It wouldn't make any sense to take a nice large, straight tree and turn it into paper of any sort. If you need a roof or wall, you have to start with a large straight tree. With paper, the tree is crushed. Why would you need a large straight tree for that? Economics re-enforces this. You're not going to pay extra for a large tree just to crush it
It amazes me that people think they are saving a tree when they don't use paper. I highly doubt they have even seen what kind of trees paper is made from. When I explain this, people usually tell me, "That makes sense." Of course it does!
This reminds me of the Mike Rowe's TED talk about how a lot of people talk about things they think they know. Until a person actually tries sheep farming, they really don't know a thing. I ask my dad (grew up on a farm) about the subject Mike Rowe covered in his talk, and sure enough, he knew about it.
Also of note, the abstract mentions that the number of trees has been too low in previous estimates. I wonder how this new estimate will change climate/CO2 modeling:
"This map reveals that the global number of trees is approximately 3.04 trillion, an order of magnitude higher than the previous estimate."