This article appears in the summer 2024 issue of Horizons, the award-winning quarterly magazine of the Lake County Forest Preserves in northern Illinois.

From a young age, we’re often taught that planting trees is good for the environment. So, why do we see large areas of trees sometimes removed from your forest preserves, leaving the land temporarily ragged and brown?

The answer is habitat restoration, a sequence of land management activities that improve the health, ecological function and diversity of species at a particular site, according to ecologists at the Lake County Forest Preserves. Sometimes that process involves removing non-native, invasive trees and other species.

During restoration efforts, you may see dramatic visual differences.

Rebuilding What’s Lost

In Northeastern Illinois, residential, commercial and agricultural development along with transportation infrastructure and underground pipes have degraded native habitats, including plants and wildlife that call them home.

“Agriculture, roadways, residential growth and business parks have fragmented the landscape and introduced invasive species. This has resulted in reduced biodiversity and ecosystem function,” said Matt Ueltzen, manager of restoration ecology.

“Illinois has lost 99.9% of its native prairies and Lake County has lost more than 88% of its remnant oak woodlands.” A remnant habitat is an area that’s experienced little human disturbance.

Restoration helps rebuild what’s been lost, Ueltzen said. “Restoring land helps connect fragmented environments. It provides a place for native plants and wildlife to survive. It increases biodiversity and makes landscapes sustainable for future generations.”

Through restoration, staff, volunteers and contractors remove many invasive species. These are usually non-native plants with growth patterns that harm native plants and wildlife, Restoration Ecologist Ken Klick said.

Invasive species are often introduced accidentally by human activity, such as shipping or gardening. They are not “bad plants” in their own right. But when removed from their original habitats, sometimes thousands of miles away, they can cause issues for native species.

“Invasives such as common buckthorn, glossy buckthorn and autumn olive grow densely, blocking sunlight from reaching the floor of some forest preserves. When these trees are removed, sunlight reaches the ground, encouraging oak reproduction and promoting growth of native grasses, sedges and wildflowers,” Klick said.

To help reduce the prevalence of buckthorn, we have cleared it from 6,133 acres in nearly 30 preserves since 2014. When reseeded with native species, these open, diverse lands help improve air quality, mitigate flooding and reduce the urban heat island effect.

The urban heat island effect involves sunlight hitting impervious surfaces such as roads, driveways and buildings. These structures hold onto and radiate heat longer than plants. Temperatures can be up to 15 degrees Fahrenheit higher in areas experiencing this effect.

Domino Effect

“Each spring and fall, trained crews of staff and volunteers conduct prescribed burns across hundreds of acres throughout the preserves,” Klick said. Prescribed burns help control invasive shrubs and trees and promote the regeneration of native plants.

Restoration essentially generates a domino effect. “The more plant diversity you have, the more bugs you have. More bugs bring more birds into the preserves, and then more birdwatchers and photographers.

“The number of people visiting the preserves then increases,” Klick said. “In addition to the biological benefits of restoration, the process makes the preserves so much more attractive.” Ueltzen agrees.

Healing Nature

A large project is currently taking place at Greenbelt Forest Preserve (North Chicago). Greenbelt sits at the headwaters of the East Fork of the North Branch of the Chicago River. Known as the Skokie River, it drains south into the Chicago River.

Crews removed a great deal of buckthorn, honeysuckle and aggressive native cottonwoods from about 40 acres on the west side of Green Bay Road in winter 2021–2022. They cut down the woody plants and later applied herbicide to the stumps with sponge tip applicators to prevent regrowth.

Greenbelt once contained large, high-quality prairies and wetlands. After removing invasive species, we found small patches of native plants left behind. Our experienced ecologists know native plants will regrow from dormant seeds in the soil and expand now that the invasives are gone.

“We’ve seen shooting star wildflowers, yellow star grass and other summer flora return,” Klick said. “It’s wonderful to reconnect with the plants and animals that have been here for thousands of years.” A similar project was conducted on the east side of Green Bay Road. Today, the eastern half of Greenbelt shows how the west side may look in 5–10 years.

“That’s how nature heals. It’s not immediate, but a gradual process. We introduce native seeds to speed up the process a bit,” Klick said. After restoration, the area should exhibit greater resilience to environmental changes such as heat, drought and cold.

Investing in the Future

In Lake County, where sprawling agricultural fields shape the landscape, a fascinating tale of innovation and unintended consequences unfolds beneath the soil. Once “a vast mosaic of wetlands,” these lands posed a challenge to early European settlers wanting to farm the land, said Pati Vitt, director of natural resources. A solution emerged in the form of clay drain tiles to transform wetlands into fertile farmland.

In the 1830s, farmers began installing clay drain tiles to solve this. Drain tiles are pipes buried underground that lower the water table. Clay and concrete tiles are installed with loose joints, or spaces between each section of tile, for water to seep through. Modern plastic tiles are perforated. Tiles usually range in size from 2” in diameter to 18” in diameter.

The widespread adoption of drain tiles by Midwestern farmers in the late 19th and early 20th centuries revolutionized agriculture. Tiles allowed farmers to use previously unfarmable or poorly performing land. Their crop yields spiked. This continues today.

About 10.5 million acres in Illinois, equivalent to 39% of the state’s agricultural lands, are equipped with tiles. Drain tiles don’t vanish after farmland is retired. They continue to reduce water quality and the size of wetlands. A common restoration step involves removing drain tiles to restore a habitat’s natural hydrology. Hydrology is the way water cycles through an area.

This type of restoration takes place throughout the county. One of the largest projects occurred at Pine Dunes Forest Preserve (Antioch). We worked with the Illinois Tollway Authority to mitigate 80 acres of wetland loss near O’Hare International Airport by restoring 235 acres of adjacent savanna and prairie habitat.

“When a farm field is retired from agricultural use, we want to keep as much of the water in the preserves as possible,” Vitt said.

At times, antiquated drain tiles, which resemble empty paper towel rolls, may simply be disabled or crushed in their original position. Alternatively, an operator might use heavy machinery to dig a trench and extract the tile.

Once tiles are removed or broken, water in the vicinity primarily permeates into the soil, rejuvenating groundwater supplies and nurturing wetlands.