Overpopulation

Climate change and the associated problems of ocean acidification, sea level rise and ocean warming are the greatest immediate threats facing our shared world. The air pollution from the burning of fossil fuels that kills millions of people world-wide each year is another huge problem.

All these are dependent on population levels; if there were half as many people in the world, all else being equal, there would be half as much human-produced greenhouse gasses and half as much pollution.

I suspect the optimal human population of the planet would be ten million to one hundred million. At the time of writing there were 7.9 billion.

Yet there is little effort being made to reduce populations. The Chinese government did try. It seems that their efforts had significant success for some years, but now China is suffering from an ageing population. The recent governments of my own country, Australia, cannot see beyond the 'need for continual growth in the economy' and if growth in the economy can be achieved by growing the population then they are all for that (in spite of the obvious impossibility of the sustainability of the policy).

I should first discuss a question to which the answer will seem obvious to many readers, but curiously not obvious to a great many others:

Is the world overpopulated?

If there were far fewer people in the world then there would be no need for starvation or malnutrition. We could all make a living by subsistence farming if no other course was available to us. In this overpopulated world there is no unused land for those who are malnourished to set up subsistence farms.

A hundred people defecating in a large river would be insufficient to cause that river to become polluted; the other life forms, bacteria, fish, invertebrates, etc., would keep the human-introduced toxins and harmful micro-organisms to levels that are harmless. If the sewage of a million people is dumped into a large river it will overload the ability of the river to clean itself.

Many of the Earth's rivers are polluted with sewage. Production of pollutants is, everything else being equal, proportional to population. If there were 80 million people on the Earth rather than eight billion, even if average living standards were much higher than today's, greenhouse gas production would be little problem.

If there were insufficient people in the world then people would be valuable. In 1850 an agricultural slave cost $30 000 (today's dollars) in Alabama, but today an equivalent slave labourer can be had for around $100. (Scientific American, April 2002.) World-wide there are millions of refugees who have to live in camps because no nations want them.

If there were one tenth as many people on the Earth then farmers would be able to farm only the best land; the marginal land could be left for nature. If there were only one tenth as many people we would not be facing the loss of most of the world's forests within a few decades, and we would not be nearing the end of petroleum reserves.

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It seems that there are only very short-term economic arguments in favour of more people; for example, more houses would be needed and this would provide a boost for the construction industry. More cars would have to be built, more refrigerators, washing machines, etc. I don't think I need point out the flaws in this type of argument.

How to limit population?

Is there hope?

It is tempting to despair about overpopulation sometimes; there seems to be so many who are blind to the problem and there are so many people in the Third World who have far more immediately pressing problems to concern them. But I suppose that when the world's population was, say, half a billion, there would have been few educated people who could have imagined that six billion would be possible. So now that we have six billion, perhaps ten billion will be tolerable, for a time; the world seems very resilient.

All nations should place a limit on family size, as China has done. (Ideally, this should be legislated by a World Government, which I have discussed elsewhere.)

In most nations people are permitted to have as many children as they choose. (Not all, Singapore provides strong disincentives for large families.) It seems generally accepted that there is an unwritten right to produce any number of children. This was acceptable when there was a perceived need for more people, but it should have been abolished long before now.

It seems to me that, ideally, the whole world should follow the Chinese example of one child per family until world population falls to, perhaps, one billion. This would be a very difficult law to get people to accept, so perhaps a limit of two should be aimed at first.

Several religions encourage the production of large families. This would be a major impediment and it is difficult to imagine how it might be changed in the time we have available to us before overpopulation brings about a disaster. (I have discussed religion under Religion, superstition, pseudoscience and other false beliefs.)

This section added
2021/08/27

Population and COVID-19

In nature populations often rise steeply when conditions are optimal and then crash due to famine or disease. Humans are now getting so crowded in our major cities that COVID-19, especially the Delta variant, is spreading out of control.

Where is this heading? I don't know.

Our beautiful environment is at risk from overpopulation

Our beautiful environment is at risk from overpopulation

Gleeson Wetlands in Clare, South Australia on a chilly late autumn morning

Gleeson Wetlands in Clare, South Australia on a chilly late autumn morning

What population level for Australia?

There has recently been some discussion over the optimal and sustainable population level for Australia. In 2020 there were about 24 million people in Australia. There have been suggestions that anything up to 40 million is desirable.

I would hold that no more than 10 million (and ideally quite a bit less) is the maximum desirable population level. Why?

Habitat

This section on habitat
added 2022/01/30

Habitat for Australia's native animals is suffering from clearing bush and draining wetlands for development. Koala populations are declining in the eastern states, black cockatoo habitat is being lost in the Perth-Mandurah area of Western Australia.
Increasing population will exacerbate this problem. Decreasing human populations could ease the pressure on irreplaceable environment.

Housing

This section on housing
added 2022/01/30

Australia has very limited arable land and cities have been encroaching on what little there is for many decades. In the couple of decades up to the writing of this section the prices of land for building housing have risen enormously, to the point where the cost of buying a house is now beyond the ability of many young people without substantial financial support from their parents.
Years ago a typical suburban house block was 1000 square metres. Now the average of new blocks would be closer to 350 square metres. There is scarcely space for a house, let alone any garden.
Increasing population will exacerbate this problem.

Fuel

Peak production of conventional oil is upon us, we are resorting to more and more unconventional ways of keeping oil production going. When world oil yields start to decline gas yields will not be far behind. In general Australia relies very heavily on the unsustainable burning of fossil fuels for its energy. What are the sustainable alternatives?
Nuclear fission could be a partial medium-term (100 years) solution, but it comes with risks, is not likely to be politically acceptable in Australia in the foreseeable future, and is of no use for powering transport at the present state of technology.
Nuclear fusion may become feasible in the future and if so could become a medium-long-term solution, however, it is not yet available and may never be.
Wind/Solar/hydro/biomass Wind does not blow all the time, the sun doesn't shine all the time. While hydro and biomass can be used to generate electricity sustainably they would not be sufficient for Australia's current population, but may be sufficient for a considerably reduced population. (As of 2022 wind and solar were generating an average of 60+% of South Australia's electricity, but lack of energy storages was a major problem.)

Agriculture

The forms of agriculture currently practiced in Australia are unsustainable for several reasons. Reducing the nation's population could proportionally reduce the problems mentioned below.
Large energy inputs required Not so much for tilling the land but for production of, in particular, the high level of nitrogenous fertiliser required; also for production of other agricultural chemicals.
Phosphate cycle At present in Western agriculture phosphate is mined, processed, and applied to the land. It is then, in a fairly short time, either removed from the land with the agricultural produce, or is leached from the soil; either way it is not returned to the soil. The end of this system comes when the readily accessible phosphate rocks are mined out, and this time might not be far off.
Pollution from excess nutrients Modern agricultural practices result in some of the nitrates and phosphates applied to the land being washed into waterways and causing problems such as toxic algal blooms and changing ecological balances.

Pollution

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Smoke Currently, as mentioned above, fossil fuels are the primary source of our energy and this is plainly unsustainable. Wood fires are a practicable alternative for home heating, however, smoke is a problem in some urban areas. Perhaps the real problem is that urban population densities have become too great; smoke from fires is, after all, a very natural part of the Australian environment. A lower Australian population level could be the answer.
A similar argument applies for several other forms of pollution.

Biodiversity

Australia's biodiversity has declined since Man came and especially quickely since white settlement. If our population was reduced we could put more land asside to try to stop the loss of species.

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