Treasure Valley​ Health and Air Quality: Analyzing Urban Heat Trends in the Context of Rapid Expansion in Treasure Valley, Idaho​

Treasure Valley, Idaho is experiencing increasing temperatures caused by urbanization and a lack of urban tree canopy. This phenomenon is the urban heat island (UHI) effect, where cities are generally hotter compared to surrounding rural areas. Municipalities within Treasure Valley are concerned about urban heat in areas without robust tree canopies. The team used the land surface temperature data from Landsat 8 Thermal Infrared Sensor (TIRS), Landsat 9 TIRS-2, and Ecosystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) to analyze urban heat and how it has changed from 2019 to 2024. The team also used National Agriculture Imagery Program (NAIP) aerial imagery to examine land cover and create a paired sample analysis of tree canopy with impervious surfaces in each municipality. The project found that while 2019 and 2024 had similar heat distribution, municipalities were hotter overall, with an expansion and increase in temperatures. The team also found that while tree canopy cover has increased, impervious surface growth outpaced it by about double. Lastly, a qualitative analysis at the neighborhood scale showed sites with (1) less tree canopy coverage and (2) more impervious surfaces were hotter than sites with the inverse. These findings will help the Treasure Valley Canopy Network (TVCN) non-profit continue to focus its tree-planting efforts on areas without robust tree canopy and/or that cannot cool down effectively. The findings will also help TVCN communicate the benefits of its programs and the importance of urban trees to the public. Lastly, the findings will help the City of Boise’s Climate Action Division understand the urban heat trend and the efficiency of tree planting plans as a mitigation solution.