World population will level off

A common perception sees the human population always growing exponentially, approaching 20 or even 30 billion crowded people, stopped only by resource depletion and violence. This assumes that birth rates remain high across the world.

It is interesting, then, to look at Totality Fertility Rates. The TFR of a population is the average number of children that an average woman will have across her reproductive life. To maintain a constant population, the TFR needs to be about 2.1 in industrialized countries, and higher in developed countries.

The UN has compiled useful TFR research and projections .
In the left window select Total fertility. In the right select a region. Now hit Display.

Here are the TFRs for the world population across time.




Note that it steadily drops, from 4.92 in 1955, to 2.56 today. We should hit replacement fertilitity rates by 2040.

Yet the population will continue to grow after this. Why? It’s because the first generation of women with TFR less than 2.1 was borne by women with TFR greater than 2.1. There are still large numbers of women giving birth faster than the older generation dies. The important thing is the trend – the population will peak. Various estimates place the peak a little above 9 billion in 2050, give or take.


Regions with Currently Low TFRs
We know industrialized countries have very low TFRs.
Japan - 1.27 today, 1.60 2050.
Russia - 1.37 today, 1.83 2050
Western Europe – 1.59 today, 1.79 2050

And China
China – 1.77 today, 1.85 2050.

Note that all of these are projected increases, even though the historical data is consistently decreasing. It’s more logical for these trends to continue their momentum. In any case, these countries are losing population, sometimes quite rapidly.

Check out the US – 2.09 now, and falling to 1.85 very soon. It takes immigration to maintain a young workforce. And Mexico? 6.70 in 1950, only 2.21 today, and dropping soon to 1.85.

Regions with Currently High TFRs (Developing Countries)
"But", people are saying, "what about developing countries? They wont stop breeding." In fact, although developing countries still have very high TFRs, they've been dropping like a rock and show no sign of stopping.





















India - 5.91 in 1950, 2.76 today, 1.85 2050
Sub-Saharan Africa - 6.57 1950, 5.08 today, 2.46 2050

And so on.

The Sweet Spot
To be productive, countries need more than a large population. The need a high ratio of labor force to dependents (elderly and children). Unfortunately countries with low TFRs are rapidly graying. They are not breeding enough workers to support their old age. Japan is concerned about this issue. The US worries about Social Security viability.

Immigration will be an increasingly important solution (current unemployment and immigration concerns don't factor here - I'm talking about future trends). Immigrants trend young, and they pay taxes and social security and medicare.

Some countries will hit the sweet spot. When a country has a high TFR, the workers must support many children. When a country has a low TFR, the workers must support many elderly. But when the TFR is dropping, there's a certain point where there's a big surge of working age people with fewer elderly and children to support, allowing great productivity. This happened previously in Europe and is going on in Asia and Latin America. When it happens in Africa, they should be ready to take advantage of it.

Conclusions
Increased standards of living decrease TFRs, and decreased TFRs increase standards of living. Female education and availability of family planning decrease TFRs. It appears that women, across regions and cultures, when given a choice, want fewer children.

The population will level off. Maybe it will be 9.3 billion as predicted. Maybe a bit more, let's say 11 for the sake of argument. But it won't follow old growth rates, so it won't jump to 30. Sure, 11 would be tough to manage. Living standards are increasing, so individuals demand more food, more meat, and more gas. Farmland will get stretched and global warming may decrease farmland availability. But it's a manageable issue. Education and birth control, good farming practices, and investment in technology will help. It's going to be alright.

Are you a Planetary Chauvinist?

I finished reading The High Frontier: Human Colonies in Space by Gerard O’Neill. He argued that orbiting colonies, rather than planets, were the superior destination for space colonists. He imagined only small outposts on Mars and the Moon, while colonies multiplied exponentially. The resources in the asteroid belt, recycled, could sustain more than 10 quadrillion people.

Orbiting Colonies
He makes great arguments. O'Neill cylinders could house large modern civilizations.




























Cylinder rotation would provide 1G (Earth Gravity) at the edges. Low gravity is available as you approach the axis. Solar energy is collected all of the time, undeterred by clouds or night. Mirrors outside reflect through windows to 3 valley living areas. The mirrors can be rotated to show the disk of the sun at the proper angle, and to give normal cycles. Weather can be controlled.

The main cylinder is all living area and recreation. An agricultural ring, with flexible use of light, can grow summer crops and spring crops simultaneously. No industry pollutes the living area. Workers move towards the axis and move out to the zero-G construction facilities. Microgravity allows purer mixes of alloys and fluids, purer crystals, and perhaps easier large-scale construction. Energy and heat are free.

The lunar colony uses a magnetic mass driver to fire up lunar regolith. This includes oxygen (air and propellant); silicon (solar panels); aluminum and iron and titanium (building materials); and recently confirmed water (life support and propellant). Launch of resources from the moon drastically reduces launch costs.

The next step is to mine asteroids. Coast up to them, attack from any angle, vacuum up the parts we like, magnetically separate, and so forth. On Earth and other planets, geological processes caused most of the useful heavy material to sink out of reach. On asteroids, it can be all on the surface. Even tiny Near Earth Asteroids contain more metal than has been mined in our history, worth tens of trillions of dollars. Since asteroids have negligible gravity, these resources can be transported cheaply back to the colonists' industries.

Planetary Difficulties
Planets, on the other hand, face difficulties.

1. They have awful gravity wells. Launches remain expensive.
2. Solar energy cannot be collected constantly.
3. They have less than 1G. We don't know whether Mars' .38G and the Moon's .18G are healthy. It would certainly be very difficult to return to earth after living under that little gravity.
4. Metals are less accessible than they are on asteroids.

Planetary Chauvinism
Isaac Asimov commented that some individuals are guilty of planetary chauvinism, favoring planets despite the obvious advantages of space-based colonies. But colonization of planets is more intuitive. And romantic. Slamming the flag in Mars, dune-bugging across Hellas Planitia, rock-climbing up Olympus Mons ... surely these are the deeds of space colonists? After landing, you don't have to create gravity, or the 24 hours, 39 minute day. There's at least some atmosphere against solar radiation, and you can make bricks to give your habitat more protection. All of the resources are there.

And although terraformation is a very difficult and longterm process (it's much easier to create a favorable environment in a small space colony), think of the end result. An entire planet, with an atmosphere tied down by gravity (I know, not completely). An atmosphere burns up meteorites. Sure a space colony will have thick plating, and the windows will be of multiple pieces attached by metal mesh, so that when one gets blown out the air releases slowly while repairs are made. But you'd be nervous in that shell.

A planet with a thick atmosphere; properly circulating weather; large oceans; plankton and moss and a full ecosystem up to whales and tigers. Ecosystems are complicated, and work better on a huge scale. Space colonies may make them, but its not trivial.

I'd also like to see other planets and moons settled. For instance, Titan is full of useful resources. But I'll leave those destinations for another post.

Am I a Planetary Chauvinist?
We need to lower the cost of access to space by orders of magnitude. Then we need to create a permanent moon colony. The colony will launch materials to the first large station. Stations will replicate, pulling in asteroidal resources, and generate the affordable ships and goods we need to settle further. Mars will be settled and covered in oceans and forests. The moon will have cities and bunkers. Other planets and moons will bear our footsteps.

Are you a Planetary Chauvinist?
Are orbiting space colonies overrated? Or are planets outdated? Is Mars a distraction to NASA? Will Earth be left behind, preserved as a historical site for tourists from space?

You've got solutions. I've got counter-arguments.