Floating Wetlands in the Chicago River

Improve Water Quality and Attract More Wildlife and Humans

It began with an experiment: Place a 10-square-foot floating wetland with native plants into the polluted Chicago River and see if anything grows. It did. Nearly a decade later, hundreds of structures spanning 22,000 square feet of floating wetlands, containing roughly 27,000 plants comprised of 80 native species, are flourishing along what’s dubbed the Wild Mile, as well as along the river’s south and north branches.

“The plants are thriving and so is community engagement,” says Maggie Cooper, manager of conservation action at the Shedd Aquarium (SheddAquarium.org). Shedd partners with Urban Rivers (UrbanRivers.org) and others to promote the floating wetlands program, which includes educational and research activities.

The floating wetlands are garden modules built on structures layered with various fibers and wood chips. “The plants grow through the fiber and hang below the water, providing surface area for fish and treatment for water quality improvement,” says Urban Rivers Co-founder and Executive Director Nick Wesley.

“Our idea is that the whole area along the east side of Goose Island becomes a floating eco-park,” says Wesley. “We are building it in stages,” he adds, noting that Shedd helped Urban Rivers secure grants to build and maintain the platforms.

Shedd became involved with the floating wetland project a few years after Urban Rivers began as a small nonprofit in 2014.

“We were looking at how you could grow food on water, and then eventually we started to look at if you can use plants to clean the water,” Wesley recalls. He met co-founder Josh Yellin, who was doing postdoctoral work at Shedd in 2016 and researching how floating wetlands affect fish habitats.

It took Urban Rivers several years to secure funding and permits to build the wetlands. “In 2017, we installed the first section of floating gardens, about 166 feet long,” Wesley says. “Year by year, we kept adding more and started working with Shedd. We also talked with the city and worked with the Department of Planning and Development to get funding for a walkway section where visitors could easily view the plantings.”    

The first phase of the Wild Mile was completed in 2022 on the Chicago River canal on the east side of Goose Island. It features a large floating platform, walkways and floating gardens.

That’s quite different from how the river looked in the 19th and 20th centuries. Charted in 1673 by French explorers, the Chicago River has since been dredged, channelized and used as a dumping ground for human and industrial waste. The polluted river caused cholera epidemics in the 19th and 20th centuries; to address the pollution, the city reversed the river’s flow to bring in clean water from Lake Michigan.

Promising Research

With the creation of the 1972 Clean Water Act, residents, nonprofits and government agencies have worked to improve the Chicago River, including establishing the floating wetlands.

At least 13 native fish species at the larval stage, including bluegill and largemouth bass, have been identified using the floating wetland ecosystems. A published peer-reviewed paper by Shedd research biologist Austin Happel explains that research in the Chicago River between 2020 and 2022 revealed 2,000 larval fish.

“This research represents the first documentation of larvae from fish species occurring within the Chicago River, indicating that recovery and restoration efforts allow at least 24 species to successfully spawn and reach the larval stage,” says Happel. “Our previous studies showed that improvements to water quality in the river increased biodiversity, and now we have more positive news as populations are proliferating locally within the river.”

While the plants attract the fish, they also draw some of the metals and gases from the river and replace them with much-needed oxygen. “Native wetland plants have root systems of 5 to 10 feet deep,” Cooper explains. That enables them to remove excess pollutants while getting the nourishment they need.   

“We’d also like to explore how floating wetlands can be used as mitigation for sewage overflow. We want to understand more about these and how they contribute to conservation and healthy bodies of water,” Cooper continues.

“We go out with volunteers in winter, and we look for native mussels in clean rivers. We’re in our waders. It’s very meditative,” Wesley says. They bring pregnant mussels back to the lab, where the eggs are released, hatch and then grow to be large enough for transfer into the Chicago River.

“We put them in sunken modules with sand. We put lids on them, so raccoons don’t eat them,” Wesley explains. “We’ll also return the mother to where we found her.”

The mussels are surviving, he says, and they’re helping filter pollutants out of the river. “There used to be tremendous populations of mussels in the Chicago River before industrialization,” he says. “Now we’re at a point where the water quality is good enough for them to survive.”

“We ask them to be community scientists to identify and keep track of the waterfowl we’re seeing, as well as the turtle species,” Cooper says. “We’re seeing more diversity and numbers of waterfowl and turtles throughout the area where the floating wetlands have been established.”

They’ve observed the state-endangered black-crowned night heron, as well as green heron and great blue heron. “We see terns and we hear kingfishers. We see snapping turtles, softshell turtles, map turtles, red-eared sliders and painted turtles,” Cooper continues. “People get so excited to see the turtles and they’re so curious about the birds.”