The "no children" thing is difficult. If you would ask me whether the planet can sustain 9+ billion humans, then I would say no. But I do understand why you would want a large family when you're in Chad , Yemen etc. Those kids may provide for you when you're old. A state pension in these parts of the wordl here may be insufficient for a comfortable life, but at least you won't die of hunger.
I never actually said 'no children', I was making the point that children are a choice like anything else from taking a holiday in Costa Rica to buying the latest marque of main suburban battle tank and they all have an impact (having a child, of course, knocks all the others into a hat, since it's an entire another breathing, consuming human). Of course, we could abandon our privileged first-world lifestyles and really reduce our mighty environmental thump but I'm as likely to volunteer to do that as anyone else, so I fritter around the edges. As the song says,
I care a lot. I suspect some of that acknowledgement (if not all) is just liberally spreading the honey of my own virtue.
That said though, and people are generally uncomfortable with Malthusian conversations, but ultimately there's too many of us humans populating the planet (and the more of us, the worse it is). Birth rates drop with economic advancement and, who knew, letting women manage their own fertility (something so elemental yet even the developed world still seems to be struggling with it). Of course, in less developed parts of the world, large numbers of children are a necessity, they're only the social support mechanism and mortality still cuts its teeth on a large number. And having major religions still pushing policies still fundamentally opposed to birth control (well, I think they're fundamentally opposed to women, but that's another argument) isn't exactly nudging up the dimmer switch of enlightenment. I don't accept the argument we must keep having children to pay our pensions and feed our voracious economies, that's just perpetuating the current unsustainable economic paradigm and nudging its collapse over to the next generation.