Big Mountain ski area in Montana has tons, as do mountains all over the world. When I saw this headline my first thought was "clickbait headline to push climate doomerism". The BBC did not disappoint.
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It's just documentation of change, with a reference to temperature trends, and to another major cause (which they do not suggest, but might also be related to temperature change, as it is thought to be in other locations).
The trees are famous, and important to local tourism. It's a story.