Tourists photograph the sunset at the summit of Cadillac Mountain in Acadia National Park. Robert F. Bukaty/Associated Press

Under current warming trends, Acadia National Park could see its average annual temperature increase as much as 8 degrees Fahrenheit and the average number of high-heat days could increase by 24 days a year by 2050, according to a new report from the National Park Service.

But it is the precipitation outlook that worries park managers the most. The report authors can envision two very different futures for Acadia: one that is warm and dry, where annual rainfall drops by 2 inches, and another that is hot and sticky, where annual rainfall increases by 8 inches.

“Eight degrees would be a huge increase, but even if that comes to pass, we’d still be pretty comfortable compared to other parks because it’s Maine,” said Abe Miller-Rushing, science director at Acadia. “Heavy rains, storms, sea level rise. Those are our biggest climate threats. They cause so much damage.”

Under the more optimistic “warm and dry” scenario, which assumes the global burning of heat-trapping fossil fuels is slashed, the temperature will increase by 2 degrees and rainfall will dip by 3.2% by 2050. The park would log an additional 9 days (rather than 24) when the daily high hits 86 degrees.

To put this in context, historically hot years at Acadia would become average under the best-case scenario. The average temperatures projected under the worst-case scenario, meanwhile, would be hotter than any year experienced at Acadia, at least in recent history.

The report, issued last week by the National Park Service’s climate change response program, emphasizes the importance of adaptation planning. Its authors urged park managers to consider both scenarios when developing strategies to protect Acadia’s natural and cultural resources.

The park’s recent temperature records suggest the best-case scenario may already be out of reach. While weather fluctuates, the average annual temperature at Acadia has increased by a half-degree – 25% of that projected 2-degree increase – in the last three years alone.

Miller-Rushing said Acadia is planning for climate change but said the National Park Service, like most conservation organizations, struggles with managing for change because that goes against its preservation and restoration mindset.

“We’ve always been about the past, about returning ecosystems to their pre-European-contact state,” he said. “Now we know that’s not possible. One out of every six plant species here when Acadia was founded 100 years ago is gone. So we realize we can’t keep it like it was.”

Acadia does have a track record of pioneering change in the National Park Service, even if it was not necessarily done in response to climate change. To combat congestion, Acadia operates a bus shuttle system, a reservation system for popular attractions, and now an online camp and car alert system.

Visitors witness the power of Thunder Hole, one of the main attractions at Acadia National Park. Michael G. Seamans/Morning Sentinel file

Acadia National Park was the seventh most-visited national park in 2023, when the wooded outcrop on the Maine coast welcomed 3.9 million travelers, according to the park service.

Schoodic Institute, the nonprofit science division of Acadia National Park that manages one of the country’s 18 park-based research learning centers, is helping managers to prepare for that uncertain future through a series of fellowships and in-the-park research projects.

And the science is clear: change is already happening, said Nick Fisichelli, the institute’s president.

“Acadia is changing fast and we are seeing this play out in real time,” he said. “Climate change is no longer a year 2050 or 2100 issue. It is a ‘here and now.’ Nature is dynamic, and trying to keep it as it was in the past is problematic.”

Schoodic’s role is to work with managers to produce the science that will inform park stewardship under continuously changing conditions, Fisichelli said. Given the pace of change, park managers can’t wait for the science to be conducted separately, in isolation, before taking action, he said.

And that stewardship must be transparent, Miller-Rushing said, with extensive public participation from local and Indigenous communities. Together — Schoodic, Acadia, the public, the tribes — we must shift the conservation paradigm from protecting the past to fostering a better future, Fisichelli said.

Hundreds of visitors flock to Cadillac Mountain in Acadia National Park to watch the sunrise in 2017. Shawn Patrick Ouellette/Staff Photographer, file

For example, the park is working with scientists and tribal representatives to decide how to revegetate the 116-acre Great Meadow wetland. The park will rid it of invasive species, drainage ditches and old roadbeds and replace an undersized culvert that left the wetland too dry at times and flooded at others.

The project will improve the wetland’s natural function and its plant and wildlife species diversity. It will reduce damage to park facilities that can occur during storms when floodwaters back up upstream of the culvert and flood the Sieur de Monts area, Miller-Rushing said.

Extreme temperatures can lead to infrastructure issues: Accelerating wear and tear, stressing power grids and cooling systems, buckling and cracking roadways, and requiring the park to build shade and cooling structures to protect visitors from the high heat.

Precipitation extremes can cause forests to struggle, becoming vulnerable to invasive species and blight under wet conditions and susceptible to wildlife during droughts. The park’s signature coastal areas can be eroded or washed away by rising sea levels and storm surges, as last winter demonstrated.

A half-mile section of state road that connects Southwest Harbor to the park’s Seawall campground and Wonderland and Ship Harbor trails washed out repeatedly in winter storms, leaving big piles of boulders atop the buckled road. Officials considered abandoning it but repaired and reopened it last month.

The stairs leading to Sand Beach at Acadia National Park. Ben McCanna/Staff Photographer, file

Likewise, the park decided to repair a 1,000-foot section of the picturesque Ocean Path, a 4.5-mile trail that overlooks pink granite cliffs and connects the increasingly at-risk Sand Beach and the ever-popular Thunder Hole on the eastern shore of Mount Desert Island.

Fixing Ocean Path was just one item on a still growing list of storm repairs that exceeded the park’s $10 million annual budget back in the spring, before park rangers were able to access the more-remote trails and assess their damage. Still, due to its popularity, Ocean Path was a must-fix, a time to resist change.

“We can’t harden the whole coastline,” Miller-Rushing said. “In some areas, we’ve no choice but accept.”

Miller-Rushing is using the buzzwords of the National Park Service’s official response to climate change: the resist-accept-direct framework, or RAD for short. In some cases, like Ocean Path or Seawall Road, a park might resist change by rebuilding.

In other cases, they might accept a freshwater wetland turning brackish, then salty, due to sea level rise. Or in Great Meadow’s case, they might direct climate change through culvert replacement and selective plantings. And in some cases, park managers play a wait-and-see game.

The storms washed away about half of the dune system separating Sand Beach from an interior wetland, Miller-Rushing said. The dunes will likely disappear in the next few years, washed out by a future storm. Without that buffer, the beach and the wetland will be at greater risk of storm erosion.

They might let the dune system go, but Sand Beach? It’s the park’s only sandy beach and one of its most popular attractions. While no decision has been made, that’s a debate – and a funding request – that will happen in the future.