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2020 Regional Tree Census: How do trees measure up?

Blond woman examines a tree while wearing a yellow surveyor vest


Over the next few months, some homeowners in the Chicago region may notice workers examining and measuring their neighbors’ trees or their own. They are gathering data for a census of trees in the seven-county Chicago region, not only counting the trees but recording their species, size, and overall health.

The Morton Arboretum is leading this effort, an update of a similar inventory 10 years ago. Again, staff from The Davey Tree Expert Company will be collecting the field data.

Managing the tree census is urban tree science leader Chai-Shian Kua, PhD, from the Arboretum. “A tree census is important because it helps to protect and improve the trees and forests in Chicago-area communities,” says Kua. “By gathering knowledge about trees, we can place a value on the ecosystem services trees provide.”

The 2010 tree census, conducted by the Arboretum along with the USDA Forest Service, found that there were 157 million trees in the seven-county Chicago region (Cook, DuPage, Kane, Kendall, Lake, McHenry, and Will counties). Using a software program called i-Tree, they calculated that those trees provided environmental benefits worth $51.2 billion a year, including storing 16.9 million tons of carbon and removing 24,170 tons of air pollution.

This year’s census will show how the tree picture has changed in 10 years. For example, it will give scientists hard data on how many trees have been lost to the emerald ash borer. It also will show the impact of land development and other challenges for urban and suburban trees.

For comparison purposes, the field workers will return to many of the same sample plots used in 2010. From those 1,600 sample plots, they will estimate the entire Chicago-area tree population. A new version of the i-Tree software will be used to analyze the data and calculate the benefits trees provide. For example, i-Tree Eco can report how much shade a neighborhood’s trees are providing and consequently how much those trees may help a homeowner save in energy costs.

The 2020 tree census is funded in part by a $100,000 contribution from the Daniel F. and Ada L. Rice Foundation. Philanthropic donations are essential to the success of The Morton Arboretum and make a difference for the future of trees.

The results of the 2010 Regional Tree Census are available online. To learn more about the region’s tree canopy, explore the Chicago Region Tree Initiative (CRTI) interactive story map, based in large part on the 2010 results.