Food for thought. In a sociology paper I read, war, hunger, financial challenges and disease-threats increase birthrates in communities. Peace & harmony lower birthrates in the same communities.

Studies have shown that it will peak and plateau as the third world countries get richer, as families start managing the number of their children. It's all in the numbers.

Here is what the PBS YouTuber, It's OK To Be Smart, presents in a video about population growth. I won't link to this video because I'll link to the first research I saw on population growth below this post. Here is a synopsis of OK To Be Smart's presentation:
"The way we feed 7 billion people today won't scale to feed 10 billion tomorrow
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The reality for most of history was that many children would die before adulthood. So you better have plenty.
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But beginning in the 1700s, advances in agriculture and transportation meant fewer people starved.
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Eventually people caught on that most of their kids are going to survive. And as education and opportunities for women improve, families started having fewer children. And population growth slowed. Eventually when births and death rates remain low, populations level off, and become stable. Or even start shrinking.
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It took the UK 95 years to halve birth rates. While Brazil did it in 26. And Iran just 10. Today birthrates are falling almost everywhere. The less time a country spends in times of rapid growth, the quicker Earth population stops increasing. It's unlikely the 12 billionth human will ever be born.
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Instead of one big population bomb. The challenge today is defusing a few population cluster bombs in pockets of the developing world."

And here is the first presentation I watched that explained this theory. It's 20 minutes long, stick with it. It's actually quite interesting. It's very visual with many well thought out and animated info-graphics. Hans Rosling knew how to present his research well.

What happens when places run out of water, refugees, food shortages. So many things will go wrong. A perfect storm of disasters.

The real problem as is with everything when it comes to us humans is moderation and greed. We always want more even when it isn't the best thing for us.

We are fucked directly because of greed and overpopulation and no respect for any other life as a species.

Not long ago, I was thinking about a study I read back in my (psych) school days. The research was set up to see the effects of population growth in eat colonies. The colony of rats was set up in a large "habitat" with plenty of space, "housing" resources (regular food source) and they were allowed to just live. Of course as will any species with resources, they multiplied, raised their young who then multiplied.
There were occasional conflicts, fights over mates or choice resources but rarely were these fatal to a colony member. However, as the colony grew, conflict and "violence" increased. Researchers did not increase resources at the same place as population increase and of course more fights broke out over food, nurseries and such. As population increased further, there were more battles for seemingly no reason and increasingly there were fatalities related to these conflicts. They began seeing infanticide, both by "strangers" and by parents. There were even some instances where 2 or more rats would band together and set about killing others.
While the colony did not return to the idyllic stage where everyone pretty much for along, it did stabilize somewhat at a population sustainable by available resources.
What do I think? I think this could pertain to humans as we may be little different than rats with better tools.

It always has been the major cause of problems and always will be. It's not just the number but the use of resources. Technology squeezes more resources out of what's available but that only leaves fewer for future generations. The formula is I = PAT (impact = Population x Activity x Technology). In the 70's, 80' and 90's this was well understood but then industry got involved and the whole concept went down the drain. Remember, our economy is based on continual growth.

I once heard a comparison to the Wild West idea (there is no more wild west is is all taken) and a space craft. We need to go to the spacecraft model and the first law is to only use what is available on the ship. More people means fewer resources to go around.