Origins of the Chicago urban forest: Composition and structure in relation to presettlement vegetation and modern land use

The ecosystem services that an urban forest provides are a function of its structure and species composition. The structure and composition of Chicago’s urban forest were studied using data from presettlement land surveys and a modern urban tree census. Forested areas that currently have a high proportion of native species (mainly oaks), a complex structure, and greater canopy cover are associated with areas whose presettlement condition was forest rather than prairie. Other parts of the city’s urban forest tend to have smaller, shorter-lived non-native species. As Chicago continues to develop and the older trees die out, the forest structure is likely to transition towards these smaller stature trees, which provide reduced amounts of ecosystem services.