This area encompasses the Trempealeau Refuge and the Upper Mississippi Refuge from the confluence of the Mississippi and Chippewa Rivers south through eight counties in southwest Wisconsin (Pools 4 to 11). Habitats include large tracts of floodplain forest, forested wetlands, bluffs, braided channels, open water, forested, islands, riverine wetlands, and prairie.
The Mississippi River is one of the great continental flyways along which birds migrate in the fall and spring. Hundreds of thousands of waterfowl and landbirds use the Upper Mississippi and Trempealeau refuges as migratory corridors and stopover sites, including over half the eastern population of Canvasbacks and twenty percent of Tundra Swans. The forests and wetlands also support significant breeding populations of many species, including Great Blue Heron, Bald Eagle, Red-shouldered Hawk, Yellow-billed Cuckoo, Cerulean Warbler, and Prothonotary Warbler.
Establishment of the two refuges has prevented extensive development and loss of habitat in the floodplain. Nevertheless, the river and associated habitats and species have experienced and continue to be subject to a variety of threats. These are identified in the Upper Mississippi Refuge?s recently completed Comprehensive Conservation Plan (USFWS 2006). Sediments, nutrients, and pesticides from extensive agriculture within the basin, as well as runoff from urban and commercial sources, have degraded water quality throughout the river. Numerous locks, dams, and levees have altered the flow of the river, increasing water levels and flood frequency and intensity. These changes in turn have altered the distribution and composition of plant communities. Wetlands created by higher water levels have filled with sediment; turbidity and lack of drying periods have degraded both submergent and emergent vegetation. Floodplain forests have declined due to higher water levels, and composition of remaining forests is becoming more even-aged and monotypic with flood-tolerant silver maple increasing in dominance and species less tolerant of long periods of inundation and higher water levels, such as hackberry and green ash, decreasing. Invasive species, including invertebrates, fish, and plants, are a widespread and growing threat, consuming and competing with native species and degrading or destroying native habitats. Increasing human recreational use, disturbance, and development also threaten species and erode habitat quality. Efforts to address these threats are underway through a variety of collaborations, control and monitoring programs, and various habitat improvement projects that involve dredging, erosion control, and water level manipulations (USFWS 2006). Halting and reversing habitat loss and improving degraded habitats should continue to be a major management focus. Mimicking or restoring natural disturbance regimes should be emphasized wherever possible.