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- The complete "Our Common Home" conference on Laudato Si' (pg. 42)
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The trees scattered across Boston College’s landscape do not appear on the school’s balance sheet, but the University would be poorer without them. Literally. The 4,615 specimens counted and measured on the Chestnut Hill and Brighton campuses by student researchers during the summers of 2008 and 2009 reduce air-conditioning costs with their shade and lower heating costs by buffering winds, remove airborne pollutants, and prevent erosion. Furthermore, the trees take in and sequester carbon dioxide, thereby offsetting a portion of the University’s carbon emissions. By just how much won’t be known until the inventory is completed (Chestnut Hill’s 118 acres have been tallied; about 16 of the 49 acres comprising the Brighton Campus remain uncharted). One hundred trees can capture 53 tons of carbon per year.
Deirdre Manning, who served as the University’s director of sustainability and energy management through last August, hired students to catalogue the trees in 2008 as part of an effort to determine the University’s net carbon footprint. After training with a local arborist in the basics of tree identification, the students went to work, using a clinometer (a $14 protractor-like device that, combined with basic trigonometry, permits calculations of height) and a 100-foot tape measure for determining trunk diameter and canopy width (measured from one edge of the drip line to its opposite)—figures that are needed for reckoning carbon capture.
The image above is largely the work of Kevin Keegan ’10, who says he signed on in 2008 as a “foot soldier” but became “fascinated by the trees and the technology”—including a software program that combines cartography with data management. Because of the margin of error inherent in the Global Positioning System, he and other student census takers (Jacqui Geaney ’10, Emily Luksha ’10, Emily Pierce ’10, Natalie Raffol ’10, Noel Schaff ’10, Katherine Walsh ’08, and Bassam Zahid ’09) utilized downloaded aerial photographs in which each pixel represents 45 centimeters. Keegan managed the data and also changed his major, from chemistry to environmental geoscience.
Highlighted on the map above are the 44 littleleaf lindens on Linden Lane (A); the tallest tree, a 100-foot oak across Campanella Way from Robsham Theater (B); and the lone giant sequoia (C), a 60-foot conifer on the grounds of Hovey House. Also evident is the abundance of Norway maples—for example, at (D)— an invasive species whose 834 plants make it the most numerous on campus. Next most populous is the eastern hemlock (E), a native evergreen. Its 412 specimens—10 percent of the campuses’ trees—are languishing due to the hemlock woolly adelgid, an Asian pest that can defoliate and kill trees within 10 years of infestation.
Read more by Thomas Cooper