Biking Mount Desert Island’s Park Loop Road over Memorial Day weekend, Friends of Acadia Conservation Director Stephanie Clement witnessed vehicular chaos. She has seen a lot in Acadia National Park over two decades but this was unprecedented. “There were cars everywhere,” she recalls, “in places I had never seen them before.”

The Island Explorer bus service, which shuttled more than a half-million visitors last year, had not yet begun its seasonal runs – exacerbating the holiday crunch of vehicles. Despite being one of the smallest national parks, Acadia recently ranked as the eighth most visited one. Its density of use far exceeds that of other national parks, with 67 visits per acre (the next closest contender, Zion, had only 29 visits per acre).

Increasingly, visitors to Mount Desert Island find, in the sardonic view of some Acadia staff, not so much a park experience as a parking experience. Cadillac Summit Road and Ocean Drive are now subject to periodic brief closures when the fruitless quest for parking spaces on peak weekends prompts egregious traffic back-ups.

Park officials and partners are working on a transportation plan that could alleviate congestion – potentially relying on approaches such as parking space reservations at peak times and increased bus service. Acadia’s Island Explorer service is still voluntary but other parks – like Zion – have gone to a mandatory shuttle. Zion’s shuttle receives positive visitor reviews and has brought ecological and economic benefits over nearly two decades.

Parks and land trusts often limit parking lot size to restrict numbers of trail users – an approach that can work well when the adjoining roadway is private. But in Acadia, where state highways and local roads bisect park lands, roadside parking restrictions would require enforcement from many municipalities.

Growing challenges with vehicular congestion and trail compaction signal the need to address a broader concern – Acadia’s long-term carrying capacity. That concept, borrowed from ecology, refers to the maximum population size (or human visitor load) a place can withstand before its resources are irreparably damaged.

Honoring that inherent ecological limit can be challenging, particularly at a popular setting like Acadia that lies within a day’s drive of one-quarter of the U.S. population. The park had an estimated 3.3 million visits last year, up a staggering 55 percent since 2006. The National Park Service anticipates that by 2060, population growth and a warming climate could drive visitation rates up to more than 140 percent of historical levels (between 1979 and 2013).

Even as visitor numbers grow at many national and state parks, public funds to manage these destinations dwindle. National parks face a multi-billion-dollar backlog of needed maintenance and improvements, and both state and national parks have seen marked declines in staffing.

With parks now chronically short-staffed, education has become a self-serve buffet – in which visitors may or may not help themselves to the guidance offered on signs. Parks stand a better chance at education and enforcement of rules when they have guaranteed contact with visitors. Acadia suffers from great “porosity,” says Park Management Assistant John Kelly, with more than 50 entry points to its MDI lands. In contrast, Baxter State Park has two main entry roads, each with a staffed gatehouse.

Baxter’s management explicitly favors resource protection over recreation (in deference to Percival Baxter’s vision) – with five pages of visitor rules, day-use parking permits, and a ban on any roadway parking outside established lots. Those strictures, notes Friends of Baxter State Park Executive Director Aaron Megquier, help make the “wilderness experience easier to find at Baxter.”

When concerns arose, for example, about impacts from the growing number of Appalachian Trail thru-hikers climbing Mount Katahdin, Baxter State Park Authority established a permit system for them. This year, it instituted a cap on the annual total of thru-hiker permits issued.

Rationing the park experience is “the most difficult [approach] culturally and socially,” notes Kelly. Yet it may be increasingly necessary to sustain the natural integrity of heavily visited parks – when other measures fail.

Acadia and other preserves could begin with a simpler, front-end solution. Why not market the place less and educate visitors more – in advance – about crowding concerns?

Local chambers of commerce and state tourism entities typically work in isolation when promoting natural destinations, without seeking input from those who manage the lands. That approach is no longer tenable. Land stewards on the front lines of visitor management – who struggle to balance recreational use and ecological preservation – need to be integrally involved in how and where properties are promoted.

At Acadia, Kelly says, “we’re trying to coordinate our messaging” with state tourism officials, encouraging them to feature the fare-free, propane-powered bus service and explain how park fees support “what we do to protect the park and offer a good experience.”

Judging from the 2017 “official travel planner” for Maine, the collaboration between tourism and park officials needs work. The guidebook’s teaser for Acadia National Park includes no mention of the bus service or park fees, and ends with the recommendation “so even if you are stretched for time, at least drive the Park Loop Road….”

MARINA SCHAUFFLER provides research, writing, and editing services to nonprofit and social enterprise organizations through Natural Choices (www.naturalchoices.com).