The Boone River at high water levels. Photo by David Morris, licensed under CC BY 2.0.

The Boone River Watershed in north-central Iowa, USA, covers approximately 581,000 acres (235,000 hectares), the majority of which is devoted to agriculture. This watershed is also home to some of the most biologically diverse and healthy freshwater communities in Iowa. This is because, for its size, the Boone River is a relatively intact watershed, and is also undergoing inspiring conservation and restoration efforts.

For the past 14 years, The Nature Conservancy (TNC), in partnership with 12 organizations, has been restoring critical oxbow wetland habitats in strategic locations throughout the watershed. Their partners include: U.S. Fish and Wildlife Service, Iowa Soybean Association, Iowa Department of Agriculture and Land Stewardship, Natural Resources Conservation Service, Fishers and Farmers Partnership, Iowa State University, Iowa Geological Survey, Iowa Department of Natural Resources, USGS Fish and Wildlife Cooperative Unit, local soil and water conservation districts, local county conservation boards, Boone River Watershed Management Authority, and local private landowners .

What is an oxbow, and why is it important?

An oxbow wetland is an old river meander that has become separated from the flow of water in the main river channel, either naturally or through man-made straightening. They vary greatly in size, some covering a 10,000 acre (4000 hectare) area and others being so small you can jump across them. Oxbow wetlands are a critical wetland habitat in the Boone River watershed. They help store excess water as a preventative tool against flooding, filter water to improve water quality, and provide habitat for a variety of wildlife, including the Topeka shiner, which is listed as endangered at both the state and federal levels.

An example of a meandering river and the formation of oxbows.

Over the last 100 years, most of the historic oxbows in the Boone River Watershed have been degraded. Habitat loss has also occurred through the straightening of streams, draining of wetlands, and the sediment deposition that has filled in oxbows. As streams are incised, they become disconnected from their floodplains, preventing wildlife including the Topeka shiners from accessing off-stream habitat.

To help combat the degradation of oxbow wetlands, TNC is restoring oxbows throughout the watershed. So far, TNC has completed projects at 47 out of over 400 potential restoration projects in the watershed. In total, over 100 oxbows have been restored in strategic locations across the state through robust and diverse project partnerships.

Continuing Restoration of Oxbow Wetlands

Led by TNC in partnership with Iowa Department of Natural Resources, a new oxbow restoration project received funding from the Microsoft and SER standards-based ecological restoration collaboration. This collaboration provides technical and field support to implement standards-based ecological restoration projects in communities hosting Microsoft datacenters across the world. Eight other projects have been funded to date.

This project aims to restore one degraded oxbow wetland in the Boone River Watershed, and reestablish the important ecosystem services it provides: flood mitigation, water quality improvements, habitat for various wildlife, including the Topeka shiner.

A Topeka Shiner (Notropis topeka) Breeding Male. Photo by USFWS Mountain Prairie.

The benefits of TNC’s wetland restoration efforts have been extensively evaluated, showing measurable and lasting impacts on improving water quality. Over 50% of TNC restoration projects in the watershed support Topeka shiners. In 2020, TNC documented the return of Topeka shiners to a sub-watershed after a 36-year absence, illustrating that restoration is key in helping species adapt to a changing climate, degraded water quality, and dysfunctional hydrology.

 

Moreover, restored oxbows capture, store, and filter agricultural runoff, naturally removing an average of 42% of the nitrates from the waterways and reducing flooding impacts for downstream communities. By restoring critical oxbow wetland habitat, TNC is helping address the biodiversity crisis, improve water quality, and provide important flood control for downstream communities, like Des Moines.

Standards-based restoration is delivering measurable results

Standards-based ecological restoration helps account for complex ecosystem dynamics, navigate trade-offs in land-use, address challenges, and increase design and implementation effectiveness, thus reducing risk and increasing the likelihood of beneficial project outcomes. TNC’s oxbow restoration project is designed to:

1. Draw on diverse, expert, and relevant knowledge and technical capacity. Over the past 12 years, TNC has worked with over 12 different partners to restore oxbows in the Boone River Watershed, actively drawing on diverse knowledge, technical expertise, funding, and outreach.
2. Promote inclusion and participation of diverse landowners and community members through field days, newsletters, and online content. TNC’s well established outreach methods effectively engage the local and downstream communities in the project, helping build awareness of the importance of oxbow wetland restorations.
3. Identify and reduce indirect and direct causes of degradation by restoring critical environmental function to degraded oxbow wetlands. The project removes sediment that has eroded into the oxbow. A vegetative buffer is also installed around the oxbow, which is paired with uphill conservation practices to further limit sediment flowing into the oxbow. A landowner maintenance agreement further ensures the health and function of the oxbow for a minimum of 10 years. Research by the U.S. Fish and Wildlife Service found only 2 inches (5.08 cm) of re-sedimentation in an oxbow that was restored 20 years ago, proving the longevity of this conservation practice.
4. Increase integrity, area, number, or viability of biodiversity within the restoration area and community. Project monitoring over the past 10 years has shown that 57 fish species and 81 bird species have benefitted from restored oxbow habitat, including the federally endangered Topeka Shiner minnow. The Topeka Shiner recovery has been so successful that the U.S. Fish and Wildlife Service is considering changing their status from “endangered” to “threatened.”
5. Achieve and sustain the greatest net gain possible for environmental benefits, human wellbeing, and social equity for the community, given project size and investment. TNC is bringing their work to scale through the creation of the Oxbow Restoration Toolkit, which has helped train over 200 conservation professionals in Iowa and was shared with over 2,000 additional conservation practitioners. TNC’s work also helped get oxbow restoration added to the Iowa Nutrient Reduction Strategy, allowing state cost share for restoration and bringing further attention to this important river and watershed restoration strategy.

A before (left photo) and after (right photo) of an oxbow restoration project implemented by The Nature Conservancy in the Boone River Watershed. Photos by Karen Wilke, The Nature Conservancy.

The scale and duration of TNC’s work on restoring critical wetland habitats in the Boone River Watershed is a resource by providing a robust framework for ecological restoration efforts for similar sites. Their work has already resulted in improved biodiversity, flood control, and water quality in Iowa. This project serves as a reminder of the critical role that wetlands play in helping species adapt to a changing climate, degraded water quality, and dysfunctional hydrology . 

Microsoft is proud to collaborate with Society and Ecological Restoration to deliver standards-based ecological restoration with the Nature Conservancy in Des Moines, Iowa, USA. Learn more here.