Sadly from the appearance of dead leaves on the lower branches I have to agree with Kyle on the bark beetles.
Keenly look at the bark and you will most likely find pin holes, a sure sign of bark beetles emerging as moths.
The other sure fire method of determining if there are bark beetles involved is climbing a ladder and removing some of the upper, dead bark, if you find larva tracks then you know for sure the tree is infested and will eventually go to the spirit world.
If this was my tree, I would make sure of the problem as I described above, then I would sit with the tree and explain that in order to protect it's brothers and sisters, I have to take it down thus ending it's struggle to survive.
I would then make sure it knew that it was not going to be wasted because I would burn the branches that were to small or damaged to make things as an offering to the spirits. Do try to use all the
wood that is not damaged and thus honor the tree's spirit.
Redhawk