The Role of Understory Vegetation in Addressing Urban Heat Island Effects in Kansas City, MO

Urban Heat Islands (UHIs), urban areas which experience significantly higher temperatures than surrounding rural areas, are a growing concern for cities worldwide due to rapid global urbanization and simultaneously rising global temperatures. Tree canopies are widely recognized for their ability to mitigate urban heat through shade and increasing evapotranspiration. This research focuses on the often-overlooked role of understory vegetation in contributing to urban heat mitigation. This study investigates the effect of understory vegetation in addition to tree canopy on cooling at the scale of an individual yard. Thermal imaging profiles under the canopy captured the heat signature from multiple sites across Kansas City with a range of understory. Sites included an experimental forested yard, residential yard, a business park and several parks. By combining observation, the quantitative analysis of thermal imaging data, and meteorological data, this project contributes a more comprehensive understanding of the capacity of understory vegetation to increase temperature reductions. The findings demonstrate locations with tree canopy plus understory have significantly lower surface temperatures, as much as 36 °F; a smaller range of daily temperature fluctuation; and lower nighttime temperatures, which contributes to reducing urban stress. These results are important as the greatest number of urban trees are located on private property. The results give property owners options at a time when individuals are seeking actions for reducing temperatures. They also provide planners support when many municipalities have ordinances against nuisance understory and promote traditional lawns.