Today I’m going to talk about overshoot. Other people have written about this far more eloquently than I can – for example, Albert Bartlett and William Catton practically made it their life’s work to educate people about overshoot – but there’s no harm in revisiting it from a slightly different perspective. I’m going to set the scene by briefly reviewing the last 11,000 years of human history. Don’t worry, I know you’re all busy people so I’m going to give you the condensed version which shouldn’t take more than five minutes.

We’ll begin at the end of the last ice age, or more correctly, glacial period. This ended about 11,000 years ago, giving rise to the current Holocene interglacial period. The great ice sheets which covered most of Northern Europe and North America retreated and the climate became warmer and more stable. These conditions enabled humans to spread rapidly across the planet and to transition from nomadic hunter-gatherer bands to settled agricultural societies and complex civilizations.

Humans are very adaptable animals and soon filled almost every available ecological niche. To illustrate this let’s fast forward to the Battle of Jericho, which is said to have taken place around 1400 BC, or 7,600 years after the ice sheets retreated. The story of Jericho is told in the Book of Joshua in the Hebrew Bible. It says that the children of Israel were slaves in Egypt, but were led out of Egypt by the prophet Moses, and after many years wandering in the desert, came to the promised land of Canaan. Moses instructed them to seize the land by conquest and placed them under the command of Joshua. Jericho was the first city of Canaan to be taken. Following God’s law of “herem” the Israelites took no slaves or plunder but slaughtered every man, woman and child in Jericho, sparing only a single Canaanite prostitute.

Most historians think that the story of Jericho is a myth, that neither the exodus from Egypt nor the battle of Jericho ever happened, and that the story was written for the purpose of nationalist propaganda or to illustrate a theological point. However, whether this particular story is historically accurate or not is largely immaterial, because the migration and subsequent conflict which it describes were probably typical of many which occurred in the Biblical era. The main points which I want you to take away from this are that (according to the story) both Egypt and Canaan were already fully occupied. The maximum carrying capacity of the land had been reached and there was no room for any more people. The only way for the Israelites to establish themselves was to displace people who had already settled in the region. As they did not have the numbers or the military muscle to displace the Egyptians, they displaced the weaker and less numerous Canaanites, and as there was no room for the displaced Canaanites, they had to be disposed of. Nothing personal; just business.

Now let’s fast forward again to 476 AD and the fall of the Western Roman Empire. The reasons for the fall are many and complex, but the main issue seems to have been an expansion in the numbers of barbarian tribes in north-eastern Europe and central Asia such as the Huns, who swept southwest across Europe, displacing other tribes such as the Goths and Vandals into the Roman Empire, who in turn displaced the Romans eastwards towards their new base at Constantinople, abandoning Rome to its fate.  Again we see the same dynamic at work: the land was occupied up to its maximum carrying capacity, there was no room for any more people, and any expansion had to be at the expense of someone else.

Fast forward once more to 1492 and Columbus’ discovery of the vast empty lands of the Americas, ripe for colonisation. The problem with this story is that it’s a Western myth. The Americas had already been discovered and every available niche was occupied by indigenous people: there was no room for anyone else. The vast empty plains of the North American Midwest discovered by the European settlers (“Oh give me a home where the buffalo roam” etc) were an illusion: every square mile of grassland was already claimed, occupied, hunted or cultivated by indigenous people. The only way the Western colonists could free up the land for their own use was by displacing the existing inhabitants by disease, war, coercion or trickery.

The point I’m making in this brief guided tour of human history is that very soon after the end of the last glacial period the planet was fully occupied by humans. What do we mean by “fully occupied”? This means that the number of humans expanded until it met or exceeded the carrying capacity of the environment. Carrying capacity varies greatly depending on the nature of the land. For example, in the frozen Canadian Arctic or in the Australian desert outback there may only be a handful of people per thousand square miles, but if this is all the land can support, then this is the carrying capacity and it’s fully occupied. In contrast, the warm and fertile farmlands of southern England can support dozens of people per square mile.


This land is fully occupied…


…and so is this.

There are a few tricks we humans can deploy to temporarily increase the carrying capacity and accommodate greater numbers. One way is to transition from a nomadic hunter-gatherer way of life to a settled agricultural way of life. This was first tried in the “fertile crescent” area of the Middle East, otherwise known as the “cradle of civilization”. Much more food can be produced by farming than by hunting, but often this is only temporary and crop yields fall as longer term complications occur, for example, depletion of minerals in the soil, or salination from prolonged irrigation. The Middle East is much less fertile now than it was 6,000 years ago.

Local carrying capacity can be increased by importing food from elsewhere; for example, ancient Rome imported large quantities of grain from Egypt, and today’s Middle East countries import food, technology and expertise into into their barren, mostly desert land, paying for them with oil revenues. This is a zero-sum game because any increase in the carrying capacity of the importing area is offset by a decrease in the carrying capacity of the exporting area. This is the problem when, for example, farmland in Africa is appropriated for growing cash crops for export.

Finally, the environment can be “mined” for resources in an unsustainable way, resulting in a population boom followed by a bust. Easter Island is one example of this – and also most of today’s “advanced” civilizations. Most of our food is made from and/or transported by oil, and farmlands are irrigated by water from deep aquifers which are being drained faster than they can be replenished. It’s logical to expect that as the availability of oil and water decline, so will the availability of food and the size of the population.

We can put some figures on this. Wikipedia’s World Population Estimates suggest that at the beginning of the Holocene interglacial period there were about 5 million humans worldwide. As the ice sheets retreated, the land warmed and the practice of agriculture spread, human numbers increased to around 300 million and stayed fairly constant at that level until around 900 AD. From 900 to 1800 AD the population slowly but steadily increased by about 100 million each century, reaching 900 million at the start of the Industrial Revolution. Since the start of the Industrial Revolution the population has exploded to over 7 billion – that’s an average increase of around 1 billion people every 30 years, far exceeding any known historical population growth rates. This has been made possible by the mining of non-renewable resources – fossil fuels, water, topsoil, minerals – and to a lesser extent, expropriating land from hunter gatherers worldwide and converting it to industrialised agriculture.

So where do we go from here? As Steincke said, it’s difficult to make predictions, especially about the future, but here is my best shot. I’ll look first at what seems to be the most likely global result, followed by zooming in on some of the finer detail.

The sustainable carrying capacity of the planet is probably around 1 billion people, similar to the pre-industrial population. There is a lot of happy talk from politicians and environmental and human rights organisations who say that population isn’t the problem, and that if we only had a more equal distribution of resources we could support even more people than we have today. I don’t buy into that because it sounds like wishful thinking. Distribution of resources never has been fair and probably never will be. A more likely outcome is that as resources become scarcer, the human population will shrink back towards 1 billion, and we will lose some 6 billion people along the way.

I think that only a minority of those deaths will be from starvation (but see below). The majority of deaths will be due to conflict: either directly from injuries sustained as a result of the fighting, or indirectly due to the mass migration of populations out of war zones. The events following the collapse of the Soviet Union also suggest that many deaths will be caused by psychological trauma; for example, alcoholism and suicide.

Conflict of all kinds will spread and intensify. As oil and food supplies dry up in the Middle East, there will be mass migrations of people out of the area. However, few countries will be willing or able to receive large numbers of refugees. This will set up conflicts between the incoming refugees and the populations of the receiving countries, and also internal conflicts between factions within the receiving countries who want to either accept the refugees, or keep them out. (Does any of this sound familiar – think Brexit?).

North America will experience an action replay of 476 AD, but with the migrations being from south to north instead of north-east to south-west. As the climate warms and the aquifers dry up, people will try to migrate from the hotter, drier regions to the cooler, wetter regions to try to achieve better economic and food security. Mexicans will migrate north across the border displacing people from the southern US, people from the southern US will try to move into the northern US, and there will be increased pressure on Canada to accept American migrants. (Again, does anything sound familiar, especially to people living near the Mexico-US border?).

Countries in possession of valuable resources will find that this is both a blessing and a curse. A blessing, because selling them to the highest bidder may bring great wealth (if wealth is worth anything), and a curse because they may attract floods of refugees and possibly invading armies. I am thinking particularly of Canada’s farmlands, forests, tar sands and fresh water and whether the US is going to want a piece of that action. The US has already invaded Canada twice: in the American Revolutionary War in 1775 and the War of 1812. What goes around, comes around.

I have a bad feeling about the Far East, and in particular India and China. They each have 1.3 billion people, that’s 2.6 billion people between them, which is one third of the world’s population. With so many people, if things start to go wrong they could go really wrong really fast, and I can see food shortages there resulting in mass starvation. In China’s Great Famine in 1959-61 there were 36 million deaths due to starvation.  India is already one of the highest ranking countries in the world for children suffering from malnutrition.

However, to prove I’m not just a doomsayer, I would like to point out one bright spot on the horizon which is southern Africa, that is to say, that part of Africa south of the Sahara Desert. I think Southern Africa could potentially come out of the Long Emergency, or whatever you like to call it, rather well. For the last 500 years the continent has suffered greatly at the hands of European colonists and entrepreneurs: we have taken their farmland and used it to grow Western cash crops, destroyed their indigenous cultures by sending missionaries, exported millions of them to work as slaves on cotton and tobacco plantations, dug up and carried away their mineral wealth (for example gold, diamonds and cobalt) and lured them into taking out unrepayable loans at high rates of interest. No wonder the place is now a mess. However, if Westerners would just leave it alone, it could come through the traumas of the 21st century relatively unscathed or even improved.

As for me, I’ve made my choice. I and my family have moved to the Isle of Man, a tiny island in the middle of the Irish Sea, human population 88,000, sheep population around 15,000. We have a fairly good idea where our next meal might be coming from, we are unlikely to get many refugees, and we don’t have any oil, gold or diamonds for invading armies to dig up or fight over. But in case you are thinking of coming here, I have some bad news for you: we’re full. No room for any more people.

Good luck.


Slaynt vie, bea veayn, beeal fliugh as baase ayns Mannin

Beware of the Sheep

8 thoughts on “Overshoot

  1. I always appreciate reading your posts. In reply I will write what I tell everyone who will listen. I live in an agricultural area in Canada, on a large farm, next to other large farms. I have lived most of my life outside, so I am familiar with the earth’s seasons. When I go to the cities I am amazed at the rapid growth, the mushrooming of houses, and the influx of new people. I marvel at the miraculous ingenuity that society has designed to provide food, water, clothing, and shelter for the rapidly expanding urban culture, but when I have returned home, i am sad because we do not have one more gallon of water or one more yard of soil to produce more food stuffs than when I left on my short trip to the city. Although the changes in the weather patterns are not overly obvious at the moment to most people, I feel the impact more each year. For example, we had sufficient rainfall over the summer for the garden but the garden still needed water. It was because of the slight increase in wind drying the foliage. Two years ago we noticed the decline of nutrients in our garden produce. We have access and use large volumes of organic matter and yet our garden plants were deficient. It is more difficult to keep animals healthy because of the use of chemicals on livestock feed. We see some evidence that animals fed forage that has been sprayed with roundup to develop gastrointestinal sensitivities similar to celiac disease. One of my biggest concerns is the lack of “good farm common sense.” I’m of the grandparents’ generation. I meet many young people who are concerned about the economy who want to grow a garden, have a goat, and a few chickens, but they lack the experience and knowledge. They don’t know the basics and many of their efforts fail. They simply don’t know. More seriously, they do not know how to learn. Certainly, tragic and harsh hardships will follow if there is an downturn in our society. We do not have the resources and the smarts to get us through a bad depression. Add the complexities of our environmental deterioration and the ever increasing population to feed and clothe, and we’re looking at a disaster of indescribable proportions.

  2. Excellent review of overshoot. Not sure about your description of Man, too many Web sites with contradictory figures, it would take me many hours to check everything. One even claims a huge loss of arable land in Man over the last 10 years, though I have no idea what that’s all about. Anyway, I always use a figure of 4 people per hectare of arable land as the maximum in the absence of fossil fuels. Man seems to be somewhere near the limit, maybe 3 or 4 people per hectare of arable land. That puts it close to Ireland’s figure. as one might expect. Canada, by contrast, is much better off, with only about 1/5 as many people per hectare of arable land.

    • I was a bit puzzled by the “huge loss of arable land” because nobody here on the island has noticed this happening. I did a bit of digging and it looks as though it came from this website owned by Knoema:


      Knoema is in the business of selling data. You might be better off buying some Tarot cards or tea leaves: they are cheaper and more accurate.

    • I like your metric “persons per hectare of arable land”. For the UK this is 10 (2013) according to the World Bank figures. Therefore the UK is in overshoot by 2.5 times if we use your figure of 4 persons per hectare max without fossil fuels.

      Therefore UK current population = 64 million, UK max population without fossil fuels = 25 million

      ps How did you arrive at the figure 4 as the max. Not that I doubt you but because I would like to know more about it.

  3. Instead of the phrase “industrial revolution”, I prefer “fossil fuel age”. The term industrial revolution gives the impression that is was due solely to human ingenuity and hence can continue as long as we have human ingenuity ie indefinitely. In reality the industrial revolution was only possible because of fossil fuels, coal initially but then supplemented later by oil and gas which are finite and therefore will not be sustainable indefinitely.

    My second point but related to the first. I noticed that in the second US presidential debate the most outrageous statement came from Trump when he said that the US had enough coal for thousands of years. Clinton didn’t pick him up on this, nor did the media and nor to my knowledge did the alternative media. Nothing. Nada, Zilch. Heard by millions of viewers who just accepted it as truth. I find this utterly staggering. It just makes me look like a nutcase to 99% of people when I tell them that all fossil fuels (that can be extracted at an energy profit) will be burnt by the end of this Century. Don’t believe me? Don’t worry, I can take it. However do the math(s) yourselves. Find official figures for world fossil fuels reserves (in barrels of oil equivalent) and divide by world annual consumption (again in barrels of oil equivalent). I got 78 years.

    OK this is a very rough calculation because reserves are being found all the time but you also have to remember that consumption is also going up at the same pace so the two roughly cancel themselves out.

    So there you go, 80 +/- years before fossil fuels all get burnt. Not 1000s of years that the vast majority thinks. Kinda makes me glad I’m 55 with no children to worry about. Overshoot will be a bitch.

  4. Some authors claim that North America was in fact largely unpopulated by the time the colonists arrived, because the explorers had brought diseases with them, a hundred years before, which had reduced the Native American population by 90%. In a hundred (or two) years, vast forests grew up in formerly cultivated land. In 1491, North America may have been at its carrying capacity, but by 1600, the remaining natives were struggling to survive the loss of culture that came with a 90% loss of population. Disease spread much more quickly and widely than immigrants.

  5. UK Science Behind Polymer Breakthrough That Can Change Our Lives

    I can’t wait to get such pieces of news coming from Botswana, Malawi, Kenya, Sierra Leone and the likes.
    Or, at least from their immigrants who live in the West.

    Problem is, with the institutional racism that must still be all round, no matter if you can see it or not, plus all the injustice that has been done them by White people, we may have to wait some 1,000, 2,000 or 5,000 years before that happens.

    I am joking.
    “I would like to point out one bright spot on the horizon which is southern Africa”

    The bright make for bright spots. They’re so bright that they’ll recover from our injustice when you say they will, and lead the world technologically, scientifically and culturally (to the extent they don’t already, truth be said).

    Can’t wait, but the wait is going to be short. Yay!

    By the way… if ” For the last 500 years the continent has suffered greatly at the hands of European colonists and entrepreneurs” they must have invented a lot and made a lot of art before then, no less than Europeans and East-Asians and Hindus.
    Sad our still-too-racist culture history accounts deny Sub-Saharan Africa’s pre-1500 triumphs the publicity they deserve.

  6. I believe free from White man injustice Africa can even get completely rid of Presidents who unlike for example Idi Amin don’t eat their opponents by the end of the 21th century (maybe even 2050).

    Great accomplishments are on the horizon for their continent.

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