CHICAGO — New data from the Chicago Region Trees Initiative paints an alarming picture of ecological decline in the metro area: nearly 80% of forest preserves and natural woodlands across Cook, Lake, DuPage, and other surrounding counties are now infested with invasive plant species. Conservationists and researchers are urging both local officials and private homeowners to act — before it’s too late.
Invasive Species Spreading Across the Region
According to a recent report covered by WTTW News, invasive shrubs and trees — especially European buckthorn, honeysuckle, and multiflora rose — are dominating local woodlands, squeezing out native vegetation that once supported biodiversity and healthy ecosystems.
“These species don’t belong here, and they’re taking over at a staggering pace,” said Carrie Heitman, a program manager with the Chicago Region Trees Initiative at the Morton Arboretum.
The Impact: From Birds to Climate Resilience
The dominance of invasives has deep ecological implications. Native understory plants, including oak seedlings, wildflowers, and important ground cover, are often outcompeted for sunlight and nutrients, leaving forests barren and degraded.
“A forest dominated by buckthorn is not functioning the way it should,” Heitman explained. “It becomes a monoculture — bad for insects, bad for birds, and bad for climate resilience.”
In fact, researchers say that healthy native forests help:
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Filter groundwater
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Store carbon
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Buffer flooding
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Support pollinators
When invasives take over, those natural systems break down.
The Numbers: Regional Trends Across Counties
The Chicago Region Trees Initiative’s 2023 Urban Forest Vulnerability Assessment surveyed 130 publicly owned forest patches in seven counties: Cook, DuPage, Kane, Lake, McHenry, Will, and Kendall. The findings were sobering:
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Nearly 80% had invasive plant presence above sustainable thresholds.
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Many forests had lost their native understory entirely.
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Patches with oak trees — a cornerstone native species — were often surrounded by dense thickets of buckthorn.
Some forests showed signs of being past the point of natural recovery without significant human intervention.
Why This Matters for Homeowners
While much of the attention has focused on forest preserves, experts stress that private property owners have a vital role to play. “The majority of land in the Chicago region is privately owned,” Heitman emphasized. “What homeowners do with their yards can directly affect nearby forest health.”
If your backyard borders a woodland or forest preserve — or even contains mature trees — you might be unknowingly harboring or spreading invasive species. Common culprits include:
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European buckthorn (often used as a privacy hedge)
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Japanese barberry
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Honeysuckle
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Callery pear (also known as Bradford pear)
These may appear decorative, but they escape into wild areas, crowding out native saplings and reducing habitat quality for birds and other wildlife.
What You Can Do
To slow the spread of invasives and support native ecology, homeowners and local governments alike can take several key steps:
1. Remove invasive shrubs and trees
Start with buckthorn and honeysuckle — the two most aggressive species in the area.
2. Replace with native alternatives
Consider planting serviceberry, dogwood, spicebush, or native oak saplings that support insects, birds, and soil health.
3. Join a local ecological restoration effort
Many organizations — such as Friends of the Forest Preserves, Openlands, and The Conservation Foundation — hold regular volunteer days to remove invasives and restore habitats.
4. Talk to neighbors
A single property change can’t halt the problem, but block-by-block efforts can restore corridors and protect nearby preserves.
Calls for Public Policy Changes
While community awareness is critical, ecologists argue that larger-scale policy shifts are also needed. These include:
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More aggressive management funding for forest preserves
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Local bans or restrictions on invasive ornamentals at nurseries
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Expanded public education campaigns on native gardening
Some towns — such as Highland Park and Glenview — have already enacted ordinances banning buckthorn. Experts hope other municipalities will follow suit.
“This Is Our Window”
“There’s still time to reverse this trend, but that window is closing,” Heitman said. “If we don’t act now, we risk losing the forests that define the Chicago region’s natural identity.”
With biodiversity declining and climate pressures increasing, the call to action is clear: everyone — from forest rangers to backyard gardeners — has a role to play in preserving Illinois’ natural legacy.
Have You Noticed Invasive Species in Your Neighborhood?
We’d love to hear from readers across the suburbs and the city. Are you seeing changes in your local forest preserve or backyard? Join the conversation and share your observations in the comments section below at ChicagoSuburbanFamily.com.
