Intense Thunderstorms Down Hundreds of Trees

Dozens of unusually intense thunderstorms marked this past summer, damaging or felling thousands of trees. Storms on July 5 and 17 downed more than 600 southside Chicago Park District trees, among them one of the district's oldest: a 200- to 300-year-old bur oak on Wooded Island in Jackson Park. Intense downbursts with gusts 80 to 90 miles per hour leveled more than 100 trees along the Illinois and Indiana state lines in the July 17 storm.

The revered ancient oak at Wooded Island once stood 45 feet tall and 90 feet wide. Brian Williquette, a Chicago Park District forester, anticipates that most of the fallen oak's broad crown will be removed because its open savanna habitat is limited and valuable in this small park. The trunk will be left as a memorial, with perhaps a portion used for research or educational purposes.

"Within the parks' natural areas, we'll leave some tree trunks and debris, if they don't pose a public hazard, as habitat for woodpeckers and other birds," said Williquette. Where it replaces trees, the district will pay attention to the original palette of landscape architect Frederick Law Olmsted, guided by soil types and the district's commitment to diversity. Weedy and invasive trees won't be replaced, but important habitat trees, such as the willows lost at Bobolink Meadow in Jackson Park, will be replaced.

Within 24 hours of the July 17 storm, the Forest Preserve District of Cook County, with the help of the Illinois Department of Transportation, was able to clear and open trails in the Lansing, South Holland, and Calumet City area preserves. Powerful downdrafts toppled mostly cottonwood and black locust that, where they pose no risk, will lie in the forested areas and decompose. "It's Mother Nature's way of pruning," said Richard Newhard, superintendent of the department of resources management for Cook County. "Young trees will now make their way to the open sunlight."

—Alison Carney Brown