Between nearly 150 years of Arbor Day and related lessons in the classroom, generations of Americans have grown up with the sense that planting a tree represents a good deed. âYouâre taught in science class that they absorb carbon dioxide and produce oxygen,â Jeff Winkle, Bethel Park interim planner, said. âThey also help with stormwater management, stabilizing the flow and providing habitat for wildlife.â Fifth-graders Raegan Exler, left, and Leah Frank get ready to plant a tree during a Tree Pittsburgh One Tree Per Child activity in April at Neil Armstrong Middle School. Harry Funk As it turns out, much of that can be accounted for in dollar values.