Comparing Species Composition and Planting Trends: Exploring Pest Vulnerability in Toronto’s Urban Forest

Urban forests represent a valuable resource for cities but are not without costs. These costs can include time, money, and the loss of beneficial services as results of pest infestations. Knowledge of an urban forest’s tree species composition and vulnerability to pests is needed to help managers enhance services delivered, while minimizing expenses over the long-term. Recent research has explored the impacts of individual pests on urban forests, but less attention has been given to the overall pest vulnerability. In this research, tree genera currently prevalent and commonly planted in Toronto, Ontario, Canada, were analyzed using a pest vulnerability matrix to explore how the city’s urban forest species composition and pest vulnerability may be changing. Current tree species composition was derived from existing inventory data, while the planting trends of a variety of local actors were determined through surveys and interviews. Results indicate there is somewhat limited diversity in current street and non-street tree populations, as well as a number of common tree species that have severe pest vulnerabilities. While new plantings replicate some current composition and pest vulnerability issues, several less common species are also being planted. As a result, overall pest vulnerability should decrease in the future, while some ongoing management concerns remain.