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Thread: The Carrying Capacity of Humanity

  1. #1 The Carrying Capacity of Humanity 
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    Years ago in Ecology I learned about carrying capacities. Here's an example of what a typical graph of a population reaching its carrying capacity looks like:



    Humanity is what is in what is called a period of exponential growth. This is the long period toward the beginning of the graph where there's a long upward slant. The carrying capacity (K) is where the populations growth becomes limited by available resources. Coming off of a period of exponential growth, there is typically an overshoot. After reaching the carrying capacity, the population fluctuates around the carrying capacity and is maintained by things such as starvation.

    The carrying capacity is not a constant. It can be effected by various things, such as depletion of a nonrenewable resource. In humanity's case, we have a triple threat: rapid population growth, overfishing of the oceans, and a finite amount of oil threatening our ability to transport food. This leads me to believe we are heading full speed toward a "Great Starvation". The big question is, "When?". It's difficult to estimate because advances in technology, like more fuel efficient vehicles for example, keep pushing the carrying capacity a little further forward in time. Still, we should be able to figure out a rough estimate.

    While we're on the subject, try to imagine what life will be like when we reach our carrying capacity. Will bodies in the streets be common place? Which nations will be affected the most? Will there be riots that topple governments? Will the developed world return to an agricultural society?


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    Human population is no longer growing exponentially but instead starting to resemble logistic curve, with every developed nation and most developing already growing as much reduced rates compared to the past.
    The UN projection is below:


    In humanity's case, we have a triple threat: rapid population growth, overfishing of the oceans, and a finite amount of oil threatening our ability to transport food.

    While these are valid concerns, they aren't serious limitations, given only a small % of food comes from the oceans and we can easily replace oil based fuels with methane and other gases which can be produced as well as virtually unlimited supply. It also ignores the huge improvement potential in agriculture from GMOs.

    Figuring out K has always been and will probably continue to be a moving target for humans. At this point don't think it's a matter of capacity as it is the quality of life for most people and other species-- something like a choice between 30 billion miserable people in the middle of the worst mass extinction event on the planet, or one of less than 10 billion with rich natural diversity and free long-lived happy peoples.


    Last edited by Lynx_Fox; May 27th, 2014 at 10:20 PM.
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    Quote Originally Posted by Lynx_Fox View Post
    Human population is no longer growing exponentially but instead starting to resemble logistic curve, with every developed nation and most developing already growing as much reduced rates compared to the past.
    I don't think that's right. Here's a graph of population growth of the world between 2004 and 2013 from worldbank.org. There's no indication that human population growth is starting to resemble a logistic curve on a global scale.
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    Quote Originally Posted by Chimoshi View Post
    Quote Originally Posted by Lynx_Fox View Post
    Human population is no longer growing exponentially but instead starting to resemble logistic curve, with every developed nation and most developing already growing as much reduced rates compared to the past.
    I don't think that's right. Here's a graph of population growth of the world between 2004 and 2013 from worldbank.org. There's no indication that human population growth is starting to resemble a logistic curve on a global scale.
    You aren't going to see much from a half a generation change. If you look at longer periods, fertility and projections human populations are clearly leveling off.

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    We have known we were reproducing ourselves into a untenable place since the 1950's. The "big death" is already starting. All governments will of course try to down play the issue, while at the same time trying to protect their nations from its effects. The societal answer to scarcity of resources will be the same one it has always been. " Division of labor", some people will do the starving and dieing for the whole of society. Society as a whole will keep on functioning fairly well because an underclass will not do well at all.
    The above is why political efforts to limit or outlaw abortion and birthcontrol are doomed. They are counter to the needs of society.
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  7. #6  
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    Quote Originally Posted by Sealeaf View Post
    We have known we were reproducing ourselves into a untenable place since the 1950's. The "big death" is already starting. All governments will of course try to down play the issue, while at the same time trying to protect their nations from its effects. The societal answer to scarcity of resources will be the same one it has always been. " Division of labor", some people will do the starving and dieing for the whole of society. Society as a whole will keep on functioning fairly well because an underclass will not do well at all.
    The above is why political efforts to limit or outlaw abortion and birthcontrol are doomed. They are counter to the needs of society.
    No. Lynx is quite right. All the forecasts show a plateau being reached, as the standard of living rises in more and more countries. In most developed countries the population is barely growing at all and in some cases declining. This effect will spread to more and more of the world. That is not to say there won't be challenges in feeding everyone at the plateau level, but hysterical talk of mass starvation and an attempt to create a class issue out of this imaginary crisis are both misplaced reactions.
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    may i throw a spanner in the works here ?

    it is clear to me that humans are already way above the carrying capacity for a mammal of our size - the only thing that keeps us afloat is our use of technology

    the moment technology can no longer keep us afloat (say because of a shortage of critical resources, but it could be anything that interferes with our ability to make use of advanced technology and maintain a global village) we're up shit creek
    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
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    There is nothing new there. Humans have depended utterly on technology since before we were Homo sapiens. From the days that someone tied a chipped stone head to a spear, we needed our technology, and would die without it. Our technology replaces sharp teeth, claws, long legs, horns, running legs etc. And the technology keeps growing. At no time in human history has there been a time when technology got less. Always it gets more sophisticated, and the rate of growth today is so fast as to be utterly unprecedented.

    The carrying capacity of the world for a human population is not fixed. It is a variable. And the primary factor determining the value of that variable is technology. Since technology is growing so quickly, we can say that the carrying capacity of the world also grows.

    If you study the United Nations web site on population information (United Nations Population Information Network (POPIN)), you will find that human fertility has dropped. From 5.5 children per woman about 50 years ago, it is now 2.4, and continues to drop, to a predicted 2.0 by 2050. This is less than replacement. However, there is another trend that is keeping population numbers up. That is the trend to increasing life span. Today, average global life span is just under 70 years. 100 years ago, it was about 30. Despite some set backs (like global obesity), average lifespan continues to grow, and is growing more rapidly in developing nations.

    The population, taking into account both trends, will not level out or start to drop till about 2100. Maximum population size should be 9 to 10 billion, with a variation possible in this of 6 to 16 billion, by the year 2100. If you are interested in population trends, the great expert is Prof. Hans Rosling, who has several lectures on the subject on the TED talks web site.

    The carrying capacity of the world, with advanced technology, will be way, way higher than the maximum the human population is predicted to get to.
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    Quote Originally Posted by skeptic View Post
    Marnix

    There is nothing new there. Humans have depended utterly on technology since before we were Homo sapiens. From the days that someone tied a chipped stone head to a spear, we needed our technology, and would die without it. Our technology replaces sharp teeth, claws, long legs, horns, running legs etc. And the technology keeps growing. At no time in human history has there been a time when technology got less. Always it gets more sophisticated, and the rate of growth today is so fast as to be utterly unprecedented.
    indeed, and it's the sophistication that unnerves me + how easy it could break down under certain circumstances
    the more sophisticated our technology, the harder the drop should it fail us
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  11. #10  
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    You are a guy with a reasonably good grasp of principles of evology. You will be well aware of the fact that greater biodiversity brings greater stability to ecosystems. I cannot prove this, but I think the same principle will apply to the "human ecosystem". That is, the more diverse the economic systems operating within that ecosystem, the more stable it becomes. Greater technology brings greater diversity, and hence greater stability.

    We have also achieved a greater social stability. By this, I am comparing today to a few hundred years ago, when small states would go to war with each other at the drop of a hat, and the country you are most likely to be at war with is the one next door. War with other nations is now rare. Civil wars are far more common, but not in developed nations. But there is little chance that any particular society is going to be turned upside down by sending its young men off to wear.
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    oh, it doesn't have to be war that brings us down

    it could be something as trivial as a major pandemic, a meteor strike or methane hydrates causing a Permian-style global extinction
    my argument is that once the number of people has been cut drastically, we might no longer have the natural resources in the abundance from when we got the industrial revolution going + we may have lost the knowledge to access more novel + sophisticated material and energy sources, thereby making it harder to recover from a population crash
    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
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    Let's try not to be hysterical. When I talk about a "big Death" i'm talking maybe as high as 10 to 20 percent. That still leaves a whole lot of people. 7,000,000,000-700,000,000=630,000,000. The ecconmy will not collapse for lack of workers.
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    normally a population crash due to overreach beyond the carrying capacity tends to be far more severe than 10%
    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
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    To marnix

    Such a crash seems very unlikely. The population is unlikely to get above 10 billion (or not much above) and the world can easily support that number, and more besides. The current trend is the opposite, with longevity increasing substantially. Fifty years ago, the developing world had a lifespan average of no more than 30 years. Today it is 69, and it is growing at a rapid pace. With human health, human welfare, and human longevity growing, along with improved technology, agriculture, and medical care, a population crash is the last thing I would expect.
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    anything that interferes with us using technology to exceed what would be the standard carrying capacity for a large mammal like us carries the potential to cause such a crash
    the probability of the various scenarios through which our current technology could become useless may be low (the most likely ones being a pandemic, stuxnet-type computer viruses, extreme global warming and a misplaced asteroid / comet, in descending order of probability) but if any of them did happen, the likelihood of a crash is rather high
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    My descending order of probability would be different, with global warming at the top. The last pandemic was the Spanish flu almost 100 years ago. World health authorities seems to be getting a pretty good handle on potential pandemics, and nipping them in the bud. While computers are vital, I cannot see a virus causing a major catastrophe. Serious damage yes. The last civilisation destroying asteroid was 65 million years ago, so I assign that a vanishingly small probability.

    Global warming is a slow developer, which gives us time to both carry out mitigating action (I see that Obama has declared an intention to close down coal burning power plants, and the Chinese are now the world leader in wind and solar generation), and also to adapt to changing conditions, like building hurricane proof homes, sea walls, and advanced air conditioning.

    Global catastrophe appears to be quite a way off.
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    I'd probably rate the big risk as follows by likelihood of event

    Highly destructive global warning, and probably mass extinction event on land and sea--likely but with lots of time to mitigate worst effects on humans.
    Global nuclear weapons exchange, unlikely but a huge bugaboo quite possibly related to climate change (as the Pentagon keeps reminding planners and policy makers is the #1 risk to world stability time and time again)
    Coronal mass ejection, unlikely but a complete random event that might well tip the balance against civilization as we know it, and one we aren't putting hardly any energy into address.
    Supervolcano, tiny chance and little chance to be able to do anything about.
    Asteroid or comet event, vanishingly small chance of a global changing event.
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  19. #18  
    Forum Radioactive Isotope skeptic's Avatar
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    Over the last 55 odd years, we have seen many global disasters predicted.
    1. "Silent Spring" and pesticide disaster.
    2. "Population Bomb" and famine disaster.
    3. Nuclear war and nuclear winter.
    4. Ozone depletion.
    5. Y2K
    6. Resource depletion (this one is repeated and recycled time and time again.)
    7. Global climate change.
    Etc.

    With the exception of the last two, which are still running, humanity has managed to avoid all those predicted disasters. We do this with determination and ingenuity. The more time that passes, the more tools we have, and the more powerful those tools become, to solve such problems. This history of solving and managing global problems leaves me an optimist.
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    Quote Originally Posted by skeptic View Post

    At no time in human history has there been a time when technology got less. Always it gets more sophisticated, and the rate of growth today is so fast as to be utterly unprecedented.
    Not true. At the end of every major civilisation, first the egyptian, then babylonian, greek and roman. A major amount of culture, technology and research has been lost. An example is the sphinx. It is older than any pyramid, but we don't know how in that time the technology was available to create a long lasting structure like that. It was lost for hundreds of years, until reinvented by the "new" egyptian culture. Same thing with the creation of paper, and the use of chemicals. Egypt used chemicals in traps or conservation methods, but this whole process was lost up to the end of the roman empire, where they started using it again. Paper was an egyptian invention also, it was budget papyrus. However it was also lost for a few thousand years up to the beginning of the germanian migration.

    Another thing, when you look at technology. Not every improvement makes a technology more sophisticated. Sometimes it takes time for the most efficient way to develop. This could apply to the old chemical determination equipment we have here at the lab. When we compare the older equipment with the new. By regulating more and more with a computer, we don't need a local control, but just a central control unit. In my opinion, using a small central control unit, even though it is technologically superior, is less sophisticated then an endless glass/plastic tubing, sensor and motor maze that is an older machine. More or less an opinion, so i understand if you don't agree.
    Growing up, i marveled at star-trek's science, and ignored the perfect society. Now, i try to ignore their science, and marvel at the society.

    Imagine, being able to create matter out of thin air, and not coming up with using drones for boarding hostile ships. Or using drones to defend your own ship. Heck, using drones to block energy attacks, counterattack or for surveillance. Unless, of course, they are nano-machines in your blood, which is a billion times more complex..
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  21. #20  
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    Often it appears that way. But generally what happens is that technology is scattered rather than lost. A great civilisation, like Rome, may fall, and its technical secrets then are no longer concentrated in one place. The indiviudals holding that knowledge and that skill are spread far and wide. But the centuries that follow the fall will show a 'recovery' of the technology at a speed way beyond that which originally led to the first such discoveries. It is most probale - almost certain - that the technology is not lost, but merely scattered.

    About the only technical secret I know of that was genuinely lost is cement. The ancient Egyptians knew this secret and so did the Romans. So it has been discovered three times. But that is an unusual case. Greek fire is often touted as another, but it has existed continuously in one form or another. We are told the original was extremely potent, but that is just hearsay. It may well be that the variations on the theme were pretty much the same as the original.
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