we'll keep seeing an uptick in world populations. IMO

...... are usually much higher than the general population. First Nations in Canada have a birth rate much higher than the replacement rate. See this link for Canada:

http://www.med.uottawa.ca/sim/data/Birth_Rates_e.htm

It is not a stretch to assume that minority groups in other countries are experiencing the same phenomenon.

Current policies will not stem the tide of overpopulation!

In the abstract, limits to the growth of food production will inevitably limit the population - Malthus at least had the broad theoretical strokes right.

In general, these UN studies don't factor in the role of external changes to things like resource availability, the climate or the global economy in driving demographic change, either in terms of falling birth rates or rising mortality rates.

I looked at the UN's population projections to 2300, published in 2004. In it they posit three scenarios, with population ending in 2300 at 36.4 billion and climbing, 9 billion and stable, and 2.3 billion and falling. In the medium case they see the population stabilizing in 2075. The low case peaks at 7.4 billion between 2025 and 2050, and falling slowly after that.

I was surprised to find that I generally agreed with their low scenario in terms of the numbers and timing of the peak. Where I part company with them is in my assessment of the downslope after the peak. I suspect that increasing mortality due to the external factors I mentioned will play a much larger role than they expect, and the resulting decline will be much steeper. Their proposed end state of 2.3 billion is easily possible two full centuries ahead of their estimate, in 2100.

The sad thing is, is that our inefficiency is going to backfire on us in a major way. I'm not saying that humanity will under-go a complete die-off or anything extreme like that.

But, even in the best scenarios, we could probably lose at least some hundreds of millions of people due to famine, disease or whatnot......I think a more realistic scenario will cut us back down to something like around 5, maybe 6, billion by the end of the century, especially as people in the third world stop having children(which I feel is pretty inevitable at some point).

And, in the event that nuclear war occurs at any time, and it is a possibility, even if a rather remote one today, we could see those numbers reduced even further. And that's not the only thing that could happen: Yellowstone could erupt or a small asteroid could take out half of West Africa, or the Midwest U.S., or Central Europe, etc.

We don't know precisely what that maximum capacity is, and we don't know how much we can expand that capacity with technology, including biotechnology. But what we do know is that the carrying capacity of the planet is not infinite, therefore there is some level of population beyond which those that cannot physically be supported by the planet's resources will die of starvation. There is NO alternative.

To say the earth's population will NOT level off is exactly equivalent to saying that I can drive my car forever on a single tank of gasoline. That is mathematically impossible. When the gas is used up the car will stop moving. When the resources are used up the population will stop growing. Period. There can be no doubt whatsoever that this is the case. It's basic physics.