Two environmental groups have issued a new report drawing attention to the effects of climate change on Glacier National Park, particularly the ongoing recession of the park's alpine glaciers. Two more of the park's glaciers have shrunk to a point where they're no longer considered glaciers.

Two environmental groups have issued a new report drawing attention to the effects of climate change on Glacier National Park, particularly the ongoing recession of the park's alpine glaciers.

Two more of the park's glaciers have shrunk to a point where they're no longer considered glaciers.

The Rocky Mountain Climate Organization and the Natural Resources Defense Council held a teleconference Wednesday to announce the report, which draws on the work of Dan Fagre, a U.S. Geological Survey research ecologist who has focused on the park's glaciers and alpine ecosystem for years.

The report, entitled "Glacier National Park in Peril: The Threats of Climate Disruption," makes the case that "human disruption of the climate is the greatest threat ever to our national parks" and that "Montana's economy is at stake" as a result.

The evidence of climate change is fairly straightforward:

In 1850 the park had 150 glaciers, of which 37 eventually were named.

Today only 25 of those 37 are large enough (25 acres or more) to still be considered glaciers. Of the 12 glaciers that have melted away, 11 have done so since 1966.

The latest two to fall below the 25-acre threshold were Miche Wabun and Shepard. Each had shrunk by roughly 55 percent since the mid-1960s. The largest remaining glacier in the park is Harrison Glacier around 465 acres.

"Small alpine glaciers are very good indicators of climate change," Fagre said.

While plants, animals and even streams can adapt to changing climate conditions, glaciers do not.

"Glaciers do not respond," Fagre said. "They are like a visual checking account of the status of the cold part of our ecosystem."

Only the larger glaciers are resistant to high rates of melt, Fagre said, and the rate of melt for smaller glaciers will increase if a trend of warmer temperatures in the park continues.

Glacier's alpine country has had higher winter and springtime temperatures for the last decade, prompting earlier runoff of the alpine snowpack.

"Now you see that this (melting) occurs earlier in the year, and now that the glaciers are smaller there is a greater rate of melt," Fagre said.

A handful of the park's largest glaciers could survive past 2020 or even 2030, he added, but by that point the ecosystem would already be irreversibly altered.

Fagre said geological evidence points to the continual presence of glaciers in the area since at least 5000 B.C.

"They've been on this landscape continually for 7,000 years, and we're looking at them disappear in a couple of decades," he said.

The question of why climate change is occurring is not specifically addressed in the report, but the underlying assumption is that human-caused warming is at fault, and that it can be addressed through social policy changes.

"Many of the threats to Glacier identified here assume continued, unchecked human changes to the climate," the report's executive summary concludes. "Sharply limiting emissions can reduce many impacts. Most important is comprehensive federal action to limit emissions of heat-trapping pollutants. Then we can ward off dangerous climate disruption, in Glacier and around the world."

The Rocky Mountain Climate Organization and the Natural Resources Defense Council contend that the effects of climate change on the park have potential economic consequences.

"If we let climate change and its impacts get to an unacceptable point, the economy of Montana will suffer too," said Stephen Saunders, president of the Rocky Mountain Climate Organization and lead author of the report along with Tom Easley.