The crunch of boots on packed snow follows hikers along the Hidden Brook Boardwalk in the Ridges Sanctuary. Trees wear the thick, fresh snowfall like a gingerbread house flocked by heavy-handed toddlers.
Covering 1,600 acres on the east side of Wisconsin's Door County peninsula, this sanctuary near Baileys Harbor preserves some of the state's unique ecosystems, thanks to its location along the Niagara Escarpment — the rocky edge of an ancient sea — and surrounded by Lake Michigan.
I spotted small shoreline sinkholes earlier in the day, evidence of the area's karst topography, where dolomite limestone bedrock has been carved by centuries of water and shifting temperatures. Wind, sand, pounding waves and even reddish, gnarled cedar roots join forces to forge layered cliffs along the shoreline of the Great Lake.
"It's a very dynamic system," said George Cobb, a naturalist at the Ridges. Inside the sanctuary's visitor center, he pointed to an aerial photo that shows how the peninsula's ridges and swales stripe the landscape with natural terraces. "It's one of the most diverse areas of the state."
About 30 ridges alternate with swales — depressions that collect and filter rainwater and melting snow. In the spring and summer, moisture-loving orchids, such as grass pinks, ram's heads, showy pink and yellow lady's slippers, draw wildflower fans.
"We have 26 different kinds of orchids," Cobb says. Along the boardwalk, where visitors can join guided winter hikes, he helps us imagine a warmer, greener sanctuary, where volunteers track climate change and bird migrations and study species such as the endangered Hine's emerald dragonfly.
We pause at a swale. Two to 3 feet deep, it looks like a river gently flowing across undulating native grasses. The watery swale's dark, cool colors contrast with the snow-flocked pines and cedars and a moody, smudgy mix of sky and clouds.
Toward the end of the boardwalk, Cobb points out a set of historic range lights, like squat lighthouses. One looks like a bell-towered pioneer school tucked into the trees; a smaller one sits closer to shore. Long-ago ships loaded with lumber and limestone navigated Baileys Harbor's treacherous shoals by lining up the two lights, offering more accuracy than a single lighthouse.