Urban forests – Different ownership translates to greater diversity of trees

Abstract

Urban forests are recognized for their multiple benefits to society, and increasingly so with climate change. However, they too are threatened by increased heat, pollution, and higher risks of pest outbreaks. Increasing the diversity of tree species in urban forests is crucial for enhancing their resilience by reducing the risk of mass tree losses. Yet, we lack the most important ingredient to act: knowledge. Traditionally, urban tree inventories only include trees on public land. This study describes the first urban forest research plot established in Montreal, Canada, encompassing 1567 trees on public and private (residential and institutional) lands from 84 species and 43 genera. Our paper significantly contributes to the existing body of knowledge by providing empirical data that enhances our understanding and provides a clearer picture of urban forests, particularly concerning total tree diversity, across public and private lands. We found that tree abundance and diversity differed depending on land ownership: the public urban forest included more trees and was slightly more diverse than the private urban forest. Acer emerged as the most abundant genus, and small trees dominated all ownership categories. Importantly, the species composition of trees in public and private spaces differed, increasing the overall diversity. Of particular interest was the presence of three species on private property that were not recorded in the larger public tree inventory. Developing inventory practices that include private trees can provide insight to strategically enhance tree diversity where needed and maximize the benefits that diverse urban forests provide.