Resilience Scanner

AI-Powered Urban Tree Canopy Mapping Using Satellite & LiDAR Data

Solution Overview

Satellite data is used to periodically evaluate tree coverage across Chicago and across the greater region.[3][5][9] A pipeline was developed that utilizes LiDAR data as ground-truth and trains a multi-task machine learning model to generate estimates of tree cover and canopy height in urban areas using multi-source multi-spectral satellite imagery for Chicago.[8][10] This technology-enabled approach supports the city's efforts to expand tree canopy coverage, particularly in historically marginalized and underserved communities where tree cover is particularly low.[1]

Technical Components

The technical infrastructure combines multiple data sources and advanced analytical methods to assess urban tree coverage. A multi-task UNet convolutional neural network was used with airborne LiDAR data to generate estimates of canopy cover and height from aerial and satellite imagery for Chicago.[6] Some of the datasets include neighborhood surface temperatures, the number of asthma cases, and social vulnerability, with certain data coming from NASA and some being three-dimensional LiDAR (light detection and ranging) data collected by using a pulsating laser to measure distances.[1] Researchers mapped tree and building heights in Chicago at a high detail 1-meter resolution using high-precision LiDAR data, building footprint inventories, and multi-band satellite images.[11] Health geographer and data scientist Marynia Kolak and a team of fellow University of Chicago researchers recently partnered with Chicago's Department of Public Health to develop a new advanced mapping tool—one that combines tree data with other metrics related to health outcomes, including air quality, surface temperature and traffic volume.[2] The Chicago Department of Public Health developed a 'community tree tool' that overlays data on tree canopy with air quality, land surface temperatures, economic hardship, and other social vulnerability and environmental factors.[3] The research team built the tree equity tool using Carto's data mapping and visualization software.[1] To create the tool, the UChicago research team harmonized multiple datasets into a standardized format for evidence-based decision making.[2]

Implementation Details

Chicago announced a $46 million project to plant 75,000 trees over the next five years—especially in historically marginalized and underserved communities where tree cover is particularly low.[1] Our Roots Chicago is a partnership between the City of Chicago, including the Department of Streets and Sanitation (DSS) and the Chicago Department of Public Health (CDPH), and non-profit partners, including Morton Arboretum and Openlands.[4] The initiative prioritizes tree planting in communities with low canopy coverage and high need across all 77 community areas.[4] Chicago will spend $46 million planting approximately 75,000 new trees over the next five years, focusing in part on census tracts with relatively lower numbers of trees.[2] The 'community tree tool' was developed by the Chicago Department of Public Health with support from the Bloomberg Philanthropies Partnership for Healthy Cities.[3][5] Bloomberg Philanthropies contributed some of the funding for the research tool pilot.[1] The tree equity research done by HeRoP directly influenced the Mayor's Office recently passed budget to commit $46 million in spending to help the city plant 75,000 trees over the next five years.[12] The canopy estimates were used to allocate 75,000 trees from Chicago's recent green initiative under four scenarios, minimizing the urban heat island effect and optimizing for equitable canopy distribution.[6] The tool will be used to identify areas that could benefit from increased canopy cover over the long term, as measured by three-dimensional LiDAR data.[2]

Benefits and Impacts

Working as part of UChicago's Healthy Regions + Policy Lab (HeRoP), Kolak and her colleagues found a relationship between these health factors and the amount of canopy cover—the extent to which tree crowns cover a neighborhood.[2] More trees were associated with a range of positive outcomes, including better air quality and lower summer surface temperatures.[2] HeRoP's Tree Equity solution uncovered that areas with fewer trees had association with higher air pollution models.[12] The mapping tool quantifies where trees exist citywide and illustrates that Chicago's historically redlined and segregated neighborhoods often contain fewer trees.[1] Currently, the city's average canopy coverage is only 16% which is below the ideal average for cities.[3] The citywide tree canopy coverage in Chicago is 16%, varying greatly between neighborhoods, ranging from under 10% to 46%.[5] In historically under-resourced and underserved community census tracts in Chicago, tree canopy coverage often varies from 4% to 10%.[3] Chicago's Englewood neighborhood is one of the lowest-income areas of the city, but it has a relatively high amount of tree canopy cover, making that neighborhood shadier and cooler during the summer than others of similar socioeconomic status.[1] Including canopy height within decision-making processes allows the distribution of new trees to be optimized to further reduce the urban heat island effect in localities where trees have the highest cooling potential and allows trees to be more equitably distributed to communities with lower quality canopies.[6] Chicago's urban forest provides ecosystem services valued at $785.7 million annually in 2020, including $740 million in carbon storage, $15.1 million in air pollutant removal, $11.9 million in avoided runoff, $11.2 million in building energy savings, and $7.5 million in carbon sequestration.[13] Chicago's urban forest sequestered 39,000 tons of carbon annually in 2020.[13] Chicago's urban forest removed 1,300 tons of air pollutants annually in 2020.[13] Chicago's urban forest avoided 100 million cubic feet of stormwater runoff annually in 2020.[13]

Climate Adaptation Relevance

The HiTAB dataset provides city planners, scientists, and government officials with new tree and building height data that is essential for urban climate modeling, tree inventory management, and green infrastructure planning.[11] HiTAB can aid in showing where the city lacks canopy cover, allowing the city to create a more comprehensive urban plan.[11] Findings derived from the HiTAB dataset will aid in addressing urban challenges such as heat mitigation, flood prevention, and pollution control in Chicago.[11]

Business Analysis

Researchers built a free, open-sourced version of the tree equity tool so residents can explore environmental data in their own neighborhoods and compare it to others.[1] The HeRoP lab also created a free and open-source version to allow everyone to explore Chicago's environment, allowing people to zoom in on their own neighborhoods to understand how they compare to nearby areas.[2] CRTI provides data and maps of tree canopy distribution across the region that prioritize communities with the greatest need for more investment in trees.[9] Community Tree Canopy Summaries provide data on the tree canopy cover, plantable space, and types of land use for community areas in the Chicago region through an interactive map and downloadable community summary reports.[9] The structural, or compensatory, value of Chicago's urban forest is estimated at $2.3 billion.[14] Chicago has about 3,585,000 trees with canopies that cover 17.2 percent of the area.[14] Trees in Chicago are estimated to reduce annual residential energy costs by $360,000 per year.[14] Chicago's trees remove about 25,200 tons of carbon per year ($521,000 per year) and about 888 tons of air pollution per year ($6.4 million per year).[14]

Sources