You should check out exactly how much land is owned/used by some of the companies. Check out for example a satellite view of southern Oregon. You'll see a check

You should check out exactly how much land is owned/used by some of the companies. Check out for example a satellite view of southern Oregon. You'll see a checkerboard pattern in the forests all over the place. Those are big patches of managed forest that are in various stages of growth. It's like a pipeline -- yes it might take 20 years to grow a patch to harvest quality, but you have 100 of these patches and only harvest 5 a year. By the time you get around to needing to reharvest patch #1 it'll have been 20 years and it will have regrown.