A woman walks past Upper Grinell Lake at Glacier National Park. (Ben Herndon)

Facebook founder Mark Zuckerberg visited Glacier National Park last weekend and saw firsthand how climate change is shrinking the glaciers in Montana’s northern Rockies.

But the area’s top climate scientist was not permitted to share his expertise on global warming’s role in the retreating ice sheets with Zuckerberg, one of the most prominent business leaders to denounce President Trump’s June withdrawal from the Paris climate accord.

Three days before the tech leader’s July 15 visit to Glacier, research ecologist Daniel Fagre said he was told that his scheduled tour with Zuckerberg of Logan Pass on the Continental Divide was off.

“I literally was told I would no longer be participating,” Fagre, who works for the U.S. Geological Survey, said in an interview Tuesday from his office inside the park. He said he asked the public-affairs officer who notified him why the briefing was being canceled.

“I’ve gotten nothing back,” he said. “We’ve definitely been left in the dark.”

Zuckerberg did meet with park rangers — and wrote a post on Facebook registering his alarm at the shrinking glaciers at the park — although it is unclear whether they discussed climate change.

Gracie the Bark Ranger is a wildlife service dog who helps keep away the mountain goats and bears from the visitors. She is a much better trained herding dog than Beast. (Sorry Beast.)

Posted by Mark Zuckerberg on Saturday, July 15, 2017

But with the park a ground zero of sorts for the unmistakable signs that warming and melting of glaciers is speeding up, the decision to keep a visitor — and a celebrity at that — from meeting with a scientist-in-residence, first reported by Mic, struck some observers as a deliberate effort by the Trump administration to minimize climate issues.

“Sure, the administration has a particular view. Fine,” said Andrew Rosenberg, a fisheries scientist with the Washington-based Union of Concerned Scientists. “But that doesn’t mean you suppress scientific information and evidence and expertise the Park Service has developed over literally decades. The park rangers are great, but this is a high-level scientist who really studies this stuff.”

I'm spending the afternoon at Glacier National Park in Montana with some National Park Service Rangers. The impact of…

Posted by Mark Zuckerberg on Saturday, July 15, 2017

The decision by Interior Department officials comes as the Trump administration moves to erase much of President Barack Obama’s environmental record, reducing the role of climate science in much of the federal government, from regulations on U.S. carbon emissions to fossil-fuel production on federal lands to pledging to bring back the coal industry.

Trump and several of his Cabinet secretaries have questioned the scientific consensus that global temperatures are warming due to human activity.

Fagre, a research ecologist who has published widely on his work monitoring the melting of the park’s remaining glaciers, seemed to be an obvious choice when Zuckerberg’s advance team asked park officials to organize a tour.

“Dan’s highly respected,” said Michael Jamison, who manages glacier programs for the nonprofit National Parks Conservation Association. “He’s a straight-up, this-is-how-it-is scientist.”

Derick Mains, a Facebook spokesman, said, “Mark’s visit was set up by Glacier National Park and they determined who would participate.”

The decline of the ice at Glacier and around the world is frequently cited as evidence of a climate undergoing rapid change, and researchers have confirmed that more than 90 percent of the world’s glaciers are retreating, with some quickly disappearing. At high altitudes where most glaciers are found, temperatures are rising faster than in the valleys below, with signs pointing to even greater melting in the decades ahead.

Heather Swift, a spokeswoman for the Interior Department, the parent agency of the Geological Survey and the National Park Service, gave a different account, denying in a statement that a scheduled meeting with Zuckerberg was canceled.

“As with any celebrity appearance that might attract national attention, Mr. Zuckerberg’s visit to Glacier National Park was highlighted to the national offices,” Swift said, adding: “After reviewing the event proposal which was sent to the National Park Service, the NPS and Interior made a number of park officials available for the celebrity tour. He was given first-class treatment by the park rangers and had the opportunity to interact with a number of park officials and Gracie the ‘bark ranger’ during his visit which came at the height of the busy season.”

She suggested that a tour may not have been the best use of Fagre’s time.

“Allocating government funds, personnel, and resources responsibly is the definition of good government and something we are dedicated to advancing at the Department,” Swift said.

But Fagre said park officials reached out to him when they knew that Zuckerberg, on a high-profile tour of states he has not been to, said he wanted to learn more about the retreating glaciers. Fagre settled on Logan Pass, elevation 6,646 feet and a popular launching point for backpackers and hikers, calling it a “very scenic alpine area for taking a little walk.”

“We were just going to be answering questions” Fagre said. “There was no preset agenda.” Glacier is one of only a handful of national parks with scientists on staff who are dedicated to studying climate change.

Fagre, who also studies global warming’s effect on aquatic resources and huckleberry crops that are essential to grizzly bears before they go into winter hibernation, said he frequently lectures on climate change in the local area and to park visitors and speaks with media.

“I’d say I was just puzzled by this more than anything else,” he said.