I find it fascinating that most plague outbreaks seem to have taken down double digit percents of the populations. That's just wild. If 50% of humanity got wiped out suddenly by a pandemic I can't begin to imagine what the consequences would be.
I'm unsure about the time scale in question, but something of this magnitude occurred to the indigenous populations of North and Central Americas, with the introduction of urban diseases (smallpox, influenza, chicken pox, bubonic plague, etc.) from Western Europe that they had no prior exposure to.
If you narrow the geographic scope and widen the temporal scope, the tolls were much higher than 50%.
The consequences are difficult to de-correlate from the other effects of colonization, but no it wasn't pretty.
Prior to the 20th century, and even in through the first half of same, famine's population reductions frequently ranged from 10% to 90% over fairly wide areas. It's useful to keep this in mind as contrasted to several major famines of the past roughly 50--60 years, including Bangladesh, Ethiopia, Somalia, Rwanda, and the like, which dire as they've been, pale by comparison.
As Communist China's Great Leap Forward and ensuing Great Famine are often mentioned in this context, it's worth noting that a roughly comparable famine had occurred only about 20 years earlier, under the Republic of China, not to mention several similarly-scoped famines in the 19th century. The incidence of famine seems somewhat independent of political structure, and has arguably stopped under Communist Chinese rule. (I draw no causal inference here, just note the fact.)
Ireland saw its population fall by half during the Great Potato Famine of ~1840--1850, through a combination of direct deaths and migration, and only matched its pre-famine population within the past decade. (I've had to consciously note that this fact has changed recently, the fact that the population hadn't recovered was so profound.)
As to impacts: past civilisations were often far less complex and hence less dependent on highly specialised technical skills. We live in a world in which a relatively modest pandemic resulted in global disruptions of trade, commerce, finance, and governance. The global "bus factor" seems to be quite low. In a world in which 90%+ of the population tended farms or herds, and interdependence between towns and villages, let alone nation-states, tended to be fairly low, gave for somewhat greater redundancy. Ironically, the combined impacts of reducing populations (and hence pulling back from the famine frontier itself), as well as increased labour bargaining power and the liberation of property ownership often meant a comparative flourishing of civilisations following a major famine or plague. This is much discussed in the context of Europe's Black Death (25%--50% population reduction over roughly a decade).
Both the Great Famine and the 1942-1943 famines were politically caused, the first by communism and the latter by Japanese invasion.
> a relatively modest pandemic resulted in global disruptions of trade, commerce, finance, and governance
The pandemic didn't result in that directly. It was the political response to it that caused that. Some places just skipped many of the most damaging responses but had identical outcomes. Africa hardly did much and you can't see it in their population figures for example. Also it seems like resilience is remarkably high. Governments went crazy and used enormous force to create as much havoc as possible, yet the core supply chains (food, water, electricity) held up very well especially after people realized how robust it was and the panic buying stopped.
> Both the Great Famine and the 1942-1943 famines were politically caused, the first by communism and the latter by Japanese invasion.
The Great Famine wasn't caused "by communism", it was caused by incompetence. Mao rejected both Western science and the expertise of Chinese farmers which agreed to it, much like the Nazis rejected "Jew science" (which luckily hampered their war effort and prevented them from developing nuclear weapons). He also established a culture of fear that led to bureaucrats lying about their numbers instead of risking admitting failure.
I guess you could say the cause of the Great Famine therefore was bureaucracy, or maybe dogmatism. Neither of which is necessary, nor sufficient, for communism[0].
[0]: ... even without getting into the distinction between what governments have justified with the excuse that they want to achieve communism and what communism itself would look like. No so-called communist government I'm aware of has ever claimed to have achieved communism. Even Soviet-era Eastern Europe at best claimed to have achieved "real socialism" when they pretty much admitted giving up on communism by calling anyone expecting more of them "utopianist".
When the black death hit Norway in 1349, 2/3 of the population was wiped out. The whole structure of society broke down. Most of the state and church was just gone. It took 300 years to get everything back in operation because most people that could read and write had died.
I don't know how you define "long term", but for several generations society didn't work, there were no justice and people really suffered.
Think about how many highly specialized jobs are needed to run modern-day society. Think about how much of the required knowledge and skill to do those jobs would be lost, not to mention available person-hours. We could be set back a century or more, but without the cheap and plentiful natural resources that got us to where we are today.
