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