There's plenty of new fuel for the perennial sport of Museum of Modern Art–bashing as the museum pursues a controversial expansion plan.  Will the architecture firm of Diller Scofidio + Renfro be able to raze the MoMA-owned and widely acclaimed former Folk Art Museum building, designed by Tod Williams Billie Tsien Architects, to accommodate an expansion of MoMA's critically derided Taniguchi-designed home? Commentary is flying. Panels have been empaneled. The issue has attracted more players into a preservation debate than there are subpoenas in Governor Chris Christie's George Washington Bridge scandal. And the atmosphere is heating up. Liz Diller survived one auto-da-fé already. The media are hyping the feud as personal because of the potential for a Grand Guignol starring two of architecture's first couples.

Setting aside such dishy digressions, it's encouraging to see this vigorous debate about an existential threat to recent work by celebrated practitioners. But where was the public discourse when Martha Schwartz's award-winning design for Jacob Javits Plaza was replaced last year by Michael Van Valkenburgh's work? Schwartz's design at 15 was barely older than the Folk Art Museum. Is it different for building architecture than landscape architecture?

Maybe the Javits situation needed a get-out-of-jail-free card, which is what MoMA officials hope they have in offering some form of increased public access to their famed Abby Aldrich Rockefeller Sculpture Garden. Well, not so fast. A recent articles in The New York Times quoted six landscape architects, including James Corner, Ken Smith, Laurie Olin, and Michael Van Valkenburgh (which may be a record for the number of landscapes architects quoted in a Times article). Opinions differ. Smith says: "It's a good idea." Olin, however, is skeptical: "They're using [a promise of increased access] to pacify people about something else that has people upset, and in the course of it, they're watering down what was special."

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If MoMA throws open its garden, what could happen? How do stewards of cultural landscapes, whether an individual site (like the garden), a larger site (like New York's High Line), or a much, much larger site (like the City of Savannah) manage the visitor experience, which ranges from restorative contemplation to active stimulation? Savannah, whose residential population is under 150,000, had more than 12 million tourists in 2011 (up from 7 million in 2006). The High Line's 2013 visitation was 4.8 million people, 50 percent of them residents, up from 3.7 million visits in 2011 and double the 2010 figure. Balancing the needs of tourists and residents is difficult work. "Our challenge is to figure out how to sustain the park as a special place for New Yorkers, and we are actively working toward this goal," writes Kate Lindquist, a Friends of the High Line staffer. "We are exploring ways to make it easier for New Yorkers to know when visitation is at its peak, such as live Web cams, Twitter updates, and more." Maybe it's time for congestion pricing, or HOV (High Occupancy Visitor) lanes.

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With increased access, a site risks being loved to death. Philip Johnson, designer of MoMA's sculpture garden, addressed its carrying capacity in the 1994 book Philip Johnson: The Architect in His Own Words. Johnson fielded the direct question:  "Is [the garden] at its best when there are very few people in the garden or when there are a lot?" He replied: "It's better to have a few, of course, because then you get the feeling of the space. But it can take solid crowds." That takes us back to how we measure success in terms of the visitor experience. Johnson himself said: "You need a place to relax after looking at the artwork. You're so relieved that there is no painting to focus on." The Central Park Conservancy has successfully implemented a sort of crop rotation for people by luring visitors north with the addition of the Charles A. Dana Discovery Center on the Harlem Meer (opened in 1993) and shifting locales for where dogs run off leash (among other steps) to meet the needs of visitors while maintaining the site's integrity.  By contrast, the lawn of the National Mall in Washington, D.C., frequently looks bedraggled; this is the biggest reason why the annual National Book Festival is being moved to D.C.'s convention center. Johnson's Glass House in New Canaan, Conn., has limited visitation, as does the Hillwood Estate, Museum and Garden in Washington, D.C., but both are in residential neighborhoods, which imposed the limits. (Glass House's stewards did apply to increase the number of visitors, but withdrew the application following backlash from neighbors.)

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The debate about MoMA's garden raises bigger issues that design professionals, stewards, and advocates must address, particularly with the renaissance and growth of the urban core. Can success be measured by valuing the quality of an experience that honors a site's design intent rather than the greatest number of visitors? Is less more?  In his 1988 treatise City: Rediscovering the Center, the great social and cultural theorist William H. "Holly" White posed this question: "What if we were to succeed too well? Conceivably, so many more people might be attracted as to crowd out the values they came to enjoy." MoMA must be careful what it wishes for.

Charles A. Birnbaum is the president and founder of the Cultural Landscape Foundation.

Images (from top): La Citta Vita/Flickr via Creative Commons license; Nicole Cash/Flickr via Creative Commons license; David McSpadden/Flickr via Creative Commons license