Comment by honr

I don't get your point. The planet will not realistically run out of either. The water price goes up, then soler + desal becomes more cost effective, then people get to use the material that covers 75% of the planet's surface a bit more. Similarly, when oil gets more limited the price goes up and the planet gets to keep its oil while people stop being able to afford burning more of it. Or perhaps this was exactly your point.