Urban Tree Canopy

Introduction and Resources

See also Introductory video about UTC and STEW-MAP: Two Tools to Improve Natural Resource Management and Outcomes

URBAN TREE CANOPY ASSESSMENT: A Community’s Path to Understanding and Managing the Urban Forest - This synthesis publication provides an overview of the approaches, methods, and data sources used in UTC assessments, focusing on the initial steps of project planning, assessment, and analysis. The report also provides general guidelines for conducting UTC assessments and analysis to ensure useful, quality results that can be applied in management and decision-making efforts.

Background

Urban Tree Canopy (UTC) refers to the layer of tree leaves, branches, and stems that provide tree coverage of the ground when viewed from above.  Today, many communities are planting trees in an effort to become more sustainable and livable. Improving a city’s urban tree canopy can have numerous benefits, including reducing summer peak temperatures and air pollution, enhancing property values, providing wildlife habitat, providing aesthetic benefits, and improving social ties among neighbors.  A robust tree canopy can also attract businesses and residents.  Scientists now have the ability to qualify and quantify the benefits of urban tree canopy, using the Urban Tree Canopy (UTC) Assessment suite of tools.  An increase in urban tree canopy brings an associated increase in the tree benefits listed above. 

Amount of tree canopy coverage is typically a reflection of a variety of factors — including intentional planning and investment.  Studies throughout the United States have repeatedly shown that most communities are losing tree canopy due to a wide range of threats, including insects, disease, natural disasters and development.  An Urban Tree Canopy (UTC) Assessment can help a community measure, monitor, and improve tree cover over time, and combat threats that can lead tree canopy loss.

Background of the UTC Assessment
The Urban Tree Canopy Assessment approach and protocols were invented by the U.S. Forest Service in 2006 to map and quantify landcover for Baltimore City.  This approach involves the development and integration of hi-resolution landcover ( <2’) and hi-resolution ownership (parcel) data from parcel to regional scales. The aim of the Urban Tree Canopy (UTC) Assessment is to help decision makers understand their urban forest resources, particularly the amount of tree canopy that currently exists and the amount that could exist at multiple scales.  The UTC Assessment protocols have since been used by the Chesapeake Conservancy to help monitor and improve Chesapeake Bay health.  The UTC Assessment protocols have also been applied to dozens of counties, cities, and towns in the United States and Canada, covering approximately 8.5 million acres, home to over 37 million people. The information from these assessments has been used to inform UTC goals, prioritize locations for tree planting efforts, establish urban forestry master plans, understand patterns of environmental justice, inform sustainability plans, and justify budget increases for urban forestry programs.  Learn more by browsing through our many completed UTC publications and reports.

UTC Prioritizations

UTC Assessments provide urban resource managers with vital information to begin the goal setting and planning processes.  However, the results may also lead to further questions like:

• Where is it socially desirable to plant trees? Or what is the Preferable Tree Canopy?
• Where is it financially efficient to plant trees?  Or what is the Potential Tree Canopy?

The NYC Urban Field Station has developed a set of UTC Prioritization tools that uses a range of urban ecological and social information to guide tree planting efforts.  This tool set  now accompanies UTC analyses.  Learn more about how these tools have been developed in New York City and applied in Baltimore.

In 2012 the University of Vermont's Spatial Analysis Laboratory, with support from the Northern Research Station, National Urban and Community Forestry Advisory Council, and the City of New York, published A Report on the City of New York’s Existing and Possible Tree Canopy (7 mb pdf).

UTC Markets

While Assessments provide answers about canopy inventory, and Prioritizations inform implantation of canopy goals, UTC Markets strive to improve communication among key stakeholder groups. A goal of UTC Markets is to match the message and the messenger to the audience of interest. This portion of the UTC Toolbox is in active development. 

UTC Change Analysis

Urban Tree Canopy Assessments can be repeated at regular intervals to examine how tree canopy is changing in a city. A UTC Change Analysis is a particularly powerful tool that can help communities assess progress toward tree canopy goals.  The change analysis does more than simply determine whether overall tree canopy increased or decreased; it helps to identify areas of gain and loss, and gives a sense of the magnitude of this change. Locally, canopy changes can lead to positive (e.g., reduced peak summer temperatures) and negative (e.g., loss of wildlife habitat) effects. Tree canopy loss, whether due to human activities, such as construction, or natural events, such as a severe storm, can be instantaneous and dramatic. Tree canopy increases resulting from new plantings, natural regeneration, and growth, are slow processes that take time and commitment.   By seeing what change is happening where over time, urban planners and forest managers can better direct and prioritize their efforts to maintain and increase canopy cover.

An example from Baltimore’s UTC Change Analysis shows an area with substantial tree canopy cover in 2007 (A) has reduced cover in 2015 (B).  This aerial imagery, combined with LiDAR data, yields tree canopy change (C) over the 2007-2015 time period. 

Using LiDAR to Quantify the Urban Tree Canopy

Although not required for the creation of a UTC Assessment, LiDAR data decreases the cost of deriving land cover data while improving the accuracy of land over mapping.  An Urban Tree Canopy Assessment that combines high-resolution imagery with LiDAR data yields information about the structure of the urban forest, and and will dramatically improve urban forest managers' ability to account for the trees they care for.  Learn more about LiDAR and how it can be used to map trees in NYC. (2.5 mb pdf)

Recognizing the importance of LiDAR for a variety of scientific and management objectives, the New York City Mayor's Office of Long Term Planning and Sustainability organized a workshop in August 2010.  Designed to leverage the City's investment in high resolution geospatial data, the event educated many city employees about LiDAR and its potential applications. Jarlath O'Neil-Dunne (a USDA Forest Service Geospatial Analyst from the University of Vermont's Spatial Analysis Lab) presented on his experiences working with LiDAR data. Recordings of his talks may be seen as videos:        

• LiDAR 101
• LiDAR: An End User's Perspective

Research Highlights

• The Urban Tree Canopy Assessment Program
• UTC Prioritization Tools

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