Who's in the dark ages?!?
Screw-in steps do NOT kill trees, nor have ANY of the landowners whom I've hunted on cared. There's too many scientific studies and research at our disposal to say otherwise. The ONLY way I could see someone caring was if they were going to veneer out a big walnut or oak, but that's not the woods I'm typically hunting. If I were worried about that, I could simply lug in my LW sticks or my Summit Bucksteps or haul in a climber, all of which I have at my disposal and more -- which serves to give my statement that none are as easy to use as Cranfords some pretty good validity.
http://www.bowhunting.net/eMagazine/Articles/KarenCranford-002.html