If you travel to Glacier National Park, Montana, you’re likely to see beautiful forests and picturesque mountains, but one thing you’ll struggle to find is glaciers. Out of the 150 rivers of ice that used to adorn the park, only 26 of them are still big enough to be officially classified as glaciers.

New research has found that it is now all but “inevitable” that the lower 48 states will be free from any glaciers within the next few decades. The analysis, carried out by the US Geological Survey (USGS) and Portland State University, looked at how warming temperatures have been impacting the 39 named glaciers found in Montana since 1966. And it’s safe to say that it’s not looking good.

They found that while on average the glaciers had declined by 39 percent, in some cases they have melted by as much as 85 percent over the last 50 years. Formed by compacted snow and ice, they officially become a glacier if they are larger than 10 hectares (25 acres) in size. By that measure, it means that the park once famed for its glaciers now only contains 26 of them, and that is only expected to get worse.

“It’s inevitable that we will lose them all over the next few decades,” Dr Daniel Fagre, lead scientist at the USGS, told The Guardian. “The Colorado glaciers started melting before Montana’s and while there are larger glaciers in the Pacific north-west that will hold on longer, the number vanishing will steadily grow until none are left.”

The amount of melt seen in Montana is greater than in other parts of the US, but it is still in line with what is being seen globally. They predict that while in other places like the Pacific north-west glaciers may cling on for a bit longer than in Montana, in just a few decades the only glaciers that will survive in the United States will be found in Alaska.

The knock-on effect of the warming will have profound impacts on the environment. “The park-wide 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,” says Dr Fagre, in a statement.

This is thought to be the first time in at least 7,000 years that these glaciers have faced such warm temperatures and low precipitation, and the first time that they are heading unwaveringly for extinction. Halting the warming of the planet will not be enough to save them. It will take a reversal in average temperatures, something which is effectively never going to happen.