Iowa
Wetlands and
Riparian
Areas
Conservation
Plan
Fens one of Iowa's unique habitats
(Statewide)
Fens are thousands of years old, spring-fed wetlands that have unusual soil and water conditions, and host a unique set of species. Because of these characteristics, fens are one of the most unusual habitats in Iowa and the United States.
The water in a fen is mostly groundwater with some surface water. Because groundwater feeds fens, the water is usually high in calcium and other ions from the underlying rock and is slightly alkaline or neutral. Usually, open water isn't apparent, although the soil is thoroughly saturated. The soil in a fen also has a very high organic content because of the large amount of decomposing plant material. The technical term for this type of soil is muck.
Another unusual thing about fens is their inhabitants. Fens host more than 200 plant species, 24 of which the Iowa Department of Natural Resources (IDNR) considers endangered, threatened or of special concern. Because of fens' special conditions of chemistry, soils and hydrology, some plants have specially adapted to them, and some animal species have adapted to these plants. Like their inhabitants, fens are also rare, but they can be found in all of the major landform regions of Iowa. They tend to be vulnerable to degradation from grazing, pesticide drift, and drainage, partly because of their small size, which ranges from one-half acre to 25 acres.
A survey by the University of Wisconsin-Green Bay of 30 counties in northeastern Iowa estimated that 2,333 fens existed in pre-settlement times. According to an IDNR survey, Iowa has about 200 fens left in 37 counties, but only a small portion of these are considered to be in good condition. This dramatic decrease in the number of fens, which has also happened in other states where fens occur, has led the U.S. Fish and Wildlife Service to list fens in our region in Resource Category 1. This means that FWS hopes to achieve "no loss of existing habitat value," because fens are considered irreplaceable. They take thousands of years to establish their mucky soils and vegetation. It is thought that some of Iowa's fens were around when the last glacier retreated over the state, but most probably formed in the past 5,000 years.
Therefore, conservation is the best, and possibly the only, means of ensuring that fens remain. No methods or techniques are known to build new fens or restore those that are highly degraded. Only a few of Iowa's fens are owned by conservation agencies such as the Nature Conservancy, Iowa Natural Heritage Foundation, county conservation boards and the IDNR. This makes voluntary landowner stewardship especially important to the survival of Iowa's fens and their associated species. If you are interested in preserving a fen, a variety of resources, including technical and financial assistance is available. To find out more, please call the contact at the end of this case study or visit some of the provided links for more information.
Contact:
- John Pearson, Iowa Department of Natural Resources, Division of Parks, Recreation and Preserves
- Phone: (515) 281-3423
- Cathy Henry, Refuge Operations Specialist
- Jim Munson, Iowa Private Lands Coordinator, U.S. Fish and Wildlife Service
- Phone: (515) 994-3400
Questions? Comments?
Contact our Webmaster