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Washington Island Wetlands

Back to Northern Lake Michigan

Counties: Door


Washington Island Wetlands, Plum Island, 22 July 1999. Kalm's lobelia (Lobelia kalmii) meadow surrounding lagoon ("Carp Lake") periodically connected to Lake Michigan. Photograph, E.J. Judziewicz.

Site Description

This site is made up of several smaller sites and includes the Coffey Swamp and Jackson Harbor Ridges State Natural Areas.

Washington Island wetlands are in a mixture of state and private ownership and are located directly north of the Door Peninsula mainland. There are three important coastal wetland areas on Washington Island - each described separately below.

Big and Little Marsh

This complex 250-acre site is located midway up the eastern coast of Washington Island and includes two primary components. First, there is a sandy barrier beach that has been mostly developed with a road and houses. At the south end of the beach there are small but good quality remnant Great Lakes Beach and Lake Dune communities, containing several rare plant species.

The barrier beach cuts off a second, larger component of the site: an extensive and undeveloped open wetland and wooded swamp (Big Marsh) located inland and west of the barrier beach. Immediately inland is a 38-acre Emergent Aquatic marsh on marl dominated by softstem bulrush. In some places there are patches of nearly bare marl with pavements of dolomite gravel and cobbles that are exposed at times of low water levels. Water depth ranges from two feet in the spring to dry by autumn and is seemingly dependent on the level of Lake Michigan, although the marsh is not directly connected to the Lake. Several rare plant species occur here.

West of the marsh are two additional communities of note. Rare plant species are present in both. To the southwest is a 60-acre Northern Wet-Mesic Forest (white cedar swamp) that is probably the highest quality representative of this community type on Wisconsin's Lake Michigan islands. Northwest of the marsh is a 7-acre Boreal Rich Fen community dominated by wire-leaved sedges, sweet gale, shrubby cinquefoil, and alder-leaved buckthorn.

Northeast of Big Marsh is Little Marsh, with smaller and lower quality wetland communities, including Northern Hardwood Swamp (black ash dominant) and an ephemeral pond.

The landscape surrounding the Big-Little Marsh Area is mostly forested with second-growth hardwoods and conifers, and, farther away, abandoned agricultural fields. The potential for additional housing developments on adjacent uplands is a concern.

Except for Percy Johnson County Park, the entire site is divided among numerous private owners.

Coffey Swamp

This area is an approximately 300-acre wetland complex located midway along the northern coast of Washington Island. At the core of the complex and located about 0.5 miles south of Lake Michigan, is a small, very hard water, shallow seepage pond with a substrate of pure marl. It nearly dries up in late summer during years when Lake Michigan is low. North of the pond is a 9-acre Boreal Rich Fen dominated by wire-leaved sedges, sweet gale, bogbean, bog goldenrod, and hoary willow. This fen has several rare plant species but also contains the exotic glossy buckthorn and the aggressive common reed grass.

Surrounding the fen, on the south side of the pond, is a large (225 acre) white cedar swamp that has been severely impacted by deer browse. To the north of the cedar swamp there is a small (10 acres) but distinctive and high quality hardwood swamp dominated by black ash. There are also small patches of Northern Sedge Meadow in various places within the complex.

The coastline of Lake Michigan is mostly an upland white cedar forest (with some balsam fir) on very thin soil over dolomite gravel and cobbles. Interspersed in this forest are a few old abandoned agricultural fields and an old channel that was blasted through the dolomite bedrock in an attempt to drain the swamp. One portion of the Lake Michigan shoreline has a unique "cobble glade" community type with a scattering of cedars among heaps and windrows of large dolomite cobbles.

A 40-acre State Natural Area is at the core of Coffey Swamp. There are several private landowners to the south and west, and a very large landowner to the north and east along the Lake Michigan shoreline. Should this owner decide to sell, there will be very high development pressures on this shoreline.

Jackson Harbor Ridges

This State Natural Area is located on the northeast side of Washington Island which contains an excellent assemblage of rare and uncommon vascular plants. The beach undulates with numerous areas of dry to wet sand and interdunal swales. These swales, including a large one near the base of a point, contain an unusual community that prefers wet calcareous soils. Characteristic plants here are Kalm's lobelia, shrubby cinquefoil, arctic primrose, low calamint, slender bog arrow-grass, bladderworts, and many sedges. The beach gradually grades into drier dunes which are stabilized with drought tolerant species such as bearberry, horizontal juniper and sand coreopsis. Behind the dunes is a mixed conifer-hardwood forest of red and white pines, white cedar, balsam fir, and American beech. The entrance to Jackson Harbor is a sand spit which attracts gulls, terns, shorebirds and waterfowl.

Washington Island Wetlands support many rare plant and animal species including some which are Great Lakes Coastal endemics.

Additional Comments

This site consists of two designated State Natural Areas and a third location that is designated as a conservation project. Though none of the individual areas is large, overall quality is high, and many rare species are present.

Text describing this site was published previously in a 2002 DNR publication entitled “A Data Compilation and Assessment of Coastal Wetlands of Wisconsin’s Great Lakes” by E.J. Epstein, A. Galvin and W.A. Smith.

NOAA logo Wisconsin Coastal Management Program logo This project was funded by the Wisconsin Coastal Management Program and the National Oceanic and Atmospheric Administration, Office of Ocean and Coastal Resource Management under the Coastal Zone Management Act.

Last revised: Wed, 20 Jun 2012 17:21:12 CDT