There used to be a mill in the town I grew up in, my father and grandfather worked there. They still exist, but the point is the company had a forestry division where they would plant their own fast-growing trees (white pine, etc.) and harvest them for the mills. They didn't do it because it was ecologically friendly, although that was certainly a side benefit. They did it because having your own dedicated supply of material for nothing more than the cost of putting it in and removing it from the ground was good, sustainable business.