Effects of Urban Heat Islands on Temperate Forest Trees and Arthropods

Purpose of Review Our goal is to provide an overview of how urban heat islands affect forests and synthesize recent literature on that topic. We focused on direct effects of high temperatures from urban heat islands on forest trees and indirect effects via changes in soil moisture and pest density. We also focused on the effects of urban heat islands on arthropods with particular emphasis on tree pests. Recent Findings Urban heat islands can push trees and arthropods closer to their thermal limits with consequences for tree growth and arthropod fitness. Urban heat islands can alter the distribution of trees and arthropods allowing species to survive at higher altitudes or latitudes than they could otherwise. A primary risk for trees is that urban heat islands can increase pest density and damage. Summary Urban heat islands can increase forest air and soil temperature and reduce soil moisture especially when combined with greater climate change. Land managers should consider the surrounding urban density and forest size when trying to determine which plants and animals can persist in urban forests. As forests are fragmented or encroached upon by urbanization, the forest environment will change and become more hospitable for some species and less hospitable for others. Overall, there is insufficient research focused on urban-forest interfaces and the consequences of urbanization for plants and animals within forests. This research is not only important for urban forest conservation. Tree and arthropod responses to urban heat islands will help scientists and land managers predict responses to climate warming in rural areas as well.