By Michael DiBerardinis

and Harris Steinberg

While going green is a phrase that's stretched thin these days, parks and other green public spaces improve the air we breathe, protect the water we drink, and make our neighborhoods better. And yet more than 200,000 Philadelphians cannot walk to a park within 10 minutes of their homes.

The city's "Green2015" plan, to be launched this week, aims to ensure that every Philadelphian has a park to call his or her own. It will make an affordable investment in Philadelphia's future using existing resources.

Commissioned by the city Parks and Recreation Department in cooperation with the City Planning Commission and produced by PennPraxis, Green2015 is a plan to add 500 acres of green public space to the city by 2015. The goal is to provide park space for residents who don't live within a half-mile of a park, and ultimately to make the city more equitable, livable, and competitive.

Green2015 offers a set of criteria to guide decisions about adding parks while at the same time maintaining and improving existing parks. It also offers a long-range vision for a citywide network connecting all Philadelphia neighborhoods to the waterfront parks and regional trails with bike and pedestrian paths.

We are already well on our way toward achieving this ambition. Since the start of the Nutter administration in 2008, people across the city have been creating parks. Government, business, nonprofit groups, and other institutions have demonstrated the power of collective action, and more than 100 acres of parkland is under way. Drexel Park, the Kroc Center, Hawthorne Park, and the greening of the Greenfield School are prime examples of parks in the works. And another 105 acres is in the pipeline.

Funded by the William Penn Foundation and the Lenfest Foundation, Green2015 started with a program run by the Penn Project for Civic Engagement and the Pennsylvania Horticultural Society, allowing citizens to inform the plan. Among other things, they urged long-term investment, collaboration across agencies and sectors, and bold thinking.

Achieving these goals in a time of fiscal constraints will not be easy. That's why our short-term recommendations point toward existing public resources and funding. This means focusing on bringing green space to existing recreation centers, vacant public land, and school yards that are completely paved over. These sites are numerous, evenly distributed across the city, and already under public ownership, so they present significant, short-term opportunities for low-cost, high-impact greening and creating viable parks in areas that need them.

As a recent Redevelopment Authority study made clear, we are paying dearly for the 40,000 empty parcels of private and public land in Philadelphia today. The city is spending more than $21 million a year on management of nonproductive, vacant land.

As the Green2015 plan tells us, there is "gold in green." Let's unleash its potential.

Michael DiBerardinis is commissioner and special adviser to the mayor for Parks and Recreation and the Free Library. Harris Steinberg is the executive director of PennPraxis at the School of Design of the University of Pennsylvania. The Green2015 plan will be launched at 6 p.m. Tuesday at the Academy of Natural Sciences. To attend the event, see http://thefirst500acres.eventbrite.com. For more information, see www.planphilly.com/Green2015.