Redlining and Tree Cover Lesson: Measuring Environmental Inequality in Baltimore

As preparation for the session, have learners read the article by Burghardt et al. (2022), paying special attention to the highlighted portions. Learners should also preview the redlining maps and introduction to redlining provided by the University of Richmond, which covers hundreds of cities across the country. Learners may be interested in browsing redlining maps from cities they know or live near, but this lesson will focus on the Baltimore map, specifically the redlined area D-4, and the greenlined area A-1. Also have learners preview the Baltimore Street Tree Inventory, a resource that provides tree species, size, and placement data across the city. 

(10 min.) After The Hook above, begin the lesson by reviewing these Lesson PPT slides.

(15 min.) Display the redlining map of Baltimore for the whole class to view. Divide the class into two groups: “greenlined” and “redlined,” and then subdivide into a total of four to eight small groups of three to four learners each. Each group will focus on a sample of trees along ~2,000 ft. of the street. Have learners open their browser windows to the Baltimore Street Tree Inventory and the city of Baltimore in Google Maps, which can help them navigate the region and provide street view images with which learners may assess the aesthetics of their assigned locale. Assign groups to these areas:

(15 min.) Allow small groups to zoom in on their assigned neighborhood in Google Maps and assess its overall appearance (street view) and nearby dis/amenities (industry, highways, parks, schools). Note: The redlined region sits just north of the infamous “Highway to Nowhere” (U.S. Route 40) that bisected a lively Black neighborhood when it cut through the city in the 1970s. The greenlined region is proximate to a number of private schools, universities (including Johns Hopkins), and parks. These two neighborhoods also have contrasting housing densities: the greenlined is single-family homes with yards, and the redlined is rowhouses with little-to-no yard space. Have learners take notes on these qualitative features and consider how they may affect quality of life and health in the local region. They may also wish to capture screenshots of street views. These notes will be important for the presentation in session two.

(30 min.) Now, have learners use the Street Tree Inventory to conduct a quantitative analysis of street tree placement, abundance, size, and diversity along their ~2,000-ft. street sample. Using a spreadsheet, groups should type data on street trees including Diameter at Breast Height (DBH); designation of small (DBH <5 in.), medium (DBH 5–20 in.), and large (DBH >20 in.); tree height; and species. They should also note stumps (black circles), vacant unsuitable tree spots (crossed-out red circles), and vacant suitable spots (green plusses). Once all data is entered, calculate the following quantitative information: number of trees; number of species; average DBH and height; distribution of small/medium/large; number of vacant spaces (both suitable and unsuitable). This exercise will take the remainder of this class period. Any groups that have not finished should complete the work as homework. Note the tree inventory database tools: Under each tree’s entry, click on the three dots at the bottom to access an attribute table that lists all trees within each category and allows users to place markers on exceptional specimens they may wish to note in their presentation.

(15 min.) In the next class session, reconvene the groups and have them review the quantitative and qualitative information on their assigned street. Each group will have 15 minutes to prepare a short (~5-7 min.) slide-based presentation of their findings to the whole class. While the exact format is up to their discretion, each presentation should provide quantities textured by qualities of their street and make specific observations about how certain factors such as housing, proximity to dis/amenities, and city investment (including new tree planting programs) affect their perception of this street’s quality.

(~40 min.) Each group now has the opportunity to present their findings and field questions. Have all the greenlined groups go first, then the redlined groups. All groups should upload their quantitative spreadsheet into a shared course space, for everyone’s access.

(20 min.) Finish this lesson with a whole-group discussion of the residual effects of redlining. The instructor may wish to emphasize certain points, such as the importance of tree species diversity (in an ecology class) or how housing type affects access to green space (in an urban-planning class). Be sure to discuss any surprises (the redlined street has more trees than the greenlined one!); strategies that cities may adopt to redress inequalities—such as investing in tree planting in public park space and public schools in redlined neighborhoods or narrowing car traffic lanes (hardscapes) to make room for street trees and other green infrastructure in blemished blocks. What are the best two or three ideas for improving the environmental quality of the most disinvested areas? How would you approach residents to seek feedback on tree planting ideas and ask for further suggestions?

As an optional extension, summarize and present the whole class dataset to Baltimore city planners, local community organizers, and nature-enthusiast groups. This project could easily be adapted to your city, provided the kind of tree database information that Baltimore has. It could also grow into a master’s or doctoral thesis applied project that targets tree programs for legacy blighted, redlined neighborhoods.