Unless you've been doing field research in Antarctica, you've probably heard that this is the 30th anniversary of Philadelphia's community-engagement juggernaut, the Mural Arts Program. It's being celebrated with a show at the Pennsylvania Academy of the Fine Arts, a lavish coffee-table book, symposia, and a greater-than-usual deluge of media coverage.

Not that the murals have ever been something Philadelphians could ignore. During those three decades, the city agency has left its mark on some 3,600 walls, mostly in the bleaker corners of the city where a little paint isn't the worst thing that can happen. But now the juggernaut is crossing into new territory: In April, it will install its first murals in Fairmount Park.

Those murals will be painted on the concrete piers that hold up the Girard Avenue Bridge - one on the east bank of the Schuylkill, the other on the west, both facing the water. Given the program's penchant for depicting the obvious, it should surprise no one that the theme is the city's rowing history, and that the imagery makes a big head-tilt to Philadelphia's most famous painter of rowers, Thomas Eakins. Anyone who walks, jogs, roller-blades, or bikes along the lush river trails will encounter the 100-foot-long paintings by Jon Laidacker, one of the program's regulars.

Whether you love murals or, like me, had your fill long ago, their incursion into Philadelphia's beloved beauty spot should be a call to attention.

While the Schuylkill greenways may not be on the same level as, say, the Grand Canyon wilderness - and the murals may not be the equivalent of painting a cliff wall - these spaces serve as Philadelphia's front door to the natural world. The park is where we go to escape the constant static of our frenetic urban lives, to forget our devices and lose ourselves amid the trees. Do we really need more manufactured images?

The serenity of the city's parks have been increasingly under assault from modern distractions - advertising, electronic signs, private restaurants. Murals, which tend to trumpet somebody else's cause or interest, risk becoming just one more intrusion. We're past due for a conversation about setting boundaries.

Let's start by examining how the city approved this pair of murals in the most heavily used section of the park. The project was initiated by a rower, Tony Schneider, who approached Mural Arts and offered them $85,000 to create a tribute painting along the river.

Mural Arts director Jane Golden took the idea to the Department of Parks and Recreation, headed by Deputy Mayor Michael DiBerardinis. Because his wife is Mural Arts' chief operating officer, he says, he recused himself, as he does with all decisions involving the group. He turned the proposal over to his deputy, Mark Focht, who worked with Golden and the artist to refine the mural. Since the Art Commission had to review the design, I suppose you can argue that the public interest wasn't completely overlooked.

But that doesn't mean the precedent-setting project got the scrutiny it deserves. Golden is a forceful advocate, and an unquestioning culture exists in City Hall in favor of murals. Focht says he recognized that this one was different and wrestled with the decision. Ultimately, he concluded the bridge made it a more urban location.

"We went back and forth for many months over the design. I met Jane at the site twice," he told me. "I was very firm that the murals should only face the river," and not the river drives, where they might interfere with traffic. He made clear that the stone at the piers' base should not be painted.

But, as Focht notes, art isn't something new in Fairmount Park. It's filled with sculpture, both traditional and modern. So, what makes murals any more intrusive than the art just a few feet south of the Girard bridge, in the elegant Ellen Phillips Samuel Memorial Sculpture Garden?

For starters, quality. Mural Arts was founded as a tool to fight graffiti, and over time shifted its mission to community engagement in struggling neighborhoods, where it employs residents to design and install murals. The end result has always been less important than its social goals.

By contrast, the modernist sculptures in the Memorial Garden were chosen after a rigorous international competition involving the Art Museum. Like all good art, they challenge how we look at the world. The murals simply will show us what we can see in front of our eyes: real rowers. The standard-issue images of Boathouse Row and scullers are cliched and already look old. On top of that, the scale of the 16-foot-high, 100-foot-long paintings overwhelms the nature around it.

Golden likes to stress that murals are really a community-building exercise. But there are many communities who use the river. And if we must have murals narcissistically reflecting our own images back at us, then why not the mom pushing a jogging stroller or the spandex-clad biker?

In fact, there already are two tributes to rowers on the river: the statue of Olympic winner Jack Kelly and Richard Haas' trompe l'oeil Chestnut Place mural, west of the river. Veteran rowers tell me they won't even have time to look at the murals because the location is an especially challenging spot, demanding all their wits.

These sorts of details call into question the form, themes, and siting of the paintings. The paths along the drives are neither blighted nor depopulated. Lined with sycamores, they are where the Schuylkill opens into a broad vista, framing the arched stone bridge that appears in several Eakins' paintings. It is an iconic Philadelphia spot.

Would we put murals along Forbidden Drive? What about on the side of a boathouse? Overlooking Pine Street's Louis Kahn Park? Near the Japanese House? In the future, the locations will be decided on a case-by-case basis, Focht told me. Right now, all we can do is cross our fingers that Parks and Rec will make the right choices.