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Wetlands: Characteristics and Boundaries 1 Introduction and Background The wealth of the United States was drawn initially from the development and exploitation of its virgin lands. Until this century, use of land for agriculture and commerce must have seemed unlikely to exhaust the country's vast reserves. Population growth and an increasingly potent agro-industrial capacity have, however, brought most of the conterminous United States under some form of management. As a result, the form and function of the original landscape have changed, and continue to change. The ecosystems that compose the landscape provide distributed benefits that extend well beyond the boundaries of any individual property. Consequently, society is a stakeholder in environmental change. It is widely accepted that a healthy environment is necessary for a healthy economy over the long term, but the appropriate balance of voluntary action and regulation for protection of the environment is often a matter of contention. Regulation of wetlands has raised this issue more forcefully than any other federal action related to the environment. The United States first became broadly committed, beyond its stewardship of public lands, to protection of public interest in the environment through laws intended to preserve or enhance the quality of air and water. Because air and water seldom can be construed as amenities of a single property, protection of the common interest can occur through regulations that are universally applicable to private and public lands. Federal regulation of wetlands was the first major step toward broad protection of landscape features, rather than protection of environmental media. Whereas regulation of air and water applies primarily to public or corporate entities, regulation of wetlands extends to individual property owners.
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Wetlands: Characteristics and Boundaries A direct connection to human health also has motivated protection of air and water, but is not a major element in the debate over wetlands. The context for regulation of wetlands thus differs from that of air and water, even though wetlands are largely regulated through the Clean Water Act. Protection of wetlands is based on the premise that preservation of a specific ecosystem type can be of sufficient common interest that its conversion or development should be prevented or restrained by law, even though much of its area might be found on private property. To some, the universal protection of wetlands seems an infringement of property rights. To others, it is a reasonable extension of the need to protect the public interest in environmental components that have exceptional value to society. Science cannot resolve the propriety or legality of regulating wetlands on private lands. Science can, however, support the development of objective and consistent means for identifying wetlands and their boundaries. 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 connotations that need to be considered in the application of any wetland definition. PURPOSES OF THE NRC REPORT Identification and Characterization One purpose of this report is to review the scientific basis for identification and delineation of wetlands as currently reflected in federal manuals and regulatory conventions. The report is intended to identify both the strengths and weaknesses of current regulatory practice. The committee's charge also asks that we deal with the basis for translation of definitions into ''practical, scientifically valid methods to efficiently and consistently identify wetlands.'' The committee decided that the translation of a definition or of particular standards or criteria into practical methods is also dependent on certain principles of regulatory practice and thus Chapter 9 titled Regulation of Wetlands and other discussion pertaining to regulation of wetlands (e.g., review of Nationwide Permit 26 and functional assessment) is included in this report. Although the identification and delineation of wetlands can and should have
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Wetlands: Characteristics and Boundaries a scientific basis, scientific principles will not always dictate the appropriate choice among several possible regulatory conventions. For example, the boundary between wetland and upland can be identified scientifically as a transition zone that incorporates a hydrologic gradient as well as gradients in soil type and in community composition of plants. If the regulatory objective is to protect the wetland absolutely, without regard to other considerations, the obvious choice would be to place a regulatory boundary at the outermost limit of the transition zone. Alternatively, regulatory practice that attempts to minimize economic dislocation while still protecting the core wetland area might set the boundary at the innermost part of the transition zone. The scientific and technical aspects of wetland identification and determination of wetland boundaries should not be confused with the matter of federal jurisdiction over wetlands. As explained further in Chapter 3, jurisdiction is to some extent severable from the delineation of wetlands insofar as laws and their regulatory interpretations may exclude, for sociopolitical reasons, certain classes of ecosystems that might be identified on scientific or technical grounds as wetlands. While any practical evaluation of the wetland regulatory system must acknowledge the importance of both scientific and jurisdictional principles, the relationship between. the two can be understood only in light of their separate origins and motivations. Identification of Functions and Values Legislation dealing with wetlands, wetland regulations, and public comment on wetlands contain references to the societal values that motivate protection of wetlands. Some functions of wetlands are directly associated with specific societal values. For example, suppression of floods is a value of wetlands, and the underlying function is seasonal water storage by wetlands. Associations between functions and values may also can be indirect. For example, the waterfowl of wetlands have value. Wetlands support waterfowl, but only as a result of hydrologic functions that maintain specific wetland vegetation, wetland food chains, and other habitat features that are necessary for the reproduction or maintenance of waterfowl. The association between the value of wetlands to society and the functions that are characteristic of wetlands is important in the design of wetland protection systems. If one objective is preservation of wetland attributes that have societal value, the association between selected wetland values and their supporting wetland functions will dictate the kinds of protection mechanisms that will be most effective. Variations A third factor to be considered in this report is variation among wetlands.
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Wetlands: Characteristics and Boundaries The diverse physiographic regions of the United States support many kinds of wetlands (Mitsch and Gosselink, 1993), which vary functionally and in their value to society. For example, cypress swamps and mangrove swamps differ greatly from northern peatlands, and tidal salt marshes function differently from inland freshwater marshes. Different kinds of wetlands also present varying kinds of technical challenges for identification and boundary setting. Physiographic regions vary not only in their assortment of wetland types, but also in the abundance of wetlands and in the degree to which the wetlands are altered or eliminated. Both within and among regions, points of particular interest for this report include the degree of variation, the practical difficulties that variation poses for centrally designed delineation systems, and the feasibility of regionalizing technical procedures to be used in the identification and delineation of wetlands. Relationships of the Three Themes The three themes for this report—wetland identification and delineation, functions and values of wetlands, and variation among wetlands—are interdependent. The identification of wetlands, the determination of boundaries for wetlands, and the characterization of wetland functions and values must be set within a framework that is broad enough to encompass the great physical and biotic variety of wetlands, while at the same time maintaining as clearly as possible the distinction between wetlands and other kinds of ecosystems. PATH TO REGULATION At the time of European colonization, the area that is now the conterminous United States contained about 220 million acres (90 million ha) of wetland, comprising about 9% of the landscape (Dahl, 1990). Colonists were sometimes attracted to wetlands because of the high agricultural potential of their rich hydric soils. For example, the wealthiest colonists of tidewater Virginia chose the lowlands for their large estates; the unproductive uplands were left to less prosperous landholders (Fischer, 1989). As the saturated wetland soils were drained and diked for agriculture, wetlands often extracted a heavy price in the form of vivax and falciparum malaria, as well as such waterborne diseases as typhoid and dysentery (Fischer, 1989). Wetlands as viewed through the agrarian eyes of early America are well portrayed by the Federal Swamp Land Act of 1850, which deeded extensive wetlands to the states for conversion to agriculture. Between the first phases of European colonization and the 1980s, about one-half of the wetland area in the conterminous states was converted to other land forms, primarily by drainage, for promotion of agriculture (Table 1.1). Federal intervention through various swampland acts and through ambitious drainage projects of the U.S. Army Corps of Engineers (USACE) promoted wetland con-
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Wetlands: Characteristics and Boundaries TABLE 1.1 Estimates of Wetland Losses in the Conterminous United States (Modified from Mitsch and Gosselink, 1993) Period Hectares (millions) Acres (millions) Percentage Annual Percentage Reference Presettlement to 1950s 18 45 35 0.14a Shaw and Fredine (1956) Presettlement to 1980s 47 117 53 0.19a Dahl (1990) 1922-1954 4.5 11a 6.4a 0.20 Zinn and Copeland (1982) 1954-1970s 6.5 16a 11a 0.55 Zinn and Copeland (1982) 1950s-1970s 3.6 9 8.5 0.42 Frayer et al. (1983) 1970s-1980s 1.1 2.6 2.5 0.25 Dahl and Johnson (1991) a Computed from the primary estimates. version, but much wetland conversion was privately motivated and resulted in the creation of productive croplands that today form an important part of the agricultural resource base of the United States (Mitsch and Gosselink, 1993). Conversion was distributed very unevenly. The conversion, which had exceeded 80% in a number of states by the end of the 1980s, was highest where conversion was both feasible and profitable (for example, in Illinois and Ohio), or where wetlands were of limited extent but coincided with the most favorable areas for agriculture and population growth (as in California). The national attitude and federal policy toward wetlands became ambivalent as early as the 1930s. The first point of national concern was a decline in waterfowl populations, which in part reflected loss of wetlands along flyways and in breeding grounds. Concern for waterfowl led to the introduction of the Federal Duck Stamp Program in 1934, which provided money for the purchase or protection of wetlands. At the same time, both the Department of Agriculture and the USACE continued to encourage, subsidize, and finance the conversion of wetlands. By the early 1970s, interest in the protection of wetlands had extended well beyond the desire to maintain waterfowl populations. Three factors contributed to a shift in national attitude. First was the environmental movement, which opened to question many established policies of land use. A second factor was the increasing evidence that wetlands were being lost and converted at a rate that projected their virtual disappearance in many parts of the country. Third was a realization that wetlands have particular value to society, not only through the maintenance of waterfowl populations, but also in support of water quality, hy-
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Wetlands: Characteristics and Boundaries drologic buffering, and provision of refugia for many kinds of organisms that cannot be found elsewhere. In the 1970s, the federal government began incrementally to protect wetlands through executive orders and legislation. Individual states also had begun their efforts as early as the 1960s. The keystone of the federal protection system was set in the early 1970s by court decisions interpreting the Clean Water Act as protective of wetlands. This was followed by a critical shift in federal policy for the agricultural sector through the Food Security Act of 1985, which contained the so-called "swampbuster" provisions denying some agricultural subsidies to property owners who converted wetlands after 1985. CURRENT CONTEXT FOR REGULATION Laws and regulations notwithstanding, the United States lacked until very recently a consistent national policy for regulation of activities in wetlands. Permitting of dredge-and-fill activities by the USACE under authority of the Clean Water Act, for example, could be administered with varying degrees of stringency ranging from virtual prohibition of wetlands conversion to accommodation of all but their most egregious destruction. Thus, the existence of laws and regulations is not a substitute for national policy. Because regulations affecting wetlands can be administered with broad discretion, the underlying national policy has often been unclear. Perceiving the need for a guiding hand to direct regulators and to inform the public, the Environmental Protection Agency called for a National Wetlands Policy Forum in 1987 (The Conservation Foundation, 1988). Participants in the forum, which was charged with making recommendations for national policy on the protection of wetlands, represented a range of political and technical perspectives. The forum's central recommendation was that a national wetland protection policy should be established around the principle of no net loss of wetlands. The recommendation was actually more elaborate, but the core concept was no net loss (Clark, 1993). For the long term, the forum recommended restoration and creation of wetlands, where feasible, leading to an increase in the quality and quantity of the nation's wetlands. The forum's central recommendation (The Conservation Foundation, 1988) was adopted by the Bush Administration and since has been endorsed by the Clinton Administration as well. At least in the executive branch, and presumably throughout the regulatory and management agencies that are directed by the executive branch, the cornerstone of national policy has been set. Both the interpretation and the application of the policy are, however, still to be worked out. The policy in its barest form seems unambiguous, but is not immune to variable interpretation. Clark (1993) points out that each of the three words that summarize the policy ("no net loss") was viewed in a variety of ways by members of the National Wetlands Policy Forum. For example, the word "no" may be
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Wetlands: Characteristics and Boundaries taken as either categorical or suggestive, and "net" can be interpreted as allowing unlimited replacement of existing wetlands by hypothetical ones to be created at a time and date not specified. The word "loss" also may be variously interpreted to mean loss of selected functions, or complete loss of identity. Consequently, the availability of a national wetlands policy statement does not chart an entirely clear course for the regulators or the regulated. Also at issue is whether the national policy of no net loss is a statement of intent to be realized quickly, or at some indefinite time in the future, or perhaps only to be approached incrementally but never actually reached. An aggressive interpretation of the policy would dictate that federal agencies charged with wetland protection use the full force of wetlands regulation to achieve the national goal as quickly as possible. This would require tightening of the permitting system, much greater investments in restoration through programs such as the Natural Resources Conservation Service (NRCS) Wetlands Reserve, further development of mitigation banking, and accurate national inventory of wetlands to establish the degree of deviation from the national goal. A more casual interpretation might emphasize flexibility and slow incremental progress. The policy statement itself does not distinguish between these two possible applications of the principle of no net loss. Regulatory practice will set the boundaries of wetlands under any wetland protection system. Protection of wetlands in the U.S. must be guided from a technical base that is consistent, reflective of legislative intent; and capable of continually assimilating new knowledge about wetlands. The following chapters deal with this issue first by considering the fundamental nature of wetlands and the essential factors that define them, followed by an assessment and critical analysis of current and past practice for identification and delineation, and finally by a treatment of regionalization, especially controversial wetlands, administrative issues, and functional assessment of wetlands.
Representative terms from entire chapter: