(CNN) The 37 glaciers remaining at Glacier National Park are vanishing.
In the past half century, some of the ice formations in Montana have lost 85% of their size, and the average shrinkage is 39%, a study released by the U.S. Geological Survey and Portland State University says.
One day, they will be gone, the study's lead scientist said Wednesday.
"The trend right now is that they are inexorably going into their final demise. There is no chance they will go into rebirth," Dan Fagre said. "In several decades they will be mostly gone. They will grow so small that they will disappear. They will certainly be gone before the end of the century."
This image shows the perimeter of Chaney Glacier in Glacier National Park in 1966, 1998, 2005, and 2015.
And humans are responsible, he said.
"There are variations in the climate but it is humans that have made all those variations warmer," he said. "The glaciers have been here for 7,000 years and will be gone in decades. This is not part of the natural cycle."
The glacial retreat has nothing to do with anything happening underground, he said.
"This is all atmospherically driven," he said.
What's happening at the park is not unique. Glaciers all over the world are shrinking as the planet warms, experts have said.
This image shows the perimeter of Sperry Glacier in Glacier National Park in 1966,1998, 2005, and 2015.
Portland State geologist Andrew G. Fountain said the amount of ice loss in Montana is more severe than other places in the United States but in line with what's happening globally.
For the study scientists looked at 39 glaciers; two were outside the 1,500-square mile park.
Of those, only 26 are bigger than 25 acres -- the standard for calling the ice formation a glacier.
The study used satellite photos and other images taken between 1966 and 2016.
The losses will impact the ecosystem in the park, Fagre said.
"The parkwide loss of ice can have ecological effects on aquatic species by changing stream water volume, water temperature and runoff timing in the higher elevations of the park," said Fagre, who is also the USGS director of the climate change in the Mountain Ecosystems project.
There are several reasons this is important, he said.
"They are only reflecting what is happening in the system. We will see an effect in our forest, rivers and streams, but those are harder to measure and see," he said. "It is easier to see with glaciers."
Most popular National Parks of 2016
The most popular national park: The most popular of the National Park Service's 59 headliner National Parks in 2016, Great Smoky Mountains National Park attracted more than 11 million visits in its centennial year. The park, which straddles the North Carolina/Tennessee border, has incredible views, like this one at sunrise of the Oconaluftee Valley.
2. Grand Canyon National Park, Arizona: The Grand Canyon is 277 river miles long, up to 18 miles wide in parts, and a mile deep. Mather Point along the park's South Rim is a spectacular place from which to view the sunset.
3. Yosemite National Park, California: President Abraham Lincoln signed legislation in 1864 protecting a portion of what is now Yosemite National Park. It was the first instance of the US government setting aside scenic wilderness for public use and preservation. Cook's Meadow and Yosemite Falls are shown here.
4. Rocky Mountain National Park, Colorado: This 415-square-mile park's elevation ranges from 7,600 feet to 14,259 feet, and the park is home to 77 peaks above 12,000 feet. The park, which hosts a diversity of animal and plant life, also straddles the Continental Divide. Dream Lake is shown here.
5. Zion National Park, Utah: Zion is the most popular of Utah's "Mighty Five" national parks, which include Arches, Bryce Canyon, Canyonlands and Capital Reef. The Zion hike to Angels Landing is hard but worth it; from there, hikers get views of the whole canyon.
6. Yellowstone National Park, Idaho/Montana/Wyoming: The world's first National Park, Yellowstone is one of the last large ecosystems on the planet's northern temperate zone. It's home to more than 300 geysers, a volcano and many waterfalls. It's also home to the few remaining members of a wild, continuously free-ranging bison herd that once roamed the Great Plains.
7. Olympic National Park, Washington: Olympic has everything an outdoors lover could ask for: over 70 miles of untamed coastline, old-growth temperate rain forests, glacier-capped mountains and this incredible view from a ridge at Deer Park.
8. Acadia National Park, Maine: The first National Park east of the Mississippi, Acadia is the most eastern park and therefore the first US National Park to welcome the sunrise.
9. Grand Teton National Park, Wyoming: The Teton Range at this national park rises 7,000 feet above the valley at Jackson Hole. The 13,770-foot-tall Grand Teton is the highest peak, but there are eight peaks more than 12,000 feet in elevation.
10. Glacier National Park, Montana: The glaciers for which this national park is named are disappearing. In 1850, there were an estimated 150 glaciers in the area now within the park's boundaries. Now there are 25, many of which are smaller versions of themselves. They may all be gone by 2030.
In the mid-1800s there were about 150 glaciers on the land, which was designated a national park in 1910. Rising temperatures caused the others to disappear, Fagre said.
"Tracking these small alpine glaciers has been instrumental in describing climate change effects on Glacier National Park to park management and the public," said Lisa McKeon, a USGS scientist who has studied these and other glaciers for 20 years.
So far, the scenery change has not affected tourism. Last year, a record 2.95 million people visited the park.
"The best time to come is early September," said Fagre, who is based at the park.