Invasives Out, Native Plants In: River-Edge Work Showing Signs of Success

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Native plant species coverage is increasing along the Chicago River system at a number of sites thanks to a volunteer-driven, years-long land restoration effort,  Friends of the Chicago River data suggest.

Removal of invasive plant species—non-natives which adversely affect wildlife habitat and water quality—by the Centennial Volunteers project at a number of targeted river-edge Forest Preserves of Cook County locations  is showing double-digit percentage increases in the coverage of native plants. The work is aimed at improving wildlife habitat, water quality, and flood reduction

Friends compiled and analyzed native plant species vs. non-natives at the targeted locations where Centennial Volunteers removed invasives such as buckthorn, garlic mustard, and honey suckle. Such projects can improve wildlife habitat, water quality, and flooding.

Centennial Volunteers is a partnership established in 2014 by Friends of the Chicago River, Friends of the Forest Preserves, and the Forest Preserves of Cook County. Funding for Centennial Volunteers is provided by the Chi-Cal Rivers Fund, a grant from the National Fish and Wildlife Foundation.

Improvement trends were also measured through a floristic quality index (FQI) based on a formula that includes the ecological condition or quality of an area.

Along the North Branch, targeted areas within:

  • Clayton Smith Woods, between Bunker Hill near Niles and Miami Woods near Morton Grove, saw native plant coverage climb from  56 percent in 2016 to 68 percent in 2019. The FQI ranking for the targeted area went from 10.3 to 16.6.
  • Somme Woods, near Northbrook, went from 50 percent native plant coverage in 2016 to 77 percent in 2017. The FQI rose from 20.8 to 26.2.
  • Blue Star Memorial Woods, near Glenview, climbed from 36 percent native coverage in 2016 to 66 percent in 2018. The FQI in the targeted area within Blue Star saw a jump from 13.5 to 21.6 in that time period.
  • Forest Glen, on the city’s Northwest Side, saw its native plant coverage skyrocket from 37 percent  in 2016 to 78 percent in 2018 in the targeted work area. The FQI went from 15.0 to 22.1.

In the south along the Little Calumet River, targeted areas within:

  • Beaubien Woods, near I-94 and East 130th St. in Chicago, saw its native plant coverage increase from 47 percent in in 2016 to 74 percent in 2019. The FQI in the target area grew from 13.5 to 21.9.
  • Whistler Woods, near south suburban Riverdale, native plant coverage increased from 37 percent in 2016 to 65 percent in 2019.  The FQI was 15.7 in 2016 and 21.94 in 2019.
  • Kickapoo Woods, near south suburban Riverdale, saw its targeted area grow from 40 percent native plant coverage in 2016 to 62 percent in 2018. The FQI increased from 19.0 to 19.9 in that time period.
  • River Oaks Woods, by the Sand Ridge Nature Center near South Holland, went from 33 percent native plant coverage in 2016 to 68 percent in 2018. The FQI  jumped from 10.7 to 14.9.

The targeted areas ranged from ten acres to 20 acres. Restoration work at non-Centennial Volunteer sites, such as Watersmeet Woods, Wampum Lake and Sag Quarries also saw improvments in native coverage and FQIs.

What's a Non-Native Plant Look Like? Download Our Guide Here

“It has been amazing to witness the changing plant community over the past few years at these sites,” said Friends Ecology Outreach Manager Mark Hauser, who compiled and analyzed the data. “Invasive thickets are transformed into diverse habitat through the work of our volunteers.”

“The Centennial Volunteers restoration work is an example of what is possible when organizations partner,” said Arnold Randall, General Superintendent of the Forest Preserves of Cook County. “Restoration in the many diverse habitats of the Forest Preserves is a high priority for us, and collaboration among like-minded organizations expands our capabilities to protect nature for generations to come."

Invasive plants choke out native growth and also block sunlight from reaching the ground. This negatively affects soil conditions and hinders habitat for wildlife such as egg-laying turtles.

Invasive plants also reduce stormwater retention: Native plants allow about 86 percent of stormwater to soak into the ground while non-natives and turf grass only allow about 28 percent. Non-absorbed runoff can lower water quality in the Chicago River system, tax sewer systems which can result in combined sewer overflows (CSOs) into the waterway, and cause basement flooding. 

In natural areas, the runoff causes erosion and sedimentation which can devastate landscape and aquatic habitat. High levels of turbidity block sunlight penetration and impede the growth of algae and aquatic plants. High amounts of sediment will reduce the river's capacity to handle flooding. This runoff can also carry chemicals into the waterway.

For more information on how to become a Centennial Volunteer, go to