Urban Tree Canopy Assessments
Learn more about the process, why you need one, and how it will benefit your community
Why Do Trees Matter?
Trees are the answer! Across cities and other urbanized areas, trees along streets, in parks, yards, and natural areas constitute a valuable urban and community forest. This resource is a critical element of the region’s green infrastructure, contributing to environmental quality, public health, water supply, the local economy, and aesthetics.
Trees are one of the few infrastructure investments that grow in value over time.
Trees throughout the world face many threats, but trees in an urban environment are especially vulnerable. Clear-cutting, compacted soils, and vandalism are just a few of the many threats these trees face. This valuable resource is under attack from many different directions in communities, small and large, across the globe. The following maps and images show examples of large-scale changes that can occur in an urban forest.
Charlotte, North Carolina, in the southeastern United States, is a rapidly growing city. With high rates of growth often comes a high level of development. Large, forested areas are quickly being cleared to make way for new housing developments, schools, and other amenities. Fortunately, the City has been planting new trees to make up for the losses, but those trees take time to grow and mature. The left image shows conditions in 2014, and the right image shows the same area in 2020 after a new school has been built where a forest once stood.
Panama City, Florida, on the coast of the Gulf of Mexico, was devastated by category 5 hurricane, Michael, in October of 2018. It's estimated that the strong winds and rain took down 1,000,000 trees in Panama City alone. Local residents are now literally feeling the impacts of losing their tree canopy with reports of higher than normal temperatures and the threat of wildfires and flooding due to the downed trees. The map below shows pre-storm (left-2014) and post-storm (right-2020) conditions.
Invasive species, pests, and disease present one of the most serious threats to urban and community forests. The City of Milwaukee, Wisconsin experienced significant loss of urban tree canopy due to Dutch elm disease. This led to the removal of over 140,000 elms from the late 1950’s to present time. The image below shows the dramatic change that occurred in many areas throughout the city. Once fully canopy covered streets became open and exposed corridors due to monoculture planting and the subsequent disease outbreak. Read more about it in our report .
Around the world, the value that trees provide to people and the environment is being realized. Many cities are initiating tree planting programs in order to engage the community and expand their urban forest. Tree canopy assessments provide detailed information on where there are trees and also where there is available space to plant new trees. Seen in the map below, the City of Mercer Island, Washington, has placed strong emphasis on their tree planting program. Their efforts can be seen in the large number of trees planted along the Mountains to Sound Greenway . These trees were planted in the late-1990s and have seen tremendous growth in the last 20 years (left-2002, right-2015), providing enhanced recreation opportunities, increased wildlife habitat connections, and improved air and sound quality.
Just some of the benefits of trees
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What is an Urban Tree Canopy Assessment?
The Urban Tree Canopy Assessment
First developed by the U.S. Forest Service in 2006, the Urban Tree Canopy (UTC) Assessment was created to understand the amount and distribution of tree canopy in Baltimore, Maryland. Since then, UTC assessments have been performed in hundreds of cities throughout the United States as well as internationally.
By creating a map of tree canopy and other land cover types, communities can use this information to understand how much tree canopy there is, where it is located, and where new trees can be planted.
Additionally, cities can also use this information to inform other planning activities such as setting canopy cover goals, prioritizing where to plant new trees to address environmental and social issues, and developing urban forest management plans (UFMP).
PlanIT Geo was founded in 2012 in Arvada, Colorado. Many of our first projects were urban tree canopy assessments. We have extensive knowledge on best practices and how to provide the most useful products to meet each individual community's needs.
There are several ways to perform a UTC assessment.
Point Sampling
The most simple method is to use a point sampling technique developed by the i-Tree Canopy tool.
Random points, like those shown in the map, are generated within an area and manually assigned a value of “tree” or “non-tree” until a 1-2% standard error is reached. By dividing the number of "tree" points by the total number of points, you can quickly get an estimate of the percent canopy cover or any other land cover type.
Explore the map to see how 1,500 points were classified to estimate 25% tree canopy cover in South Bend, Indiana.
The downside to this method is that there is no way to understand the location and distribution of tree canopy, plantable space, or other land cover types within various planning scales.
Read more about how this method was used to measure canopy change in Colorado Springs, Colorado on page 28 of our report .
i-Tree Landscape
Another way to measure tree canopy is through the i-Tree Landscape tool. This tool uses land cover data from the National Land Cover Database. Once a location is selected, an estimate of the amount of tree canopy is provided. You can also explore location data (census data, forest risk, future climate, etc.), see tree benefits, prioritize tree plantings, and generate reports.
This is a great, free tool from i-Tree with lots of information to explore. However, the land cover data is typically lower resolution (30-meter) than what the third method provides (60-centimeter).
High resolution land cover data are critical for understanding canopy cover in urban landscapes where much of the urban forest is comprised of street and park trees that are not visible with 30-meter pixels.
High Resolution Land Cover Mapping
The third method uses remote sensing technology and high resolution imagery (aerial or satellite) and elevation (LiDAR) datasets to create detailed land cover data. These data inform all other aspects of the project by categorizing a given landscape into specific classes such as tree canopy, other non-canopy vegetation, impervious or hardscape, bare soil, or water.
With this information in hand, you can then look at the quantity and geographic distribution of each type of land cover and ask many questions like:
- Where is there existing tree canopy? How much?
- How much gray infrastructure (roads, buildings, parking lots, etc.) is there compared to green infrastructure (trees, grass, other vegetation)?
- Where are there potential planting opportunities to increase canopy coverage and address specific issues?
Explore detailed land cover data in the City of Salem, Oregon by moving the spy glass in the map.
Geographic Assessment Scales
UTC assessments provide decision makers with a top-down view of canopy cover throughout a city and across various spatial scales. These scales can benefit many city departments by providing detail on the current level of canopy cover, where plantable spaces exist, and where trees can be planted to address specific issues and to achieve goal.
Stormwater staff may be interested in expanding canopy cover to help reduce runoff. Streets staff may be interested in increasing canopy cover within the public right-of-way to help offset urban heat islands. Council members may interested in expanding canopy, green space, or recreation opportunities for their citizens.
A wide variety of local scales can be used, some of which may benefit non-forestry users.
Plantable Space and Planting Prioritization
Another key element of a UTC assessment is locating plantable or open space and identifying the most suitable areas for tree planting to address specific issues. Using a variety of tools and datasets, cities can determine the areas that would benefit the most for environmental, social, and economic reasons. The following series of maps from Jacksonville, Florida, show the most suitable areas (in blue) for each listed issue.
Air Quality
Identifying and planting in areas with high road density can help improve air quality for residents.
Energy Conservation
Residential areas with low amounts of tree canopy can benefit from tree plantings by helping to reduce energy costs through shade and wind blocking.
Underserved Populations
Tree canopy cover is often greater in areas with higher median income. Planting trees in lower income communities can support environmental equity. This indicator shows the percentage of residents living below the poverty level.
Public Health - Asthma Rates
Trees help clean the air by absorbing dangerous pollutants. Planting trees in neighborhoods with high asthma rates can help improve living conditions in these communities. Public health data are only available at the census tract level, but notice how in Jacksonville these areas also generally coincide with income levels. This indicator shows the crude prevalence of current asthma among adults aged >=18 years.
Priority areas can then be combined with different weights or levels of importance to provide targeted planting areas that align with community goals.
Trees and People
Since trees can help address a wide variety of economic, health, and equity issues, understanding the connections between canopy cover and human populations is becoming an increasingly important set of information for city planners.
Census data (age, income, race/ethnicity, etc.) and public health metrics can be correlated with tree canopy cover to analyze whether trees are lacking for certain groups of people and where an expanded canopy could help improve living conditions. This map shows the percent canopy cover (proportional green dots) for census tracts in Jacksonville, Florida along with mental health cases from the Centers for Disease Control and Prevention (CDC).
There is a strong negative relationship between tree canopy and mental health (r = -.40). Higher levels of canopy coverage are associated with lower rates of mental health cases.
Similar results were observed for:
- lack of health insurance (r = -.43),
- smoking (r = -.39),
- obesity (r = -.31), and
- asthma rates (r = -.29).
Setting canopy cover goals
Establishing a canopy cover goal requires knowing what you already have. It also requires knowledge of local issues: is Downtown hotter than other areas? Do the streets flood during heavy rain events? Are there certain segments of the population that don't have equal access to green space?
With a UTC assessment, you'll get the information you need to set realistic goals based on the existing canopy cover, available planting space, and specific locations affected by these local issues.
You'll also gain understanding of the effort needed to reach this goal. Will it take planting 1,000 trees or 100,000 trees? Will you need to focus on public outreach and engagement in order to expand the urban forest in private residential areas?
What else do we offer?
Not only are you provided with the raw data and information, but we've also developed an interactive, online tool to help you interact with the data and gain a better understanding for your community's needs.
Assessment Report
Our reports aim to summarize our methods, findings, and general recommendations on how best to put your new data to use. The data are analyzed to find the most meaningful and practical outcomes such as advocating for public education and outreach programs, locations of the areas that need more trees, the number of trees that need to be planted to achieve goals, and other data-driven advice that can be applied in an urban forest management plan (UFMP).
Meet TreePlotter CANOPY
Our decision support tool allows you to view, plan, and grow tree canopy. The distribution of tree canopy and where planting space exists can be easily visualized using the View tool. To learn where to plant trees in order to address environmental or socioeconomic and demographic issues, use the Plan tool. Creating simple planting scenarios to understand what it takes to meet canopy cover goals can be performed with the Grow tool. Try it out below in our demo app, or click here to learn more about TreePlotter CANOPY...
TreePlotter CANOPY
Who else has done a tree canopy assessment?
Since 2012, we have helped over 80 communities in the United States, Canada, and Australia gain a better understanding of their tree canopy and identified strategic ways for them to improve conditions for residents, visitors, and their local environment. In addition, many other communities have had similar projects done by internal staff or other groups. As the importance of trees has become more widely understood, the number of cities that have recognized the importance of these assessments has increased. Explore a few of them in the map below.
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1
Washington, D.C.
The District's tree canopy has been studied for over 20 years: by American Forests in the late 1990's and then by PlanIT Geo in 2006, 2011, and 2015. They are working towards a 40% canopy cover goal and have achieved 38.7% as of 2015. Explore the data...
2
West Palm Beach, Florida
The City achieved 4-STAR certification in the STAR Community Rating System in 2016. To expand and maintain their certification, the City elected to perform an accurate and comprehensive analysis of their tree canopy because of its importance to the long-term environmental health and sustainability of the community. With their complete urban tree canopy assessment, correlations and relationships were analyzed between current canopy coverage and potential planting areas to four sustainability themes: urban heat island, public health, socioeconomics and demographics, stormwater indices. Read the report...
3
King County, Washington
King Conservation District (KCD) is tasked with one of the most interesting and multi-faceted opportunities facing any conservation district: to extend its traditional reach and work in the backyards, public easements, and parks and open spaces in the incorporated landscapes of the 34 cities they are proud to call their partners. KCD contracted with us to work with their municipal partners across south King County, Washington to plan and conduct tree canopy assessments. We mapped tree canopy and other land cover types, performed canopy change analyses in cities where prior studies had been conducted, and provided land cover metrics for 18 different cities. Learn more about the project...
4
Dallas County, Texas
The Dallas-Fort Worth (DFW) metroplex in North Texas is home to nearly 8 million people. Urbanization and losses of natural spaces has brought an increased focus on and need for creating a baseline and benchmark of tree canopy. We are working with Texas Trees Foundation to create canopy cover data to be used in urban heat island and public health studies.
5
Colorado Springs, Colorado
The City embarked on a comprehensive project in 2018 to better manage its urban forest. The first steps were to complete an urban tree canopy assessment and sample tree inventory in order to gain better understanding of the existing resources. An urban forest management plan is now being developed with these data and stakeholder input. Learn more...
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