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City of Somerville Massachusetts URBAN FOREST MANAGEMENT PLAN 2021 DRAFT PREPARED BY: Public Space Urban Forestry Division Mayor’s Office of Strategic Planning and Community Development City of Somerville* City Hall 93 Highland Avenue Somerville, Massachusetts 02143 This document was adapted from an Urban Forest Management report provided by: Davey Resource Group, Inc. 1500 N. Mantua Street Kent, Ohio 44240 800-828-8312 *This institution is an equal opportunity provider. Notice of Disclaimer: Inventory data provided by Davey Resource Group, Inc. “DRG” are based on visual recording at the time of inspection. Visual records do not include individual testing or analysis, nor do they include aerial or subterranean inspection. DRG is not re- sponsible for the discovery or identification of hidden or otherwise non-observable hazards. Records may not remain accurate after inspection due to the variable deterioration of inventoried material. DRG provides no warranty with respect to the fitness of the urban forest for any use or purpose whatsoever. Clients may choose to accept or disregard DRG’s recommendations or to seek additional advice. Important: know and understand that visual inspection is confined to the designated subject tree(s) and that the inspections for this project are performed in the interest of facts of the tree(s) without prejudice to or for any other service or any interested party. Photograph credit, front cover: Victor Nascimento, City of Somerville SOMERVILLE URBAN FOREST MANAGEMENT PLAN TABLE OF CONTENTS Vision Statement 2 Letter from the Mayor 4 Letter from the Urban Forestry Committee 5 Executive Summary 6 Introduction 12 Section 1: The Importance of Trees in the City 14 Section 1.1: Somerville’s Tree Canopy 16 Section 1.2: Somerville’s Street Trees 30 Section 2: Somerville’s Tree Inventory Data 42 Section 3: Expand, Preserve, and Maintain 68 Section 3.1: Tree Planting Plan 70 Section 3.2: Tree Maintenance Program 89 Section 3.3: Invasive Insect and Disease Management Strategy 109 Section 3.4: Storm Preparedness Plan 132 Section 4: The Road Map 156 Section 4.1: Operations Review 158 Section 4.2: Funding Analysis 182 Section 4.3: City of Somerville Tree Ordinance & Policy Review 191 Section 4.4: Public Engagement 205 Section 5: Action Plan 212 Glossary 228 References 236 Appendices A. UTC Assessment Methodology 245 B. i-Tree Streets Inputs and Reports 254 C. Data Collection and Site Location Methods 264 D. Suggested Tree Species for Future Planting 275 E. Tree Planting 284 F. Risk Assessment and Priority and Proactive Maintenance 325 G. Invasive Pests and Tree Diseases 330 H. Tree Emergency Plan Worksheet 340 I. Potential Plantable Area by Ward 352 VISION STATEMENT Somerville’s vision for its trees is to create the best forest for a city, and the best city for a forest. This Urban Forestry Management Plan (UFMP) serves as a guiding document for the expansion, preservation and maintenance of a healthy and diverse urban forest to maximize environmental, economic, safety and aesthetic tree benefits for the Somerville community today and in the future. AACCKKNNOOWWLLEEDDGGMEEMNETSNTS This Somerville Urban Forest Management Plan was made possible by grant funding from the Massa- chusetts Department of Conservation and Recreation in cooperation with USDA Forest Service and through its Urban and Community Forestry (U&CF) Grant Program. The U&CF Grant Program is designed to encourage communities to create and support long-term and sustained urban and community forestry programs throughout Massachusetts. In addition, the following people were instrumental in completing this document: City of Somerville, Mayor Joseph Curtatone Engineering Department Brian Postlewaite, Director of Engineering Office of Strategic Planning and Community Jess Fosbrook, former Director of Engineering Development (OSPCD) George Proakis, Executive Director Urban Forestry Committee Luisa Oliveira, ASLA, Director, Althea Northcross (co-chair) Public Space and Urban Forestry Chris Dwan (co-chair) Vanessa Boukili, PhD, MCA, Senior Urban Jennifer Clifford Forestry and Landscape Planner; Amy Mertl Principal Author Sharon Komarow Malik Drayton, Urban Forestry Tori Antonino and Landscape Planner Sarah Sweeting Conor Guidarelli Cortney Kirk, RLA, ASLA, Senior Public Space Planner Henry Ayanna Vanessa Boukili (ex-officio) Arn Franzen, Senior Project Manager/ Mark Lawhorne (ex-officio) Director of Parks Andrew Louw, RLA, Public Space Planner Special thanks to: George Ackerson, Consulting Arborist at Department of Public Works (DPW) Horticultural Technologies, Inc. Jill Lathan, Acting Commissioner Keith Johnson, GIS Coordinator, IAM of Public Works All residents who read and gave thoughtful Steven MacEachern, Commissioner comments on prior drafts of this document of Public Works Eric Weisman, Director of Operations Graphic Design by: Mark Lawhorne, Superintendent of Highways Kim Schmidt Design 3 MAYOR’S LETTER It is my pleasure to release Somerville’s first comprehensive Urban Forest Management Plan. Trees are an essential part of our community both for quality of life and for our environment. They provide shade, help to clean our air and stormwater, calm traf- fic, increase property values, and are a vital component of making Somerville the best place to live, work, play, and raise a family. Trees are also a crucial part of our urban ecosystem as they are a source of food and habitat for our city’s pollinators and other wildlife. Trees provide us with countless benefits, and we need to take proper care of them to help them survive in tough urban conditions. Reg- ular tree maintenance will not only encourage proper growth and longevity, but also support public health and safety. This Urban Forest Management Plan provides a data-driven ap- proach to understanding the current conditions and needs of Somerville’s urban forest, as well as detailed recommendations to grow our tree canopy. Not only does this Plan include an assessment of the city’s complete public tree inventory and a canopy cover analysis of all public and private trees, but it also includes guidance for maintaining our urban forest, planting more trees, improving our urban forestry operations, and enhancing public engagement. This Plan builds upon the important work and ideas provided in Somerville’s Open Space and Recreation Plan (2016-2023), Somer- ville Climate Forward (2018), and SomerVision 2040. All of these plans call for the creation of an Urban Forest Management Plan and identify a need to increase the City’s tree canopy. Now, with this Plan, we have a framework for growing a healthier urban forest. The pages that follow provide us with an understanding of Somer- ville’s urban forest today and a roadmap for how to continue to grow and improve it. As with all important things, it will take a vil- lage to make our urban forest the best that it can be. City staff and residents alike share an immense passion for Somerville’s trees and, armed with this Plan, I am confident that together we can enrich our urban forest! Joseph A. Curtatone Mayor City of Somerville 4 Urban Forestry Management Plan Foreword from the Urban Forestry Committee City of Somerville The Urban Forestry Committee (UFC) held its first meeting in July 2019. The formation of the UFC came after recognizing that the city’s Tree Preservation Ordinance called for a committee and in response to increasing public concern over the state of the urban forest after the removal of trees on Beacon Street and along the GLX corridor. The following pages contain the City’s newest Urban Forestry Management Plan. The development of this document is a critical step in the process of building and protecting Somerville’s urban forest. This document lays the foundation necessary to develop and maintain tree plantings and other green spaces in our city over the next five to ten years. As with all Somerville’s documents, this one will evolve over time according to science and our social needs. Trees in our landscape provide monetary benefit by way of energy costs, health benefits, and crime reduction. They also provide ecological benefits through carbon sequestration, mitigating urban heat, and providing food and habitat for insects, birds, and other animals who underpin the very foundation of human existence. These benefits and how they are quantified are outlined in detail in the following pages. What is more difficult to quantify is the value of connecting and interacting with nature. Observing nature offers tremendous value: it connects community, provides respite from busy and stressful lives, and creates learning opportunities for our children. Learning about ecology, biodiversity, and the importance of healthy ecosystems can lead to more formalized study, investigative research and career choice. These, in turn, inform climate policy and create tools and structure for the protection of all wildlife. The UFC recognizes the importance of the moment, how we need to modify our behavior if we are to meet the challenge of the climate crisis. We are dedicated to serving the community and helping to reach the goal of creating a sustainable and equitable pathway for planting, maintaining, and protecting our urban forest and green spaces. This includes creating pollinator corridors to support native insect populations, advocating for healthy soils, and championing biodiversity. The UFC is aware of the decimation of our local insect, bird and wildlife populations. The return of pollinators will be a crucial next step in the development of this plan. We must commit to converting to sustainable and ecological landscaping habits and using indigenous species in our public and private plantings. Although Somerville is only 4.1 square miles, we are confident that our actions will inspire communities throughout the Commonwealth. Sincerely, The Urban Forestry Committee January 28, 2021 UFMP Executive Summary 5 EXECUTIVE SUMMARY As part of the City’s commitment to its urban forest, this Plan was developed by the City of Somerville’s Public Space & Urban Forestry (PSUF) Division based on a tree inventory and other research conducted by its consultant, Davey Resource Group (DRG). Somerville’s trees provide a wealth of benefits to our residents, such as providing shade, cleaner air and water, habitat for wildlife and pollinators, and safer streets, as well as increasing property values and improving people’s quality of life. In addition to providing an overview of the existing state urban forest, this Plan creates a vision and road map for preserving and expanding our urban canopy. It includes specific recommendations for addressing short-term and long-term maintenance needs for inventoried public trees, as well as suggestions for improving urban forestry operations and public outreach. 6 UFMP Executive Summary Canopy Cover STATE OF THE EXISTING Current: 14.6% URBAN FOREST Goal: 16% An analysis of aerial imagery from 2018 reveals that Somerville’s tree canopy covers 14.6% of the land area. Somerville aims to increase canopy cover to 16%, which will require preserving existing Three Dominant trees, and planting new trees on both public and private property. Tree Species Three species comprise a large percentage of the City’s trees. A more diverse species distribution is desirable to 1036 Ash Trees assure biodiversity and health. Threatened by Emerald Ash Borer The 1036 Ash trees identified on public property (and an unknown number of ash trees on private property) are threatened by the invasive insect Em- 44% Native erald Ash Borer. The City is currently using an organic insecticide to treat Approximately 44% of the City-owned ash trees that are healthy inventoried trees are native to enough to treat. A modified strategy New England, whereas 16% of are that includes additional removals and invasive species as defined by the replacements is recommended, as well Massachusetts Prohibited Plant as an educational outreach campaign List. Increasing the proportion of would help raise awareness of this pest. native species and decreasing the proportion of invasive species in the population will be beneficial for the ecosystem. Somerville’s street trees provide approximately $1,047,466 14,486 sites recorded in quantifiable annual A total of 14,486 sites on publicly-owned land were recorded during the 2018 tree ecosystem service benefits. inventory: 13,604 trees, 255 stumps, and 627 vacant planting sites. 13,604 Trees 255 stumps 627 vacant planting sites UFMP Executive Summary 7 EXECUTIVE SUMMARY REMOVAL Municipal Tree Maintenance & Total = 864 trees Planting Recommendations High Risk = 11 trees Moderate Risk = 200 trees Low Risk = 653 trees Stumps = 231 The many environmental and economic benefits that trees provide justify the time and money invested in planting and maintenance. Identified mainte- PRIORITY nance needs for the sites inventoried in 2018 include: tree removal (8% of inventoried sites), PRUNING stump removal (2% of inventoried sites), tree Total = 333 trees pruning (64% of inventoried sites), young tree High Risk = 8 trees training (19% of inventoried sites), and tree Moderate Risk = 325 trees planting (4% of inventoried sites). These needs can be divided into “priority” and “proactive” maintenance. ROUTINE PRUNING CYCLE Priority Maintenance Total = 7,593 trees 6-year pruning cycle Prune ~1,265 trees per year Maintenance should be prioritized by addressing trees with the highest risk first. High and Mod- erate Risk trees should be removed or pruned immediately to promote public safety. Low Risk YOUNG TREE trees should be addressed after all elevated risk TRAINING CYCLE tree maintenance has been completed. Trees should be planted to mitigate removals and in- Total = 2,483 trees 3-year cycle crease canopy cover. Prune ~827 young trees per year TREE PLANTING Goal number of trees to plant = at least 350 per year 8 UFMP Executive Summary