Those are all very good points. But the point I was making is that it's not impossible to have two or three times our current population. Humans always find ways to survive, and if arable (new word for me, thanks
) land runs out, there will be other ways to make better use of that land, or even advances in GM foods.
Idealy, the worlds population shouldn't increase anymore because the increase comes from the poorer countries, which in turn wastes lives as there IS a lack in food, water land etc. With that said, if there is a solution to this, then an increase in population wouldn't be such a problem.