Walking around Penn’s verdant campus today, it’s easy to take the abundant tree canopy for granted. But at various points in history, the University was not as bucolic. Until as recently as the 1950s and 1960s, city streets brought vehicular traffic through what eventually became the now-familiar, tree-lined pedestrian walkways, like Locust and Woodland walks.

“Today, you can walk through campus from 40th Street to Penn Park, a distance of over a mile, and only cross two roads,” says Bob Lundgren, Penn’s landscape architect in the Division of Facilities and Real Estate Services. “That’s remarkable. Not many urban campuses can say that.”

In a piece in the journal Environmental Management, a team including current and former Penn students and staff, led by alumna Lara Roman of the U.S. Forest Service, used archival materials and aerial photography to provide an account of the past 150 years of thought and effort that went into creating Penn’s current tree canopy.

The paper didn’t begin as a history project. Roman, a graduate of the College of Arts & Sciences and the Master of Environmental Studies (MES) program, was working on an analysis of more recent changes in the canopy on campus, using comprehensive, tree-by-tree inventories from Lundgren’s records collected 10 years apart.

“In the process of speaking with Bob and Chloe [Cerwinka, Penn’s landscape planner], I learned not just about recent changes, but that the campus wasn’t always as green and pretty as it is today,” Roman says. “We decided to do a more thorough analysis of tree cover change.”

Roman, Cerwinka, and Lundgren, together with Jason Fristensky, a 2014 graduate of PennDesign’s Landscape Architecture program; Caitlin Welsh, an MES student; and Theodore Eisenman, who earned his Ph.D. from PennDesign in 2015, dug through Penn’s archives, relying on photographs, century-old campus plans, meeting minutes, and decades-old aerial photos to trace the ebbs and flows of concern about trees through the 19th, 20th, and early 21st centuries.

The late 1800s and early 1900s saw “a heyday of greening,” Roman notes, with the creation of James G. Kaskey Memorial Park, widely known as the Biopond, the planting of the iconic “Treaty Elm” in front of College Green, and the development of Smith Walk and Hamilton Walk as pedestrian thoroughfares. In this period, Ellen Harrison, wife of Provost Charles Harrison, who served from 1894-1910, was a champion of greening efforts.

This was followed by a long period of decline from a landscape-focused perspective, as economic circumstances and then a focus on acquiring property meant resources were channeled more into building construction and less landscape management.

By the late 1950s and 1960s, this trend began to change, as proposals to close off Locust Walk to vehicular traffic circulated, the trolley lines were buried, and Ian McHarg, a landscape architecture professor, emphasized the connection between ecology and landscape planning.

“His work set the stage for the 1977 master landscape development plan,” Lundgren says. That document set in motion the planning and investment in green spaces and landscape design the authors credit with influencing “all subsequent campus landscape projects,” including the creation of Lundgren and Cerwinka’s positions.

Many other landscape architecture scholars at Penn contributed to landscape enhancement in this period, including George Patton, Peter Shepheard, and Laurie Olin.

Indeed, the subsequent decade, 1980 to 1990, saw a 38 percent increase in canopy cover on the “core” campus (roughly 32nd to 40th streets, Chestnut to Pine streets). Overall, from 1970 to 2010, campus tree cover more than doubled.

More recent efforts have focused on sustainability planning, embracing relationships with the community through conducting neighborhood tree plantings with University City Green, and stepping up tree management with involvement from the Morris Arboretum. Penn’s commitment to caring for its trees led the University to be designated a Tree Campus USA each year since 2009, and obtain an official designation as an arboretum earlier this year.

The report “is more than just the story of an Ivy League campus planting trees and green spaces,” Roman emphasizes, “it’s the story of college campuses as microcosms for cities.”

Roman and her coauthors are hopeful that lessons learned from greening an urban campus like Penn’s can be applied by municipalities trying to make their urban areas greener.

“It wasn’t a simple linear trajectory to get to how Penn looks today,” Roman says. “Trees take decades to grow, ongoing maintenance, and a commitment to planting the next generation of canopy. Just like cities, you can’t have one university administration make a plan and be done with it. What we’re trying to argue is, we need people continually recommitting to making the landscape beautiful.”

Additional authors on the paper include Penn lecturer David Hewitt and the U.S. Forest Service’s Eric Greenfield.