I remember passing through Rocky Mountain National Park and there was a great die-off of the lodgepole pines. The ranger explained that they were all planted around the same time after logging, and they were just hitting their old age.
I wonder how much of this is the same - the trees were planted around the same time, and have just hit their time to die.
hemlock trees were dying in the Smokey Mts and Alghore blamed acid rain. It was later found out to be a beetle killing them.
Pine Bark beetles. Along with YUGE fires in JellyStone a few years back.
And I love that National Park.
Sycamores are super long-lived. Willow are usually the opposite.
In the case of the sycamore it is under attack from an insect introduced to the US via goods imported by ship on wooden pallets, as I recall.
bingo