Landscape Ecology of the Upper Mississippi River: Lessons for Restoration

A backwater of the Upper Mississippi River. USGS.

A river of international importance

The Upper Mississippi River System (UMRS) is a mosaic of channels, backwater lakes, floodplain forests and marshes, home to over 150 fish species, 40 freshwater mussels, 50 amphibians and reptiles, and over 360 bird species, many using it as a migration route. It is also a hotspot for processing nutrients from its basin, and a Ramsar wetland of international significance.

In the Water Resources Development Act of 1986, Congress declared its navigable parts a "nationally significant ecosystem and nationally significant commercial navigation system" and launched the Upper Mississippi River Restoration (UMRR) Program — the first comprehensive program of restoration, monitoring and research on a large river. This USGS work supports its decisions.

The Upper Mississippi River System flowing through its basin. USGS.

Two centuries of change

Navigation works and the conversion of vast areas to farmland have reshaped the river and changed conditions for nutrients, fish, mussels, plants and birds — but how much, and where restoration would help most, is not well quantified.

Landscape indicators

• Past and future: analysis of land cover from about 1890 to 2000, projected to 2050, found that in the north, dams expanded open water at the expense of floodplain forest, backwater lakes and side channels; in the south, channel constriction and levees expanded farmland at the expense of forests and side channels.
• Climate: current and future changes were most sensitive to regional climate, which drives river flows and shifts in land cover — so climate change could matter a great deal.
• Choosing sites: maps and metrics of forest fragmentation and aquatic-area diversity reveal the marks of navigation, farming and urban development and help set regional priorities for restoring forests, backwaters, islands and side channels.

Today's water over historical river maps: areas flooded by navigation dams in the north (left) and channelized in the south (right). USGS.

Ecological relationships

• Nutrients: in one study, patches of high and low nitrogen and phosphorus tracked the distribution of backwaters, and concentrations tracked current velocity — showing which kinds of aquatic areas deliver and cycle nutrients differently.
• Floodplain forests: trees with low flood tolerance, and soils high in sand, were mostly on higher ground that floods less than 40 days of the growing season; silver maple rose sharply in the overstory as flooding increased from 10 to 40 days. That helps planners match tree species to topography in forest restoration.

Forest cover and fragmentation maps help identify where forest restoration could help. USGS.

Challenges and opportunities

• A regional approach is hard with complex land ownership and competing ecological, economic and navigation needs — but the five bordering states (Illinois, Iowa, Minnesota, Missouri and Wisconsin) are strong partners.
• Predicting results is hard, too: floods or droughts just after a project, and unpredictable species interactions such as invasive species, can change the outcome. The answer is to pair ecological studies with real restoration projects.

The UMRR is a partnership of the U.S. Army Corps of Engineers, the USGS, the U.S. Fish and Wildlife Service and the five states; more on its Long Term Resource Monitoring element.

Sources

Based on Landscape Ecology of the Upper Mississippi River System: Lessons Learned, Challenges and Opportunities, USGS Fact Sheet 2016–3007, a product of the U.S. Army Corps of Engineers' Upper Mississippi River Restoration Program, U.S. Geological Survey (DOI), citing De Jager and others (2011, 2012), De Jager and Rohweder (2011) and De Jager and Houser (2012); a work of the United States government in the public domain. The maps and photograph come from the fact sheet's PDF. More: Upper Mississippi River Restoration Program.