[QuickSlash]

Well, I'm not sure if I read anything about it all in the books, but I have a personal opinion. That would be that during the beginning of his reign (after he defeated the armies that'd oppose him), Sauron would make most people into slaves. Those who were problematic would be tortured and/or killed. Most plants and animals would be destroyed, maybe all, except what was *needed* for food.

There probably wouldn't be many babies made at this point, and the free peoples would soon die out. As they did, I believe that Sauron would abandon his races to whatever would come of them. In time, they'd die out, too. This'd leave the earth barren and empty.

Now, what he'd do with this, I'm not sure, but I think that it would (soon or eventually) come to this.