The Relationship between Urban Forests and Income: A Meta-Analysis

Abstract

There is well-documented evidence that urban trees benefit the physical, mental, and social health of urban residents. The environmental justice hypothesis posits that environmental amenities like urban forest cover are inequitably low in poor and minority communities. If so, these communities experience fewer urban forest benefits, and so experience a form of environmental injustice. While some previous, mostly city-specific, studies have found that urban forest cover is inequitably distributed by race, other studies have found no relationship, or even negative inequity. Both the city-specific nature of the existing literature and its conflicting results suggest a need for a research synthesis. Using a systematic literature search and meta-analytic techniques, this paper examines the relationship between urban forest cover and race. First, it estimates the average (unconditional) relationship between urban forest cover and race across studies and finds evidence of significant race-based inequity in urban forest cover. Second, by including characteristics of the original studies and study sites in meta-regressions, it illuminates some of the drivers of variation in the distribution of urban forest cover between studies. Meta-regressions reveal the magnitude and significance of the relationship varied across racial groups and methodological choices, cautioning authors to make methodological choices and interpretation carefully. Models reveal significant inequity on public land across racial groups and that environmental and social features of cities help explain variation across studies. As tree planting and other urban forestry programs proliferate around the world, urban forestry professionals and policy makers are encouraged to investigate current tree cover in their city and consider the equity consequences of urban forestry activities, particularly on public land.