Nonsense. Efficiency is not the problem.
The problem is that demand is not there.
You cannot abort 50 million children and expect for there to be no consequences.
That's a point, but it only serves to show that capitalism is predicated on growth, which essentialy implies an exponential growth of the population. We're at 7 billion, so how far can it grow? 70 bilion? 700 billion? 7 trillion? Surely not. To argue that 7 billion is not the limit is a quibble. This is already way beyond anything Malthus imagined, I'm sure, but the limit has got to be around here somewhere.