Replacing Trees Lost

to Emerald Ash Borer

in Illinois Reduces Stormwater, Flooding

Replacing trees lost to invasive emerald ash borer in the greaters Chicago area has reduced stormwater and flooding and provided habitat for wildlife.


For over 15 years, the Chicago metropolitan area has been combating the emerald ash borer, an invasive species that feeds on the inner bark of ash trees, disrupting their ability to transport water, and ultimately killing them. Since its discovery in 2002, the non-native beetle has killed tens of millions of ash trees in North America, including nearly 13 million in the Chicago metropolitan region.

About 20 percent of trees in Chicago parks are ash trees. These trees provide the community shade, cooling and crucial stormwater sinks, as well as reducing air pollution. Due to the infestation of the emerald ash borer, however, millions of these trees have had to be destroyed.

Thanks to a series of grants from the Great Lakes Restoration Initiative, the Morton Arboretum has been able to help communities in Cook and Lake Counties plant 772 new trees to replace the ash trees lost to the emerald ash borer. Some of these areas include the Cook County Forest Preserve and the cities of Chicago, Glenview, Highland Park, and Orland Hills. These trees have had a tremendous effect on the communities in which they were planted.

“Each [mature] tree can handle an average of 1000 gallons of stormwater per year,” said Lydia Scott, Director of the Chicago Trees Initiative of the Morton Arboretum. This stormwater block helps relieve overburdened stormwater systems and reduce flooding.

“The trees provide improved habitat for wildlife, especially migratory birds,” Scott said. The arboretum takes special care to plant trees that are native to the Chicago region. “We try to replace [lost ash trees] with native species such as oaks and hickories – trees that are native to the Chicago region. They’ve co-evolved with the birds and insects here. Birds know to look for those trees.”

Resource Challenges Addressed

  • Tree Loss
  • Habitat Loss
  • Invasive species


A worker replaces trees lost to the Emerald Ash Borer in the Chicago area. Photo Credit: The Morton Arboretum

Results and Accomplishments

Planting more than 772 new trees has reduced stormwater surges and prevented flooding in several Chicago-area communities. The project has also replaced lost habitat for migratory birds in the region, as well as providing shade, cooling and improved air and water quality for the communities in the area.