One Finite Planet

One Finite Planet

The Potential Scale and Impact of population growth: 7 trillion humans?

Date Published:


7 trillion looks like a typo, but no, the maths shows that either by continuing the actual global population growth levels typical the 20th century, or achieving 2% per year (or far less than what is currently happening in Nigeria), the maths produce this number in a relatively short time!

Alternatively, consider that if we had peak 20th century population growth rates from 1650 until now, we would already have 1 trillion humans.

While population growth itself is currently not the threat that it once was, we are still overpopulated, as any suggestion that returning to the out of control population growth of the 1960s and 1970s would cause even more long term damage to a world with 8 billion people, than that growth did on a world with 4 billion people.

  • Introduction.
  • How Bad Could it Get?
  • How could we reach such levels?
  • Why is ridiculous growth advocated?
  • Why high birth-rates would deliver no economic benefit.
  •  Other motivations for promoting population growth?


Economic policy has yet to adapt to the reality of slowing population growth.  Population growth has slowed since the 20th century, and growth is not at 2% as some dangerous people advocate as the entire world is not like Nigeria. It is still worth understanding just how quickly things can escalate,  and not take for granted the slowing population growth that is both happening, and needed, to avert crisis.

How Bad Could it Get?

Does it feel crowded now?  Can you imagine Earth inhabited by not 7 billion (7,000,000,000) humans (actually 7.8 billion), as we have now, but 7 trillion (7,000,000,000,000). That would be one human for every 3.3 meters x 3 meters of habitable land on the planet (calculation below).  Around 10 square meters allocation per person to live, grow food all of one food and that is without allocating any wilderness for other living things or trying to allow space (corridors?) to move outside your own space.  This is a level we would reach if were able to continue peak 20th century population growth rates.

How could we reach such levels?

Peak 20th century growth rates (1965-1970) of 2.1% annual growth, result in a doubling of the population in 34 years.  Double any number 10 times, and you get 2^10 = 1,024 times the original number.  So if we had that peak growth rate from around 1650, when there were estimated to be around 500 million people, we would already have 1 trillion people on earth today (almost 11 doubling cycles).  Alternatively, if we have those same 20th century population growth rates for 10 cycles of 34 years, we would in theory reach that 7 trillion population in around another 300 years.

Of course it is not possible to run at these population growth levels again for any length of time, as world systems would literally collapse under the strain well before we reached 7 trillion.  In fact, as I have posted elsewhere, population growth has effectively collapsed since 1990.  However, there are people who declare that return to running at these growth levels or even higher, is exactly what the economy needs!

Why are such ridiculous levels advocated?

Answer: economics.  If you are a nationwide business, then you can deliver 2% growth every year if the population grows by 2% every year.  Since stock market indexes are almost exclusively such businesses, this is a formulae for the stock market to perform well. The economy to be ‘strong’. The reality is the effect is to make the rich richer, but most of the population poorer. However, big business and the very rich are great political donors and have influence, so politicians are inclined to listen. Just how significant is 2%?2% growth means 1.02 times more than last year.  1.02^35 = 2 (or 1.9999 anyway). So 2% growth produces 1,000 times more people just that little faster than our examples.

Why high birth-rates would deliver no economic benefit.

I have just explained how a growing population delivers a growing customer base, which delivers growth to any business which enjoys a market share of the national market. However, that is a simplification.  Consider this graph of the population of Nigeria. This is the dream of the described ‘big business’. In five years, every age group would move up one division, and the pyramid shape ensures the result is always an increase in population for that age group as a result.  For example, the 15-19 year olds is clearly a larger group than the 20-24 year olds, so in 5 years, the number of 20-24 year olds will be a larger number. Good news if you sell to 20-24 year olds.  Now consider the graph for the USA. This time the number of 20-24 years will be quite static over 5 years.  Better for our national insurance company than Japan, where clearly customer numbers will decrease over the same period. The problem with changing the birth rates, is that in five years the only age group changed in the next five years is the 0-4 year olds.  Very little comfort for the majority of businesses that sell to adults.  Some may not realise this and still try to encourage higher birth rates, but more astute will instead try to increase immigration where ‘people prepared earlier’ are available.

 Other motivations for promoting population growth?

National pride, increased representation for religion or racial group are other reasons for people to push for population growth. “If we don’t increase our population, they will out number us!”.  Search ‘overpopulation’ myth and you discover the passionate arguments raised.  The arguments generally miss the question of where are we heading rather than were are we now, and tend to say ‘growth has been ok so far, so it must be ok forever”. The arguments focus on ‘population growth has not killed us yet’ rather than ‘have we gone past the ideal’. The arguments also generally look at the current population and miss the real issue of how much room for more population growth we have without negative consequences which may occur well before people actually starve, and what is happening to the other creatures on Earth.

Wasn’t the period of extreme growth great economic times?

No. Thinking this misses the key point of the lag between birth rates, and those newborns becoming the mainstream part of society. The graph of Japan population growth has peaked, corresponding to events 60 and 40 years ago. The people born during the big boom up until 1980 started being mainstream society from 1980 until now,  not during the years they were born.  If those were great years, then the great years may have resulted in people having lots of babies at the time, but babies are not productive for at least 20 years, so the productivity was not a result of lots of babies.

Footnote: The land calculations from ‘how bad could it get’.

**Land Area Calculations.

OK, these tend to be pointless, but here are some calculations on people per area of land anyway.  In reality it is growth rate that is important, not fixed numbers.  The fixed number could be fine, but in a time frame which from a historical perspective is very short time, all changes with the wrong growth rate.  Here is a link to someone who was so anxious to show that all is ok with an opportune argument, he miscalculated by a factor of 1,000.  Here is another where the calculation is ok and shows dividing Texas would produce enough land for all, but like the first, assumes we need no roads, no businesses, no parks, stadiums or anything else but homes…and of course we do not need farms to produce food, nor land for the rest of the animals in the world nor rainforests or ……..but at least that last one thinks about where things are going and is confident that the population will peak within 30 years. Fingers crossed!

The land area of the earth is approximately 150 million sq kilometers. With 7 billion people, that is 0.02 sq kilometers per person. A sq kilometer,  is 1 million sq meters each, so we still have 20,000 sq meters each.  Ok, that total land is approximately 33% desert, and 25% mountains, so only 10,000 sq meters is useful, and we do have to share that with all the other living creatures and grow all our food on our allocation, but it clearly is workable.  But if we had 1,000 times more people (our allow just over 300 years of 20th century growth levels), there would be 10 sq meters usable land each to live and source all our food.  3.3 meters by 3.3 meters.

Table of Contents


Ideal population of humans: How many people can, or should, each country, and the whole planet support?

It seems like the human population has forever been growing, but any analysis makes it clear growth must stop eventually at some level. The question becomes at what level should growth stop?

Do we go for the maximum possible people just before everything collapses, even if average living standards could be far better with a smaller population? With caged hens being farmed for eggs people advocate for a lower free-range population instead of denser living caged hens as it provides a better existence, but does anyone advocate against multinationals and politicians pushing for denser and denser housing for humans in order to allow bigger populations of humans for them to farm?

It seems to be accepted that global population growth should stop but claimed that countries who end population growth face economic disaster.

Read More »

Overpopulation: starvation is not the symptom.

The Myth: We are not starving yet means we aren’t overpopulated. The Truth: Overpopulation is defined as when population reaches a level resulting in damaging to the environment and is unsustainable. Starvation only happens if overpopulation continues until a final catastrophic environmental collapse and is no more a symptom of overpopulation than death is a symptom of disease. Unsustainability is a symptom.

Consider grazing animal on a farm. Overpopulation means unattainability and the animals eat grass faster than it grows, starvation when there is no grass left.

We are not yet starving, but unsustainability means we are overpopulated, and progressively, all but perhaps the richest 1% must suffer if we fail to constrain population.

Read More »

Peak Population 2055: Really? That soon?

Is it realistic that Earth could reach peak population by 2055, there really the largest number of under 35s on Earth there will ever be? Peak newborns already? What is the reality, and what are the implications?

Read More »

Next steps for mankind don’t include the Sci-Fi dream of a new home planet.

There is a dream, often explored in science fiction, where humanity inhabits not just one planet, but many.

While the dream is still centuries away, as is ‘Earth 2.0‘, the reality, working towards small outposts on Mars or the Moon or even beyond is overwhelming compelling and can provide many rewards.

Humanity may get back up outposts, but for centuries, will have no real second home, and over 99% of us will still need to live on our one finite planet.

Read More »