There can be no greater act of selflessness than deciding to forgo having children.
ateday,
Yes, no argument from me about people with that degree of integrity. However, most people I know who chose/choose not to have children are purely for utterly selfish reasons.
There is no greater human & animal love than the one for your children. The people, or rather humanoids who choose against the responsibility, care & pleasure of children are the ones who pollute the Planet with saturation travel & generally polluting activities or as in some groups kill other peoples' children by cowardly using them as shields. Then there are those who seek pleasure in molestation of other peoples' children, exploit other peoples' children for financial gain etc etc. These humanoids aren't "foregoing" having children, they're too selfish to miss out out on selfish activities that can't be engaged in when children require their presence !
I agree with you that there are many selfless people but they're not the ones deliberately not to have children !

Indyvidual,
I choose to not add to the planet`s population when I was about 25 or 30, some 50 or so years ago. I realised then that the Earth had enough people. I was not wrong.
I have no regrets.

As an aside I have no problem with those who choose to have replacement number of naturally conceived children. Those whom I consider very selfish and irresponsible are those with large families who consider themselves as doing a wonderful job by so doing. Religions must share much of the blame for this.

ateday,
What's you opinion on the genocide against the West by out-breeding it ?

ateday,
what's your opinion on those who support the out-breeding of their own ? Leftists who don't want to curb the willy nilly influx of those whose agenda is to annihilate the ones who let them in ?

Dear Paul,

Your 4 question have more than one set of answers:
I can assure you that these practical issues can be solved, but the exact solution would depend on the implementers' overall values.

I could tell you what I would personally do.

I could tell you for example that as I value non-violence, I would not sterilise anyone by force, but use education and financial incentives instead - but someone else could carry forced sterilisations, historically some already did.

I could tell you that I will begin everywhere simultaneously, that I would not make exception of any country or continent - but someone else could.

I could tell you that while concentrating on breeding alone, I would gently loosen the pressure when population comes down to around 400 million, so from then on the curve would gradually smoothen - but someone else could in parallel or instead also take action against older people.

I could tell you that along with the reduction in population I would also allow the level of material technology to be reduced and replaced with quality spiritual satisfaction that does not require such specialised skills - but someone else might insist on maintaining the same level of hi-tech and the skills it requires, thus as you suggest they might need a big police force.