A global basis of urban tree inventories: What comes first the inventory or the program

Abstract

While efforts to standardize urban forest inventory data have occurred, the information collected from community to community remains quite variable. In this study, we conducted a global review of peer-reviewed and published research that collected tree inventory data to assess what information is being collected. In addition to this review, we also present results from national surveys conducted in the United States and Sweden that specifically asked urban forest managers about how their inventories informed their urban forest management efforts. In the literature review, tree species and stem diameter were the most collected structural parameters and planning and estimation of ecological services were the most common research objectives. The surveys conducted in Sweden and the USA found communities commonly collected records about tree species, diameter, and condition and that inventories were more common as community size increased. Street and park tree inventories were the most common inventories. Inventories of public trees on greenbelts and woodlots were less common and private tree inventories were relatively uncommon. Additionally, professional staff and consultants were more likely to collect inventory data than interns and volunteers in both countries. Despite these similarities, significant differences exist between the USA and Sweden, with several parameters (i.e., adoption a management plan, presence of an inventory, collection of inventory data digitally, collection of tree planting/removal records) being more common in the USA — possibly reflecting a longer history of urban tree management in the latter country. In modelling the survey results from Sweden and the USA, we found that having a strategic plan, a governance mechanism (tree board), financial resources (per capita budget), and the adoption of greater systematic care of trees were significant predictors the presence of an inventory. Study results also suggest that having a tree inventory reflects the advancement of an urban forestry program along a continuum of initial program adoption to more fully developed and sustained urban forestry program.