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Between sky and shore
Wisconsin's coastal wetlands
Defined by great waters
Wherever dry land meets water there is a contest for territory: one seeks to conquer the other, and though at times one may succeed, neither has the upper hand for long. So Wisconsin rests uneasily within the watery boundaries of its two Great Lakes, knowing that in an earlier time, they were considerably greater than they are today.
Lakes Superior and Michigan hold particular sway over the land along their edges. This is Wisconsin's coast: roughly a six-mile-wide strip of soil, sand and rock caught between sky and shore, subject always to the whims of weather and wave.
Wisconsin's 820-mile Great Lakes coast contains wetlands couched in landforms found in few other places on the planet. The coastal wetlands are home to some of our rarest plant species. They are the places where migrating birds congregate in stunning numbers. And they are the gentle buffers that mediate the eons-old competition between wet and dry.
Most of Wisconsin's coastal wetlands are privately owned. Fortunately, there are many public parks, forests and natural areas along the coast with remnants of these special wetlands that you can visit. You'll find a list of the suggested stops at the end of this web presentation.
The glaciers' touch
They were cold and heavy and left their mark wherever they went. For a million years, glaciers ruled the landscape. Ice sheets up to 6,500 feet thick compressed the land, scouring out the deep basins of the future Great Lakes and leaving deposits of boulders, sand and clay. With each advance and retreat of the glaciers, the land was altered.
About 10,000 years ago, the climate warmed enough to melt the glaciers. The Great Lakes basins gradually filled with meltwater, and along their shores wetlands formed behind sandpits near drowned river mouths, along wave-cut cliffs and on clay bluffs. Above the beaches, wetland plants took hold in the swales, or low spots, between the ridges of land running parallel to shore.
When the glaciers receded, the land began to rise – a process which is still occurring in northern regions of the Great Lakes. The "tilt", precipitation and stream flow cause lake levels to fluctuate, which in turn affects the coastal wetland ecosystems.
Coastal lands where wetlands form
"Inland" wetlands – marshes, bogs, fens, sedge meadows and shrub swamps and coniferous swamps – are also found along the coasts, with many familiar wetland plants and animals. Cattail, arrowhead, tag alder, tamarack and bur reed grow in coastal wetlands; red-winged blackbirds and great blue herons cruise the coasts; muskrats build their lodges and northern pike spawn inwetlands near shore.
A few coastal landforms differ from their inland counterparts. Formed by the geological forces that created the lakes, dominated by lake weather and changing lake levels, these lands with wetland communities thrive in tandem with the Great Lakes. For example:
Weather and wetlands
Large bodies of water greatly influence local climate. Dry air traveling across lakes Superior and Michigan picks up plenty of moisture, which then falls as rain or snow on the coasts. Because such large lakes warm slowly in spring and cool down just as slowly in winter, the adjacent land areas experience more moderate year-round temperatures than the searing summers and bitter winters inland.
The coasts of lakes Superior and Michigan are cooler, more humid, and receive more precipitation than other parts of the state. The species that thrive in coastal wetlands have adapted so well to these climatic conditions that some of them – lake cress, for example – cannot survive anywhere else.
All wetlands change in response to the amount of water available in any given season or year. Coastal wetlands can bear harsh Great Lakes storms and survive fluctuating lake levels because they are dynamic, changing as the lakes change, yet achieving an equilibrium or balance over time. Plants and animals may be present one year and not another, depending on conditions.
Coastal weather even governs avian aerodynamics. In spring, the cold waters of Lake Superior trap warm air near the surface, preventing it from rising. Migrating birds can't get any "lift" in the air and are "grounded" at coastal wetlands until the weather changes – to the delight of birdwatchers on shore!
Plants of the coast
Call them fussy if you like. Some of Wisconsin's rarest flowers and grasses can exist only in specific coastal wetlands. Lake cress favors the sheltered waters of Lake Superior's coastal lagoons, while butterwort prefers semi-shaded, wet crevices on Lake Superior's cliffs. The carnivorous English sundew digests its prey on floating sedge mats in Lake Superior; the auricled twayblade, an orchid, grows near the lake on sandy riverbanks under tag alder.
Coast sedge floats in mats on both lakes, but non-wetland plants like Pitcher's thistle will not stray from Lake Michigan's dunes. The dwarf lake iris keeps to Lake Michigan's boreal forest and adjoining habitat, much as marsh grass-of-Parnassus sticks to the interdunal wetlands, wet dolomite outcroppings and seeping clay bluffs of Lake Superior.
And then there is the reclusive fly honeysuckle; the rarest, not seen in Wisconsin since 1897. This denizen of Lake Superior's tamarack swamps was rediscovered in 1995!
These rare gems are supported by a cast of more common beach and wetland grasses, reeds, shrubs and trees. Together, the plants of the coast anchor and protect our shores.
Birds and other coastal creatures
Wisconsin's Great Lakes coasts provide safe harbors not only for ships, but also for countless birds migrating along the east-west axis of Lake Superior (in spring) and the north-south axis of Lake Michigan (in fall). Canada geese, tundra swans, waterfowl , songbirds, merlins and other raptors follow the shore in great numbers in search of places to rest, feed and nest. Cormorants and gulls join in, too, though they'll remain after the others have flown on.
The range of habitats within coastal wetlands can accommodate even the most particular of species.
The common tern, an endangered shorebird in Wisconsin has two stable nesting colonies on Lake Superior. The endangered Caspian tern is attempting to breed on Lake Michigan after a long hiatus. The merlin, a falcon of special concern in Wisconsin, hunts open wetlands on long coastlines, choosing to nest in tall conifers near shore.
Wetland regulars, including muskrats, shrews, salamanders, frogs, turtles and snakes, appear in coastal sites. Rarer appearances are made by the Lake Huron locust at the coastal dunes, and Hine's Emerald Dragonfly near alkaline streams on Lake Michigan. In the water, the Atlantic elliptio, a mussel, rests in coastal estuaries.
Fish benefit from coastal wetlands. Different species take refuge from the cold, deep lake waters in the warm, fertile wetland shallows, where food is abundant and aquatic plants like the bulrush provide cover from predators. Juvenile smallmouth bass and other young fish stay in sheltered costal wetlands until they are mature enough to move into deeper waters. Northern pike use wetlands as spawning grounds. The species was once quite common in southern Lake Michigan – until the wetlands around Milwaukee were drained. Now pike populations have moved up the coast to Green Bay and Door County, where the lush Mink River Estuary offers the wetland habitat northern pike require to reproduce.
Rare...and getting rarer
Coastal wetlands can withstand the brunt of nature's watery fury. What they can't endure is human enthusiasm for the shore. Building and developing on lakeshores damages or destroys wetland habitat. Altering water levels by stabilizing shores and building piers and breakwaters interferes with natural lake fluctuations. Excessive nutrients from runoff and toxic substances in sediments harm water quality. Exotic species, including purple loosestrife, zebra mussel, ruffe, carp and the spiny water flea, threaten native species.
The rugged shores and long beach vistas draw visitors as no other natural attraction can. The natural features of the coasts, however, are extraordinarily fragile. If we want to keep on enjoying these special places, we must protect and preserve them.
Visit the shore
You can tour a coastal wetland on foot, or by canoe or skiff. Please follow paths or boardwalks and do not pick blossoms, dig plants or gather seeds. On the water, paddle or row gently and stay in travel lanes if they are marked to avoid disturbing plants, birds and animals.
The wonders of coastal wetlands can be brought nearer with binoculars and a small hand lens. Spring and fall outings will be best for birding, while plants will be in flower and changing as the spring and summer progress. Expect to get some sand in your shoes!
About the author Maureen Mecozzi is the associate editor of Wisconsin Natural Resources magazine.
Produced by the Wisconsin Coastal Management Program and the Wisconsin Department of Natural Resources. Funded by a grant provided under the Coastal Zone Management Act and approved by the Wisconsin Coastal Management Council.