You are correct, trees are pretty tough, but it varies by species, climate and pests. By virtue of the fact that they are parks, tolerance to damage is lower than it is in a managed stand of timber.
My goal is to find a lighter way while maintaining or reducing the impact of the anchor over the standard 1" webbing. Webbing is the single heaviest component in any hammock suspension in my estimation. Hardware is the second heaviest component (and the one most responsible for wear on the other components - but the convenience makes it worthwhile for many).