COVID-19 has not, and will not, cause the death of between a third or half the population as the Black Death did between 1349 and 1370. But in Australia (with immigration on hold) it will produce a significant slowing, if not a fall, in population growth.

This week, even pro-immigration Coalition ministers say our external borders will not open until next year. It means no immigration for a year or more.

That means Australia will not have to build the equivalent of a city the size of Canberra. We will not have to find the money to build schools, hospitals and roads for that many people. The pressure on waterways, wilderness, agricultural land, and housing prices will be a little less.

Existing residents, whether white, black, yellow or in between, speaking whatever language or practising whatever religion or none, will be better off, just like those 14th-century peasants.

Britain in the early 14th century was horrendously overpopulated. The property-owning classes lapped it up, with a vast reserve of inexpensive manpower to draw upon. When that labour force dried up through Black Death mortality, they desperately sought to retain the status quo.

The law was changed to say: "It was lately ordained by our lord king, with the assent of the prelates, nobles and others of his council against the malice of employees, who were idle and were not willing to take employment after the pestilence unless for outrageous wages, that such employees, both men and women, should be obliged to take employment for the salary and wages accustomed to be paid in the place where they were working in the 20th year of the king's reign [1346], or five or six years earlier; and that if the same employees refused to accept employment in such a manner they should be punished by imprisonment."

Typical Tory response - blame the worker. So much for free enterprise and market forces.

Australia, since Howard opened the immigration floodgates two decades ago to allow his Coalition-supporting mates to import cheap labour, has been in a similar position (if not as dramatic) as mid-14th-century Britain.

And with COVID-19 we are now in a similar (if not as dramatic) position as Black Death Britain. The coronavirus is showing that you can deal with congestion, stressed hospitals and schools not by building more roads and buildings, but by having fewer people.

The rules to contain COVID-19 have resulted in huge unemployment. If we get a vaccine and/or treatment enabling restrictions to be lifted, we should recognise that our first obligation must be to those who lost their job through no fault of their own. That means putting economic immigration on hold - maybe forever. Very few other countries have economic immigration programs.

Without doubt Australia has benefited from immigration in the past, but that does not mean we will benefit from it in the future. In the past we got cultural diversity and skills from elsewhere, but that need has passed.

COVID-19 should make Australia question its Ponzi scheme immigration program which benefits the few at the cost of the many.

We should get smarter, more resilient and self-reliant. Governments should promote innovation, especially in renewables, education and training.

Alas, all indications are that the federal government is more interested in 10,000 dead-end coal jobs than 12,000 jobs in renewables. And it is more interested in hobbling broad university education which has trained people to think and served the nation well.

COVID-19 has now shown that tertiary education's dependence on foreign students has been a mistake.

Post-COVID-19, any pressure to resume high immigration should be resisted. Big business, which profits hugely from converting agricultural land to residential land, from cheap labour, and from consumer demand, will push for a return to high immigration and the benefits it brings to them personally - while average taxpayers pick up the cost.

Australia has already reached and passed its optimum population and would be worse off with more people, COVID-19 or not.

COVID-19 has enabled government to resist big-business demands for more cheap labour, mainly because in this environment big business is too embarrassed to ask for it. But as soon as the COVID-19 crisis is over they will be like the feudal lords in 14th-century Britain demanding their cheap labour. They should be resisted for the sake of our environment and our people's access to health, education and general wellbeing.

I do want to alarm you. For all the talk and action on renewables and reducing carbon emissions, the stark, irrefutable facts about carbon going into the atmosphere and causing global warming are expressed by the Keeling Curve, which has measured the amount of carbon dioxide in the atmosphere (on a mountain in Hawaii above the boisterous surface weather) since 1958.

Despite Kyoto, Copenhagen, Paris, the advance of renewables, targets, aspirations, hand-wringing and so on, the brutal fact is that carbon dioxide parts per million in the atmosphere caused by the burning of fossil fuels has been steadily and relentlessly increasing. The curve can be seen here. For sanity's sake, I urge you not to look at it.

Carbon dioxide in the atmosphere is now recorded at more than 410 parts per million, up from 280ppm in pre-industrial times as measured in extracts of air from drillings into the Greenland and Antarctic ice sheets.

The resulting scientifically measured increase in temperature from multiple independent measuring sites is now at least 1 degree above pre-industrial times.

The only rational reason for not acting swiftly and dramatically to slash carbon emissions is that, having increased emissions from 280ppm to 410ppm, it is now too late to save ourselves, so we may as well party on. With that level of carbon in the atmosphere and that level of heat already in the oceans, and no way to take it out, it is only a question of time before that heat inevitably and inexorably melts the tundra and the Greenland and Antarctic icesheets.

Without drastic action, the oceans will rise by several metres. Even with it, it may be too late. But we should at least try.

The trivial arguments over the marginal effects on the economy that might come with mandated carbon reduction are like kids on the beach arguing over a sandcastle, while the tide sweeps in to destroy the lot.