Wetland policy in the United Stales is guided by the goal of no net loss of wetland habitat and is enforced primarily through the permitting requirements instituted under the Clean Water Act, which regulates the waters or the United Slates. Under these regulations, a permit applicant may be required to provide compensatory mitigation or restoration when wetland loss cannot be avoided or minimized. The practice has been to measure gains and losses primarily in terms of functions and values, the assessment of which has been rendered difficult because the agencies operate under limitations of time and experience, and because there are large areas of uncertainty in wetland science. itself. The purpose of this paper is to develop the principles for a manageable and practical set of performance criteria that will reasonably assure no net loss in a situation in which it cannot be absolutely assured. To this end, the performance criteria proposed for 116 compensatory wetland projects on file with the Army Corps of Engineers in San Francisco, between 1988 and 1995, were examined. The trends discerned in the project proposals were analyzed and evaluated in light of the current state of wetland science. Specific suggestions for the development of uniform criteria in each of four major wetland types-riparian, perennial tidal, perennial nontidal, and seasonal-are discussed, and a system of regulation tying qualitative assessment with quantitative requirements is outlined as a reasonable solution to the enforcement of the no-net-loss policy.
