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.

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

FRONT MATTER (R1-R20)

EXECUTIVE SUMMARY (1-12)

1 INTRODUCTION AND BACKGROUND (13-19)

2 ECOLOGY OF WETLAND ECOSYSTEMS (20-42)

3 WETLAND DEFINITIONS: HISTORY AND SCIENTIFIC BASIS (43-64)

4 WETLAND DELINEATION: PAST AND CURRENT PRACTICE (65-89)

5 WETLAND CHARACTERIZATION: WATER, SUBSTRATE, AND BIOTA (90-148)

6 ESPECIALLY CONTROVERSIAL WETLANDS (149-167)

7 REGIONALIZATION (168-189)

8 MAPS, IMAGES, AND MODELING IN THE ASSESSMENT OF WETLANDS (190-206)

9 REGULATION OF WETLANDS: ADMINISTRATIVE ISSUES (207-214)

10 FUNCTIONAL ASSESSMENT OF WETLANDS (215-226)

REFERENCES (227-252)

APPENDIXES (253-296)

INDEX (297-306)

LIST OF PUBLICATIONS (307-308)