Do Income, Race and Ethnicity, and Sprawl Influence the Greenspace-Human Health Link in City-Level Analyses? Findings from 496 Cities in the United States.

Matthew Browning,Alessandro Rigolon

doi:10.3390/ijerph15071541

Abstract

Examination of the greenspace—human health relationship operates in at least four dimensions: what is considered greenspace? which moderators and mediators are included? what outcomes are measured? and which units of analysis (e.g., individuals, cities) are studied? We examined three of these four dimensions in a cross-sectional study of 496 of the 500 most populated US cities (total population size = 97,574,613, average population per city = 197,920). Spatial average models tested the effect of two greenspace measures (Normalized Difference Vegetation Index greenness and tree cover) on two outcomes (obesity and mental health), while adjusting for income, race and ethnicity, sprawl, age, sex, physical inactivity, median age of housing, and total population. We conducted analyses at the city scale, which is an understudied unit of analysis, and compared findings to individual- and neighborhood-level studies. In two of four models, greenspace was associated with better health. We found race and ethnicity moderated this relationship with varying results. In full sample analyses, cities with greater percentages of non-Hispanic Whites showed links between higher tree cover and lower obesity but marginal relationships between higher greenness and lower obesity. In subsample analyses with majority-non-Hispanic Black cities, higher tree cover was associated with lower obesity and better mental health. These findings advance previous research by showing that race and ethnicity moderate the greenspace—health link at the city level.

Highlights

Policymakers and communities around the world almost universally recognize the benefits of urban greenspace for human health, wellbeing, and ecosystem services
We found that sprawl does not have a significant moderating effect on the greenspace-health link, which suggests that tree cover is beneficial for obesity outcomes and overall greenness is beneficial for mental health outcomes regardless of a city’s population density
We found some evidence that greenspace is positively associated with better health outcomes— obesity and mental health—at the city level

Summary

Introduction

Policymakers and communities around the world almost universally recognize the benefits of urban greenspace for human health, wellbeing, and ecosystem services. Urban planning, and environmental organizations in the US and around the world have recommended including large amounts of greenspace in cities and neighborhoods to improve human health and environmental sustainability [2]. Academics have discussed urban greenspace and other natural environments “as a panacea”, or as an infrastructure investment that can cure almost all ills of urban regions if properly maintained [3]. An overly simplistic portrayal of greenspace as a universal cure for all health problems is problematic, because there are still many unknown aspects about the link between greenspace and health. A recent workshop of leading international experts conceded, “While the existing evidence affirms the beneficial impacts of greenspace on health, much remains to be learned about

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Conclusion