Cities take up only 2 percent of the space on our planet yet 50 percent of the world’s population live in them and they consume 75 percent of its resources. That, said Warren Karlenzig, is a problem. The research director for SustainLane, an information clearing house for all things green, was in town for Penn’s recent “Growing Greener Cities” symposium.

Figuring out how to lighten our cities’ environmental footprints has become an urgent matter, said Karlenzig, speaking at a session in Houston Hall on Oct. 16. With the effects of global warming now becoming evident, our urban areas, he said, are increasingly threatened by flooding, heatwaves and other natural disasters. “It’s not just about cleaning up,” said Karlenzig, “but about creating a common future.”

This message was reiterated many times over the course of the three-day symposium, which was co-sponsored by Penn’s Institute for Urban Research and brought Nobel peace prize winner and Green Belt Movement founder Wangari Maathai to speak at the University, as well as experts in urban planning, landscape architecture and sustainable development.

Leading by example
“Are we greening because we all like the color green?” asked James Corner, professor and chair of Penn’s Department of Landscape Architecture at another session. “No, we’re doing it because we can improve stormwater management, grow habitat … avoid flooding.” To make that point, Andy Lipkis, founder of Los Angeles’ TreePeople, explained that a typical California oak tree with a canopy of 100 feet across has the capacity to capture and hold 57,000 gallons of water in a flash flood.

“It’s not just about making a city prettier,” he said. Trees are part of the infrastructure of the city and this, he said, “is a time for bold action.”

“Clean and green”
In Philadelphia, reclaiming and greening vacant lots has become a key anti-blight strategy. According to Eva Gladstein, director of the city’s Neighborhood Transformation Initiative (NTI), Philadelphia has more than 30,000 vacant lots. That’s one of the highest numbers in the nation, and NTI’s “clean and green” solution aims to make even the most embattled neighborhoods viable. By clearing away rubble and debris, adding top soil and trees and enclosing the lots with low wooden fencing, the city has “stabilized” 3.7 million square feet of vacant land. “This is not necessarily a permanent use,” said Gladstein, “but it makes the lots look cared for and they’re respected by the community—the trash dumping stops.”

Cleaning and greening also increases the value of nearby properties, as proved by a recent Wharton study by Susan Wachter, professor of real estate, finance and city planning. Wachter’s study showed that while proximity to a neglected vacant lot subtracts 20 percent from the value of a neighboring home, adjacency to a stabilized lot increases the home’s value by approximately 15 percent. “We’ve known it anecdotally,” said Gladstein, “but it’s important to be able to have the metrics to make the case for future investment.”

What we love most
Though many at the three-day symposium stressed that greening was not about prettifying, there’s no denying, said Blaine Bonham, executive VP of the Pennsylvania Horticultural Society, which cosponsored the event with the Media and Policy Center Foundation, that what we love most about many of our favorite cities are the parks and outdoor spaces. Philadelphia, he said, is emerging from the dark ages of urban decline, and now has the potential to be, as National GeographicTraveler has already dubbed us, the “Next Great American City.” With more than 400 community gardens in the city and a vastly improved green infrastructure it’s no surprise, said Bonham, that “greening is having synergistic results.”
After all, he said, “it’s what makes urban societies hum.”

Originally published on November 2, 2006.