How Green Are Trees? — Using Life Cycle Assessment Methods to Assess Net Environmental Benefits

Abstract

This study used life cycle assessment methods (LCA) to assess the carbon footprint of an urban tree from propagation to disposal, expanding on recent works focused primarily on inventorying the inputs for woody ornamental nursery production. Urban forest managers from the Chicago metropolitan area were surveyed on their plant selection, planting, maintenance, removal, and disposal practices to generate the model inputs. Alterations to management practices such as the pruning cycle can significantly reduce the age at which a tree changes from being a carbon emitter to being carbon neutral. Highly mechanized tree care practices extend the time to 33 years whereas less mechanized scenarios are 26 years. An annual windshield survey conducted by many municipalities will extend this period by two to three years. Results of this work offer a more accurate assessment of ecosystems services offered by urban forests and serve as a first step in identifying tree care practices which offer an optimal environmental return on investment.