INTRODUCTION: Why does the urban tree canopy matter? The composition of built and natural elements can substantially affect the health of people that live within a city. A primary mechanism that relates human health impacts and the built environment is the “urban heat island” effect – a phrase derived from the “island” of hotter air that is situated around an urban environment. The urban heat island phenomenon is characterized by empirical observations of higher temperatures within built environments when compared to more natural environments. Although many variables affect the magnitude of the UHI, the urban tree canopy (UTC) is one of the most influential. The UHI effect presents a serious hazard to human health, as increased temperature can cause respiratory difficulty, increase the chance of heat-stroke, exhaustion, and heat-related mortality. Just as planning operations can influence the UTC, they can also influence the level of impact that temperature increase will have on people by implementing measures (like preserving or increasing UTC) that mitigate the heat island effect.