Not exactly sure what this means, but I'm assuming it's referring to strangling trees with cords? As with anything, there are bad actors and good. The bad actors use cord for anchors around trees, the good use webbing, which, in my experience, doesn't even flake bark if done correctly. In very well used areas I suppose there might be posts erected or trees identifies for use in the same way that tents are given a designated tent pad, choosing to kill all the on the ground flora in one spot instead of allowing grass wrangling. But, really, if you know what you're doing and you take care you can hang a hammock from trees without harming them at all.