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)
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
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
