CBS, I don't see much erosion between those bolts and that tree. As for your second point, a sling birth hitched around a tree doesn't do much (if any) damage.
edit: that was accidental, I swear.
The one time I climbed at Erie, I remember there were three or four anchor stations (two bolts each) within about 25 feet of each other along the top of some short slabby wall to the climbers right of the powerline wall.
All four climbs could have shared one single anchor setup a little higher up.