Effecting a change in philosophy to ensure the sustainability of ecosystems will require education, research, and changes in law.



The Upper Mississippi River extends from River Mile (RM) 218.0 near St. Louis, Missouri, to RM 854.0 at Upper St. Anthony Falls Lock in Minneapolis-St. Paul, Minnesota. The Illinois Waterway extends from Grafton to Chicago, Illinois. The total Illinois and Mississippi River navigation system contains 37 locks (of which 35 are included in the proposed renovation program of the U.S. Army Corps of Engineers) and 360 terminals. Lock and Dam 26 (RM 202.9, Alton, Illinois) was replaced in 1989 by the Melvin Price Locks and Dam (RM 200.8); a second lock opened in 1994.


The National Environmental Policy Act (NEPA) was passed by Congress in 1969 in part to integrate environmental considerations into the decision making process for "every recommendation or report on proposals for legislation and other major federal actions significantly affecting the quality of the human environment" (§102[2][c]). NEPA put in place the requirement for impact analyses that have evolved from limited assessments that meet the letter of the law to comprehensive assessment programs that meet the spirit of the law. The role of NEPA in ensuring that the proposed changes in the UMR-IWW navigation capacity meet the spirit of the law has been discussed elsewhere (Cox et al., 1993a; Schaeffer et al., 1988, 1993).


Before 1972 the Federal Water Pollution Control Act (FWPCA) left it up to the states to develop ambient water quality standards to protect interstate and navigable waters for uses the state wanted to facilitate (e.g., agriculture, industry, recreation, human consumption, prevention of imminent health hazard). The 1972 amendments established a system of national standards, permits, and enforcement "goals" of "fishable and swimmable" waters by 1983 and total elimination of pollutant discharges into navigable waters by 1985. Following amendment of the FWPCA in 1977, it was designated the Clean Water Act.


Factors that alter an ecosystem from the conceptual image of that ecosystem embodied in a particular law (e.g., "fishable and swimmable") pose excess risk. The term de minimis risk is widely used in federal risk analysis (see Whipple, 1987) to mean a specific level below which a risk estimate is so small that it can be ignored i.e., a threshold (Schaeffer and Cox, 1991). A legal threshold for sustainability is the level of risk a given law accepts; for example, a game fish with a sustainable population but which is not edible due to contamination. An ecological threshold is the value of a relevant ecological parameter at the point at which the risk becomes adverse. For example, based on Karr's (1981) Index of Biotic Integrity, Khan (1992) found that the quality of Illinois fisheries usually was less than "good" if there were fewer than 17 species.


These include habitat for desired diversity and reproduction of organisms; phenotypic and genotypic diversity among the organisms; a robust food chain supporting the desired biota; an adequate nutrient pool for desired organisms; adequate nutrient cycling to perpetuate the ecosystem; adequate energy flux for maintaining the trophic structure; feedback mechanisms for damping undesirable oscillations; capacity to temper toxic effects, including the capacity to decompose, transfer, chelate or bind anthropogenic inputs to a degree that they are no longer toxic within the system.


Colborn, T., F. S. vom Saal, and A. M. Soto. 1993. Developmental effects of endocrine-disrupting chemicals in wildlife and humans. Environmental Health Perspectives 101:378-384.

Costanza, R., B. G. Norton, and B. D. Haskell, eds. 1992. Ecosystem Health: New Goals for Environmental Management. Washington, D.C.: Island Press.

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