Understanding and assessing demographic (in)equity resulting from extreme heat and direct sunlight exposure due to lack of tree canopies in Norfolk, VA using agent-based modeling

Abstract

Prolonged exposure to extreme heat and direct sunlight can result in illness and death. In urban areas of dense concentrations of pavement, buildings, and other surfaces that absorb and retain heat, harmful environmental exposures to extreme heat and direct sunlight for residents can occur on a daily basis during certain parts of the year. Tree canopies provide shade and help to cool the environment, making mature trees with large canopies a simple and effective way to reduce urban heat and avoid direct sunlight. We develop a demographically representative agent-based model to understand the extent to which different demographics of residents in Norfolk, VA are (in)equitably shaded from direct sunlight and extreme heat conditions during a walk on a clear summer day. In the model each agent represents a different resident of Norfolk, VA. We use the model to assess the extent to which the city’s tree planting plan will be effective in remediating any existing inequities. Our results show that inequitable conditions exist for residents at (1) different education levels, (2) different income levels, and (3) living in different census tracts. Norfolk’s Tree Planting Program effectively reduces the distance residents of all demographics walk in extreme heat and are exposed to direct sunlight. However, residents of the city at lower income levels still experience statistically significantly more extreme heat and direct sunlight exposure due to a lack of tree canopies in summer months than those at higher income levels.