A framework for urban forest naturalization

Abstract

The way we design and manage cities directly impacts our quality of life. Urban ecosystems differ markedly from their rural surroundings due to the high density of built infrastructure, and are considered ‘unnatural’. Naturalization is the process of altering the characteristics of urban greenspaces so that they resemble nearby reference ecosystems. Increasing naturalness has social, ecological, and economic benefits. The two objectives of this thesis were to create a conceptual framework for urban forest naturalization and test its use in guiding management decision-making. Thirty-eight framework dimensions were determined from a literature review on naturalness assessments and urban ecology, and using professional judgment. Sixteen urban sites in Halifax, Nova Scotia, and Winnipeg, Manitoba were visited that represented a broad range of urban settings, from an untreed roadside field to old-growth portions of parks. Each site received a score from 0 to 1 on each of sixteen naturalness dimensions. Applications of the framework to the sites demonstrated that management activities typically fell into one of three categories: stand initiation, site transformation, or monitoring. Within individual sites, the actions to achieve these goals differed. For instance, some ‘transformation’ sites required the introduction of native ground flora coupled with the removal of invasive species, while others required an increase in canopy differentiation and species composition. The framework thus helped pinpoint individual actions or goals that could be targeted to increase overall naturalness. Future research should consider how urban residents perceive different scores along the various framework dimensions, as psychological benefits may relate to perceived rather than ecological naturalness. Some dimensions may contribute to perceived but not ecological naturalness, or vice versa. It is important for managers to understand how their activities impact the experience of urban residents in greenspaces as well as non-human species.