Assessment of Land Cover, Tree Canopy, and Plantable Space on Virginia Tech Campus
Byers, Alexander M.
Wiseman, P. Eric
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To better understand the extent, distribution, and value of Virginia Tech’s tree canopy cover, students in a senior-level urban forestry course in the Department of Forest Resources and Environmental Conservation conducted a land cover and tree canopy cover assessment of campus during the spring 2020 semester. The assessment was performed using a software application called i-Tree Canopy. The application combines aerial photographs of the landscape with ecosystem models to derive estimates of land cover types and the ecosystem services provided by tree canopy cover. The land cover data is created through a process called sample-based photo interpretation. In this process, an analyst views randomly sampled scenes of the landscape using Google Earth imagery and classifies each scene into predetermined cover types. For this assessment, the imagery was dated June 2019. The campus area included in the assessment comprised most all of central campus east of US Route 460, south of Prices Fork Road, north of Virginia Tech Airport, and west of Main Street. The study area was subdivided using two different geographic schemes, one that used Campus Districts (16 total subdivisions) and one that used Tree Maintenance Zones (42 total subdivisions). The largest existing land cover type was impervious surface at 24.4%, totaling 257 acres. Turf and building were nearly identical at 11.8% (124 acres) and 11.2% (118 acres), respectively. Existing tree canopy cover was estimated at 16.9%, totaling 177 acres. Existing tree canopy cover in the Campus Districts geographic scheme mitigates 8,790 pounds of air pollution annually (95% confidence interval: 8,546 lb – 9,034 lb). Mitigation includes removal of harmful pollutants that are by-products of fossil fuel combustion: carbon monoxide, ozone, nitrogen dioxide, sulfur dioxide, and particulate matter (PM2.5 and PM10). Total value of air pollution mitigation across Campus Districts subdivisions is $4,630 per year (95% confidence interval: $4,495–$4,764).