Redevelopment and the urban forest: A study of tree removal and retention during demolition activities. (May 2017) - Morgenroth, Justin
Abstract: Though relationships between urbanization and tree cover are generally well studied, the effect of redevelopment on urban trees, at the scale of the individual property, is not well understood. Developing knowledge in this area is important in order to limit tree loss during redevelopment and thus, ensure sustained ecosystem services. Here, we explore the removal or retention of trees adjacent to building demolition in Christchurch, New Zealand. We mapped the presence or absence of individual trees on 123 properties prior to, and following, building demolition. Using a classification tree (CT) analysis, the presence or absence of 1209 trees was modelled as a function of: tree-related variables, property-related variables, and economic variables. The CT model estimated tree presence/absence with overall accuracy of 80.4%. Results show that 21.6% of all trees were removed as a consequence of building demolition, resulting in a tree canopy cover reduction of 19.7% across all 123 properties. The CT showed that tree crown area was the most important variable for predicting the presence/absence of trees, whereby trees with small crown areas (<7.9 m 2 ) were most frequently removed, especially if they were within 0.7 m of a demolished building. Land value was also an important determinant of tree presence/absence, such that tree removal was more prevalent on properties with higher land value ($/m 2 ). The results provide important new insights into some of the reasons for tree removal or retention during redevelopment at the scale of the individual property where most tree-related decisions are made. Highlights: This research explores redevelopment consequences on urban tree cover. 21.6% of all surveyed trees were removed during building demolition. Building demolition resulted in tree canopy cover loss of 19.7%. Small trees near buildings were most likely to be removed during demolition. Trees were more likely to be removed from properties with high-value ($/m 2 ) land.