Actually from a biological/environmental perspective, it is totally about the number. John Q Citizen requires X litres of clean drinking water per day and X litres of clean air per day and X amount of nutrient rich food per day. The finite resources of the planet absolutely care about the actual number. Your 1, 3, 9 or 17 children could all be fabulous souls, productive and caring and live as sustainably as possible, but if they need to share access to limited water with 10billion other people, none of their best traits will solve that dilemma.
It could very well be one of those 1, 3, 9 or 17 children who grow up & DO in fact solve those dilemma's though..


Personally if Australia ever brought in a limit on the number of children a family could have, I would vote against it. I would hate to think of how things would go when there was a limit on children. Some of the things I have read/seen about in countries where this is enforced, makes me sick to the stomach.