Most of the things at the top of the slippery slopes seem so reasonable. As always, the big question is what divine personage gets to decide what "useful" is, what the "good of society" is, and whether or not someone's property meets that standard. You might have noticed a recent trend in confiscating "blighted" private property and turning it over to developers because they can make it more "useful."

If, in a theoretical situation, all forest land was privately owned in a free market society, several things could happen to it (this is not a complete list by a long shot):

Owner A could harvest it and replant it, and make money off lumber forever. He harvests the easily accessible trees, but has to pay for access roads and such himself. A lot of trees aren't practical to harvest under these conditions.

Owner B could harvest it, and not replant it. If he's in the lumber business, this isn't very bright, and the owner would have to get into another line of business quickly. Owner B would probably move to one of the following categories.

Owner C could harvest the lumber and replant something else that makes him more money. Say, artichokes. Assuming the land is reasonably flat, of course. If too many forest owners do this, the value of remaining forest land goes up drastically. Owner A is doing pretty good in this situation, and it didn't take him any more work at all. At some point, trees become a more valuable crop than artichokes, and the trend reverses. Repeat as necessary.

Owner D cuts down the trees and builds houses. Again, if too much forest land is taken out this way, the price of lumber--and houses--goes up. Owner D also notices that people will pay more for houses with parks nearby. Hmmm...

There are many other paths. Capitalism is immensely complex, and organic system like a rain forest. That's why it works as well as it does.

I suppose you could screw it all up by doing something stupid, like nationalizing all the forest land and the government selling the trees for a fraction of market price, pr the government subsidizing the industry to try and force prices to stay low in a time of increasing scarcity, or building roads for free so people can get to the rain forests.