Quantifying urban forest structure, function, and value: The Chicago urban forest climate project

Abstract

The 3-year Chicago Urban Forest Climate Project examined how trees affect these components of the regional urban ecosystem. The region`s tree cover has increased from a presettlement level of about 13 percent to nearly 20 percent today. There are an estimated 50.8 million trees in the region; 66 percent in good or excellent condition. The trees tend to be small; 77 percent less than 15 cm d.b.h. Street trees are only 10 percent of the city`s trees, but 24 percent of leaf surface area because they are typically larger than off-street trees. During 1991, the region`s trees removed an estimated 6,145 tons of air pollutants, providing air cleansing worth $9.2 million. Each year they sequester an estimated 315,800 metric tons of carbon and provide residential heating and cooling energy savings that, in turn, reduce carbon emissions from power plants by 12,600 tons annually. Increasing tree cover 10 percent or planting about three trees per building lot is estimated to save annual heating and cooling costs by $50 to $90 per dwelling unit once the trees mature. The net present value of services trees provide is estimated as $38 million, or $402 per planted tree. The present value of long-term benefitsmore » are more than twice the present value of costs.« less