In my musings, I'm building a world where most of the human population has been wiped out by a currently unnamed biological warfare element.

I've been wondering about what a society that lost 70 to 80 percent of its population would look like.

I'm not asking about:

  • How the society would function
  • Follow on consequences
  • How people would behave
  • Governance

Assuming the same distribution of people in the world as there are today and given that the impacts were spread evenly on a global scale over the course of 3 months, I am trying to understand how the world changes based on the human population:

  • How common/uncommon it would be for people to run into each other?
  • How would population densities change?
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    $\begingroup$ What does "aesthetically" mean as opposed to "how would it function"? $\endgroup$ – djechlin Jun 28 '16 at 21:28
  • $\begingroup$ I'm not sure what you're asking. Are you referring to an even distribution of population loss, or is there favoritism? What do you mean when you say you want to know about the "aesthetics"? $\endgroup$ – Frostfyre Jun 29 '16 at 0:35
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    $\begingroup$ All significant international shipping currently relies on operational satellite/GPS technology. If institutions such as NASA can't be effective, catastrophic results follow. Most/all industrialized nations would lose electric generation capability within perhaps a year as necessary imports of rare-earth metals ceased (no possibility of manufacturing all of the needed repair parts for the high-energy generators, etc.) Each tiny failure would cascade, and repair personnel are likewise less available. Those not killed by bio-warfare would mostly die soon after. $\endgroup$ – user2338816 Jun 29 '16 at 6:31
  • $\begingroup$ I'm not particularly asking about how the society would develop and function, but rather what it would truly look like in comparison to now. It's a question of how dense or not dense with people the world would look with only the remaining population. I'm not totally sure how else to phrase it, but if you have any suggestions I would be open to them. $\endgroup$ – Terri Davis Jun 29 '16 at 10:13
  • $\begingroup$ I think you answer your own question really. If you are asking how common it is to see people and what population density would look like...well then population densities would 70-80% lower and you would be 70-80% less likely to see people while out and about. $\endgroup$ – James Jun 29 '16 at 15:35

One interesting thing to look at, even if only 50% of the world's population dies, you're looking at some 3.7 billion bodies. The average human weight is about 135 pounds, so the remaining people would have to cope with about 5x10^11 pounds of dead people. That is a lot of bodies that will decay very quickly, especially in the more humid parts of the world.

Dealing with the bodies of the deceased was a huge issue during the Black death in the mid 1300's, and has been a problem whenever massive amounts of people die. In World War 1, people would live in trenches made out of the bodies of the recently killed as there was no point in trying to bury them, and this has been seen in wars and after famines since then. Even with current technologies would be almost unfathomable. Besides burning corpses, huge swaths of land (probably close to cities where populations are the most dense) would have to be devoted to burying, or even just piling bodies. It would be so overwhelming that the efforts to remove this mass of decaying bodies wouldn't be worth it, and much of the 20-50% of surviving people would move far out into the country side where the quantity of dead is more manageable.

On a three month timeline, the areas that the small communities of survivors would be living in now would be focused mainly on getting food and staying alive, as most of modern infrastructure would be gone. Cities would slowly be over run with carnivorous animals and eventually vegetation. Almost certainly some people would remain in the cities, deciding that living with the dead is worth whatever food and shelter remains. It would take decades, even centuries, for anything resembling a recovery.

  • $\begingroup$ "... much of the 20-50% of surviving people would move far out into the country side where the quantity of dead is more manageable." Maybe they already live out in the country side, which is why they survived? More than half of humanity does live in cities, now. $\endgroup$ – CircleSquared Jun 29 '16 at 0:55
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    $\begingroup$ Some major cities would still have populations in the millions even if reduced by 80% $\endgroup$ – Separatrix Jun 29 '16 at 7:08
  • $\begingroup$ Yes, there would still be billions of people on the planet as well, but this doesn't mean that society can still function the same way. My guess is that if you and a few million other people were living in a city surrounded by tens of millions of dead people, you would choose to leave. $\endgroup$ – matt_Vera Jun 29 '16 at 14:55

Well, if you're "only" losing 80% of the population, most cities will still have quite a lot of people.

However, the premise of "same distribution of people in the world as there is now" isn't very plausible. If the die-off was due to biological warfare then the agent was presumably transmissible from person to person, and that would have resulted in a lot of people isolating themselves, either by forting up to keep everyone else away, or trying to go somewhere where there are very few people. So that would move people around.

The other problem is that food production and distribution would be severely affected by losing 70-80% of the population of agricultural areas, so the ability of cities to import food would vanish, and many city-dwellers would have to go and work on the land, or starve. 20% of the population will eat up all the stockpiles with a few months.


Any aesthetic considerations will be heavily dependent on what populations this plague kills most heavily, and will depend even more heavily on what the post plague society looks like.

Your society will be much poorer than we are today, and unless you selectively spare engineers and scientists, it will have a much lower level of technology. This could mean agrarian, or it could mean early industrial.

In both cases, there would probably be a lot of deforestation in places with significant numbers of people as people struggled to grow food locally now that shipping food has become so expensive.

Some cities or parts of cities would revert to farmland or be taken over by wildlife, as would a great deal of suburban land because no one would be able to maintain it if people weren't living there.

If an industrial base remains, it would probably give off much more pollution than is allowed in the US or western Europe. This would result in dead patches of land, and probably dead or very sick rivers where nothing can survive. Look into conditions at and around factories in poorer countries with loose environmental regulations.

  • $\begingroup$ Deforestation seems unlikely. With three or four out of five people gone, the previously used and mostly cleared space will immediately become available. It's difficult to clear even a few square yards of forest. (I do it regularly.) And city space will take perhaps decades at best to be reclaimed. No one will have time to (manually?) tear down steel-framed buildings nor uncover asphalt/concrete covered land, especially if there's little need to do it. $\endgroup$ – user2338816 Jun 29 '16 at 6:17
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    $\begingroup$ A fairly easy, quick, and historically common method to clear forest and create farmable land is: simply set it on fire. Then run away, and come back later to a mostly cleared and bonus: well-fertilized piece of land. $\endgroup$ – Syndic Jun 29 '16 at 12:25
  • $\begingroup$ The densest parts of cities with almost no greenery may take decades. Places where people have patches of yard, or where there are parks and trees will become overgrown faster. Even people's small yards can overshadow their houses within a couple decades. The buildings and much of the pavement will still be present for a while, but that will just provide extra shelter for the animals. $\endgroup$ – Karen Jun 29 '16 at 12:55

If your main concern is about how often people would run into each other, all you have to do is model your world on the real world in the historic time of your choosing, then add in whatever form of transport you want your folks to have. After all, a population of billions is a relatively recent phenomenon. This graph shows the world population since the end of the Ice Age.

So if you want them still to have cars and planes, at worst they'll run into each other as often as modern folk do in, say, rural Australia. If they are back to travelling on foot or in horse-drawn transport, it will be more like the Wild West (pre-railways) or Medieval Britain or the Roman Empire... or whatever historical period you fancy.


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