Population Overflow

What are the consequences (political, economic, military, social) of an 'overflowing' populace?

Wikipedia has a great list. It has just about everything I could think of, except for my personal speculation that war would become more frequent. I say that because you have countries that have guns but not butter, and butter but no guns- if you don't mind my mixed metaphor.

On a larger scale, there is a concept referred to as the Malthusian Catastrophe, which states that a population of humans which exceeds the carrying capacity of the Earth will deflate via famine, war, disease, or another, unknown, factor.

How big is too big? Is there a too big?

The loyal opposition! Just for kicks. These dudes think that it's not a problem... They also do the "not all scientists agree" thing with respect to global warming, so I'm inclined to just say religious devout.

The C3PO's! (yes, I'm a geek. here's the reason.) Another one, less hysterical. And, one more. Teh internets have spoken. It's real. I know that isn't and end-all, but... sometimes the crowd is right.


Too big is called carrying capacity in ecology. Carrying capacity is, basically, the largest sustainable population of an an environment.Thomas Malthus, an English clergyman, was the first to suggest that the human population would eventually exceed this number. He said this in 1798. Another old issue. Well, the carrying capacity of the earth varies depending on how you estimate it (duh). The variation, though, is huge, 2-40 billion. (this site) However, the number that is more useful is the American limit: 2 billion. If everyone lived like a middle class American, the carrying capacity is only 2 billion. Keep in mind, though, that carrying capacity is sustainable. before you tell me that the world population is 6.7 billion, give or take a few hundred million. In essence, technology allowed us to escape the geometric progression in a linear world problem, but at the cost of sustainability. My personal estimate of the carrying capacity is optimistic, from what I've read, it seems like lifestyles can be rearranged to allow for 5, give or take 1, billion people. Still, though... We're screwed.
The magic date is 2030, give or take a bit. All of the major forecasts predict a perfect storm around that date.

What advantages are there of a high population?

Other than big parties... More production, and, to a certain point, you have specialization in the economy, which brings you cotton underwear, among other wonderful things.
Other than that, not much I can think of.

What are the largest cities in the world? Can they shed any light on the first question?

The largest city in the world is Tokyo. It is recognized as a central node of the world economy, along with London and NYC; it also has the largest metro economy. Also, it has an absolutely amazing public transit system, and is rated as one of the best (and most expensive) places in the world to live. In the politics of Japan, Tokyo (the greater metro area) is treated as the equivalent of a state (they call them prefectures, not as a city. Japan in general has almost no crime (right here, and Tokyo is the same way.
So yeah... This kinda puts a damper on the apocalyptic predictions of overpopulation. I guess I'll go ahead and just say that the Japanese are really civilized.

Is there a capacity of the Earth? If so, what is it, and how is it calculated?

 See the question about how big is too big. Basically, about 5 billion. The calculations are beyond my ability, if I find a good explanation, I'll add a link.

What literature is there on this subject?

Off the top of my head- Hot, Flat, and Crowed comes to mind, but I can't recall the author.

Are there population control laws in places other than China?

Again, the Greeks did it first- Aristotle, among others, first discussed the idea, but with the Christian faith gaining traction after the fall of the Roman Empire, population control was ignored. (be ye fruitful and multiply).
Later, you have Malthus, who said you could have 'positive checks' or 'preventive checks'. Anything that increases the death rate is a positive check, anything that decreases the birth rate is a preventive check. From an ecologist's point of view, the preventive checks are the ones that are insituted voluntarily, and positive checks are the ones imposed by reality.
In the world, only India and China have actual laws, China with their one-child policy, and in India, only people with two or fewer children are eligible for election to local political office.
EDIT: Oh, the law of unintended consequences strikes again! In China, the male-female birth ratio is so far out of whack that there will be something like 30 million more men than women by 2020. They are worried about social insatbility because of this. The irony is crushing- social instability by overpopulation- avoided! Social instability because of large amounts of young men without dates- crap...
More details here.

Will population control laws be needed in the future? If so, what could they be?

I'm going to say that they either will be enacted- or we end up with a Malthusian catastrophe. Personally, I think the best ones would be something like what is used in Ender's Game, progressively worse economic sanctions for every child beyond two. Because not everyone would bow to the sanctions, replacement fertility (2.1) is still achieved. If you needed more, I am moderately intrigued by the idea of a lottery system, as described in the person of Teela Brown in the Ringworld novels.

However, fertility tends to decline with prosperity, so it is possible that the geometric curve of population will flatten and none of this will occur. However, because of the developing world, this is unlikely to occur without extreme upticks in wealth in the developing world.

Could there be a ecumenopolis (planet wide city) like Coruscant in the future?

Well, you'd have to do something with the oceans- so that's a problem. What is more likely is ribbons of city crisscrossing the globe. 

If so, what would some consequences be?

This one. I know that there are a lot of Star Wars references here, I promise I'll try to stop.

In sci-fi, most planet cities have extremely volatile weather. The huge amounts of heat produced, with the wind tunnel effects of the skyscrapers produce hurricane force winds regularly, and with the high winds comes lightening storms. Despite the vicious storms, it probably wouldn't rain much, because most or all of the water of the planet would be stored somewhere. Because of that, the humidity would likely be really low, kind of like high-altitude places today.

The above assumes an open air city, instead of a domed planet, like Asimov's Trantor in the Foundation novels. With a domed city, you get the same volatile weather, but it doesn't matter much, except for the damage it may inflict.

Of course, that is all guesswork.

This is getting really long, so I'll stop here, but I get the distinct feeling this is a big topic.