Always plan for the worst-case hypothesis!
The four horsemen of the apocalypse by Albrecht Durer (1498): famine, plague, war, and death itself. For sure, the ancients understood that collapses come from a combination of several different factors. It is the essence of what I call the "Seneca Effect." Today, if the coronavirus remains isolated as a threat to human life, it won't cause a population decline. But if the other horsemen intervene, then things could change for the worse.
The data about the coronavirus epidemic are starting to look scary. Yes, the Chinese government has taken draconian measures. And it is also true that the spreading of the infection in China is slowing down. So, if nothing unexpected happens, it is likely that the epidemy will be contained. But, as we all know, the real world always has ways to surprise us. So, let's drop for a while the "likely" adjective and ask the uncomfortable question: what is the worst that can happen? Could we see a serious collapse of the world's population?
As usual, if we want to understand the future, we need first to understand the past. So, let's look at some data for the greatest pandemics of the past, those that swept Europe during the Middle Ages and afterward:
European Population in history (from Langer, W. L. The Black Death. Sci. Am. 210, 114–121 (1964))
These data are somewhat uncertain, but there is a general agreement that the great plague of the 14th century (correctly termed "Black Death") wiped out about 40% of the European population, some say more than that. As worst cases go, this is surely one.
Could a new plague do the same to us? Why not? If it happened in the past, it could happen again. But, of course, it can happen only if similar conditions will occur. If we examine the case of the European plagues in detail, we see that they never struck at random times, they struck already troubled populations. Viruses and bacteria are opportunistic creatures that tend to expand when they find a weak target.
In the case of the 14th century Black Death, it hit Europe after the failure of the attempt to expand to the East with the crusades. Europe found itself overpopulated, in the midst of a social and cultural crisis, and with no way out. The result was a series of famines, internecine wars, and social and political turmoil that opened the door for the plague to strike. Something similar happened with the second main plague burst of the 17th century. It arrived after the 30-years war had destroyed the very fabric of European society, creating poverty, famines, and the displacement of entire populations.
The rule that pandemics come with famines holds also for the last (so far) great world pandemic: the Spanish flu of 1918-1920. It was associated with the extensive famines generated by the first world war. Unlike the case of the Black Death, though, the Spanish flu struck against a background of economic expansion and population growth. By all means, it was a disaster: it may have killed about 1-2% of the world population of the time (that is 20-50 million victims out of a population of about 2 billion). But it barely caused a dent in the population growth curves of the 20th century. Other modern epidemics, AIDS, Ebola, SARS, etc., either do not exist in the West or, as in the case of AIDS, are expanding only in poor countries suffering from lack of food and poor health care systems (again, so far).
Conversely, famines can cause extensive depopulation even when not associated with plagues. A good example is the Irish famine of 1848. It wiped out about half of the Irish population in a few years, but it was not associated with a specific human disease. Sometimes, you don't even need famines to cause depopulation: social and economic stress is enough. A good example in modern times is that of Ukraine, where the population started declining in the early 1990s and it is still declining after the loss of some 20% of the total. There were no epidemics nor famines involved: the Ukrainians died as the result of a combination of poor quality food, lack of health care facilities, bad government, depression, heavy drugs, alcohol, and more.
There is a general rule, here: disasters never come alone (when sorrows come, they come not single spies, but in battalions). It is because when a complex system is in overshoot, it is fragile: it is sensible to even minor perturbations from the outside. These perturbations tend to generate a cascade of failures that brings the whole system down. It is the essence of what I call the "Seneca Effect" stating that growth is slow, but decline is rapid.
Coming back to the coronavirus of today, we can conclude that it won't cause great disasters as long as it remains alone in attacking humankind. The world is not seeing large wars and it is not suffering from major famines. So, even if the virus were to spread outside China, maybe it could kill 1% of the current population. That would be a terrible disaster, of course, but it wouldn't change the growth trajectory of the world population, just like the Spanish flu didn't.
Yes, but, as I said at the beginning, reality has plenty of ways to surprise you. Maybe you don't need major famines or wars for a population to be weakened enough to be a good target for a viral attack.
Think of pollution: in large part, it is a modern phenomenon. At the time of the Spanish flu, people were hungry, but not carrying in their bodies the amounts of heavy metals, pesticides, chemicals, microplastics, and other weird stuff we all have nowadays. And they didn't live in a hot world with 410 ppm of carbon dioxide in the atmosphere, as we do. To say nothing about the rapid decline of the health care services, the poor quality of the average diet, the spread of alcohol and heavy drugs, the health effects of depression, the damage done by bad governments, and don't forget the risk of being shot.
As a result, the population of many Western countries seems to have started to move along the same trajectory that the Ukrainian population started to follow 30 years ago. Life expectancy has been declining in the West starting with 2014.
Life expectancy in selected Western countries. Data from World Bank
In addition to the already weakened population, there is another factor that may favor the plague horseman: the economic crisis that's being created by the fear of the virus. Don't forget that if nearly 8 billion people can survive in the world today, it is because they can purchase food and have it delivered to them by means of that stupendous commercial system that we call "globalization" and its container ships crisscrossing the oceans. But if people stop moving and goods stop being transported, then food will stop being shipped to the places where it is needed. As a result, one more of the four horsemen, famine, will start galloping. And the third horseman, war, may decide to start galloping too, taking with him the last one, death. Then, yes, we could see a new Black Death.
Don't forget that this is a scenario: a story that we are telling to each other. It is up to us to make sure that it remains a story and it doesn't become reality. The future is never predictable, we can only be prepared for it.
A comment by Ugo Bardi's personal troll, Mr. Kunning-Druger
"And here you are, Mr. Bardi. I knew you would have arrived to this: I figure that you and your friends of the Club of Rome must be very happy, now. Isn't the coronavirus exactly what you always wanted? From the very beginning, the Club of Rome has been working at planning the extermination of most of humankind. And now the flag of the enemies of humankind has been taken by the little monster called Greta Thunberg. But we know who you are and we know what you are doing. If your plan ever becomes reality, we'll know who are the criminals behind it."
