Jack Potter worked with the trail crew in the early days of his career at Glacier National Park. Back then, he recalls, there was only snow and ice at the end of the long trail up to Grinnell Glacier.

“My first year up there was 1969, and the glacier pushed all the way out to the rock,” said Potter, retired chief of science at the park. “Now, it has retreated so much that there is a sizable lake at the toe of the glacier.”

Grinnell Glacier on the park’s east side once measured 710 acres. It is now about 150 acres — clinging to the shaded north face of Mount Gould. The newly formed lake at its toe is nearly 190 feet deep.

Grinnell Glacier’s story of recession is not singular. Scientists predict that, at the current rate of melting, by 2030 all the glaciers in Glacier Park will vanish.

Retreating glaciers are just one impact on the park that Potter says is tied to a warming climate. Recent massive wildfire events and the spread of insect diseases in trees are two others he witnessed in his 40-year career.

Potter was one of four local experts to discuss climate change and melting glaciers recently in front of a packed house at the O’Shaughnessy Center in Whitefish. Other experts on the panel were Chas Cartwright, former superintendent of Glacier Park; Dan Fagre, U.S. Geological Survey ecologist and glacial expert; and Clint Muhlfeld, Geological Survey ecologist and fisheries expert.

Global warming skeptics were not represented on the panel. In general, such skeptics tend to agree that warming may be occurring but question the extent to which it is manmade. In addition, they question the extent to which warming is likely to occur and the ability of people to greatly reduce it.

The Whitefish panel discussion was part of the Extreme Ice Survey’s “Chasing Ice” film tour that uses time-lapse photography to document melting glaciers in Alaska, Greenland and Montana.

In 2007, photographer James Balog and his crew set up two remote cameras in Glacier Park above the Swiftcurrent and Grinnell glaciers. These cameras record changes in the glaciers every half hour, year-round during daylight, yielding about 8,000 frames per year. The photos then are edited into a time-lapse video.

While cameras in Greenland and Alaska have documented massive retreating events, the glaciers in Montana are already so small it’s difficult to see them recede in a few years of photographs. Images from Glacier have yet to be edited into a time-lapse sequence and one of the cameras keeps getting crushed by falling rock.

But other repeat photography projects conducted in the park clearly show shrinking glaciers.

In 1850, Glacier Park had about 150 glaciers. Today, Fagre estimates there are about 85 pieces of ice, of which only 25 qualify as actual glaciers. All totaled, there are 16 square kilometers of ice in the park.

He says the number of glaciers is less important than the rate at which they are retreating.

“Glaciers have lots of important functions in the ecosystem,” Fagre says. “They hold historic water from decades ago and release it in the summer when all the snow melts. They’re a vital lifeline for a lot of organisms.”

Fagre says a thinning snowpack and shorter snow seasons also are changing the dynamic of Glacier’s alpine environment.

“We’ve seen an increase of 18 days a year with bare ground,” Fagre said. “No snow means plants grow earlier, the tree line expands and encroaches into subalpine meadows.”

More trees equals more wildfire fuel near krumholtz stands in the highest elevations.

Cartwright says an increasing number of rain-on-snow events due to a warming climate makes him question how long the recently rehabilitated Going-to-the-Sun Road will last.

Muhlfeld cites the looming extinction of the meltwater stonefly that lives in the water of glacier melt zones. If a glacier totally melts, that water will no longer be available for stonefly habitat.

“It could be one of the first to go extinct due to climate change,” Muhlfeld said.

“There is very little we can do to protect that species. We could move them around, but then all the glaciers will be gone by 2030.”

So what, if anything, can be done to address the impacts of a warming climate on the park’s ecosystem, the panel was asked?

Cartwright says policy decisions at the park should focus on programs that are effective, “not just on things that make us feel good.”

He gave the summer shuttle system as an example.

“The reaction has been positive for its convenience, but is it meeting sustainability standards? These are questions I ask myself.”

He says there has been an absence of effort on a national level to address climate change.

“That says to me that we need to do more work on education,” he said. “We’re working on it, but we have a lot more work to do.”

Fagre says the damage has been done and that to reverse the atmosphere’s current carbon dioxide levels will take “a very, very long time.”

“CO2 from Henry Ford’s first car is still up there,” he said.

“We have to stop making it worse. That’s simply common sense. If you’re headed in the wrong direction, you don’t keep going there.”

Muhlfeld says not all hope is lost.

“This is one of most biodiverse and intact ecosystems on the Rocky Mountain chain,” he said. “All of the pieces are still there. But now is the time. We have to be proactive.”

To learn more about the Extreme Ice Survey, go online to www.extremeicesurvey.org.