Arlington County’s tree canopy is highly valued by both the citizens and County staff. Generally speaking, tree canopy refers to the part of a city that is shaded by trees. As much as Arlington values its trees, the County is challenged by its increasing population and the development that this brings. Several studies have been performed on our urban tree canopy using satellite imagery to understand the extent and change in our tree canopy throughout our community.
As part of the Urban Forest Master Plan, Arlington County government monitors the tree canopy of our community on a regular basis. The data can provides information on success of preservation and planting programs, helps us understand change and structure of our urban forest, and in turn provide guidance for planning.
2017 Tree Canopy Study Highlights
Our most recent study showed some trends in our tree canopy:
- Arlington reversed the decline in tree canopy found in 2011 (40%) but has not rebounded from our first measurement in 2008 (43%). Our overall 2017 tree canopy, while shifting in places across the county, remains fairly stable, with an increase of 1% overall. Find the Current Urban Tree Canopy Analysis here.
- Tree canopy has increased in our parks, with very few parks showing significant reductions in tree canopy, since 2011
- Private residential properties show the greatest opportunity for more trees. Penrose, Aurora Highlands and Bellevue Forest have had the greatest increase since our last measurement. The Rosslyn/Courthouse area, and the northwestern area of Rock Spring, down to Dominion Hills, have shown the greatest decline in trees since our last measurement. You can find changes in tree canopy by civic association for 2008-2011 Here, and for 2011-2016 Here.
We can use this data, as a community, and a government, to prioritize preservation and planting in some regions showing canopy reduction, and maintaining high tree canopy in areas of improvement.
A presentation on the report is available here, and an overview of tree canopy percentages from the three studies can be seen in Table 1.
|Tree Canopy Excluding DOD and Airport||6,349||43%||5,883||40%||6,015||41%|
|Tree Canopy Including DOD and Airport||N/A||N/A||6,191||37%||6,356||38%|
Table 1. Tree Canopy of Arlington County Excluding and Including Department of Defense (Pentagon, Arlington Cemetery, and other properties) and Airport Data
While coarse data about historic tree canopy exists (and can be found in the Urban Forest Master Plan) the first detailed tree canopy study was performed in 2008, by Virginia Tech. This study did not include Department of Defense land (such as the Pentagon and Arlington Cemetery), and the airport. Subsequent studies did include this data.
About Tree Canopy Studies Performed
Tree canopy studies are performed using satellite imagery, either collected specifically for an area, or extracted from existing data sets. The first detailed tree canopy study for Arlington County was performed in 2008, by Virginia Tech, and did not include Department of Defense Land (such as the Pentagon and Arlington National Cemetery), or National Airport. Prior to 2008, Arlington has coarse data about historic tree canopy, which can be found in the Urban Forest Master Plan (Pages 9-11).
Arlington was included in a Casey Trees study in 2011, and while the data was shared, no specific report about Arlington was prepared, like the 2008 or 2017 report. Analysis was performed by staff to find areas of change. One of these change analyses can be found in a civic association-focused map, in the links, below.
The 2017 Tree Canopy Study and analysis Report was developed by the Davey Resource Group, using the most recent publicly available data (from 2016).
Frequently Asked Questions
How accurate are these studies?
The resolution of the three studies is a 1 Meter resolution. This means that any tree smaller than 1 X 1 Meter, may not be captured in the study. While this creates some level of error of omission, this level of accuracy, along with a Quality Control/Quality Assurance protocol, allows for a high level of confidence. For more information, see the Accuracy Assessment Protocol in our 2016 study.
Why is the 2017 study using 2016 data?
The data used was aerial imagery flown by the National Agricultural Imagery Program, which is flown every 2 years. The most recent data was from 2016.
If we have potential planting area, can we reforest these areas?
We will work with everyone to help increase our tree canopy, where appropriate, but plantable areas may be used for other purposes, including other ecological systems, such as meadows, recreational fields, or programmed space, such as the County Fair. Much of this area is also in private ownership, and while we can encourage planting on these properties, and aid them through the Tree Canopy Fund, ultimately, the owners of those properties define their land use.
For more questions, you can reach the Urban Forestry Office at firstname.lastname@example.org