Well, God's magik skillz will prevent what you are talking about, just like he had skillz back in the day with Noah and his awesome ark.
The real question is whether people will have free will in da new earth. Because if they do, they will eventually get fucking tired of petting panda and koala bears. Which means they will start fukkin each other outside of marriage (assuming they still have dicks and vaginas, questionable based on WT doctrine) or they may start smokin weed, snorting coke, or just going ape shit crazy on each other because they are stuck in a so called paradise being ruled by WT dickhead elders. Anyway, paradise earth under JW rules and regulations is nothin' I want to endure...