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Chapter 2 AN ECOLOGICAL OVERVIEW OF THE UPPER MISSISSIPPI RIVER SYSTEM: IMPLICATIONS FOR POSTFLOOD RECOVERY AND ECOSYSTEM MANAGEMENT By Charles H. Theiling I PURPOSE AND SCOPE This chapter was prepared at the request of the Scien- tific Assessment and Strategy Team (SAST) of the Admin- istration Floodplain Management Task Force. Interagency Floodplain Management Review Committee, The inter- agency task force was formed to make policy decisions regarding recovery from the "great flood of 1993," The SAST is responsible for providing scientific advice regard- ing hydrology. geomorphology. habitat. plants. and fauna. Findings of the SAST will be used to guide future manage- ment and development of natural resources in the upper Mississippi River system (UMRS), This chapter presents a generalized description of upper Mississippi River (UMR) ecology (exclusive of the Missouri River; see Chapters 5 and 6), I emphasize aquatic resources and habitat transformations resulting from devel- opment in the UMRS river-floodplain environment. I refer to floodplain wetland habitats and their relation to the river, Other contributors to the SAST provide details on UMRS forest ecology (Chapter 3). wildlife (Chapter 7). and mus- sels, and commercial fishing and shelling (Chapter 4) in the UMRS, I try to describe both the historical and current ecology of four reaches of the system: the upper floodplain reach (Pools 1-13). the lower floodplain reach (Pools 14-26), the middle Mississippi River (Alton. Illinois. to Cairo, Illinois). and the Illinois River (Lake Michigan to Grafton, Illinois) (Lubinski. 1993). The divisions are based on ecological and social criteria that differentiate each reach such that separate management goals/opportunities must be considered, I dis- cuss ex.otic species. local extirpations, and contaminants briefly. but suggest sources for further information. I con- I Illinois Natural History Survey, Long Tenn Resource Monitoring Program (currently with Ecological Specialists. Inc.). elude with ecological observations from the summer of 1993 and offer management considerations for the future, The goal of this chapter is to provide individuals and decisionmakers with a concise ecological overview ofthe UMR and humanity's influence on it; it cannot provide the level of detail that has been completed for other efforts. Readers are directed to the studies of the Great River Envi- ronmental Action Team (I 980a. 1980b: Brietenbach and Peterson. 1980). the Comprehensive Master Plan for the Management of the Upper Mississippi River System pre- pared by the Upper Mississippi River Basin Commission (UMRBC) (1981, 1982). the various reports from the Upper Mississippi River System Nine-Foot Navigation Channel Project environmental impact studies, and the Illinois River Diversion Report (Havera and others. 1980) for detailed analyses of economic, recreational, and environmental needs. conflicts. and potential of the UMRS, Jabn and Anderson (1986) provide an excellent overview of UMR ecology. More recent environmental information is avail- able from the investigations of the U,S, Army Corps of Engineers and National Biological Survey. Long Term Resource Monitoring Program (LTRMP) (1992). Despite efforts to document impacts from navigation, much basic ecological information is still lacking. [nforma- tion on species distribution, life histories, production rates, response to abiotic factors, and the role of development (urban. agricultural. and navigation) in the river-floodplain ecosystem is necessary for effective ecosystem management in the UMRS, Ideally. models will be developed to predict the future ecological condition of the UMRS, LARGE RIVER-FLOODPLAIN ECOSYSTEMS The rivers and biota of the UMRS (fig. 2-1) developed in response to and are strongly influenced by abiotic con- 3