Why colonizing space?
Now we will talk a bit about demography.
I said that resources can't keep up with population growth. It is not really about minerals (which we can recycle) nor fossil fuels (let's suppose we can replace them in time with other energy sources), but mostly about agricultural resources.
If we gathered all mankind in a single community, with the population density of New York city, it would only cover the area of Texas. I heard some use this argument for denying the overpopulation problem. Indeed living space is not an issue now (but, logically thinking, it will become somewhere in the far future). The problem is a basic ecological law that states that for each kilogram of body mass a population produces, it needs about 10 kilograms being produced at the lower trophic level. In simple words, in order to be properly fed, one needs a biomass of prey organisms ten times larger. By prey I mean primary producers (plants, in our case), but also consumers, that in turn need ten times their biomass of producers. If one 80 kg man fed exclusively on cattle products (meat, milk) it would need a constant 800 kg biomass of bovine population, and 8 tons of forage plants biomass. Primary production is based largely on photosynthesis (carbon dioxide assimilation using solar energy), thus being surface-dependent. If we all gathered in Texas, we still needed a much larger agricultural surface (and keep in mind that not all the landmass area is suitable for this).
So it's reasonable to think that, with all the scientific progress, the available agricultural resources will end, Earth having a finite land area (consuming this area with biofuel-producing plants, or, worse, with "ecological" agriculture just makes things worse).
Having this in mind, it results that mankind needs a demographic solution to this problem. Many talk about population control, and I will show you why this is terribly wrong. But first let me show you three examples of demographic evolution.
First, we have regions and countries with rapidly growing populations. We may think of Egypt, Pakistan or the Philippines (but, also, to some degree, the U.S.A.; some underdeveloped countries also have a population boom, but also a high mortality due to war, famine, diseases - think of Congo). Larger and larger young generations are permanently coming. Pension systems work, and also it seems favourable to democratic progress (see the Arab Spring). The major drawback is unemployement, but for this, my second example here helps.
We are speaking about Europe (but also Russia, Japan etc.). Due to various economical and social causes, natality is dropping, while people tend to live longer. Some European countries have a stable demography (France, Finland), other have quickly shrinking populations. The result is fewer workers and more assisted people. Left untreated, this situation leads to the collapse of the pension system, and of the whole economy. The solution, in this case, are immigrants from the first group of countries, whatever far-right "geniuses" think of this.
The third example, and the one which I wanted to get to, is that of mainland China. The Communist dictatorship in Beijing (although I prefer using the expressions Bolshevik or Leninist, since, as I will probably show elsewhere, the Leninist ideology is not Communism and, hell, no! is not Socialism) has taken strict population control measures - the (in)famous "one child policy". Other goverments take inspiration from it, and many think this would be a Global solution to the demographic problem. My answer is NO, NO, NO! And I'm going to show you the main three drawbacks of population control.
First, it must be repressive and in total contradiction with Democracy. More than this, it is inhumane: who didn't hear about forced abortions and Chinese newborn children abandoned to avoid sanctions? Speaking about abortions, whatever "Pro-choice" Fascists say, killing defenseless human beings is murder; morally, pursuing such a strategy is just like proposing to regulate the World's population by nuclear war or death camps.
Second, as you already know from the European example, stopping natality leads to population aging and, finally, to economic collapse. Some countries solve this by immigration, but if this would be a Global problem, how are we going to proceed? Bringing E.T. workers?
Third, one of Leninist China's problems (caused by selective abortions) is a shift in the sex ratio. There are more men than women in mainland China. They also use immigration for this, but it's not a Global solution. Such a disproportion in genders leads only to another resource shortage (my female readers should forgive this cynical saying), the resource being the access to sex and reproduction. The Party "Nomenklatura" and pro-regime businessmen are favoured, but more and more poor men become frustrated. Having this situation perpetuated in a nuclear superpower is not a wise choice, not to say about a Global implementation.
Seeing these three strategies, we see that, oddly, the first one may be sustainable: population growth can be slowed down a bit, but not stopped. The one thing we need is more space.
Did I say "space"? More than this, it's "Space", the extraterrestrial space, "the final frontier" etc. Earth is finite, but the Universe is not. Since Homo sapiens first evolved, it colonized more and more territories, from a small area in NE Africa or the Middle East, to the whole planet. Now it's time to break the limits again.
Now, you may say that our neighboring planets are arid, incompatible with human life. You imagine some domed colonies on the face of Mars, as you saw or read about in SciFi movies and literature, and you wonder how many people can get into those, and if it's economically feasible to build such expensive habitats hosting just a few thousand people, and you are right.
That's where TERRAFORMING comes...