Risk

How marginalized communities are disproportionately at risk to urban heat islands

Marginalized communities have been found to be at disproportionately higher levels of risk to urban heat islands. This is largely the consequence of historical "redlining" practices where certain neighborhoods, often those predominantly inhabited by racial and ethnic minorities, were marked as "high-risk" for real estate investment, resulting in systematic disinvestment and neglect. From 1934 to 1962, $120 billion in home loans was issued, and 98% of this went to whites.1

A study using Landsat-derived surface temperatures found that across 108 U.S. urban areas, places that were previously redlined experienced higher temperatures than their non-redlined counterparts by up to 7°C.2

In San Francisco, the distribution of green space and tree coverage in cities is influenced by the legacy of racist policies like redlining that institutionalized disinvestment. This has resulted in the warmest neighborhoods often being located in the central, southern, and eastern portions of the city.3

Although race-based zoning was deemed unconstitutional in 1917, local officials used economic zoning ordinances to zone communities of color for multifamily, commercial, and industrial use whereas predominately white areas were zoned for single-family residential development.

These policies have entrenched marginalized communities in neighborhoods that have increased risks of air pollution and urban heat islands and denied them the necessary means to move out to other areas.

Sources

CalEPA. “Pollution and Prejudice.” ArcGIS StoryMaps, 17 Aug. 2021, https://storymaps.arcgis.com/stories/f167b251809c43778a2f9f040f43d2f5.
Hoffman, Jeremy S., et al. “The Effects of Historical Housing Policies on Resident Exposure to Intra-Urban Heat: A Study of 108 US Urban Areas.” Climate, vol. 8, no. 1, Jan. 2020, p. 12. Crossref, https://doi.org/10.3390/cli8010012.
“Climate Health and Equity.” Climate Health and Equity | San Francisco, sf.gov/reports/may-2023/climate-health-and-equity#:~:text=Urban%20Heat%20Islands,-Vulnerability%20to%20heat&text=The%20distribution%20of%20green%20space,20%20th%20century%20into%20today. Accessed 4 Dec. 2023.

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