Five small islands roughly the size of backyard swimming pools float next to the concrete riverbank of Bubbly Creek, a stretch of the Chicago River named for the gas that once rose to the surface after stockyards dumped animal waste and byproducts into the waterway. Clumps of short, native grasses and plants, including sedges, swamp milkweed, and queen of the prairie, rise from a gravel-like material spread across each artificial island’s surface. A few rectangles cut from their middles hold bottomless baskets, structures that will, project designers hope, provide an attachment surface for freshwater mussels that once flourished in the river.

Three thousand square feet in total, these artificial wetlands are part of an effort to clean up a portion of a river that has long served the interests of industry. This floating wetland project is one of many proliferating around the world as cities increasingly look to green infrastructure to address toxic legacies. In the United States, researchers are conducting experiments in Boston and […]