I was not aware gophers were a threat to any tree. That is one critter I don't have to worry about where I am. Such a shame to loose trees ya got a couple years invested in.
In ag/farm country I have seen the holes result in broken livestock legs in pastures and busted equipment in the fields. This is all costs money to fix. Ground hog is also an eating machine. They will destroy fresh soybeans and corn....again more loss of $$. I like to sit up on a hillside that overlooks a lower field with my 22-250 and nail them when I see signs of their activity. The one thing many folks don't know is that they can climb trees to some extent. I actually shot one out of a tree once. I am told they climb trees to get off the ground to avoid predators and then stretch out on the limb to sun themselves.Groundhogs, we call them woodchucks, are just fox den contractors. Assuming they keep their distance from any structures, I let them go about their days in peace. That said, I took great pleasure in locating the camp outhouse directly over a chuck-hole that was just a little too close! Pay back is hell.