Fewer people means fewer ideas. Resource consumption is a problem with our current technological base - but it has ALWAYS been a problem, and a solution has always been developed that results in higher overall quality of life. Agriculture was the technology that allowed more than a few hundred thousand humans to live on the planet. Humanity has a pretty good track record of coming up with the next tech in plenty of time.
Panglossian? Maybe. But I'd rather be Pangloss (syphilis and all) than a misanthrope like Ehrlich or Malthus.
Good ideas come from a very small segment of the population. Just having more people doesn't mean we'll have more philosophy, science or art, except from scaling. If you want more creative people, then make that your goal.
Overpopulation destroys quality of life. You can't fix that by throwing more technology at the problem. Technology isn't going to make more nice beachfront property accessible and affordable for middle class family vacations. Technology isn't going to make more high grade wild tuna, or quiet walks in empty woods.
With an ageing population you need someone to "work" in order to cover state-subsidised health care, housing, unemployment, pensions and other living costs for those that are still alive but not working.
And technology can absolutely solve a lot of problems. Being able to grow commercial quantities of meat in laboratories will change the world overnight. As will revolutionising public transportation, power grids, storage technologies, cars etc.
A contracting population is clearly a big problem for the capital class. It's bad for stock and bond holders, employers of labor, politicians, and I guess people who made poor retirement preparations. But I don't buy that it's a problem for workers Joe and Jane Blow. They eventually get cheap, high quality housing, and are more inclined to start a family.
Anyway, I also think the various futurist techno fantasies are wrong. Unless liquid thorium reactors or such-like come online next month we're entering an age of permanently escalating energy and food costs. Technology still runs on energy. The Jetsons future of electric cars and soylent for growing billions is not going to happen. The future for most is bicycles with rice and beans.
Yeah, I got mine. Fuck all those foreigners whose ancestors didn't get here fast enough.
If you're concerned about the purity of your nation there's no need to be a stereotypical liberal about it either. Allow me to present a policy package that costs the state basically nothing and improves the lives of many not currently within the borders of your state.
1. Move from jus soli to jus sanguinus; no one without a parent who is a citizen of the state automatically becomes a citizen.
2. Any foreigner convicted of any crime gets deported. One may wish to have different visa categories for foreigners of a higher class/who have more money. The big thing is that it be clear that begging, petty theft and homelessness are deportable offences.
3. After five years you can either go home with all the money you paid in taxes/social security minus an actuarial average of your cost to the state or you can stay and forfeit it. South Korea does something roughly similar and it works pretty well at discouraging settlement.
If you're feeling really humanitarian you can allow third generation non-citizen residents over 30 an opportunity to naturalise.
In Stanislaw Lem's book the main character lived on Greenland warmed up from space to allow subtropical climate. I guess this idea will cause any environmentally-aware hipster from California to have a heart attack.
Nobody is being thrown overboard. The article is just pointing out that it may not necessarily be catastrophic if population growth slows or even reverses for a time. We're all just speculating, whether you agree or disagree.
In support of the article, slower population growth would reduce resource consumption. Rampant population growth would speed up the resource depletion process. As certain crucial resources become more scarce, conflict is likely to follow. It'd only be a matter of time before large scale war followed, perhaps leading to an extinction event.
There are definite positives and negatives to slowing growth rates, but I think there are probably more positives if we're talking about a gradual slowing (as opposed to a sudden tanking). We can do a lot more with a lot less today. Many of us don't need massive families anymore, and that's OK.