An empirical analysis of the relationships between tree cover, air quality, and crime in urban areas.

摘要

A number of studies produced in recent years have highlighted how urban forests, or urban tree cover (UTC), can contribute to a wide range of environmental, public health, societal, and economic benefits. Few studies have evaluated how the relationships between UTC and air quality and crime vary across a sample of cities and neighborhoods. This study attempts to "tease out" the particulars of the relationships between (1) UTC and air quality measures, including levels of ground-level ozone and particulate matter, and (2) UTC and crime rates, at both the city and neighborhood level while controlling for various demographic, socioeconomic, and climate variables. Evaluating these relationships will lead to better understanding of how unique local characteristics should be considered when local policy makers develop UTC goals and policies.;Based on a series of regressions using data from a sample of over 200 cities across the United States, as well as a sample of 59 communities within a single city, this study shows that in some cases the relationships between UTC and air quality and crime are consistent across the city and neighborhood levels. For example, the results show that UTC has a statistically significant relationship with levels of ozone (positive relationship) and property crime rates (negative relationship) at both the city and neighborhood levels. The results also show that in some cases there are substantial differences in city- and neighborhood-level relationships between UTC and air quality and crime. For example, UTC has a statistically significant relationship with asthma prevalence at both the neighborhood and city levels, but with different signs (negative at the neighborhood level and positive at the city level). In addition, UTC has a noticeably more statistically significant and robust negative relationship with violent and property crime rates at the neighborhood level than at the city level. The results also show that there are statistically significant differences between cities with low and high UTC baselines in terms of how changes in UTC may affect air quality and crime. Overall, the results of this study suggest that policy makers should avoid adopting general, high-level UTC policies that are not substantiated by tailored implementation plans. For example, UTC policies aimed at improving air quality should be specific to the pollutant and should account for the variable pollution-removal capabilities of different tree species. Topics for potential future research in this area are identified in the study.