Arboriculture & Urban Forestry 43(2): March 2017 ſt2 (178.3 m2 ) of canopy, representing 7.7% cover- age], its canopy is valued at 5% of the sale price. Additional Regression Explorations The modeling results led to an effort to identify a more nuanced explanation of the impacts of tree canopy. Other formulations of the canopy-price relationship were explored, but these failed to yield significant findings. First, the presence of a tipping point in the value of canopy cover was explored. A tipping point would be consistent with the thinking that some tree canopy is valued (due to the aesthetic, heating, cooling, or other benefits), but that too much canopy would be a negative influence on price (e.g., lack of sunshine, increased maintenance) (Sander et al. 2010). The study authors did not find evidence of this relation- ship in the hedonic modeling of the study area. Similarly, researchers investigated to see whether the amount of canopy mattered not on a percent- by-percent basis, or a square-foot-by-square- foot basis, but on the basis of broad amounts of canopy. The motivation here was thinking that households might not distinguish between 4% and 6% canopy, but they might make judgments or have preferences relating to none, some, more than average, or a lot of canopy. Quartiles were used, and modifications of quartiles to approxi- mate these categories. The study authors did not find evidence of this relationship in the study area. Based on a non-random subset of the sales data, and using supplementary data gleaned from Google Earth, researchers explored the impact on price of tree type, height, and placement for the subdivisions identified as having compact densities. Previous stud- ies that have explored these relationships have used photographic images of the house lot, typically taken from the public right-of-way. Researchers sought a new method for obtaining information about trees on the lot that could be analyzed for economic impact. Site-specific tree characteristics included: • The relative height of individual trees in one of three categories: • Dominant over story (mature trees that tower over most others in the land- scape); • Codominant over story (mature trees that are roughly equal in height to other nearby trees); and 67 • Understory (small-growing mature or immature trees that are shorter than the adjacent house). • Yard placement – Trees were identified by their placement relative to the house, includ- ing street trees (planted along the edge of the street), front yard, side yard, or backyard. • Tree type – Trees were identified as either conifer (e.g., pine, spruce, fir, hemlock) or broadleaf (e.g., maple, oak, ash, birch). This process was accomplished by a detailed visual inspection of each parcel in question using Google Earth. Within the mapping service, dif- ferent aerial views with various axis and zoom settings were used in order to orient the parcel with the lighting at the time the parcel was pho- tographed. Researchers were able to measure and explore the impact of the following attributes: his- toric land cover (forested or field), density (low or high), and current tree canopy/preservation information. Pre-development land cover was con- sidered “forested” if it had 25% or more canopy coverage. Trees were considered “preserved” if the canopy on the development site was 4% or greater. While none of these regression explorations were fruitful, neither were they systematic, as the subsequent modeling was completed for the par- cels located in higher density subdivisions (800 parcels). A more rigorous treatment of these rela- tionships, for all 184 subdivisions identified and all parcels, for example, could yield different results. The study authors have, however, developed the method by which this analysis can be accomplished. Qualitative Analysis: The Value of Trees in the Market Developers Developers note that when building larger de- velopments, they do preserve trees, but typically on the periphery of the subdivision, to act as a buffer to other developments or dis-amenities, such as roads. All the developers explained that it is very difficult to preserve trees on more compact (smaller lots) subdivision home sites because construction and infrastructure com- pact soils and damage tree roots. Unless there is a significant tree or the tree is in a strate- gic location, they will clear cut on the lots and leave trees on the periphery. This was consis- ©2017 International Society of Arboriculture
March 2017
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