That photo is a sharp (and fascinating) reinforcement of the grazing sheep point. Is there any other reason those trees would grow clustered right there and nowhere else? Was that area not accessible by sheep?
As you can see somewhat in the photo, this island is isolated from grazing by the river and the steep rocky sides of the island. You could probably get a mountain goat to climb up there with some prodding, but sheep and horses that range on the slopes behind wouldn't.
