We are all dismayed to see so many trees removed when an old house is torn down and a new one built. Arlington County follows The Chesapeake Bay Preservation Ordinance which requires a Landscape Conservation Plan for any site disturbance greater than 2,500 sq. ft. Department of Parks and Recreation forestry staff reviews and enforces the requirements of the Landscape Conservation Plan. Residential properties must demonstrate how the site will have 20% forest canopy in twenty years. This can be achieved by using existing trees or trees proposed for planting.
In 2018, 320 private properties were developed in Arlington County. For each of the 320 properties, a site plan was required by the County which showed 1) the trees to be removed due to construction, 2) the trees to remain after construction (conserved trees), and 3) any trees that need to be planted to provide the 20% canopy density after twenty years (planted trees)if the credit for conserving existing trees is not sufficient. Note that this requirement only applies to the development of the property, and legal restrictions to removal of trees after the completion of the development may be limited. In summer 2024, ten Tree Stewards conducted a survey of 90 such sites under the direction of Urban Forester Vincent Verweij to determine the answer to this question. We based the survey methodology on a smaller pilot project of 32 properties done the year before.
Spoiler alert: An aerial survey using 2023 data did show these plots had 23.9% average tree canopy for these lots. This would imply that on average, the lots are meeting the goals of the Chesapeake Bay Preservation Ordinance, but do not yet meet our County goal of 40%. Please continue reading for detailed analysis of how the survey was conducted and number of trees found.
This time we notified homeowners before we knocked on their door. Each of the homeowners selected was sent a letter describing the reason for the survey and asking for Tree Steward Volunteers to be permitted to enter the property. We decided to have the letter printed on Tree Steward letterhead with the signature of the TS coordinating the project and the county forester, believing that a citizen science study can be welcome whereas a government study may not. With this method, we gained access to 84 of the 90 properties, with the few not surveyed because we couldn’t reach the homeowners after two visits; only 1 asked not to be in the survey.
The volunteer work was fun and instructive. First, we learned how to read the intricate site plans required at each development so we could tell how many trees should have been conserved, and how many new plantings should have been installed on what spot in the property. (See example below) Then in pairs we went to that address, knocked on the door, and asked if we could count their trees. Usually the homeowner welcomed us, proudly showing off their beautiful trees conserved, planted during development and those they’ve added over the five years! Only a few were skeptical and refused admittance to the property, and several were not home leaving us to determine how many trees existed on the property from public sidewalks. We must have looked strange to neighbors, wearing our yellow TS vests, standing on tip toe to see over fences, and making notes on clipboard!
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