This is happening naturally in a lot of countries already:
> According to projections of the population with the current fertility rate, over 65s will account for 40% of the population by 2060,[10][11] and the total population will fall by a third from 128 million in 2010 to 87 million in 2060 https://en.wikipedia.org/wiki/Aging_of_Japan#Effects
If China's population had continued growing at the rates seen ~1962 - 1968, then eyeballing, its present population would be on the order of 1.8 billion, some 300 million greater than today. Whether or not that would be sustainable, or whether it would have resulted in events that would make the Great Chinese Famine or various 20th century Chinese political disruptions look like a brief fast or student rally, we simply cannot say.
https://en.wikipedia.org/wiki/One-child_policy#/media/File%3...
Regional (and global) population trends ~1955 - 1965 were terrifying, and reading contemporaneous analysis of the period is sobering. That's mostly associated with left-wing environmentalists now, but in fact was a largely mainstream view.
China's population growth rate fell. The present population of 1.43 billions is over twice that of the time of the Great Famine, and is well fed (though with significant food imports from the US and Africa). China's current food production practices pose a significant global epidemic threat as a reservoir and evolutionary pool for influenza. (Have you had your flu shot yet?)
It's not a system I've had to live with. There's some comparision looking at India, which has seen less effective population control practices. Though the total populations of both countries are now equivalent, India started with a much lower population.
Via Wolfram Alpha: https://www.wolframalpha.com/input/?i=population+of+china+vs...
Or 1950 - 2100 (projected): http://statisticstimes.com/population/image/world/india-chin...
Fertility rates: http://statisticstimes.com/population/image/world/india-chin...
The trade-offs and choices are not easy. A challenge as you approach environmental limits (or any other constraints) is that your options become increasingly few.
Or, as a corollary, if you want to preserve freedoms, stay well inside your possiblity frontiers.
Of course it should. Taking off my shoes when I go through airport security is a pain in the ass but, in the grand scheme of things, a relatively minor inconvenience.
Telling me that I'm not allowed to have a child is a fundamental restriction on my humanity.
The need to save the planet is more important than a person's desire to have kids.
And how are you going to police that in Africa, India, or any Catholic or Muslim country? It's a dumb idea.
Simply removing a tax break at child number 2 would have a substantial impact.