Same thing happened in North Dakota 15-20 years ago. It's a great deal for the workers who show up, but a better deal for anyone who can sell them trucks or rent them apartments. It's a raw deal for anyone growing up there because you either have to work in the oil patch, find a way to cater to the travellers, or go broke.

The Appalachians are covered in trees, as are large swathes of the subtropical southeast.

Land tends to become forest if it has enough moisture, isn't suppressed by critters, and doesn't burn. Human forest fire suppression has tended to increase forest cover, although some of that is self-interest. Lots of tree farms out there, but the biodiversity of a quarter of identical-aged pine trees destined for the sawmill is nothing compared to an old-growth forest (or something disrupted by a tornado/fire/etc.)

The benefit/adverse effect of grazing livestock depends on the land. The prairies were well-adapted to handle and benefit from bison. Grazing in the desert takes a *long* time to recover from. I've been to Big Bend and Organ Pipe NM and both parks talk about trying to restore the land after overgrazing in the early 1900's. If they remove too much vegetation (or selectively eat certain species) it will have a negative effect - promote erosion, allow non-native invasives to move in, or shift the water.