The Sustainable Urban Forest: A Step-by-Step Approach: ‘…the quality of the urban forest is as important as the number of trees that comprise it. “Quality” in that sense covers tree health, age and species diversity, strategic location, and other such factors – all intended to maximize the desired ecosystem services, whatever they may be.’

ABSTRACT:  The Sustainable Urban Forest: A Step-by-Step Approach, Michael Leff , Davey Institute / USDA Forest Service, USFS Philadelphia Field Station, September 27, 2016 states “This guide is designed primarily to help municipalities assess the state of their urban forest, identify management concerns, and chart a path forward, step by step, toward long-term sustainability. It presents a scalable approach that can be adapted by any “community” that seeks to pursue a similar path in its realm of responsibility.” Importantly, “…the quality of the urban forest is as important as the number of trees that comprise it. “Quality” in that sense covers tree health, age and species diversity, strategic location, and other such factors – all intended to maximize the desired ecosystem services, whatever they may be.”

Other links:tree

Two publicly available assessment tools – i-Tree Eco and i-Tree Streets – were developed by the USDA Forest Service and its partner organizations to aid in conducting bottom-up assessments of urban trees and forests, and for calculating their ecosystem services and values. ( www.itreetools.org)

i-Tree Canopy program (www.itreetools.org/canopy)

Estimating Ecosystem Services with i-Tree Design

i-Tree Design is a free web-based tool that allows anyone to make a simple estimation of the benefits of individual or multiple trees. By inputting location, species, tree size, and condition, users gain an understanding of tree benefits related to greenhouse gas mitigation (carbon emission reduction), air quality improvements, and stormwater interception. With the additional step of drawing a building footprint – and virtually “planting” trees around it – the impact on building energy use can also be evaluated. Among other things, i-Tree Design enables users to assess and plan the optimal placement of trees to maximize energy savings. Tree benefits are estimated for the current year, for a user-specified future year, and cumulatively over that timeframe. This tool is intended to serve as a simple and accessible starting point for understanding the value of individual or groups of trees to the community or a local landowner. For more information: www.itreetools.org/design.

Healthy Trees, Healthy Cities Tree Health Initiative, The Nature Conservancy 

(http://healthytreeshealthycities.org/ )

Excerpts, Trees and Forest  “Targets” T1-T7:

Target T1: Relative Tree Canopy Cover

Key objective: Achieve desired degree of tree cover, based on potential or according to goals set for entire municipality and for each neighborhood or land use.

Performance indicators:

Low – The existing canopy cover for entire municipality is <50 canopy.="" desired="" o:p="" of="" the="">

Fair – The existing canopy is 50%-75% of desired.

Good – The existing canopy is >75%-100% of desired.

Optimal – The existing canopy is >75%-100% of desired – at individual neighborhood level as well as overall municipality.

Target T2: Age Diversity (size class distribution)

Key objective: Provide for ideal uneven age distribution of all “intensively” (or individually) managed trees – municipality-wide as well as at neighborhood level.

Performance indicators:

Low – Even-age distribution, or highly skewed toward a single age class (maturity stage) across entire population.

Fair – Some uneven distribution, but most of the tree population falls into a single age class.

Good – Total tree population across municipality approaches an ideal age distribution of 40% juvenile, 30% semi-mature, 20% mature, and 10% senescent.

Optimal – Total population approaches that ideal distribution municipality-wide as well as at the neighborhood level.

Target T3: Species Diversity

Key objective: Establish a genetically diverse tree population across municipality as well as at the neighborhood level.

Performance indicators:

Low – Five or fewer species dominate the entire tree population across municipality.

Fair – No single species represents more than 10% of total tree population; no genus more than 20%; and no family more than 30%.

Good – No single species represents more than 5% of total tree population; no genus more than 10%; and no family more than 15%.

Optimal – At least as diverse as “Good” rating (5/10/15) municipality-wide – and at least as diverse as “Fair” (10/20/30) at the neighborhood level.

Target T4: Species Suitability

Key objective: Establish a tree population suited to the urban environment and adapted to the overall region.

Performance indicators:

Low – Fewer than 50% of all trees are from species considered suitable for the area.

Fair – >50%-75% of trees are from species suitable for the area.

Good – More than 75% of trees are suitable for the area.

Optimal – Virtually all trees are suitable for the area.

Target T5: Publicly Owned Trees (trees managed “intensively”)

Key objective: Current and detailed understanding of the condition and risk potential of all publicly owned trees that are managed intensively (or individually).

Performance indicators:

Low – Condition of urban forest is unknown.

Fair – Sample-based tree inventory indicating tree condition and risk level.

Good – Complete tree inventory that includes detailed tree condition ratings.

Optimal – Complete tree inventory that is GIS-based and includes detailed tree condition as well as risk ratings.

Target T6: Publicly Owned Natural Areas (trees managed “extensively”)

Key objective: Detailed understanding of the ecological structure and function of all publicly owned natural areas (such as woodlands, ravines, stream corridors, etc.), as well as usage patterns.

Performance indicators:

Low – No information about publicly owned natural areas.

Fair – Publicly owned natural areas identified in a “natural areas survey” or similar document.

Good – Survey document also tracks level and type of public use in publicly owned natural areas.

Optimal – In addition to usage patterns, ecological structure and function of all publicly owned natural areas are also assessed and documented.

Target T7: Trees on private property

Key objective: Understanding of extent, location, and general condition of privately owned trees across the urban forest.

Performance indicators:

Low – No information about privately owned trees.

Fair – Aerial, point-based assessment of trees on private property, capturing overall extent and location.

Good – Bottom-up, sample-based assessment of trees on private property, as well as basic aerial view (as described in “Fair” rating).

Optimal – Bottom-up, sample-based assessment on private property, as well as detailed Urban Tree Canopy (UTC) analysis of entire urban forest, integrated into municipality-wide GIS system.

Resource Management Approach

Target R1: Tree Inventory

Target R2: Canopy Cover Assessment and Goals

Target R3: Environmental Justice and Equity

Target R4: Municipality-Wide Urban Forest Management Plan

Target R5: Municipality-wide Urban Forestry Funding

Target R6: Municipal Urban Forestry Program Capacity

Target R7: Tree Establishment Planning and Implementation

Target R8: Growing Site Suitability

Target R9: Tree Protection Policy Development and Enforcement

Target R10: Maintenance of Publicly Owned, “Intensively” Managed Trees

Target R11: Management of Publicly Owned Natural Areas

Target R12: Tree Risk Management

Target R13: Urban Wood and Green Waste Utilization

Target R14: Native Vegetation

SOURCE:  The Sustainable Urban Forest: A Step-by-Step Approach

Michael Leff

Davey Institute / USDA Forest Service

USFS Philadelphia Field Station

September 27, 2016