I think humanity has already more or less solved that problem. Due to effective birth control, almost all developed countries have birth rates below replacement. As developing countries get access and go through the required cultural changes (that we went though 50 years ago), birth rates will fall there too. The human population in 100 years will probably be below that of today by virtue of falling birth rates.
As a Realist, I`m afraid you are too optimistic, even this country. Compare birth rates and reproduction statistics here for Caucasians vs. Blacks & Hispanics... Our population is growing...
In the rest of the world particularly Arab, African and other nations that can`t produce food to sustain themselves, are causing population issues in the rest of the world. Then there`s India, China (who has reversed the 1 child law to provide a larger work force and military).
The rest of the world is forced to feed, water etc. to sustain them while they continue breeding.
then who do we cull, from this planet? before you start culling folks from this planet.. should you not look at ones own family first? not so easy, yes.. but easy to cull anyone else?
Re: Family. There were only 2 kids in my family. I decided in the early `70` that I wanted no children. I did adopt my 3rd wife`s son, and that`s my contribution.
My current wife had one son. A colonel in the USAF, with 2 kids. I dread the world that they will mature into, here in the USA.
Probably the best place to start population control is in Congress. W-T-F are they thinking???