Even as we discover the incredible benefits of the world's most ancient trees, we are losing them to climate change.

In 2005, several of the centuries-old ponderosa pine trees on my 15 acres (0.06 sq km) of forest in the northern Rocky Mountains in Montana suddenly died. I soon discovered they were being brought down by mountain pine beetles, pernicious killers the size of the eraser on a pencil that burrow into the tree.

The next year the number of dying trees grew exponentially. I felt powerless and grief-stricken as I saw these giant, sky-scraping trees fading all around me, realising there was nothing I could do to stop it.

While the native bugs were the proximate cause, the underlying reason for the unprecedented mortality in my home state and throughout the Rockies was that winters had stopped getting really cold. When I first moved to Montana in the late 1970s, temperatures of -34C (-30F) or even below -40C (-40F) were common in winter, sometimes for weeks at a time. The coldest temperature on record in Montana is –57C (-70F). These days wintertime minimum temperatures rarely get below -18C (0F) or so. If they do, it is usually just for a day or two. That's not nearly cold enough to kill pine beetles, which make their own natural antifreeze.