Renters, Buildings and Scale: A Spatial Analysis of Urban Tree Cover in Chicago
Creators: name: Joyce, Samuel
Publisher: name: University of Chicago
Year: 2020
Subjects: subject: Chicago
subject: Urban forestry
subject: Environmental justice
subject: Homeownership
subject: Urban planning

description: Trees play an important role in the function of urban ecosystems. Beyond their role as a habitat for birds and other animals, trees provide an array of essential ecosystem services: stormwater management (Berland et al. 2017), temperature control (Coseo and Larsen 2014), air pollution reduction (Nowak, Crane and Stevens 2006), and carbon sequestration (Kendall and McPherson 2012), among other ecosystem services. Recent research has focused on the relationship between rentership rates and the distribution of this environmental amenity in residential areas. The landmark research on this subject is from Perkins, Heynen and Wilson (2004), who examined a tree-planting program in Milwaukee and found a statistically significant negative correlation between rentership rates and residential canopy cover at the census tract level. Based on their review of the literature on differences between renter and owner-occupied housing, the authors suggest two factors that may produce this relationship: residential mobility, as renters are relatively transient and are unlikely to ever benefit from the trees they plant, and housing maintenance, as it is disadvantageous for renters to invest in improvements that enhance property values and may result in rising rents. Several other studies have investigated this relationship and have similarly found an inverse correlation between rentership and lower tree cover, in various cities at various spatial scales (Heynen, Perkins and Roy 2006; Landry and Chakraborty 2009; Koo et al. 2019). Although tree cover is not necessarily a perfect proxy for the ecosystem services provided by the urban forest, as Riley and Gardiner (2020) found in their comparison of tree canopy cover with a spatial measure of ecosystem service dollars, it remains a readily-available and widely-used figure to assess the distribution of these benefits. One potential explanation for this relationship that appears under-studied, however, is the role of the built environment in shaping disparities in tree cover. Renters tend to live in neighborhoods with a greater proportion of impervious surfaces, as well as other land-use types that leave less space for planting trees; it seems reasonable to question the extent to which the observed relationship between renters and tree cover is merely the product of renters disproportionately living in neighborhoods where the built environment allows less space for the growth of urban trees. This paper addresses that gap in the literature by investigating the relationship between tree cover, rentership, and a variety of built environment variables in Chicago. In this study, I found that considering aspects of the built environment, including single-family housing, housing age, and transit use, erases the apparent relationship between rentership and tree cover. While a "traditional" model using the socioeconomic indicators commonly used in the literature shows a negative relationship between rentership and tree cover in Chicago, I found that this relationship between rentership and tree cover may, in fact, be the product of other factors in the built environment. This finding indicates that previously-accepted explanations for the relationship between tree cover and rentership — residential mobility, housing maintenance, and the increased political influence of homeowners discussed by Landry &amp; Chakraborty (2009) — have to be re-evaluated in the light of this new evidence. While additional research is necessary to firmly establish that the observed relationship between rentership and tree cover is the product of urban form, these results provide a preliminary indicator that previous explanations for the spatial distribution of tree cover may not fully reflect all drivers of that distribution, requiring a re-evaluation of the broader literature around the distribution of environmental amenities.