After spending some time on knots, edges, and the localized burden they put on ropes, I wondered about the local load on trees. (I guess "tree-hugger" has different and uncertain meanings here.)
With ropes, investigators have looked at just where the rope breaks; I haven't gotten as far as to find the reports of engineers and materials scientists who have measured strain within the rope at different points. But it is intuitive to rope users that some knots and edges are tougher on the rope than others.
Now, with trees: We all have the experience of preferring loaded straps on our shoulders to loaded thin cords. Straps distribute load and cut less. So, we load trees less with straps than with line. But, exactly where is the load put on the tree by a loaded hammock? It would seem that would depend on the adhesion of the line or straps to the tree. If there is adhesion, all the load might be just behind points of tangency of line or straps to the tree.I dunno what that means in real usage.
So, are there some prof or amateur engineers with knowledge or insight on this? And some tree experts who know something about the pressure below which the trees we'd hang from cannot be said to have even detected the hammock load after the hammock is taken down?
Finally, for now, is there a guideline somewhere here, for good hygiene on this issue: pressure on the tree bark,-- based on science and engineering analysis?