Can we really avoid the ‘train crash’?

The idea that humanity will not prevent the approaching disaster is beyond belief!

One of the results of all you great people signing up to follow Learning from Dogs is that it encourages me to share things that strike me as so, so important.

Another of the results in there being, as of today, 3,349 following this place, is that I get the sense of what many of you good people also feel is important. Ergo, it is clear to me, clear beyond doubt, that caring and loving a dog or two makes you a person who cares and loves passionately this beautiful planet that is our home.

The emotion that is spilling out of me via these words to you is a result of having just read an essay published recently on The Conversation site and shared with you today.

Directly, it has nothing to do with our dear dogs. Yet, in a way, it does!


7.5 billion and counting: How many humans can the Earth support?

By Associate Professor of Mathematics, College of the Holy Cross, July 9th 2018.

Humans are the most populous large mammal on Earth today, and probably in all of geological history. This World Population Day, humans number in the vicinity of 7.5 to 7.6 billion individuals.

Can the Earth support this many people indefinitely? What will happen if we do nothing to manage future population growth and total resource use? These complex questions are ecological, political, ethical – and urgent. Simple mathematics shows why, shedding light on our species’ ecological footprint.

The mathematics of population growth

In an environment with unlimited natural resources, population size grows exponentially. One characteristic feature of exponential growth is the time a population takes to double in size.

Exponential growth of world population

It took 127 years for the world population to double from one billion to two. By contrast, it took only 47 years, from 1927 to 1974, to double from two billion to four. Since 1960, world population has grown by about one billion every 13 years. Each point represents an additional one billion people.

[Ed: Text taken from a chart displayed in the article.]

Exponential growth tends to start slowly, sneaking up before ballooning in just a few doublings.

To illustrate, suppose Jeff Bezos agreed to give you one penny on Jan. 1, 2019, two pennies on Feb. 1, four on March 1, and so forth, with the payment doubling each month. How long would his $100 billion fortune uphold the contract? Take a moment to ponder and guess.

After one year, or 12 payments, your total contract receipts come to US$40.95, equivalent to a night at the movies. After two years, $167,772.15 – substantial, but paltry to a billionaire. After three years, $687,194,767.35, or about one week of Bezos’ 2017 income.

The 43rd payment, on July 1, 2022, just short of $88 billion and equal to all the preceding payments together (plus one penny), breaks the bank.

Real population growth

For real populations, doubling time is not constant. Humans reached 1 billion around 1800, a doubling time of about 300 years; 2 billion in 1927, a doubling time of 127 years; and 4 billion in 1974, a doubling time of 47 years.

On the other hand, world numbers are projected to reach 8 billion around 2023, a doubling time of 49 years, and barring the unforeseen, expected to level off around 10 to 12 billion by 2100.

This anticipated leveling off signals a harsh biological reality: Human population is being curtailed by the Earth’s carrying capacity, the population at which premature death by starvation and disease balances the birth rate.

World population projections

In 2020, the UN predicts that there will be 7,795,482 people worldwide.

[Ed: Text taken from a chart displayed in the article.]

Ecological implications

Humans are consuming and polluting resources – aquifers and ice caps, fertile soil, forests, fisheries and oceans – accumulated over geological time, tens of thousands of years, or longer.

Wealthy countries consume out of proportion to their populations. As a fiscal analogy, we live as if our savings account balance were steady income.

According to the Worldwatch Institute, an environmental think tank, the Earth has 1.9 hectares of land per person for growing food and textiles for clothing, supplying wood and absorbing waste. The average American uses about 9.7 hectares.

These data alone suggest the Earth can support at most one-fifth of the present population, 1.5 billion people, at an American standard of living.

A man works recycling plastic bottles outside Hanoi, Vietnam. REUTERS/Kham

Water is vital. Biologically, an adult human needs less than 1 gallon of water daily. In 2010, the U.S. used 355 billion gallons of freshwater, over 1,000 gallons (4,000 liters) per person per day. Half was used to generate electricity, one-third for irrigation, and roughly one-tenth for household use: flushing toilets, washing clothes and dishes, and watering lawns.

If 7.5 billion people consumed water at American levels, world usage would top 10,000 cubic kilometers per year. Total world supply – freshwater lakes and rivers – is about 91,000 cubic kilometers.

World Health Organization figures show 2.1 billion people lack ready access to safe drinking water, and 4.5 billion lack managed sanitation. Even in industrialized countries, water sources can be contaminated with pathogens, fertilizer and insecticide runoff, heavy metals and fracking effluent.

Freedom to choose

Though the detailed future of the human species is impossible to predict, basic facts are certain. Water and food are immediate human necessities. Doubling food production would defer the problems of present-day birth rates by at most a few decades. The Earth supports industrialized standards of living only because we are drawing down the “savings account” of non-renewable resources, including fertile topsoil, drinkable water, forests, fisheries and petroleum.

The drive to reproduce is among the strongest desires, both for couples and for societies. How will humans reshape one of our most cherished expectations – “Be fruitful and multiply” – in the span of one generation? What will happen if present-day birth rates continue?

Population stays constant when couples have about two children who survive to reproductive age. In some parts of the developing world today, couples average three to six children.

We cannot wish natural resources into existence. Couples, however, have the freedom to choose how many children to have. Improvements in women’s rights, education and self-determination generally lead to lower birth rates.

As a mathematician, I believe reducing birth rates substantially is our best prospect for raising global standards of living. As a citizen, I believe nudging human behavior, by encouraging smaller families, is our most humane hope.


This essay from Professor Hwang is one of those articles that one frequently sees online that comes across as really interesting but, in the end, only gets a skim read; at best.

So if you didn’t fully comprehend what the good Professor included then ‘Stop‘ and go back and read it all very carefully.

Don’t just be alarmed at Professor Hwang writing:

This anticipated leveling off signals a harsh biological reality: Human population is being curtailed by the Earth’s carrying capacity, the population at which premature death by starvation and disease balances the birth rate.


Though the detailed future of the human species is impossible to predict, basic facts are certain. Water and food are immediate human necessities. Doubling food production would defer the problems of present-day birth rates by at most a few decades. The Earth supports industrialized standards of living only because we are drawing down the “savings account” of non-renewable resources, including fertile topsoil, drinkable water, forests, fisheries and petroleum.

Be concerned that each and every one of us, as in you and me, can only prevent the train crash by making a change in how we live: Today!

Otherwise ….

In so many ways we are such a clever and inventive race, capable of exploring the farthest reaches of outer space and the innermost aspects of quantum mechanics. Surely we must learn to live sustainably on beautiful Planet Earth!

38 thoughts on “Can we really avoid the ‘train crash’?

  1. Great article. I think if we move to a whole food plant based diet, even the way we grow crops could change. It would take some innovation to keep growing mediums organic, self supporting and full of microbial activity, but we could eliminate pest activity by growing under cover in high rise green houses where water could be filtered from the top, down each layer below and collected at the bottom, filtered through cleansing reed beds (possibly outside the complex), through rocks, where it could demineralize and be collected for renewing the process. Of course a natural, clean water source must also be available, but the wastage from run off and evaporation would be curtailed. This is not a far off dream, but one that can be implemented, even in the driest parts of the planet today. Solar generation can supplement sunshine, and waste gases can be used to generate electricity. There is no reason that this cannot happen now. Instead, our governments put aside more and more tax money for the war machine and weapons of mass destruction. This is one of the reasons that I have become apolitical – even anarchistic, if you like. I see the reduction of population coming at the end of a firearm, perpetrated by the rich and the powerful. Where is Avalon?


    1. John, I have said this before, in an earlier reply to your goodself if I recall, that while my heart hopes you are wrong, my head fears you are right! My hopes are built on the extraordinary power of so many ordinary folk using this 21st Century digital world to make their voices heard!


  2. Great post Paul. I think religion holds the keys to our human fate. As long as most of the world is competing for members by fertility rates we are doomed. Also, this belief that someone is going to come down from heaven and fix everything has been in its “last generation” phase for 2000 years. Nobody is coming to fix this. It’s up to us and as long as the churches control societies with this attitude, our only hope would be massive natural disaster, war, and near global famine for a serious reboot.


    1. Jim, I am aware of that old saying about prediction being the worst form of forecasting! I say that in the sense of thinking that if we look back at the present times, say in 2030, we will be aware of sociatal changes that just could not have been anticipated. It most certainly is up to us but one does wonder about the ‘fickle finger of fate’!

      Lovely to hear from you and thanks for your ideas.

      Liked by 1 person

  3. Population stays constant when couples have about two children who survive to reproductive age.

    I don’t profess to be a mathematician, but this cannot be right. First there are two. They have two children: that’s four. When the two children achieve reproductive age they will probably, between them, generate another two children. That makes six. It depends what the lifespan of an individual in the population is, but this does not represent a static population, by any means; it’s a growing one.

    Coincidentally, this week I posted a short video that may be of interest.

    Can we avoid the train crash? No, we can’t, because the only thing supporting this quantity of human animals on this planet is oil. And at the rate we’re using that up, that will be gone, all too soon.


      1. I don’t think so. Because for every two adults that have two offspring those adults will eventually die. Even if life expectancy is increasing this will only cause a small blip upwards, eventually reversed, in that constant population.

        Indeed, my sense is that just having two children causes a slow decline in population owing to a small percentage of those children dying from disease or accidents before they are sufficiently old to procreate.

        Liked by 1 person

    1. Thank you! Trust me, I am as surprised as anyone that so many choose to follow my doggie ramblings! Regarding your wonderings, all you, and all of us, can do is to set an example to others.

      Liked by 1 person

  4. A great article. Thank you Paul.
    Accompanying human overpopulation, the problem of over-consumption (and its associated waste problems), is putting tremendous strain on the environment in every corner of the globe.
    Given the problems of climate change, soil depletion, loss of biodiversity (including declining bee and insect populations), loss of fisheries, ocean acidification and declining fresh water resources, the ability of our planet to sustain present levels of population and consumption for the foreseeable future is seriously in doubt.
    And then there is the question of energy.
    Current levels of world population, food production and modern civilisation generally, are highly dependent on fossil fuels, especially oil. Despite steadily increasing growth rates, renewable energy still represents only a small fraction of today’s global energy consumption and it is highly doubtful if its production can be ramped up in time to avoid a crash of our current economic system.
    This interesting article discusses a 21st century population crash from the perspective of oil supplies.


    1. What a great article, Margaret. That ZDNet one. It does seem that many different and disconnected viewpoints come together to suggest (predict?) that a world population crash is inevitable. I really hope I can retain sufficient ‘marbles’ for, say, another 10 years because it really feels that we are in those border lands!


  5. I remember reading somewhere in the past Paul that one day we would all live under domes.. We certainly need to wake up to the facts that if we continue upon the course we are on, then sustainability will diminish. We really should be looking at Water, and pollution and seeing just how the Cowspiricy is having its effect upon the environment. But lets not forget that science has also been tampering with the climate in Geoengineering and weather control is a fact not fiction..
    I am also aware of how we each play our parts no matter how small..
    For the first time in years we have gone six weeks here without rain.. We now have a pending water pipe ban.. Not that we use one, we have to use watering cans to carry water to water our allotments crops Hubby carries he calculated 60 gallons every morning in two 2gallon watering cans.. up and down the plot..

    We also have to look at Food Waste and the amount that never reach the supermarkets because it deemed not the certain size or funny shape.. Farmers plough back thousands of tons of food, not to mention the supermarket sell by date waste..
    We ALL have to alter our ways and habits as consumers, we have been brought up in a throw away society.. What we have to understand if we do not wake up and alter our ways, we are literally throwing away our future.

    But I do feel Paul that before we get to overload in people, the world is already falling apart at the seams.. The train crash is coming, but not as many think..

    Love and Blessings, and you knew I would have something to say lol when I read this.. A great share by the way.


      1. HI Paul.. just about to call it a night after my hour on here this evening, and so pleased to see your replies before Log out.. And the pleasure is all ours who visit here Paul.. 🙂


    1. Yes Sue, As you say, we have no choice – we must alter our ways.
      Australian academic Ted Trainer’s ‘Simpler Way’ and how it could save us. ( Maybe…..?)
      If we are to survive, our future homes and gardens may have to be along these lines –

      Liked by 1 person

      1. Hi Marg, thank you kindly for these links, I visited and read them before answering, And yes Sustainability in growing our own food and living a more simple way of life is what we ALL should be thinking of.. Instead most have been so brain-washed into their ‘Devices’ of one sort or another that they have no concept than in an emergency the supermarket shelves would empty in a matter of hours.
        Growing our own is a start and we have been doing that for years, Though I have not gone as far as grinding my own flour.. 🙂 These are the people who Would survive if needed, all depending on what kind of Crisis we are heading for both Politically or Universally!.. As we are witnessing radical climate change and weather extremes.
        But as consumers its no good us moaning about waste when we still support it via our contributing to it by buying it. Its all a case of supply and demand.. When we no long demand it then it will no longer need be supplied..
        We many not make huge dents into making change happen, But all change has to start with ourselves, to alter our ways of being, our thoughts, our actions etc..
        Many thanks for picking up my comment here on Pauls Blog, and for taking the time and effort to forward these links..
        I hope others who read here also click them to read.
        In the mean time I will leave you with a quote which has always resonated with me..

        Many thanks 🙂


      2. Thanks for your feedback Sue. Agree with you wholeheartedly. Despite being lucky enough to live in a relatively underpopulated part of the world, I am still somewhat of a pessimist when it comes to the future well being of humankind generally as well as that of the non human life on our planet. Nevertheless, I am inspired by the many individuals and groups around the world actively seeking to lessen their impact on the environment and to build resilient localised sustainable communities, (such as the Transition Town movement).
        On the subject of inspiration – Thanks also for that wonderful quotation by Confucius. It says it all really. – Margaret

        Liked by 1 person

      3. Thank you Margaret. People are waking up, all be it slowly.. And it is inspiring to know many think as we do.. We will keep on keeping on.. And thank YOU. 🙂


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