Story highlights There once were 150 glaciers; now there are fewer than 40

Federal scientist says they will all disappear this century

(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.

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