>What is a sustainable global population? How many people can we sustain?

>”The biggest single challenge facing the Earth…is not global warming. That is a secondary challenge. The primary challenge facing our species is the reproduction of our species itself.”

Boris Johnson, The Telegraph

These are the forecasts for population growth up until 2050. The world’s population growth rate peaked in the early 1970s. The global population doubled from 3 billion in the 1960s to 6 billion in mid-1999, and continues to rise — but at a slower rate. The question is where on that chart above should we draw a line, saying ‘population must not exceed!’?


  • >There should definitely not be a specific limit to the world's population. It's one of those things of where there's a will, there's a way.We can see from mega cities like Tokyo, London, etc that people can live in high density environments, although i personally don't want to. The only issue is that a lot of these peoples needs are serviced by less densely populated environments, i.e. their need for food.But with improvements in food sciences and redesigning of urban environments to include rooftop market gardens, etc, it is not a case of one determinant being fixed while the other grows unabated.It is a headline statistic that you quoted though, 3 to 6 billion in 40 years. It would definitely make past generations shake their heads in disbelief.But the modern world has spawned many big numbers, amount of galaxies, distances, time, money, crops harvested, etc ,etc,. So in this context 6 billion fits right in.Plus if we look on the brightside, apparently that global warming is going to open up new areas of arable land, mainly siberian permafrost, and more CO2 might make the plants grow faster too 😉

  • >I like this comment: "We can see from mega cities like Tokyo, London, etc that people can live in high density environments, although i personally don't want to". I find this a very under-discussed issue. I think most people now live in urban areas (92% in Luxembourg apparently), but can we really live there or not? Alongside increasing urbanisation mental illnesses have skyrocketed, and there are few people who are happy living in cities for their entire lives. I spent 6 weeks living in London, able to look out of my window only onto a brick wall, and I was already getting really frustrated with the lack of countryside (in what is supposedly the greenest capital city in Europe).Nice comments on global warming too! Lol. There are two things I'll say in response. Firstly, yes we have managed to hugely increase food production so far, and are likely to in the near future as well, but there is no evidence to say that we will be able to do this forever. Can it really be an infinite process? At some point there simply won't be enough space, and we'll have to colonise new planets and moons. Secondly, although we've managed fairly well what about all the other species? We tend to ignore animals and plants far too often. Science tells us that there between 5 and 40 million species alive today (we haven't discovered many). Dr Edward Wilson of Harvard University estimates that between 20 to 30 thousand species are becoming extinct every year! And that's just in the world's tropical rainforests! So it's not just about our food.

  • Two Sean’s now heh, I will have to denote myself differently, although his comments were good so I don’t mind stealing them either. Anyway….

    I will start with a fact I think I used before somewhere. Everyone can live in Texas….

    Almost 7 billion people in the world today
    Family unit – 4.5 people
    1.55 billion family units

    State of Texas is 696,241 sq. km

    Space per unit = 450 sq. metres

    Or about one-tenth an acre per family.

    And they will all fit inside the state of Texas………………

    To me the melodramatic claims of over-population make me think of all those stereo-types we have about the dark ages, the sky is falling in, etc, etc,.

    So there is obviously enough space/room for all the people (the whole rest of the world in fact).

    So usually after pointing this out, the medieval folk start screaming about not enough natural resources.

    Well let’s see.

    Water – 2/3 of the world is covered in it, but it is salty. However, desalination plants like the one in Perth, Australia are continually coming on-line, and this one specifically supplies 17% of Perth’s needs, with 10% more capacity being added. Also, this plant is powered exclusively by wind power.

    Food – one of my favourite things to argue with people about is the criminally poor land use in New Zealand. Yes there are 34 million sheep, but you’ll be buggered if you see many of them. This is because the stock unit density (basically sheep per acre) on New Zealand farms is 4.

    Yes, 4 sheep per acre. And each ewe lives until about 3 years old, so you are just above 1 sheep per year per acre.

    So we need to stop eating bloody sheep.

    Imagine how much fruit, beans, and veges we could get out of that acre.

    What about meat ? Well birds live in trees so they can share the same acre as well without missing a beat.

    Shelter – I’m not sure about the eco-building improvements of homes recently but combinations of earth, straw, and natural materials with new low impact processed materials should be enough to keep us warm and cosy.

    So, there we go, Land, Water, Food, and Shelter, and all without using much more than a couple of Texas sized areas.


  • Hi Sean 2, lol. Thanks for your comment; it’s a very good argument. In reply I have two questions:
    1. What do you think about those reports produced by scientists saying that we already consume more resources as a species than we can do sustainably?
    2. What about other species? The extinction rate has gone up at quite a pace recently. How do we stop this from happening if we are continually encroaching on the habitats of others?

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