial opinions, which substantially expanded the concept of navigability (FWPCA, Legislative History, Vol. 1: p. 250). The conference report states that ''the conferees fully intend that the term navigable water be given the broadest possible constitutional interpretation unencumbered by agency determinations which have been made or may be made for administrative purposes" (FWPCA, Legislative History, Vol. 1: pp. 250-51).
Judicial Interpretation of the 1972 Statute
In commenting on judicial expansion of the concept of navigability, Congress was well aware that the trend of U.S. Supreme Court decisions had, in the words of one authority, reduced the idea that navigability was a limitation on federal jurisdiction to "a near fiction" (Tarlock, 1988). For example, cases such as United States v. Grand River Dam Authority, 363 U.S. 508 (1960) had extended federal jurisdiction to nonnavigable tributaries of navigable rivers.
In 1975, the Federal District Court in the District of Columbia ruled that the definition of navigable waters in Section 404 of FWPCA had the same meaning as did the broad definition used elsewhere in the statute, thus extending coverage of the act to wetlands regardless of actual navigability. Natural Resources Defense Council v. Callaway , 392 F. Supp. 685 (1975) held invalid USACE's earlier interpretation of the act, which had excluded some 85% of the nation's wetlands, and opened a new chapter in the history of wetland regulation (Tarlock, 1988). When the government accepted the new judicial interpretation of the act, USACE and EPA needed for the first time to adopt a regulatory definition of wetland.
EVOLUTION OF THE REGULATORY DEFINITIONS
Only in the 1950s were scientists beginning to use the term "wetland" as a category that would encompass terms such as bog, swamp, and marsh. Attempts of government agencies to define wetlands began at that time but developed momentum only in the 1970s.
1956 Fish and Wildlife Service Definition
The first official use of the term wetland in a government report was in 1956, when the U.S. Fish and Wildlife Service (FWS) issued Circular 39, a landmark report about the wetlands of the United States (Shaw and Fredine, 1956). Because the work was financed largely by the sale of federal duck stamps, the report focused on wetlands valuable to waterfowl, as was reflected in the definition from Circular 39:
The term "wetlands," as used in this report and in the wildlife field generally, refers to lowlands covered with shallow and sometimes temporary or intermittent waters. They are referred to by such names as marshes, swamps, bogs, wet meadows, potholes, sloughs, and river-overflow lands. Shallow lakes and ponds, usually with emergent vegetation as a conspicuous feature, are included in the definition, but the permanent waters of streams, reservoirs, and deep lakes are not included. Neither are water areas that are so temporary as to have little or no effect on the development of moist-soil vegetation. Usually these very temporary areas are of no appreciable value to the species of wildlife considered in this report.
Circular 39 described 20 types of inland fresh, inland saline, coastal fresh, and coastal saline wetlands. Several of their names were or became standard terminology among wetland scientists and are still in common use. Even though Circular 39 was officially replaced in 1979, several states continue to use modifications of the original classification system in wetland regulations because of its simplicity.
1974 Wetland Inventory Project
In 1974, FWS directed its Office of Biological Services to design and conduct a new national inventory of wetlands. To prepare for this project, a dozen wetland scientists met in Bay St. Louis, Mississippi, in January 1975 to prepare the first draft of a new classification system for the new inventory (Cowardin and Carter, 1975). Six months later, FWS convened a workshop to review the draft (Sather, 1975). Several federal agencies with wetland-related missions gave presentations at the workshop: USACE, EPA, the U.S. Geological Survey, the U.S. Forest Service, the Soil Conservation Service (SCS), the Bureau of Reclamation, the Bureau of Land Management, the National Marine Fisheries Service, the Office of Coastal Zone Management, and the Tennessee Valley Authority, as did the Canadian Wildlife Service, the Nature Conservancy, the Wildlife Management Institute, the Institute of Ecology, the Sport Fishing Institute, the Conservation Foundation, and representatives of state wetland programs (Kusler and Bedford, 1975). Thus, the new classification system was subject to diverse influences, both organizationally and geographically.
1975 USACE Proposed Definition
Meanwhile, after the 1975 Callaway decision invalidating the initial USACE regulations that had excluded most wetlands from the jurisdiction of USACE, USACE quickly issued new proposed regulations that included the first regulatory attempt to define wetlands (40 Fed. Reg. 31, 328; July 25, 1975). USACE proposed a new definition that classified wetlands by function and treated as important only those lands that performed specific wetland functions. The 1975 definition is as follows:
Wetlands are those land and water areas subject to regular inundation by tidal, riverine, or lacustrine flowage. Generally included are inland and coastal shallows, marshes, mudflats, estuaries, swamps, and similar areas in coastal and inland navigable waters. Many such areas serve important purposes relating to fish and wildlife, recreation, and other elements of the general public interest. As environmentally vital areas, they constitute a productive and valuable public resource, the unnecessary alteration or destruction of which should be discouraged as contrary to the public interest.
Wetlands considered to perform functions important to the public interest include:
Wetlands which serve important natural biological functions, including food chain production, general habitat, and nesting, spawning, rearing and resting sites for aquatic or land species;
Wetlands set aside for study of the aquatic environment or as sanctuaries or refuges;
Wetlands contiguous to areas listed in paragraph (g)(3)(ii) (a) and (b) of this section, the destruction or alteration of which would affect detrimentally the natural drainage characteristics, sedimentation patterns, salinity distribution, flushing characteristics, current patterns, or other environmental characteristics of the above areas;
Wetlands which are significant in shielding other areas from wave action, erosion, or storm damage. Such wetlands often include barrier beaches, islands, reefs and bars;
Wetlands which serve as valuable storage areas for storm and flood waters; and
Wetlands which are prime natural recharge areas. Prime recharge areas are locations where surface and ground water are directly interconnected.
As required by the Administrative Procedure Act, USACE published the proposed definition in the Federal Register and asked for comments.
1976 FWS Interim Classification
Concurrently with the work of USACE, the outcome of the 1975 FWS work
shop was published in 1976 as the "Interim Classification of Wetlands and Aquatic Habitats of the United States" (Cowardin et al., 1976), which served as a precursor to the current FWS wetlands classification system (Cowardin et al., 1979). The four authors were wetland scientists from FWS, the U.S. Geological Survey, the University of Rhode Island, and the National Oceanic and Atmospheric Administration. The introduction to the document explained their concept of wetland (Cowardin et al., 1976):
For centuries we have spoken of marshes, swamps and bogs, but only relatively recently have we attempted to group these landscape units under a single term, wetland. The need to do this has grown out of our desire: (1) to understand and describe the characteristics and values of all types of land, and (2) to wisely and effectively manage wetland ecosystems. Effective management requires legislation; out of such legislation, legal definitions are born. Unfortunately, legal definitions are usually based as much on facility and pragmatism as they are upon accuracy of meaning. Hence, legal definitions of wetland may bear little resemblance to the ecological concepts embodied in the term. There is no single, correct, indisputable, ecologically sound definition for wetland because the gradation between totally dry and totally wet environments is continuous. Moreover, no two people view the identity of any object in the same fashion. For these reasons, and because the reasons for defining wetland vary, a great proliferation of definitions has arisen. Our primary task here is to impose arbitrary boundaries on natural ecosystems for the purposes of inventory, evaluation and management. We are obliged to use sound reasoning as we attempt to describe the concepts of wetland and aquatic habitats in terms that past, present and projected future users will accept.
The concept of wetland embraces a number of characteristics, including the elevation of the water table with respect to the ground surface, the duration of surface water, soil types that form under permanently or temporarily saturated conditions, and various types of plants and animals that have become adapted to life in a "wet" environment. The single feature that all wetlands share is the presence of more soil moisture than is necessary to support the growth of most plants. This excess of water creates severe physiological problems for all plants except hydrophytes, which are adapted for life in water or in saturated soil. Rather than attempt to place arbitrary limits on the fluctuation of the water table for the purpose of defining wetland, a task of great complexity at best, it seems more reasonable to define wetland broadly and simply, and then to place limits on the concept. The definition of wetland contained in the Interim Classification is as follows:
Wetland is land where an excess of water is the dominant factor determining the nature of soil development and the types of plant and animal communities living at the soil surface. It spans a continuum of environments where terrestrial and aquatic systems intergrade. For the purpose of this classification system, wetland is defined more specifically as land where the water table is at, near or above the land surface long enough each year to promote the formation of hydric soils and to support the growth of hydrophytes, as long as other environmental conditions are favorable. Permanently flooded lands lying beyond the
deepwater boundary of wetland are referred to as aquatic habitats. In certain wetland types, vegetation is absent and soils are poorly developed or absent as a result of frequent and drastic fluctuations of surface-water levels, wave action, water flow, turbidity or extremely high concentrations of salts or other substances in the water or substrate. Wetlands lacking vegetation and hydric soils can be recognized by the presence of surface water at some time during the year and their location within, or adjacent to, vegetated wetlands or aquatic habitats.
There is great similarity between portions of this definition and the one that was adopted a year later by USACE.
1977 USACE Definition
USACE was inundated with comments on the definition of wetlands that it had proposed in 1975. As a result, its final definition of wetlands, which was issued in 1977 (42 Fed. Reg. 37, 125-26, 37128-29; July 19, 1977), was substantially revised:
Those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs, and similar areas.
In explaining the new definition, USACE emphasized four important definitional issues. First, it noted that it was making no reference to traditional high-water-line boundaries or to distinctions between fresh and salt water. "Water moves in hydrologic cycles," it said, and the pollution of any part of the aquatic system will affect the water quality of the system as a whole. "For this reason, the landward limit of Federal jurisdiction under Section 404 must include any adjacent wetlands that form the border of or are in reasonable proximity to other waters of the united States, as these wetlands are part of this aquatic system."
Second, the USACE described the frequency with which a wetland is inundated:
The reference to "periodic inundation" has been eliminated. Many interpreted that term as requiring inundation over a record period of years. Our intent under Section 404 is to regulate discharges of dredged or fill material into the aquatic system as it exists, and not as it may have existed over a record period of time. The new definition is designed to achieve this intent. It pertains to an existing wetland and requires that the area be inundated or saturated by water at a frequency and duration sufficient to support aquatic vegetation.
Third, USACE dealt with the issue of normality:
The term ["normally"] was included in the definitions to respond to those situations in which an individual would attempt to eliminate the permit review re-
quirements of Section 404 by destroying the aquatic vegetation, and to those areas that are not aquatic but experience an abnormal presence of aquatic vegetation. Several such instances of destruction of aquatic vegetation in order to eliminate Section 404 jurisdiction actually have occurred. However, even if this destruction occurs, the area still remains as part of the overall aquatic system intended to be protected by the Section 404 program. Conversely, the abnormal presence of aquatic vegetation in a non-aquatic area would not be sufficient to include that area within the Section 404 program.
But USACE said that it "did not intend, by this clarification, to assert jurisdiction over those areas that once were wetlands and part of an aquatic system, but which, in the past, have been transformed into dry land for various purposes."
Finally, USACE commented on the methods of identifying wetland vegetation. It noted that it was continuing to use the term "prevalence" so that it could eliminate reference to "those areas that have only occasional aquatic vegetation interspersed with upland or dry land vegetation." But it added language referring to vegetation ''typically adapted for life in saturated soil conditions" because the old definition, by describing the vegetation as that which required saturated soil conditions for growth and reproduction, excluded "many forms of truly aquatic vegetation that are prevalent in an inundated or saturated area, but that do not require saturated soil from a biological standpoint for their growth and reproduction."
The 1977 definition is the one currently used by USACE and EPA.
Clean Water Act of 1977
In 1977, while USACE was revising its definition, Congress was adopting major amendments to FWPCA (and renaming it the Clean Water Act [CWA]). Congress expanded Section 404 by the addition of general permit provisions, exceptions, and provisions for the delegation to the states of Section 404 permitting responsibility. Although the legislative history provides little assistance in determining what Congress meant by the new reference to wetlands, that history does illustrate the extent to which Congress understood wetland issues.
The Senate Committee on Environment and Public Works, in its report, noted that "the 1972 Federal Water Pollution Control Act exercised comprehensive jurisdiction over the Nation's waters to control pollution to the fullest constitutional extent." Quoting a 1972 Senate report, the new report stated (FWPCA, Legislative History, Vol. 4: p. 708):
that "waters move in hydrologic cycles and it is essential that discharge of pollutants be controlled at the source," and that the objective of the 1972 act is to protect the physical, chemical, and biological integrity of the Nation's waters. Restriction of jurisdiction to those relatively few waterways that are used or are susceptible to use for navigation would render this purpose impossible to achieve. The committee amendment does not redefine navigable waters. In-
stead, the committee amendment intends to assure continued protection of the Nation's waters, but allows States to assume the primary responsibility for protecting those lakes, rivers, streams, swamps, marshes, and other so-called phase I waters.
During the Senate debate, Sen. Lloyd Bentsen (D-Texas) introduced an amendment to Section 404 that would have redefined and narrowed the term "navigable waters" and would have defined the term "adjacent wetlands." Under Sen. Bentsen's amendment the discharge of dredged or fill material into waters other than "navigable waters" and in wetlands other that ''adjacent wetlands" would not have been prohibited unless USACE and the governor of a state entered into a joint agreement that the waters should be regulated. In support of his amendment, Sen. Bentsen stated that Section 404 had "assumed an importance that extends far beyond dredge and fill activities; it has become synonymous with Federal overregulation; overcontrol, cumbersome bureaucratic procedures, and a general lack of realism'' (FWPCA, Legislative History, Vol. 4: p. 901). The amendment drew some substantial support because of the court decision in N.R.D.C. v. Callaway, which had provoked opposition from agricultural and forestry interests (FWPCA, Legislative History, Vol. 4: pp. 931-936). Ultimately, the Senate rejected Sen. Bentsen's amendment, 51-45. Sen. Muskie stated that the Bentsen amendment, if adopted, would have left 85% of the wetlands of the United States unprotected (FWPCA, Legislative History, Vol. 4: p. 948).
The House committee proposed an amendment that was similar to the Bentsen amendment in that it would have limited the requirement for a permit to "navigable waters and adjacent wetlands," and would have defined "navigable waters" to mean those used or usable with reasonable improvement to transport interstate or foreign commerce (FWPCA, Legislative History, Vol. 4: p. 1195). In the debate, Rep. Smith (D-Iowa) supported the amendment that was designed to reverse the "March 25, 1975, District of Columbia District Court decision" (FWPCA, Legislative History, Vol. 4: pp. 1346-47).
The conference substitute left intact the prior definition of navigable waters (FWPCA, Legislative History, Vol. 3: p. 284), but also added subsection (g), which allowed a state to assume the authority to issue dredge-and-fill permits if EPA approved. The only place in the bill in which the term "wetland" appeared was in Section 404(g)(1), which dealt with the potential delegation to the states of administration of the section 404 program. It provided that the governor of a state could administer a dredge-and-fill permit program for navigable waters "other than those waters which are presently used, or are susceptible for use in their natural condition or by reasonable improvement as a means to transport interstate or foreign commerce shoreward to their ordinary high water mark, including all waters which are subject to the ebb and flow of the tide shoreward to their mean high water mark, or mean higher high water mark on the west coast, including wetlands adjacent thereto." This language meant that if EPA approved
delegation of permitting authority to a state, USACE would retain permitting authority over tidal waters and adjacent wetlands, and perhaps over large, inland navigable bodies of water such as the Great Lakes, while the state would have permitting authority over all other types of navigable waters, including nontidal wetlands.
The House debate on the conference report reflected the dissatisfaction of some members with the greatly expanded authority given to USACE by the courts, and the language relating to state delegation in Section 404(g) caused the members of the House to exhibit some jurisdictional confusion. On the other hand, some legislators expressed concern over the possibility of giving the states increased jurisdiction over wetlands. Rep. John Dingell (D-Michigan) said: "I personally do not think that transferring permit authority to the states in this regard is sound.... This is the dumping of dredge material and fill in our Nation's waterways and most importantly in our estuaries and wetlands which are important to our fish and wildlife resources, and yes, to pollution control. The states have shown a remarkable penchant toward development of those valuable and irreplaceable wildlife resources" (FWPCA, Legislative History, Vol. 3: p. 417). The result of this legislative process was to leave the Section 404 program substantially intact and to give the administering agencies little new guidance for the definition or delineation of wetlands.
1979 Cowardin Report
During this Same period, FWS continued to work on its new definition and classification system to replace Circular 39. In 1979, the final report of the study that began in 1974 was issued under the title "Classification of Wetlands and Deepwater Habitats of the United States" (Cowardin et al., 1979).
The definition of wetlands contained in the final version of the new classification was substantially edited from the interim version, but contained the same basic concepts:
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 substrate 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.
The limit between wetland and upland was further defined as:
the boundary between land with predominantly hydrophytic cover and land with predominantly mesophytic or xerophytic cover; (2) the boundary between soil that is predominantly hydric and soil that is predominantly nonhydric; or
(3) in the case of wetlands without vegetation or soil, the boundary between land that is flooded or saturated at some time each year and land that is not.
Limits between wetland and deepwater systems also were distinguished, as they had been in the Circular 39 definition. Although the boundary between wetland and deepwater systems is important for inventory purposes, it is rarely at issue in regulatory disputes, and is not referred to at all in the regulatory definitions of wetland.
The 1979 report is significant for several reasons. First, it introduced the concepts of hydrophytes and hydric soils, and it was the impetus for the development of official lists of these (Chapter 5). Second, it embraced the concept of predominance (hydrophytes or undrained hydric soils had to be "predominant" in wetlands). Third, it introduced the use of three factors for wetland identification: soils, vegetation, and hydrology. Finally, it included some areas that lack vascular plants or soils. Each of these concepts was later developed in one or more of the wetland delineation manuals.
The hydrologic portion of the FWS definition is invoked only when the substrate is nonsoil, in which case the wetland must be "flooded or saturated at some time during the growing season of each year." This is the first appearance in a wetland definition of the concept of inundation or saturation during the growing season. Duration of flooding or saturation is not specified, although the classification system contains "water regime modifiers" that describe the duration of flooding in general terms.
Riverside Bayview Decision
Ten years after USACE began to regulate wetlands intensively, the Supreme Court, in United States v. Riverside Bayview Homes, 474 U.S. 121, 138 (1985), held that USACE had jurisdiction over discharges into wetlands adjacent to navigable waters, but it expressly left open the question of jurisdiction over wetlands that were not adjacent.
The Court looked at the legislative history of FWPCA and concluded that Congress's broad concern for protection of water quality and aquatic ecosystems made it reasonable for USACE to interpret the term "waters" to encompass wetlands adjacent to navigable waters. The Court also looked at the language in Section 404(g) concerning "adjacent wetlands" and construed the language to indicate that Congress intended "waters'' to include "adjacent wetlands.'' However, the Court stated that "section 404(g)(1) does not conclusively determine the construction to be placed on the use of the term 'waters' elsewhere in the Act (particularly in section 502(7)), which contains the relevant definition of 'navigable waters'."
FOOD SECURITY ACT
In 1985, in response to the concern of agricultural interests about wetland issues, Congress enacted specific definitions of wetlands, hydric soils, and hydrophytic vegetation for Department of Agriculture programs. The "swampbuster" provisions of the Food Security Act (FSA) (P.L. 99-198, 99 Star. 1504) were enacted on Dec. 23, 1985, with the premise that persons converting wetlands to agriculture would be denied agricultural loans, payments, and benefits. Further amendments were made by the Food, Agricultural, Conservation, and Trade Act of 1990 (P.L. 101-624, 104 Stat. 3587). The legislation now includes the following definition (16 U.S.C. § 801(a)(16)):
The term "wetland," except when such term is part of the term "converted wetland," means land that—
has a predominance of hydric soils;
is inundated or saturated by surface or ground water at a frequency and duration sufficient to support a prevalence of hydrophytic vegetation typically adapted for life in saturated soil conditions; and
under normal circumstances does support a prevalence of such vegetation.
For purposes of this Act and any other Act, this term shall not include lands in Alaska identified as having high potential for agricultural development which have a predominance of permafrost soils.
FSA directs the U.S. Department of Agriculture to develop criteria and lists of hydric soils and hydrophytic vegetation, and defines those terms as follows:
"Hydric soil" means soil that, in its undrained condition, is saturated, flooded, or ponded long enough during a growing season to develop an anaerobic condition that supports the growth and regeneration of hydrophytic vegetation.
"Hydrophytic vegetation" is a plant growing in
a substrate that is at least periodically deficient in oxygen during a growing season as a result of excessive water content.
The 1987 rule implementing FSA (7 C.F.R. § 12) further defines hydric soils as those that meet the criteria set forth in "Hydric Soils of the United States 1985" (National Technical Committee for Hydric Soils). It also states that a plant is considered to be a hydrophytic plant species if it is listed in "National List of Plant Species that Occur in Wetlands" (P.B. Reed, 1988), and it includes the formula for calculating the prevalence index that is used in determining whether hydrophytic plants predominate.
STATUS OF DEFINITIONS
Three definitions of wetlands are currently used in the United States: the 1977 USACE definition, the Natural Resources Conservation Service definition (1985 FSA definition), and the 1979 FWS definition, as derived from Cowardin et al. (1979). The USACE and FSA definitions have direct regulatory significance through implementation of the CWA and FSA. The 1979 FWS definition, although not directly regulatory, is also significant because it captures the perspective of a federal agency that interacts constantly with the regulatory agencies, comments on permits, and is charged with reporting to Congress on the status of the nation's wetlands.
1977 USACE Definition
The 1977 USACE definition references the importance of inundation and saturation—hydrologic conditions—as the prime determinant of wetland status. This definition also cites vegetation as a critical indicator of the hydrologic conditions that lead to the formation of wetlands. Although it refers to soil, it does not indicate that the physical and chemical condition of soil (or, more properly, substrate) is a critical criterion for distinguishing wetlands from other environments.
In referring specifically to soil, the 1977 USACE definition implies that wetlands cannot be supported on nonsoil substrates. Although most wetlands do form on soils and are specifically associated with hydric soils, a few types occupy substrates that are nonsoil or nonhydric soil (Chapter 5). Another difficulty is the specific reference to vegetation, which is commonly interpreted to mean vascular plants. For most regions of the United States, this is a reasonable approach, but some regional wetland types lack vascular plants entirely and instead show their wetland status through the presence of algae, mosses, and even invertebrates that require the basic hydrologic conditions associated with saturation or inundation of the substrate (Chapter 5). Finally, the 1977 USACE definition does not make sufficiently clear that wetlands are ecosystems, i.e., functionally integrated systems that reflect the hydrologic conditions leading to their formation.
1985 FSA Definition
The FSA definition emphasizes the importance of hydric soil as a critical indicator of wetland status. It implies that wetlands cannot exist without hydric soils. The vast majority of wetlands do in fact have hydric soils, and they can be identified by the presence of hydric soils in the absence of hydrologic alterations. Some wetlands do, however, develop on substrates that are not now classified as hydric soil (Chapter 5). Given that the FSA definition of wetlands was intended for application to agricultural areas, the emphasis on hydric soil is understand-
able. At the same time, it is clear that omission of wetlands lacking hydric soil renders the FSA definition inadequate for full coverage of wetlands (Chapter 6). In addition, the reference to vegetation, which is commonly presumed to be a reference to vascular plants, shows the same weakness as the 1977 USACE definition through its omission of wetlands that show a dominance of other indicator organisms that can be shown by field studies to be clearly indicative of wetland conditions. The FSA definition also does not underscore the importance of hydrologic factors in producing and maintaining wetlands.
The FSA definition of wetlands explicitly excludes Alaskan wetlands that have high potential for agriculture (Chapter 6). The connection of the FSA definition, and potentially any regulatory definition, to policy is evident from this example. Policy can legitimately dictate exclusion of any class of wetlands, but it should be clear that such exclusions are not based on scientific distinctions related to the characteristic properties of wetlands.
1979 FWS Definition
The FWS definition from the 1979 report of Cowardin et al. refers to wetlands as "transitional between terrestrial and aquatic systems," and in doing so introduces a potential complication that is not found in the 1977 USACE or the 1985 FSA definition. Wetlands are not always transitional either geographically or functionally. They are often found between deepwater and upland features of the landscape, but not necessarily. For example, wetlands sustained by ground water often are not bounded by deepwater habitats, and some wetlands that are bounded on all sides by water do not adjoin uplands. Furthermore, it is not always justifiable to invoke the concept of transition for the functional characteristics of wetlands. Functions and processes overlap across wetland boundaries, but they are not necessarily transitional. For example, the accumulation of organic matter under anaerobic conditions occurs not only in wetlands but also at the bottoms of lakes, and the retention of nutrients that occurs in wetlands can also occur in uplands and deepwater systems.
The special strengths of the 1979 FWS definition include its specific reference to nonsoil environments that can support wetlands and its reference to "systems," a critical concept that should always be coupled to wetland definitions.
FRAME OF REFERENCE FOR REGULATORY DEFINITIONS
The refinement and analysis of definitions is useful insofar as it focuses attention on the key characteristics of wetlands and on the factors that unify wetlands and separate them from other kinds of ecosystems. Of the three broadly recognized definitions of wetland, two are regulatory (USACE and FSA) and one serves as the basis for national assessment and mapping of wetlands (FWS).
These definitions reflect, in varying degrees, the intent of legislators, the missions of government agencies, and the influences of politics and administration on the evaluation of a technical issue. For these reasons, a separately derived reference definition is useful as a basis for the evaluation of regulatory definitions. A reference definition also highlights the substantive issues that need to be considered in the development of delineation manuals or in the design of research programs that are intended to make delineation more efficient and reliable.
The Committee on Wetlands Characterization has developed a broad reference definition of wetland:
A wetland is an ecosystem that depends on constant or recurrent, shallow inundation or saturation at or near the surface of the substrate. The minimum essential characteristics of a wetland are recurrent, sustained inundation or saturation at or near the surface and the presence of physical, chemical, and biological features reflective of recurrent, sustained inundation or saturation. Common diagnostic features of wetlands are hydric soils and hydrophytic vegetation. These features will be present except where specific physicochemical, biotic, or anthropogenic factors have removed them or prevented their development.
All definitions, including this reference definition, are too broad to be applied directly to regulatory practice without substantial accompanying interpretation (Figure 3.1). Much of the following text of this report is devoted to a consideration of the evidence that supports the prevailing and alternative interpretations of regulatory definitions. The reference definition will provide a framework, outside of regulatory practice, against which current definitions and their interpretations can be compared.
The reference definition refers explicitly to the ecosystem concept of wetlands. The ecosystem concept, which is now being invoked widely in the management and regulation of environmental resources, acknowledges the integration of physical, chemical, and biological phenomena in the environment. Attempts to regulate, manage, protect, restore, or even identify wetlands without recognition of this underlying principle are likely to be ineffective. Consequently, the ecosystem concept is of definitional importance for wetlands.
The reference definition also recognizes the centrality of water in creating and sustaining wetland ecosystems. At the same time, the definition requires that wetlands show physical, chemical, and biological features that are manifestations of the hydrologic driving force.
The reference definition describes the biotic and physicochemical conditions of wetlands with sufficient breadth to encompass all wetlands. According to the definition, the physicochemical conditions of a wetland, which are properties of its substrate, must reflect recurrent, sustained saturation with water, but these
substrate characteristics can take a range of forms, as described in Chapter 5. The redoximorphic features of hydric soils, which develop under low redox potentials that are produced by the repeated exclusion of oxygen from the soil, are the most common and easily recognizable examples of physicochemical conditions produced by saturation. The definition leaves open the possibility that other conditions, some of which might be more subtle, typify some wetlands. For example, soils and nonsoil substrates with especially small amounts of labile organic matter might show oxygen depletion in the pore waters without developing sufficient chemical reduction to create visible redoximorphic features. Similarly, the definition specifies that wetlands will have biotic features that reflect recurrent, sustained saturation, but these features can vary broadly among wetlands. The definition thus encompasses wetlands that do not support hydrophytes, but do support unicellular algae or invertebrates that have a scientifically demonstrated requirement for recurrent, sustained saturation. Inclusive phrasing of the physicochemical and biological portions of the definition is explicitly constrained by connection with the hydrologic driving factor of the definition: Physicochemical and biotic evidence of wetlands must be demonstrably maintained by recurrent, sustained saturation of the substrate at or near the surface to fall within the definition.
The last portion of the definition makes specific reference to the two most pervasive and reliable indicators of wetlands: hydric soils and hydrophytic vegetation. The definition acknowledges that these two indicators are so likely to accompany the presence of a wetland that their absence must be specifically explained in a wetland that lacks them. The most pertinent cases will be of a regional nature, as explained in Chapters 5 and 7.
The reference definition could be reworded several ways, but in any form would need to incorporate the concept of a wetland as an integrated ecological system (an ecosystem) that is distinguished from upland and deepwater systems by recurrent, sustained shallow inundation or saturation at or near the surface, and by a substrate and biota that show evidence of this distinctive hydrologic condition.
Terminology: Parameters, Criteria, Indicators
Application of regulatory definitions of wetlands is accompanied by confusion caused by three terms: parameter, criterion, and indicator. The term "parameter" is troublesome to the discussion of wetlands. This term is derived from mathematics and statistics, for which it refers to a component of a mathematical function or statistical distribution that determines the expression of the function or distribution. Transfer of this concept to a definition of wetlands is difficult at best. Except in relation to some specialized types of wetland research, wetlands are not defined by mathematical functions, nor do properties of wetlands show good analogs to mathematical or statistical parameters.
The 1977 USACE definition of wetlands and its accompanying regulatory guidance documents are often referred to as a "three-parameter approach" to the definition of wetlands because they mention three related factors: water, soil, and vegetation. These can be referred to more clearly and correctly as factors or variables than as parameters. The reference definition endorses the use of three factors, but designates the factors more generically than does the USACE definition.
It is important that both scientific inquiry and regulatory practice related to wetlands recognize the special status of hydrologic conditions in creating and maintaining wetlands. Recurrent saturation of the substrate at or near the surface is the one condition that sustains all other characteristics of wetlands. Water at or near the surface supports the development of characteristic organisms (hydrophytic vegetation) and substrate (hydric soils), rather than the reverse. Although there is some feedback between organisms and water (Chapter 2, Figure 2.2), the primary control is of water on substrates and organisms, rather than the reverse. Removal of water destroys the wetland, regardless of substrate or organisms. Thus, in the hierarchy of control or causation, the hydrologic factor has special status.
Criteria and Indicators
A criterion is a standard of judgment or principle for testing; it must relate directly to a definition (Figure 3.1). Wetlands are associated with specific conditions (variable states) for the master variable (water) and the two primary dependent variables (substrate, biota). These specific conditions are criteria in that they correspond to boundaries or thresholds that can be used to determine whether a particular ecosystem is a wetland.
The primacy of the hydrologic criterion must be recognized explicitly when wetlands have been altered or newly created by natural or anthropogenic processes. Removal of the hydrologic basis for the wetland eliminates its potential to remain a wetland, even if hydric soils and long-lived wetland vegetation persist. Also, if the hydrologic basis for a wetland exists and can be expected to persist, but the characteristic substrate or biota have been removed or have not had time to develop, their potential future development can be presumed. When hydrology has not been altered, it is sometimes possible to infer information about hydrology from the substrate of biota. This matter is discussed more fully in Chapter 5.
Any kind of evidence that bears on the evaluation of a criterion is an indicator. Indicators vary in specificity and are sometimes hierarchical: A specific indicator can support a more general one. For example, hydric soil is a general indicator that supports the substrate criterion, and characteristic chroma, or brightness of soil color, is a specific indicator that supports the identification of hydric soil.
The most general indicators often are confused with criteria. For example, because the substrate criterion is typically satisfied by the presence of hydric soils, except where hydrology has been altered, it is tempting simply to refer to hydric soil as a criterion. The reference definition of wetlands specifies, however, that hydric soil is an indicator, albeit a powerful one, whereas the criterion is somewhat broader because it extends to substrates other than hydric soils. Similarly, hydrophytic vegetation often is called a criterion. Hydrophytic vegetation, which customarily includes only vascular plants, is the most general biological indicator for wetland status, but it is not a criterion because other biological indicators, such as algae, mosses, or invertebrates, extend beyond hydrophytic vegetation. The distinction between indicators and criteria is valuable in maintaining a connection between a definition of wetland and the use of field evidence to support identification of wetlands.
APPLICATION OF DEFINITIONS
Any regulatory definition of wetlands has full practical significance only through interpretation at three levels: criteria, indicators, and recognition of regional variation. Criteria follow directly from the definition, and each must be dealt with explicitly by any regulatory system. Indicators then develop around the criteria. At this level, the interpretation of a definition becomes multifaceted and technically complex. Each of the criteria must be expressed in terms of empirical measurements or objective observations that can be used in establishing thresholds. This raises many questions. For example, what biotic indexes will best capture the presence of a substantial abundance of wetland organisms? How should the best possible biotic indicators be balanced against indicators that are slightly less accurate but more practical to use in the field? How should wetland substrates be identified in the field? What durations and recurrences of inundation or saturation are associated with the formation of physical, chemical, and biological features of wetlands?
The development of indicators is an endless process of refinement that is facilitated by research on wetlands. Research offers the possibility of improvement in indicators, with the beneficial consequence of greater reliability and repeatability in identifying and finding the boundaries of wetlands. Indicators are subject to strong regional variation that complicates the evaluation of criteria; this complexity can be revealed only through regional studies of wetlands (Chapter 7.)
A reference definition of wetland that is derived from scientific principles may include some wetlands that the nation does not wish to regulate. Federal laws could for this reason exclude some wetlands from regulation. In such a case, a regulatory definition of wetlands might by intent fail to cover all wetlands. For this reason, it is important to maintain the distinction between a reference defini-
tion, which ignores the matter of jurisdiction, and a regulatory one, which reflects the intent of laws that do not necessarily encompass all wetlands.
The application of any definition to regulatory practice can be rational and defensible even when it is not very precise. Where the hydrologic conditions are marginally sufficient to maintain ecosystem characteristics that distinctively reflect recurrent inundation or saturation, the indicators of wetland often will be mixed, and regulatory practice must find a means of weighing indicators so that a final determination of wetland status can be made (Chapter 5). The same applies to the identification of wetland margins where the transition from wetland to upland is gradual. Although the weighing of mixed indicators is a form of judgment, and thus can be subject to multiple interpretations, the adoption of a fixed system for weighing indicators against one another can and should produce an outcome that is repeatable and in this sense reliable, even though it could be changed later as the understanding of indicators evolves.
A reference definition of wetlands is independent of legal jurisdiction and of administrative objectives and thus is distinct from a regulatory definition, which takes into account laws or policies that do not necessarily encompass all wetlands. A reference definition of wetlands should be used as a basis for evaluating regulatory definitions.
A reference definition of wetlands is as follows: A wetland is an ecosystem that depends on constant or recurrent, shallow inundation or saturation at or near the surface of the substrate. The minimum essential characteristics of a wetland are recurrent, sustained inundation or saturation at or near the surface and the presence of physical, chemical, and biological features reflective of recurrent, sustained inundation or saturation. Common diagnostic features of wetlands are hydric soils and hydrophytic vegetation. These features will be present except where specific physicochemical, biotic, or anthropogenic factors have removed them or prevented their development.
Three factors must be assessed in the identification or delineation of wetlands: water, substrate, and biota. It is not useful or correct to refer to these factors as parameters.
The states or conditions of the three factors (water, substrate, biota) that define wetlands are the criteria for identification and delineation of wetlands.
Indicators, which are the measurements or observations by which criteria are evaluated, should accommodate regional variation.