Mississippi River Priority Site

Lower Cedar River

The watershed shelters more than 400 plant species and two globally rare plant communities.

Despite covering only about 1,070 square miles, the watershed of the Lower Cedar River in southeastern Iowa shelters a remarkable assemblage of plants and animals. Two globally rare plant communities—swamp white oak savannas and rich peat fens—can be found there, and its sandy soils provide habitat for more than 400 documented plant species.

The oak savannas established themselves when fire and seasonal floods kept the forests more open. Now, without adequate fire, trees grow in an unnatural density, preventing new oaks from becoming established. Meanwhile, the Cedar River floods unnaturally, causing declines in populations of some plants and animals. Reed canary grass, garlic mustard and other non-native, invasive plant species pose another ecological threat.

The watershed also harbors 70 percent of the reptile and amphibian species found in Iowa, including rare massasauga rattlesnakes and stinkpot and ornate box turtles. The Southeast Iowa Reptile and Amphibian Conservation Area—the first in the nation—was designated along the Lower Cedar in 2007.

Strategies and Progress

The Nature Conservancy is working in multiple ways to preserve and restore the habitats and water quality upon which the watershed's biological diversity depends.

The Conservancy and its partners share a long-term goal of conserving and restoring 5,000 acres of swamp white oak and floodplain savannas within the Lower Cedar River watershed. We are undertaking floodplain savanna restorations at several sites including the 652-acre Swamp White Oak Preserve, a prime example of floodplain savanna located on a low sand terrace along the Cedar River; the 137-acre Greiner Family Nature Preserve, where oak savanna, sand prairie and open sandy areas are all essential to rare nesting turtles; and the Fred Maytag II Family Preserve, which harbors a globally rare central tallgrass fen. Intensive management efforts at these preserves include prescribed fire, removal of non-native species and planting of native species.

The Conservancy is currently collaborating with the Iowa Department of Natural Resources and Grinnell College on a study of the interaction between surface water and groundwater at the Swamp White Oak Preserve. When completed, the results will enable us to quantify the "ecosystem services" provided by the swamp white oak woodland community. Being able to quantify the amount of nutrients and water that cycles through this system, for example, will give the Conservancy valuable information about how floodplain savanna restoration can reduce flooding downstream.

Another aspect of the Conservancy's work is its effort to demonstrate through the Pike Run Creek Watershed Project that agricultural uses and freshwater ecosystems can be compatible. Pike Run Creek, a tributary of the Lower Cedar, provides habitat for uncommon species of fish such as pirate perch, grass pickerel and black-striped topminnows.

Although the creek's water quality remains high, oxygen levels are declining due to elevated nutrient levels and deposition of organic matter and silt in the stream channel caused when levees cut Pike Run off from frequent flood events on the Cedar River. Lack of fire and the subsequent encroachment of woody plants are also rapidly changing the character of this prairie stream and eliminating the habitat of many rare prairie and wetland plants and animals.

With a $390,000 gift from the Monsanto Fund in 2003, the Conservancy spearheaded a multi-partner effort to promote the use of techniques to maintain and improve the creek's waters. Some of these include nutrient management comparisons, filter strips and riparian buffers.

Through the Pike Run project, a watershed plan was developed by the project stakeholders. Many local producers evaluated their fertilizer use through the Iowa Soybean Association's on-farm network and worked with a watershed coordinator, funded by the Conservancy and the Muscatine County Soil and Water Conservation District, to explore other best management practices that improve water quality. Throughout the process, water quality and aquatic life were carefully monitored to provide feedback on project management.

Project partners included the Muscatine Soil and Water Conservation District, Iowa Soybean Association, Iowa Department of Natural Resources, University of Iowa, the Natural Resources Conservation Service and the Environmental Protection Agency.

The work along the Lower Cedar River is important locally and on a much wider scale. Lessons learned within the watershed will be shared through the Conservancy's Great Rivers Partnership to advance the Conservancy's national and global efforts to protect the Earth's critically important freshwater resources.