An analysis of trees in the Chicago region of Illinois reveals that this area has about
157,142,000 trees with tree and shrub canopy that covers 21.0 percent of the region. Chicago’s regional forest is estimated to reduce annual residential energy costs by $44.0 million/year.
Nowak, D.J., et al (2013). Urban Trees and Forests of the Chicago Region. US Forest Service, 1-98.View Resource