The Space Reviewin association with SpaceNews

space colony illustration
Space colonies and other off-planet settlements were once seen as a means to help reduce overpopulation on Earth, but will demographic and economic trends render that argument moot? (credit: NASA/Ames)

Planetary demographics and space colonization

The idea that population growth will drive space expansion is an old one. In 1758, the Danish Reverend Otto Diederich Lutken made reference to the settlement of human beings on other planets as a way to alleviate population pressure in his article, “An enquiry into the proposition that the number of the people is the happiness of the realm, or the greater the number of subjects, the more flourishing the state.” It was also much on the mind of Nikolai Fedorov in his development of his important ideas about space travel. The population explosion of the 20th century and the increased concern about the planet’s ecological limitations have kept these concerns alive and well, figuring prominently in visions like Gerard K. O’Neill’s 1976 book The High Frontier, and a great deal of space opera.

Today the world is still seeing large-scale migrations, but it seems highly unlikely that they will translate into a “push” off-planet, even were the technology to become available in this century as O’Neill (and many others) have predicted. An important reason is that the affluent, technologically advanced states that are most capable of conducting the effort seem least likely to generate space colonists, given their tendency to receive rather than export immigrants in recent decades. This pattern is reinforced by the fact that their populations are aging, and appear to be either stabilizing or gradually declining—not the demographic picture usually associated with such dramatic expansion.

This may suggest that the rich industrialized countries will be the main providers of the money and technology for the enterprise, while the fast-growing developing nations provide a disproportionate share of the colonists, but the facts of the situation are more complex. (O’Neill, certainly, was concerned by the need to redress Third World poverty when he wrote The High Frontier.)


However, even assuming that the cooperation necessary to make this highly unequal arrangement work is somehow achieved, the fact remains that most developing states are actually well along the demographic path already taken by the industrialized nations. The pundits who dismiss Europe’s future on demographic grounds, while celebrating (or dreading) the rise of China, tend to overlook the reality that Europe and China are in the same boat with regard to family sizes. The Total Fertility Rate (TFR)> for the People’s Republic of China is actually 1.77 births per woman, well below the replacement level of 2.1, and slightly below Norway’s. (The trend is even more marked among the “overseas” Chinese: the four countries with the lowest TFRs in the world being Hong Kong, Macao, Singapore and Taiwan, respectively.) While countries like the Philippines have higher fertility rates, a similar drop is already evident in several other developing East Asian countries (Burma, Thailand, Vietnam), as well as industrialized Korea and Japan.

The same trends are evident in the Middle East as well, contrary to what some sectors of the media proclaim. In Turkey, Algeria, Tunisia, Lebanon and Iran, in fact, birth rates have already fallen below replacement level, with fundamentalist Iran’s 1.7 children per woman below the levels of Finland, Denmark, Luxembourg and France.

The trends are less advanced in southern Asia, but still evident there too, with India’s TFR at 2.8 and Bangladesh’s at 3.0. Pakistan’s is 3.6, relatively high, but also representing a sustained drop from nearly twice that in the early 1960s, and likely to fall to 2.3 by 2025 according to a United Nations study. (In the same time frame, India’s birth rate is likely to fall to replacement levels, or very close to them.)

The situation is similar in the Western hemisphere, and not only in the United States and Canada. While fertility remains relatively high in Central America (Guatemala’s TFR is 3.6 births per woman), these countries still represent a relatively small share of the population of the region as a whole. In populous Brazil, by contrast, births have fallen to fewer than two per woman, and the same goes for Uruguay, with Argentina not far behind. Cuba’s TFR is among the lowest in the world at 1.6. Even in Mexico, the source of so much consternation in the United States, the figure is under 2.4 and dropping.

In short, very high fertility rates have become a thing of the past outside sub-Saharan Africa, and even there the likelihood is that development will mean this changes here as well. Of course, that leaves the possibility of population growth from the other end of the telescope: greater longevity, but the prospects for this also seem to have been exaggerated. For American women, life expectancy improved from 47 years in 1900, to 71 years in 1950—a 50 percent increase in that half-century. From 1950 to 2000, this was extended by another eight to ten years, a much more modest 10–15 percent growth in the same length of time. (The profile of male life expectancy in the US followed a similar course.)

This is a broad slowdown in the extension of the human life span, despite the skyrocketing cost of health care. Accordingly, just going by the established trends, life is unlikely to get very much longer in the foreseeable future. Indeed, there are signs that this progress is being reversed, with smoking and obesity commonly attacked as the culprits. Of course, there are those who predict revolutionary advances in medicine which will radically extend life and health in the near future, and perhaps even eliminate death, but there has been little in the way of tangible results to support such promises.

This may mean that it is not human beings, but the robotic “mind children” of humanity, that will leave the Earth to explore the universe beyond it, with the vast majority of the flesh-and-blood humans sitting out the adventure at home.

Because of these trends, where global population nearly quadrupled in the last century, it may actually crest and start to drop by the middle of this one. Of course, none of this is to dismiss claims that the world faces serious population stresses, or to argue that even slower population growth would not be desirable. According to the Worldwatch Institute, the world economy was already consuming the resources of 1.2 Earths by 1999, a figure that had risen to 1.4 Earths by this year. The addition of two to three billion people in the coming decades as the drop in population growth catches up with the drop in fertility rates, as well as the struggle to give billions more of those already here a decent life, will increase it (all other things being equal). The fact that the increase will overwhelmingly occur in the poorest countries also poses important challenges.

Of course, it may seem a world of nine billion people or more on a planet facing ecological degradation and resource crunches will still suffice to drive a torrent of settlers out to the rest of the solar system. However, the same economic constraints discussed above would preclude that. Even were space settlement to appear an attractive palliative under those circumstances, it seems unlikely that a really struggling planetary economy would be up to the job of delivering demographically significant numbers of people to new homes in orbit and beyond and equipping them to live off the resources in space, rather than depending on Earth’s limited stock of them.

In other words, the motivation would exist, but not the means, and the opposite also seems to be true: that a world economy capable of building habitable space colonies is likely to be one significantly more prosperous than that of today, rather than poorer. For that reason, life would probably be more comfortable for most of the planet’s inhabitants rather than less, diminishing the “push” factor that has historically been so important in such movements in the past. (That this population would on the whole be older—and in that, hardly the demographic profile of a pioneering culture—should also be noted in such a consideration.) This may mean that, as writers like Hans Moravec and Ray Kurzweil have suggested, it is not human beings, but the robotic “mind children” of humanity, that will leave the Earth to explore the universe beyond it, with the vast majority of the flesh-and-blood humans sitting out the adventure at home.