One Finite Planet

How long can/should/will population growth continue?

First Published:

Does population growth increase or erode wealth?

There are at least four conflicting perspectives to population growth.

  1. Continued population growth is an economic requirement, is the optimum path for economic prosperity, and therefore must continue indefinitely.
  2. Global population will peak at approximately 9 billion around 2050 (official UN projection according to wikipedia page at time of writing), or at most around 11 billion.
  3. Even the UN project of 9 Billion is actually too high, and active steps must be taken to limit population growth to the lowest level practical.
  4. This is an emergency, and we need to end population growth immediately.

This is an exploration of the merits of each of these arguments.

Continued population growth is an economic requirement.

This belief is based on the premise that either we can keep growing the population forever, or at least, for such a long time that it may as well be forever.

The belief is based on:

  • Population growth increases GDP, which also drives up share prices.
  • Food production has managed to increase beyond expectations, and we already know how to feed far more people than we feed today.
  • Sustainability is about reducing our footprint per person, and we have not reached the limit of reducing that footprint.
  • While there is land not occupied by humans, there must be room to grow.

There are arguments against each of these points:

  • Population growth increases GDP, but often decreases GDP per capita, meaning less wealth per person on average, although population growth does tend to increase the wealth of those with the greatest wealth, even if decreasing overage wealth.
  • We do know how to feed a larger population with basic staples such as wheat, but all luxury foods such as even coffee and chocolate will become available only to a smaller and smaller percentage of people, as prices will be forced to rise for all but the simplest staples.
  • Humanity currently living unsustainably, and increase population and environmental impact prior to getting sustainability under control is just reckless.
  • The amount of life on Earth reached a peak back at the time of the dinosaurs, and ever since then, increase in the numbers of one species requires decreases in the numbers of other species. As we occupy more land just for housing, the rest of nature must die, and we still need a certain level of the rest of nature.

I will put further links, but on the basis that environmental damage is the real overpopulation indicator, we are already at level of population that results in the degradation of the environment, which ultimately results is a drop in average quality of life.

Eventually population on earth has to stop, as there is a finite number of atoms on the planet and at some point there is simply not enough to go around.  The argument against this, is that the limit will come so far into the future that it is not our problem, but the problem of a future generation who will have technology such as space colonisation.

I encourage searching on ‘limit to population’ or similar.  The arguments do not need repeating here that it is very difficult to see how the Earth can sustain a population of, lets say, even 15 billion.  And if we were successful at maintaining the population growth the economic proponents desire, we would reach this unsustainable 15 billion by around 2070 and well before we are able to colonise space.  2070 is only 2 or 3 generations from now, so to deliberately seek to grow our population for economic motives is to create a problem for future generations.

Yet, artificially growing our populations is exactly what some western countries wish to do. The problem is that some western countries are taking what steps they can drive population growth against a backdrop of the population growth naturally trending towards zero.  If sufficient countries achieve their goal, then the UN predictions of a peak of 9 billion will most certainly be too low.

Yes advanced economies are seeing population growth naturally decline.  Countries like Japan have zero or below population growth already and are facing problems from an economic system geared for population growth. The Australian government took measures such as a ‘baby bonus’ to economically reward families to have more children.  The wikipedia page on population growth projections specifically nominates the USA as managing to continue population growth despite being one of the most advanced economies in a world where population growth is naturally declining in advanced economies.

Global population will peak at approximately 9 billion.

Strangely, many of the same people who advocate that it is in our best economic interests to continue with population growth, also point to the fact that predictions for various bodies are that we will reach a peak population of around 9 Billion anyway, so we do not have to be concerned. But why argue for population growth to stop ‘the aging population problem‘ or to deliver economic growth, if you believe population growth will stop?

The reality is, the global population peaking at 9 billion or any other number, will only happen if those who push for continued population growth do not manage to change current trends.

The reality is we are headed to a peak population number, but that will only eventuate if mindsets pushing the economic growth requires population growth are silenced. If these voices are not silenced, then population will only decline of inevitable war or problems from an inevitable environmental collapse.

Even 9 billion is too high, we need to do something!

The reality is the population pipeline means that population growth ending before 9 or even 10 billion requires moving to dramatically low birth-rates.

The late great Hans Rosling.

Most of the future population growth is already ‘in the pipeline’, and will result from not more children, but increased numbers of older people as the greater number of people in age groups 20 to 50 replace smaller previous cohorts.

We appear to be at around the level of ‘peak child‘ already, so the only way to prevent 9 Billion is to move to birth rates well below replacement level.

While it can be argued that below replacement birth rates for a period of time would, in the long run, be best for humanity, it is very difficult to win political support, since most governments would prefer their population at very least remains at current levels. I will look to add more on this point.

It’s an emergency, and we must stop population growth now.

What is needed to stop population growth immediately, is to ensure births match deaths.

Given the average life-span is approximately 73 years of age, the world can expect a number equivalent of all people exactly 75 years old to die each year.

At first, it seems logical that since the an average births per woman of 2.2, should produce a stable population as it allows for some percentage of people to die before having their full quota of children, is what is necessary to stop population growth. In fact, this birth-rate does end population growth, but it takes around 73years to stop population growth. In fact we are very close now to this ideal birth-rate, and population growth has not stopped.

Why hasn’t population growth stopped? The reason is best explained in the population pipeline, but it can be considered again from the specific perspective of what is needed to stop the pipeline.

There is still growth because the cohort of old people, which determines the number of people dying, were on average born just before 1950, when the world had a total population of 2.5 million people, and around 100 million women in each of the 20-24 and 25-29 year old prime motherhood age groups. In 1950, there were 166 million boy babies and 172 million girl babies under 5, for a total 338 million babies under 5 in 1950.

Today in 2015, due to population increases since 1950, we have around 3x as many women in those potential motherhood age groups to have babies, with 300 million in each group. The good news is these women are having around the correct number of babies for stable population at just 10 percent more than 2 babies woman, and the number of people in the world aged 0-4 is just 10% more than the number of people aged 25-29, at 660 million.

However, while 2 parents, 2 children (or just over 2 to allow for misadventure) will eventually result in stable population, it will take almost a lifetime for stability. Before stable number has to run through the entire pipeline, ensuring all age groups become based on starting with the same new child population number.

To stop population growth immediately, requires births not match population of their parents, but matching the population born 73 years ago, to on average, achieve births equals deaths. Since in 1950, just under 73 years ago, there were 338 million children under 5, approximately equal to current number of woman of child bearing age (300 million), we need to reproduce that number today, would require 1 child per woman globally, just as China did back in 1979.

There are two problems with introducing such a policy:

  1. Countries like Japan already have stable or declining population, and a global policy to accelerate population decline in these countries, while even with 1 child per family, other countries would still have growing populations is unjust.
  2. The policy cannot run forever, as this would soon result in spiral of population decrease which would continually see population halve in number approximately every 50 years.

Given the radically different population pyramids of countries such as Niger and Japan, any ‘one size fits all’ solution would be unjust, and the only practical approach to an initiative to control population growth, is a global accord with countries signing up to targets, as has been proposed to address climate change.


Even though there is still growth ‘in the pipeline’, the drivers for population growth have actually ceased in almost every country around the world.  The concern is that government policies may force population growth to restart and build continue until overwhelming problems occur.

What is needed is a global population accord, just as there is a global forum on CO2 emissions.


Table of Contents


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