Every Tree Counts: Using PhillyTreeMap for Collaborative Urban Forestry

GIS Contributor


Philadelphia, like many American cities, has a wealth of urban trees.  Collectively known as the “urban forest,” these are the trees that line our city streets and river banks and adorn our urban parks and private lawns.  Healthy trees improve the look and feel of city neighborhoods by providing shade and natural beauty, but they also provide valuable ecosystem services with a far-reaching impact on global climate change.  Urban trees store millions of tons of carbon each year and slow the accumulation of greenhouse gases.  Urban trees provide stormwater mitigation by intercepting rain on their leaf, branch and stem surfaces and by absorbing water through their roots.  Urban trees improve air quality by lowering air temperatures and removing air pollutants through their leaves.  A properly shaded urban neighborhood provides heat island mitigation in the summer and windbreak in the winter that can significantly reduce business and household energy consumption.

Managing and maintaining our urban forests provides clear environmental, economic and quality of life benefits.  Such maintenance is more effective when there is an accurate and current inventory of all the trees in the municipal area. Having an up-to-date tree inventory enables organizations to better maintain the urban forest and plan future planting and renewal efforts.  Creating an accurate inventory of urban trees, however, has been a difficult and time-consuming process for many municipalities.  The responsible agencies are often under-funded and short-staffed, and their priorities are necessarily driven by weather damage, the impact of trees on electrical lines and other reactive activities.  With limited resources and a long list of other necessary activities, how can a city or a region possibly find time to inventory every single tree?

Web-Based Urban Forestry Tools

Azavea is a geospatial software design and development firm based in Philadelphia.  As a certified B Corporation whose mission is to apply geographic data and technology to creating sustainable, livable and vibrant communities, Azavea took on the challenge of designing a web-based solution that would help make the tree inventory process easier and more affordable for urban communities nationwide.  The result is PhillyTreeMap.org, a wiki-inspired, web-based geography-enabled urban tree inventory application that serves as the prototype of a larger OpenTreeMap project.  The goal of the OpenTreeMap project is to enable citizens, students and nonprofit organizations that are passionate about greening their communities to come together with local government agencies and other stakeholders in a joint effort to map, tend and preserve the urban forest.

PhillyTreeMap.org was developed using funding received from the USDA National Institute of Food and Agriculture as part of the Small Business Innovation Research Program (Grant Number 2010-33610-20937).   The prototype was rolled out on April 29, 2011 – Arbor Day – as part of a Green Tech Showcase event held during Philly Tech Week.

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The PhillyTreeMap prototype includes data for more than 177,000 trees within the larger thirteen-county, tri-state area surrounding the City of Philadelphia.  The site can be searched by location, species, or more advanced criteria including diameter and date planted.  Dropdown lists enable users to navigate quickly to a specific neighborhood of interest or explore only a particular species of tree.  Each tree is represented by a marker on a large map with additional information available on a detailed profile page. The detail page for each tree provides an inset map of the tree’s geographic location as well as a street-level view of its surroundings as seen in Google Street View.  The detail page also includes identifying information about each tree such as its species, height, diameter and overall health or condition.

The PhillyTreeMap home page
The PhillyTreeMap home page provides a quick overview of the website, including dropdown lists that enable users to filter tree data by location or species or link to an FAQ page with how-to information about the tree inventory process.

While the site was populated initially with data sets from the Pennsylvania Horticultural Society, Philadelphia Parks & Recreation, and the Township of Lower Merion, public users can also edit the existing information or add new trees.  To contribute to the inventory, users create a free account and then edit existing tree details, upload an image of a tree or add a new tree to the system.   All changes are immediately visible on PhillyTreeMap, but a group of trained administrators also reviews the site for inaccurate or inappropriate entries.

PhillyTreeMap also generates estimates of the environmental impact of each tree on the urban environment.  This includes stormwater interception, carbon sequestration, air quality and other metrics.  The economic benefits are calculated using parameters generated by iTree, an urban forestry analysis and benefits assessment software suite developed by the USDA, and are automatically updated each time a tree is added or removed from the inventory.  This is an important feature that could help municipalities justify their tree maintenance expenditures and determine the tree species best suited to targeted remediation tasks ranging from stormwater mitigation to air quality improvements to energy savings.

PhillyTreeMap search page
The PhillyTreeMap search page provides a dynamic overview of the yearly impact of Philadelphia’s trees on the regional ecosystem. The information is automatically updated as trees are added or removed from the inventory.

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