For two years, I watched as the mega Whole Foods rose at 22nd Street and Pennsylvania Avenue. I waited for its completion with the kind of excitement I usually reserve for counting down the days until winter's thaw. But when the project was finished, the building dubbed Dalian on the Park, which houses luxury rentals and retail, looked oddly bleak. Something was missing.

Trees.

In the project's renderings, 33 trees filled in the landscape between the Dalian and the street. They helped the building fit in near the leafy Parkway and elegant Rodin Museum. Today, the main trees onsite are the ones in the building's private terrace three stories off the ground. Two scraggly, weed-ridden saplings grace Spring Garden Street.

The Dalian on the Park is far from the only project to include trees in its renderings and eliminate them in reality. The so-called Fergie tower on Walnut Street did the same. So did the East Market development, where none of the trees meant for 11th Street materialized. The newly opened Lincoln Square at Broad and Washington has a clutch of trees around its Sprouts grocery store, but none on the sidewalk around either corner. Same for the Walnut Estates, on 22nd Street, where trees grace the front of the townhouses, but not the main building on Walnut Street (the street isn't completely paved so there's still hope!).

The trend isn't limited to profit-driven developers: Penn's new Perelman Center for Political Science and Economics sits on a formerly green lot and has no trees on its sidewalk. And Project HOME's JBJ Soul Homes at 15th and Fairmount has but one tree despite intentions of more.

Like many other major cities, Philadelphia has made a commitment to planting them because of their aesthetic, environmental, social, and economic value to the city. If trees' well-known environmental attributes, such as their ability to absorb climate-change causing carbon dioxide and to divert water during storms, weren't enough, trees also have myriad health benefits.

Shady streets in Philly can be 20 degrees cooler than those in full sun — in a heat wave this can mean life or death for residents. Urban tree cover has been shown to play a protective role against urban violence, suggesting that there is something about trees and green space that improves mental health. They also have a positive economic impact. A 2008 study by Penn professors Susan M. Wachter and Grace Wong Bucchanieri mapped Philadelphia house sales and new tree plantings between 1998 and 2003, and found that houses within 4,000 feet of a newly planted tree — an astonishingly large area — sold for 7 percent to 11 percent more than those without trees.

The Pennsylvania Horticultural Society, in collaboration with partners in Delaware and New Jersey, committed to planting 1 million trees in the Greater Philadelphia region. About seven years after the project started, 549,000 trees have been planted (according to a website updated eight months ago).

The City is doing what it can. "Our goal is to increase the tree canopy; we want as many trees as possible," says Sue Buck, deputy commissioner for operations at Philadelphia Parks and Recreation. But Buck acknowledges that planting trees isn't as simple as putting a shovel in the ground. Often times, developers submit renderings for review by Parks & Rec's district arborist, and even deposit $700 per tree, but don't always plant the number intended. If they don't plant the trees, Parks & Rec uses the deposits to plant trees, but there's a backlog.

This issue gets to the heart of what we want contemporary Philadelphia to look like and how we set standards for development. Tree-lined streets are what make Center City's residential neighborhoods a joy to stroll. The planted bollards along Broad Street bring a note of celebration to that corridor. But greenery also serves as a reminder of our link to nature and our responsibilities to the environment.

As we slowly watch trees get developed out of the city, I wonder what other city aesthetics we'll let disappear without a fight.

Diana Lind is managing director of the Penn Fels Policy Research Initiative. She is on the board of the Philadelphia Citizen, where a version of this piece originally appeared.