Treebeard seems to think he got a bit of a raw deal. He says:
I am not altogether on anybody’s side, because nobody is altogether on my side, if you understand me: nobody cares for the woods as I care for them, not even Elves nowadaysJ.R.R. Tolkien, The Lord of the Rings, The Two Towers, “Treebeard”
This statement seems a bit odd, considering that the Sylvan Elves of Mirkwood and the Galadhrim of Lothlórien lived not too far north of his domain. But I think this oddness is intentional on Tolkien’s part, as diving into it helps us understand life from the perspective of a tree.
If you read Walden or some of the poems of Robert Frost or so many other writers and poets over the years, you realize that there’s a difference between being in nature and stopping in nature. You can care for the woods, or you can care for the woods.
Maybe the best example I can give is the difference between someone who visits his aging relative every day versus someone who chooses to put his life on hold, move in with his relative, and devote the next several years to being the relative’s caretaker.
As one of the oldest living creatures in Middle-earth, Treebeard would have seen Elves come and go. An Elf spending 100 years caring for the trees and then moving on might seem to him like a brief visit. The Elves were being summoned Westward, and it was only the power of the Three Rings keeping large populations of Elves in Middle-earth. To Treebeard (who, despite his age and experience, had a very narrow view of the world), this would surely feel like an abandonment.
Stepping outside the story for a second, Tolkien no doubt put his own feelings into that line. The pace of modern society makes it much more difficult to ramble. To dedicate the time to just being. And the all-consuming drive toward progress will leave nothing intact in its path, including old-growth forest. He referred to the countryside of Berkshire and Oxfordshire as “vanishing”, and no doubt felt that there were fewer and fewer who cared for the woods left in our modern world.
It is dangerous to take pretty much anything Treebeard says as absolute truth, but in this case I believe he’s expressing a profound feeling that’s difficult to convey with words.