The tree cover and temperature disparity in US urbanized areas: Quantifying the association with income across 5,723 communities

Abstract

Urban tree cover provides benefits to human health and well-being, but previous studies suggest that tree cover is often inequitably distributed. Here, we use National Agriculture Imagery Program digital ortho photographs to survey the tree cover inequality for Census blocks in US large urbanized areas, home to 167 million people across 5,723 municipalities and other Census-designated places. We compared tree cover to summer land surface temperature, as measured using Landsat imagery. In 92% of the urbanized areas surveyed, low-income blocks have less tree cover than high-income blocks. On average, low-income blocks have 15.2% less tree cover and are 1.5⁰C hotter than high-income blocks. The greatest difference between low- and high-income blocks was found in urbanized areas in the Northeast of the United States, where low-income blocks in some urbanized areas have 30% less tree cover and are 4.0⁰C hotter. Even after controlling for population density and built-up intensity, the positive association between income and tree cover is significant, as is the positive association between proportion non-Hispanic white and tree cover. We estimate, after controlling for population density, that low-income blocks have 62 million fewer trees than high-income blocks, equal to a compensatory value of $56 billion ($1,349/person). An investment in tree planting and natural regeneration of $17.6 billion would be needed to close the tree cover disparity, benefitting 42 million people in low-income blocks.

Forest structure and composition alleviate human thermal stress

“…One priority should thus be to improve accessibility to cool forest microclimates, small urban forest stands could, for example, be fairly distributed over populous areas and especially in the vicinity of vulnerable age groups and communities (Harlan et al, 2006;McDonald et al, 2021). Aligning with that idea, the recently proposed 3-30-300 rule in recommends that every urbanite should be able to see three trees from their home, that every neighborhood should have a canopy cover of at least 30% and that no citizen would live further than 300 m of a greenspace (≥0.5 ha) (Konijnendijk, 2021).…”

Environmental justice criteria for new land protection can inform efforts to address disparities in access to nearby open space

“…Enhancements to urban greenspace can include permanently protecting spaces for urban food production (e.g. White 2011, Cahn andSegal 2016), improving forest canopy in marginalized communities (McDonald et al 2021), adding greenways along waterways or former rail lines, and promoting plantings that increase biodiversity. In addition to new greenspace, conservation organizations can also focus on institutional reform including changes in mission and programming or partnerships that can increase community access to existing spaces (e.g.…”

Frameworks to envision equitable urban futures in a changing climate: A multi-level, multidisciplinary case study of New York City

“…As such, those most likely to be disproportionately affected by a specific climate risk should be identified early on and their experiences should be centered throughout the planning process. For example, when planning for climate hazards such as heat, individuals who are likely to be more susceptible to increases in temperature must be identified such as individuals in areas with less tree canopy (due to the heat island effect), older residents (due to their decreased ability to adjust to changes in temperature or lack of mobility), individuals with disabilities (due to increased sensitivity to heat or lack of mobility) and residents without AC or without access to cooling centers (due to the lack of ability to cool the environment) (Herreros-Cantis and McDonald et al, 2021). Thus, in order to ensure equitable climate mitigation and adaptation measures, city and regional stakeholders projecting climate impacts would be better primed to address the needs of residents if they had access to sub-city level, socio-economically nuanced projections on the spatial distribution of the population by combinations of key vulnerability metrics (e.g., age, race/ethnicity, income, housing tenure, linguistic isolation, disability), aspects of the builtenvironment (e.g., access to cooling, basement dwelling) and their environmental exposures (e.g., tree canopy, flood proneness).…”

“…In comparison to the average American, African Americans are 75% more likely to live in "fence-line" communities-"communities that are next to a company, industrial, or service facility and are directly affected in some way by the facility's operation (e.g., noise, odor, traffic, and chemical emissions)" (NAACP, 2017). Studies of urban areas across the US show that tree canopy is also unevenly distributed with low-income areas having significantly lower tree cover than high-income areas, and that these associations are correlated with housing segregation (Locke et al, 2021;Zhou et al, 2021) and differential heat exposure (McDonald et al, 2021). Vulnerabilities are neither solely placebased nor only associated with race and ethnicity, but are salient across a variety of dimensions.…”