Program on the Environment

Worsening climate change is increasing the frequency and intensity of extreme weather events, with urban areas disproportionately affected due to the urban heat island effect (UHI). This poses significant public health risks and exacerbated inequalities, as vulnerable communities are more susceptible to higher exposure to heat. Urban trees have been identified as a potential mitigation strategy. The purpose of this study was to examine the mechanisms behind urban tree’s cooling capacity and evaluate their ability to mitigate urban heat. To accomplish this, I completed an internship with Public Health, Seattle & King County to conduct a literature review of studies between 2010-2025 on the relationship between tree canopy coverage, public health, and equity. I also reviewed King County specific data regarding climate patterns, canopy coverage, change in canopy coverage, and demographic distributions. My findings indicate that attributes like tree spacing, leaf type, height, and density influence cooling capacity. These findings are important in determining next steps for tree policy throughout King County. I also found that less-vegetated neighborhoods are statistically warmer than more-vegetated neighborhoods. Furthermore, less-vegetated neighborhoods have lost more of their tree canopy coverage than more-vegetated neighborhoods since 2016, further intensifying disparities. These results highlight how important targeted urban forestry policies that prioritize canopy maintenance and expansion and tree placement in vulnerable communities. These efforts are essential in reducing heat related health risks and promoting environmental inequity in King County.