Places We Protect

7-Mile Fen Preserve

South Dakota

Thunderstorm © Joe Blastick/TNC
Thunderstorm. 7-Mile Fen Preserve © Joe Blastick/TNC

Originally a showcase for wetland restoration, 7-Mile Fen now supports a diversity of wildlife.



This preserve is located in the Crystal Springs complex, a mixture of tallgrass prairie and pothole habitat in the Prairie Coteau region. Established in 1998, the purpose of the preserve was to showcase wetland restoration, in part by restoring seven small basins and large drainage area found on the preserve. Area managers for TNC at first didn’t realize what a gem 7-Mile truly was, and it wasn’t until some months later that staff discovered two small calcareous fens on the property. 

As TNC began to restore the property, using tools such as controlled fire, native grasses and forbs burst forth abundantly. Today, this mosaic of wetland and prairie attracts a diverse array of waterfowl and grassland birds.


From Clear Lake, SD, go seven miles east of town on Highway 22. The preserve is located on the northeast side of the intersection with the County Road.

Plants and Animals

As prairie and wetland plants began to re-emerge, so did the wildlife. The water-loving muskrat, which makes it homes in marshes, lakes and streams returned, as did many grassland birds, such as sandpipers and bobolinks. Canada geese and several species of ducks can be found nesting here annually. During spring migration, 7-Mile Fen is heavily used by waterfowl.

Why TNC Selected This Site

This site originally was selected because of its position within the Crystal Springs region. Today, it is valued not only for its contribution to the health of ecological communities in this region but for the diversity of plant and animal life it supports.

What TNC Has Done/Is Doing

Working with the U.S. Fish and Wildlife Service, TNC restored a 60-acre wetland basin in 2003. Through this effort, water now is held back on the site, which creates great wildlife habitat.  In turn, TNC then donated a permanent conservation easement on the property, the value of which could be used by USFWS as match money for future grants, which will help fund grassland protection programs on private lands in the region.

In places where the original prairie had been lost, TNC is working to restore it. In fall 2003, 20 acres near this new basin was planted, which are part of the overall restoration project.

Additionally, this landscape is being managed by controlled fire, which helps prevent the spread of harmful, non-native plants while stimulating the growth of desirable native species. 




217 acres

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