It might sound like this is about a fashionable department store, but beach ridges and the shallow, watery swales between them are natural features of the Great Lakes shorelines. We hiked at one example of this complex ecosystem at the Ridges Sanctuary in Bailey’s Harbor on the eastern side of the Door peninsula.
The entrance walkway to the Sanctuary crossing over a swale, with the shoreline lighthouse at the end.
Ridges and swales are most likely to develop where coastal land is uplifted or where lake levels fall, which is probably what has been happening here in the past 10,000 years since the last glacial recession. Sediments are deposited with gentle wave action against the shoreline in a protected harbor, leaving behind a low hill of sand and gravel in which hearty colonists establish themselves.
Map of the Ridges Sanctuary, showing the parallel rows of beach ridges separated by low-lying wet swales. Black lines are the trails through the area.
The most recent beach ridge on the shoreline is being colonized by 3-foot tall conifers and grasses, which will slowly add humus to the sandy matrix, improving conditions for further growth.
Between each of the Ridges, is a low, wet area (the swale) where sedges thrive, and assorted moisture-loving plants, like orchids thrive.
Raised walkways guide hikers across the swales and provide views of wildlife and exotic plant species along the edges of the ridges.
The variation in environment from dry to wet, or coastal to inland makes this an extremely diverse ecosystem, home to more than 500 species of plants, 60 some species of birds, and more than a dozen mammals.
Fringed Gentian is one of the 500+ plant species to be found in this diverse ecosystem. Summer blooms include at least 25 species of native orchids, along with bog species like pitcher plant and sundew.
The ridge furthest from the coast begins to look more like mature coniferous forest, with tall red pine, white cedar, and fir trees. The path here is spongey, needle duff rather than sandy gravel.
The Ridges Sanctuary was founded in 1937, becoming Wisconsin’s first land trust, designed to protect the state’s most biologically diverse ecosystem.