Where do we grow the hemp to replace that much wood? A forest of trees would yield a lot more pulp per square foot than a field of hemp.

So do we replace the paper forests with hemp fields, and then plant additional fields to make up the volume?

Or do we dedicate food farming land to hemp? And with the continuing population growth, how long could we afford to do that?

None of these questions have simple, clear cut answers. [Pun intended.]

(PS: I know hemp and marijuana are not the same thing, and am in favor of more usage of hemp. I just don't think it's a valid answer to this particular problem.)