Comparing the Structure, Function, Value, and Risk of Managed and Unmanaged Trees along Rights-of-Way and Streets in Massachusetts

Abstract

Trees provide numerous benefits in urban areas, including improving stormwater retention and filtration, removing gaseous and particulate pollutants from the air, sequestering atmospheric carbon, and reducing ambient temperature. However, trees also pose risks in urban areas. Trees growing near overhead electrical utility lines cause a large proportion of electrical power outages. To mitigate this risk, arborists frequently and sometimes severely prune trees near overhead utilities for clearance and to reduce the likelihood of failure. Ostensibly, urban trees distant from utility lines are not pruned as frequently or severely. This study aimed to (i) assess factors related to both individual trees and the sample populations of trees growing near and away from overhead utility lines, and (ii) determine whether those factors differed between the two groups. In total, 200 utility easement plots and 200 non-utility control plots were distributed in Eversource Energy’s distribution territories, encompassing 2361 trees in total. Diameter at breast height (DBH), crown height and spread, percent crown missing, percent twig dieback, and likelihood of failure were gathered for each tree in the study. These variables were compared individually among study groups, and used as inputs to calculate estimated ecosystem service delivery using USFS iTree Eco v6. Overall, trees in control plots were larger and delivered more ecosystem services, per tree, than trees in utility plots. However, on a population level, trees in utility plots were more populous and delivered more aggregate ecosystem services than those in control plots. Although the aesthetics of utility tree pruning is often debated, there were no differences in likelihood of failure ratings between trees in control and utility plots. These findings may help to frame trees near overhead utility lines, commonly seen as risks or eyesores, as valuable green infrastructure and community assets.

Spatial Analysis of Risk Exposure of Urban Trees: A Case Study from Bologna (Italy)

“…This study provides evidence, combined with other precautions, that specific analyses performed on open data could help in the optimization process of the management of urban trees. Below are some inputs and suggestions on how to optimize the urban tree management: maximize the positive effects of vegetation on the urban environment through integrated and innovative management capable of combining environmental needs with economic ones [87][88][89]; promote knowledge and monitoring of the natural heritage of urban greenery through innovative mapping and representation tools [90,91]; make the management interventions of the urban greenery system systematic and homogeneous by preparing appropriate plans and programs [92,93]; carry out maintenance interventions according to the most up-to-date criteria and in compliance with scientifically based cultivation techniques aimed at reducing external inputs [94][95][96]; guarantee transparency in every action and make citizens an active part in the knowledge and care of greenery through communication, information, teaching, and active discussion actions [97,98]. Among these, the implementation of a tool using open data and providing quantitative evaluation for the assessment of trees' failure risk could provide an interesting contribution to the scientific discussion on this topic.…”