Midwestern Fens

Fens which are groundwater-fed wetlands represent some of the rarest and biologically diverse wetlands in the United States. In areas where this has been recognized, it may lead to either a greater level protection for fens than most other wetlands or at least an emphasis on protection and acquisition. Unfortunately, it is often unclear what defines a fen. I and several colleagues (Jim Miner, Illinois; Quentin Carpenter, Wisconsin, and Jim Amon, Ohio) have investigated fens over much of the Midwest and we feel it is now possible to clarify what makes a fen unique, what similarities a fen has to other wetlands, and the nature of transition to non fen wetlands. Our goal is to produce a definition which fits the observed aspects of most sites generally recognized as fens and to eliminate from the definition the characteristics which make them regionally specific. We hope to also suggest process by which fens form so that these sites may be recognized in the field irrespective of their descriptive characteristics. What we are working on is a classification scheme to facilitate fen description. We intend to describe fens in a way that clarifies their definition for the glaciated parts of the midwestern USA where they occur frequently. In so doing, we intend to stimulate comparisons to similar habitats outside of the region and to demonstrate the importance of the hydrogeologic regime to the formation and function of fens. A clearer notion of the fen concept should help those evaluating or delineating wetlands and preparing environmental assessments.

Some fen articles:
Thompson, C.A., Bettis, E.A., III, and Baker, R.G., 1992, Geology of Iowa Fens: Journal of Iowa Academy of Science, v. 99, p. 53-59.

Thompson, C.A. and Bettis, E.A., III, 1994, Development and Evolution of Iowa Fens. Journal of Iowa Academy of Science, v.10, p.73-77.

Thompson, C.A., 1990, Iowa's Peatlands, Iowa Geology, no. 15, p. 18-21.


Some fen pictures:


 Kinney-Lindstrom Fen, Iowa

 Sumen Fen, Indiana
   Sieben-Thelen Fen, Ohio
   Silver Lake Fen, Iowa
   Silver Lake Fen, Iowa