I agree that 10 billion is too many people.
A nuclear war would change population more than any war in history, but conventional wars don't tend to reduce world population by much. WW II was the bloodiest war in history, but it was just a small hiccup in world population growth. The post war baby boom erased the losses and then some in almost no time. World population growth was so strong that the totals for the world grew until 1943 or 1944 and only had a slight dip back to early 1940s levels in late 1945.
War can be very devastating to individual regions' populations. The western USSR took staggering losses in the war and so did Poland. Germany didn't fare very well either.
Disease thins the population much more thoroughly than war does. Probably because disease hits women just as hard as men and even in modern conventional war, men tend to die in larger numbers than women (though civilian casualties can be a lot higher).
Modern medicine may not be able to cure all disease, but it is very effective at containing outbreaks and nursing the sick so secondary infections are less common. The ebola outbreak a couple of years ago got more of a foothold than they usually do because the World Health Organization was in a depleted state and couldn't respond as quickly as they usually do. But even at that once they got going the outbreak was contained and ended in a few months.
Humans are outstripping the world's ability to support us. We have badly over fished and polluted the oceans to a point ecosystems are collapsing. I found an article I read a few years ago that I found terrifying:
The ocean is broken
People in he developed world can beat themselves up about this, but they aren't the major culprits. I heard a story on NPR last week about plastic in the world's oceans. 88-95% of it comes from 10 rivers, 8 of them in Asia and the other two in Africa:
95% of plastic in oceans comes from just ten rivers | Daily Mail Online
Scientists trace path of inland plastic pollution from rivers to ocean
Getting enough to eat in a lot of countries is so difficult, people who have access to the oceans are going out and getting whatever they can. Eating ocean fish is a luxury for people in North America and Europe, but it's a necessity in a lot of parts of the world where there is little else to eat.
Add to this China and India's massive dependence on limited ground water to grow food and you have a ticking food time bomb.
If food production collapses in some parts of the world, everyone will feel it. China will have to buy a lot of its food and that would probably mean higher prices in North America, but probably not much of a caloric reduction for most. It would be felt hardest in Asia and Africa.
Than as the populations starve on levels never seen before, the weakened population will be hit with some kind of disease outbreak. It could be something basic and easily treated in the developed world like the common flu, but with a large, concentrated population already weakened by starvation, it could cut through the population like a buzz saw.
There may be some regional wars over resources, but there will be large regions of haves and large regions of have nots and the have nots will largely have to travel long distances to get to the have regions. It means pressure on Europe's borders, but most of the other regions with enough food will also have the benefit of being mostly if not completely surrounded by large oceans like Australia/NZ and North America.
There would be little point for a starving country in Asia or Africa to go to war with their neighbor because their neighbor is probably staving too.
There has been a lot of hand wringing about CO2 in the atmosphere and what impact that may have on the climate, but I see lack of fresh water and damage to the oceans as far worse. Geologically, we are in a very cold period right now. World temps are warmer now than during the last glacial period, but we are in a small window of reduced ice in the middle of an ice age. For most of Earth's history CO2 levels and world temperatures have been much higher than they are now. Only a few million years ago the Caribbean extended up to Montana. Montana has a lot of coal because of the forests on the edge of the sea that were buried over millions and millions of years.
Rising sea levels would be bad short term for coastal cities and it would be a disaster, but compared to the oceans dying or a continent with more than 1/4 the world's population not being able to feed itself, it's a speed bump.
The biggest problems in the world right now are due to overpopulation stripping the resources of the planet too quickly, but nobody wants to address them because the only short term solutions are horrific.
A nuclear war would change population more than any war in history, but conventional wars don't tend to reduce world population by much. WW II was the bloodiest war in history, but it was just a small hiccup in world population growth. The post war baby boom erased the losses and then some in almost no time. World population growth was so strong that the totals for the world grew until 1943 or 1944 and only had a slight dip back to early 1940s levels in late 1945.
War can be very devastating to individual regions' populations. The western USSR took staggering losses in the war and so did Poland. Germany didn't fare very well either.
Disease thins the population much more thoroughly than war does. Probably because disease hits women just as hard as men and even in modern conventional war, men tend to die in larger numbers than women (though civilian casualties can be a lot higher).
Modern medicine may not be able to cure all disease, but it is very effective at containing outbreaks and nursing the sick so secondary infections are less common. The ebola outbreak a couple of years ago got more of a foothold than they usually do because the World Health Organization was in a depleted state and couldn't respond as quickly as they usually do. But even at that once they got going the outbreak was contained and ended in a few months.
Humans are outstripping the world's ability to support us. We have badly over fished and polluted the oceans to a point ecosystems are collapsing. I found an article I read a few years ago that I found terrifying:
The ocean is broken
People in he developed world can beat themselves up about this, but they aren't the major culprits. I heard a story on NPR last week about plastic in the world's oceans. 88-95% of it comes from 10 rivers, 8 of them in Asia and the other two in Africa:
95% of plastic in oceans comes from just ten rivers | Daily Mail Online
Scientists trace path of inland plastic pollution from rivers to ocean
Getting enough to eat in a lot of countries is so difficult, people who have access to the oceans are going out and getting whatever they can. Eating ocean fish is a luxury for people in North America and Europe, but it's a necessity in a lot of parts of the world where there is little else to eat.
Add to this China and India's massive dependence on limited ground water to grow food and you have a ticking food time bomb.
If food production collapses in some parts of the world, everyone will feel it. China will have to buy a lot of its food and that would probably mean higher prices in North America, but probably not much of a caloric reduction for most. It would be felt hardest in Asia and Africa.
Than as the populations starve on levels never seen before, the weakened population will be hit with some kind of disease outbreak. It could be something basic and easily treated in the developed world like the common flu, but with a large, concentrated population already weakened by starvation, it could cut through the population like a buzz saw.
There may be some regional wars over resources, but there will be large regions of haves and large regions of have nots and the have nots will largely have to travel long distances to get to the have regions. It means pressure on Europe's borders, but most of the other regions with enough food will also have the benefit of being mostly if not completely surrounded by large oceans like Australia/NZ and North America.
There would be little point for a starving country in Asia or Africa to go to war with their neighbor because their neighbor is probably staving too.
There has been a lot of hand wringing about CO2 in the atmosphere and what impact that may have on the climate, but I see lack of fresh water and damage to the oceans as far worse. Geologically, we are in a very cold period right now. World temps are warmer now than during the last glacial period, but we are in a small window of reduced ice in the middle of an ice age. For most of Earth's history CO2 levels and world temperatures have been much higher than they are now. Only a few million years ago the Caribbean extended up to Montana. Montana has a lot of coal because of the forests on the edge of the sea that were buried over millions and millions of years.
Rising sea levels would be bad short term for coastal cities and it would be a disaster, but compared to the oceans dying or a continent with more than 1/4 the world's population not being able to feed itself, it's a speed bump.
The biggest problems in the world right now are due to overpopulation stripping the resources of the planet too quickly, but nobody wants to address them because the only short term solutions are horrific.