There's a way of leaving your mark on the world without ruining anything, and it's rock sculptures. Well, rock piles, really, that tower anywhere from four rocks to 15 rocks.
I see them pretty regularly along my trail hikes, and I saw several along the way up and down the Sedona outdoor trip. I love the idea and practice behind these markers, and fully support them.
Of course, only us humans have the pathological need to leave some evidence of us being somewhere, but given that need, the rock pile is the best way of doing that while not injuring the environment. Worst-case scenario is that the rocks fall, and stay where they fell. There's certainly no harm in that. I have yet to create my own rock pile, but I definitely appreciate them when I come across them.