Every other species ratio's flatten out, due to various ecological circumstances (lack of food, increase in predation, and just can't get jiggy with it) yet we humans are the exception. We don't have a primary predator (shark attacks need to happen on land dammit), we always find a new food source and well, when in doubt there is porn.
Sustainably I always found it interesting that if every person in the world lived as an American does, I think there needed to be seven and a half earths in order to have enough resources for everyone.

GPFontaine wrote:

It isn't the first world countries that have population explosions. Over time as countries evolve into modern nations the birth rate stabilizes. It doesn't mean that we will see the population decrease, but it does mean that over time it will even out and we'll be ok.

True, since Europe's birth to death ratio has evened out and in some case death has over taken births.
The main concern is China, India, Bangladesh and many of the Eastern Countries.