 Koehn's 12 years on the Board of Supervisors (1986–1998) is one of the longest tenures in elected office for any Green Party member, and after Dave Conley (22 years) is the second longest among Wisconsin Greens.Koehn has also been active in environmental, treaty rights and human rights causes including opposition to the Crandon and White Pine mines, support of Ojibwe treaty rights, and support for the proposed Seventh-Generation Amendment to the US Constitution.Koehn has paid particular efforts to preserving Lake Superior.