Malthus vs. Boserup - a steel cage match to the death!
I was sent a link to an interesting link to a crowd-sourced world population simulation by an outfit called Wikistrat: The World at Global Population Peak.
The "simulation" appears to be a cross between true crowd sourcing and a Delphi method forecast: the invited opinions of experts leaven the random opinions of the great unwashed contributors. What they wanted to know was something like, "When the world reaches peak population of 9 to 10 billion by 20450, what is the sociopolitical landscape going to look like?" When the dust settled, they had divided the opinions into four quadrants or "Master Narratives", complete with illustrative sci-fi movie titles for each:
Nerdless to say, I have strong opinions about this kind of stuff 
Overall, I fall neatly into the bottom half of their quadrant graphic, where the overwhelming peak strains live, and especially the left-hand quadrant labeled "A World Undone": the Soylent Green/Bladerunner world… I know, you're all completely amazed, you had no idea I thought that.
Here are a few personal comments:
I don’t think the world is going to see 9 or 10 billion people by 2050, largely because of climate change and energy shortages. I expect population to peak around 8 billion by 2030, and begin to slide after that, due to the overshoot-driven erosion of global carrying capacity (and the lack of fossil fuels to re-inflate it) and increasing crop failures due to extreme weather.
I expect to see a lot of regional fragmentation and realignment as international trade breaks down, along with drastic increases in wealth disparity in both fortunate and unfortunate regions. Variants of neo-feudalism will become more common. Regional wars, disease and famine will soak up a lot of people.
Also, we will try to keep the “survive and propagate” program running as long as possible. We will fight to keep our corners of “civilization” operating, regardless of the cost to the biosphere. Think of it as our genetic expression of the thermodynamic principles that drive all life.
One last note on the layout of the graphic. The bottom half is quintessentially Malthusian – the environment will present us with limits we can’t overcome. The top half is represented by the views of Ester Boserup, the Danish economist who studied agriculture. In her view, any encounter with limits always triggers a burst of human ingenuity that transcends those limits.
In a sense Boserup and Malthus represent opposite sides of the growth cycle. A lot of the outcome depends on how ingenious you think people are, how resilient the environment is to our schemes, and how firm the natural limits are. Until now Boserup has been right – human ingenuity and environmental resilience have allowed us to transcend apparent limits as we encountered them. Norman Borlaug’s Green Revolution is the canonical example of this, but Craig Dilworth’s recent book “Too Smart for Our Own Good” contains many others.
This kind of transcendence of limits is only possible if the environment is resilient and the limits are not hard. I think it’s becoming fairly obvious that we have tested environmental resilience to the breaking point, and we may be starting to encounter hard limits. That’s especially true with the climate, limits to expanding the liquid fuel supply (Peak Oil), ocean acidification, soil and water depletion, species extinctions, and on and on. To my mind, that whole sad litany is evidence of the biosphere frantically signalling that we’re at the edge of the cliff.
I've always been pretty sure that Malthus would win the debate in the end.