Why societies collapse
Throughout human history societies have prospered and collapsed leaving behind tantalizing glimpses of their magnificence in crumbling temples, ruins and statues. Why did these ancient civilisations fall apart? Why did some collapse and not others? And what lessons do they have for our civilisation?
Locals of Easter Island may have cut a substantial amount of its trees down to use as rollers to raise the giant Moai statues. (Source: Wikimedia Commons)
The collapse of ancient societies poses a very complicated problem. One can also think of places in the world where societies have gone on for thousands of years without any signs of collapse, such as Japan, Java, Tonga and Tikopea. What is it then that made some societies weaken and other societies robust? It's also a complicated problem because the collapses usually prove to be multi-factorial. What is it then that makes some societies more vulnerable than others?
Environmental factors clearly play a role, but in trying to understand the collapses of ancient societies, it's not enough to look at the inadvertent impact of humans on their environment. It's usually more complicated. Instead I've arrived at a checklist of five things that I look at to understand the collapses of societies, and in some cases all five of these things are operating. Usually several of them are.
1. Environmental Damage
Environmental damage involves inadvertent damage to the environment through means such as deforestation, soil erosion, salinisation, over-hunting etc.
2. Climate Change
People can hammer away at their environment and get away with it as long as the climate is benign, warm, wet, and the people are likely to get in trouble when the climate turns against them, getting colder or drier. So climate change and human environmental impact interact, not surprisingly.
3. Hostile Neighbours
Most societies have chronic hostile relations with some of their neighbours and societies may succeed in fending off those hostile neighbours for a long time. They're most likely to fail to hold off the hostile neighbours when the society itself gets weakened for environmental or any other reasons, and that's given rise for example, to the long-standing debate about the fall of the Western Roman Empire. Was the conquest by Barbarians really a fundamental cause, or was it just that Barbarians were at the frontiers of the Roman Empire for many centuries? Rome succeeded in holding them off as long as Rome was strong, and then when Rome got weakened by other things, Rome failed, and fell to the Barbarians.
And similarly, we know that there were military factors in the fall of Angkor Wat in Cambodia.
4. Friendly neighbours — Trade
Similarly, relations with friendly neighbours is also relevant. Almost all societies depend in part upon trade with neighbouring friendly societies, and if one of those friendly societies itself runs into environmental problems and collapses for environmental reasons, that collapse may then drag down their trade partners. It's something that interests us today, given that we are dependent for oil upon imports from countries that have some political stability in a fragile environment.
5. Cultural Response
Why is it that people failed to perceive the problems developing around them, or if they perceived them, why did they fail to solve the problems that would eventually do them in? Why did some peoples perceive and recognise their problems and others not?
Easter Island
Easter Island is the simplest case we've got of a collapsed society. It's the closest approximation to a collapse resulting purely from human environmental damage.
Easter is the most remote habitable scrap of land in the world; it's an island in the Pacific, 2,000 miles west of the coast of Chile, and something 1300 miles from the nearest Polynesian island. It was settled by other Polynesians coming from the west, sometime around AD800 and it was so remote that after Polynesians arrived at Easter Island, nobody else arrived there. Nobody left Easter as far as we know, and so the Easter story is uncomplicated by relations with external hostiles or friendlies. There weren't any. Easter Islanders rose and fell by themselves.
Easter is a relatively fragile environment, dry with 40 inches of rain per year. It's most famous because of the giant stone statutes — those big statues weighing up to 80 tons — stone statues that were carved in a volcanic quarry and then dragged up over the lip of the quarry and then 13 miles down to the coast and then raised up vertically onto platforms, all this accomplished by people without any draught animals, without pulleys, without machines. These 80 ton statues were dragged and erected under human muscle power alone. And yet when Europeans arrived at Easter in 1722 the islanders were in the process of throwing down their own statues. Easter Island society was in a state of collapse. How, why and who erected the statues, and why were they thrown down?
Well the how, why and who has been settled in the last several decades by archaeological discoveries. Easter Islanders were typical Polynesians, and the cause of the collapse became clear from archaeological work in the last 15 years, particularly from paleo-botannical work and identification of animal bones in archaeological sites.
Today Easter Island is barren. It's a grassland, there are no native trees whatsoever on Easter Island, not a likely setting for the development of a great civilisation, and yet paleo-botannical studies (identifying pollen grains) and lake cores show that when the Polynesians arrived at Easter Island, it was covered by a tropical forest that included the world's largest palm tree and dandelions of tree height. And there were land birds, at least six species of land birds and 37 species of breeding sea-birds, the largest collection of breeding sea-birds anywhere in the Pacific.
Polynesians settled Easter, they began to clear the forest for their gardens, for firewood, for using as rollers and levers to raise the giant statues, and then to build canoes with which to go out into the ocean and catch porpoises and tuna. They ate the land birds, they ate the sea-birds, they ate the fruits of the palm trees. The population of Easter grew to an estimated 10,000 people, until by the year 1600 all of the trees and all of the land birds and all but one of the sea-birds on Easter Island itself were extinct. Some of the sea-birds were confined to breeding on offshore stacks.
The deforestation and the elimination of the birds had consequences for people. Without trees, they could no longer transport and erect the statues, so they stopped carving statues. Without trees they also had no firewood. They suffered from soil erosion and hence agricultural yields decreased. They couldn't build canoes, so they couldn't go out to the ocean to catch porpoises and there were only a few sea-birds left.
The largest animal left to eat were humans and Polynesian society then collapsed in an epidemic of cannibalism. The spear points from that final phase still litter the ground of Easter Island today. The population crashed from about 10,000 to an estimated 2,000 with no possibility of rebuilding the original society because the trees, most of the birds and some of the soil were gone.
I think one of the reasons that the collapse of Easter Island so grabs people is that it looks like a metaphor for us today. Easter Island, isolated in the middle of the Pacific Island, nobody to turn to for help, nowhere to flee once Easter Island itself collapsed. In the same way today, one can look at Planet Earth in the middle of the galaxy and if we too get into trouble, there's no way that we can flee, and no people to whom we can turn for help out there in the galaxy.
I can't help wondering what the Islander who chopped down the last palm tree said as he or she did it. Was he saying, 'What about our jobs? Do we care more for trees than for the jobs of us loggers?' Or maybe he was saying, 'What about my private property rights? Get the big government of the chiefs off my back.' Or maybe he was saying, 'You're predicting environmental disaster, but your environmental models are untested, we need more research before we can take action. 'Or perhaps he was saying, 'Don't worry, technology will solve all our problems.'
The Anasazi
Today, the ruins of skyscrapers erected by native Americans, the Anasazi, can still be found in the south west of the United States — in the four corner area of Arizona, New Mexico, Colorado, Utah. The skyscrapers were up to 6-storey buildings, with up to 600 rooms.
The Anasazi build-up began around AD600 with the arrival of the Mexican crops of corn, squash and beans in that relatively dry area. It's very striking today to drive through an area where today either nobody is living at all, or nobody's living by agriculture and realise that this used to be a densely populated agricultural environment.
The Anasazi were ingenious at managing to survive in that environment, with low fluctuating, unpredictable rainfall, and with nutrient-poor soils. The population built up. They fed themselves with agriculture, in some cases irrigation agriculture, channelled very carefully to flood out over the fields. They cut down trees for construction and firewood. In each area they would develop environmental problems by cutting down trees and exhausting soil nutrients, but they dealt with those problems by abandoning their sites after a few decades and moving on to a new site.
It's possible to reconstruct Anasazi history in great detail for two reasons. Firstly, tree rings; from tree-rings on the roof beams you can identify precisely what year — 1116, not 1115 AD — the tree in that roof was cut down. And secondly, those cute little rodents, the pack rats, that run around gathering bits of vegetation in their nests and then abandoning their nests after 50 years. A pack rat midden is basically a time capsule of the vegetation growing within 50 yards of a pack rat midden over a period of 50 years.
Julio Betancourt was near an Anasazi ruin and happened to see a pack rat midden. He was astonished to see in it the needles of pinion pine and juniper, in what is now a treeless environment. So Julio wondered whether that was an old midden. He took it back, radio carbon-dated it, and lo and behold it was something like AD 800. So the pack-rat middens are time capsules of local vegetation allowing us to reconstruct what happened.
What happened is that the Anasazi deforested the area around their settlements until they were having to go further and further away for their fuel and their construction timber. At the end they were getting their logs from the tops of mountains up to 75 miles away and about 4,000 feet above the Anasazi settlements. These logs had to be dragged back by people with no transport or pack animals. So deforestation spread. That was the one environmental problem.
The other environmental problem was the cutting of arroyos. When water flow is channelled, for example in irrigation ditches, then large flows such as the run off in desert rains dig a trench within the channel. This trench digs deeper and deeper with time, and today we can see examples of arroyos up to 30 feet deep. If the water level drops down in the arroyos today then that's not a problem for farmers, because we've got pumps. But the Anasazi did not have pumps, and so when the irrigation ditches became incised by arroyo cutting and when the water level in the ditches dropped down below the field levels, they could no longer do irrigation agriculture.
For a while the Anasazi got away with these inadvertent environmental impacts. There were droughts around 1040 and droughts around 1090, but at both times the Anasazi hadn't yet filled up the landscape, so they could move to other parts of the landscape not yet exploited. And the population continued to grow.
Then in Chaco Canyon when a drought arrived in 1117 there was no more unexploited landscape. At that point, Chaco Canyon was a complex society. Lots of stuff was getting imported into Chaco — stone tools, pottery, turquoise, probably food was being imported into Chaco. Archaeologists can't detect any material that went out of the Chaco Valley, and whenever you see a city into which material stuff is moving and no material stuff is leaving, you suspect that the city has political or religious control in return for which the peasants in the periphery are supplying their imported goods.
When the drought came in 1117 it was a couple of decades before the end. Pueblo Benito was a big, six storey, unwalled plaza, until about 20 years before the end, when a high wall went up around the plaza. And when you see a rich place without a wall, you can safely infer that the rich place was on good terms with its poor neighbours, and when you see a wall going up around the rich place, you can infer that there was now trouble with the neighbours. So probably what was happening was that towards the end, in the drought, as the landscape is filled up, the people out on the periphery were no longer satisfied because the people in the religious and political centre were no longer delivering the goods. The prayers to the gods were not bringing rain, there was stuff to redistribute and they began making trouble. Chaco Canyon was eventually abandoned. The Anasazi had committed themselves irreversibly to a complex society, and once that society collapsed, they couldn't rebuild it because again they deforested their environment.
In the Anasazi case we have the interaction of environmental impact and climate change.
Norse Greenland
The Vikings settled in Greenland in AD 984, where they established a Norwegian pastoral economy, based particularly on sheep, goats and cattle for producing dairy products, and then they also hunted caribou and seal. Trade was important. The Vikings in Greenland hunted walruses to trade walrus ivory to Norway because walrus ivory was in demand in Europe for carving, since at that time with the Arab conquest, elephant ivory was no longer available in Europe.
Then in the 1400s the Vikings vanished from Greenland. Of their two settlements; one of them disappeared around 1360 and the other sometime probably a little after 1440. Everybody ended up dead.
The vanishing of Viking Greenland is instructive because it involves all five of the factors that I mentioned, and also because there's a detailed, written record from Norway, a bit from Iceland and just a few fragments from Greenland: a written record describing what people were doing and describing what they were thinking. So we know something about their motivation, which we don't know for the Anasazi and the Easter Islanders.
Of the five factors, first of all there was ecological damage due to deforestation in this cold climate with a short growing season. The deforestation was especially expensive to the Norse Greenlanders because they required charcoal in order to smelt iron to extract iron from bogs. Without iron, except for what they could import in small quantities from Norway, there were problems in getting iron tools like sickles. It became a big problem when the Inuit, who had initially been absent in Greenland, colonised Greenland and came into conflict with the Norse. The Norse then had no military advantage over the Inuit. It was not guns, germs and steel. The Norse of Greenland had no guns, very little steel, and they didn't have the nasty germs. They were fighting with the Inuit on terms of equality, one people with stone and wooden weapons against another.
The second factor was climate change. The climate in Greenland got colder in the late 1300s and early 1400s as part of what's called the Little Ice Age. Hay production was a problem. Greenland was already marginal because of it's high latitude short growing season, and as it got colder, the growing season got even shorter, hay production got less, and hay was the basis of Norse sustenance.
Thirdly, the Norse had military problems with their neighbours the Inuit. The only detailed example we have of an Inuit attack on the Norse is in the Icelandic annals of the years 1379 which says 'In this year the scralings (which is an old Norse word meaning wretches, the Norse did not have a good attitude towards the Inuit) attacked the Greenlanders and killed 18 men and captured a couple of young men and women as slaves.' Eighteen men doesn't seem like a big deal but when you consider the population of Norse Greenland at the time, probably about 4,000 people, 18 adult men stands in the same proportion to the Norse population then as if some outsiders were to come into the United States today and in one raid kill 1,700,000 adult male Americans. So that single raid by the Inuit did make a big deal to the Norse, and that's just the only raid that we know about.
Fourthly, there was the cut-off of trade with Europe because of increasing sea-ice, with a cold climate in the North Atlantic. The ships from Norway gradually stopped coming. Also as the Mediterranean reopened Europeans got access again to elephant ivory, and they became less interested in the walrus ivory, so fewer ships came to Greenland.
And finally, cultural factors — the Norse were derived from a Norwegian society that was identified with pastoralism, and particularly valued calves. In Greenland it's easier to feed and take care of sheep and goats than calves, but calves were prized in Greenland, so the Norse chiefs and bishops were heavily invested in the status symbol of calves. The Norse, because of their bad attitude towards the Inuit, refused to learn from the Inuit and refused to modify their own economy in a way that would have permitted them to survive. They did not adopt useful Inuit technology, such as harpoons, hence they couldn't eat whales like the Inuit. They didn't fish, incredibly, while the Inuit were fishing. They didn't have dog sleighs, they didn't have skin boats, they didn't learn from the Inuit how to kill seals at breeding holes in the winter. So the Norse were conservative. They also invested heavily in their churches, in importing stained-glass windows and bronze bells for the churches, when they could have been importing more iron to trade to the Inuit, to get seals and whale meat in exchange for the iron.
The result was that after 1440 the Norse were all dead, and the Inuit survived. This example is particularly instructive in showing us that collapse due to environmental reasons isn't inevitable. It depends upon what you do. Here are two peoples and one did things that let them survive, and the other did things that did not permit them to survive.
There are a series of factors that make people more or less likely to perceive environmental problems growing up around them. One is misreading previous experience. The Vikings came from Norway where there's a relatively long growing season, so the Greenland Vikings didn't realise, based on their previous experience, how fragile Greenland woodlands were going to be.
They also had the difficulty of extracting a trend from noisy fluctuations. We now know that there was a long-term cooling trend, but climate fluctuates wildly up and down in Greenland from year to year; cold, cold, warm, cold. So it was difficult for a long time perceive that there was any long-term trend. That's similar to the problems we have today with recognising global warming. It's only within the last few years that even scientists have been able to convince themselves that there is a global long-term warming trend. And while scientists are convinced, the evidence is not yet enough to convince many of our politicians.
The Vikings short time scale of experience in Greenland was a disadvantage. In the Anasazi area, droughts come back every 50 years, in Greenland it gets cold every 500 years or so; those rare events are impossible to perceive for humans with a life span of 40, 50, 70 years. They're perceptible today but we may not internalise them.
The Norse were also disadvantaged by inappropriate cultural values. They valued cows too highly just as modern Australians value cows and sheep to a degree appropriate to Scotland but inappropriate to modern Australia. And Australians now are seriously considering whether to abandon sheep farming completely as inappropriate to the Australian environment.
See the problem, take no action
Why would people perceive problems but still not solve their own problems?
A theme that emerges from Norse Greenland as well as from other places, is insulation of the decision making elite from the consequences of their actions. That is to say, in societies where the elites do not suffer from the consequences of their decisions, but can insulate themselves, the elite are more likely to pursue their short-term interests, even though that may be bad for the long-term interests of the society, including the children of the elite themselves.
In the case of Norse Greenland, the chiefs and bishops were eating beef from cows and venison and the lower classes were left to eating seals. The elite were also heavily invested in the walrus ivory trade. In the long run, what was good for the chiefs in the short run was bad for society.
We can see those differing insulations of the elite in the modern world today.
Holland is the country with the highest level of environmental awareness, a higher percentage of people belong to environmental organisations than anywhere else in the world. The Dutch are also a very democratic people. There are something like 42 political parties but none of them ever come remotely close to a majority, which means that the Dutch are very good at reaching decisions. In Holland everybody lives in the Polders, whether you're rich or poor. It's not the case that the rich people are living high up on the dykes and the poor people are living down in the Polders. So when the dyke is breached or there's a flood, rich and poor people die alike. In particular in the North Sea floods in Holland in the late '40s and '50s, when the North Sea was swept by winds and tides flooded 50 to 100 miles inland, all Dutch in the path of the floods died. In Holland, rich people cannot insulate themselves from the consequences of their actions.
Whereas in much of the rest of the world, rich people live in gated communities and drink bottled water. That's increasingly the case in Los Angeles where I come from. So that wealthy people in much of the world are insulated from the consequences of their actions.
Challenges to modern civilisation
There are obvious differences between the environmental problems in the past and the ones that we face today. Some of those differences make the situation for us today scarier than it was in the past. Today there are far more people alive, packing far more potent per capita destructive technology. Today there are 6 billion people chopping down the forests with chains and bulldozers, whereas on Easter Island there were 10,000 people with stone axes. Today, countries like the Solomon Islands - wet, relatively robust environments, where people lived without being able to deforest the islands for 32,000 years — are undergoing rapid change. Within the past 15 years the Solomon Islands have been almost totally deforested, leading to a civil war and collapse of government within the last year or two.
Globalisation
Another big difference between today and the past is globalisation. In the past, you could get solitary collapses. When Easter Island society collapsed, nobody anywhere else in the world knew about it, nobody was affected by it. The Easter Islanders themselves, as they were collapsing, had no way of knowing that the Anasazi had collapsed for similar reasons a few centuries before, and that the Mycenaean Greeks had collapsed a couple of thousand years before and that the dry areas of Hawaii were going downhill at the same time.
But today we turn on the television set and we see the ecological damage in Somalia and Afghanistan, or Haiti, and we pick up a book and we read about the ecological damage caused in the past. So we have knowledge both in space and time, that ancient peoples did not. Today we are not immune to anybody's problems. A collapse of a society anywhere is a global issue, and conversely, anybody anywhere in the world now has ways of reaching us.
We used to think of globalisation as a way to get out our good things, like the Internet. Particularly since September 11th we've realised that globalisation also means that they can send us their bad things like terrorists, cholera and uncontrollable immigration. So those are things that are against us.
But globalisation also means the exchange of information and that includes information about the past, so we are the only society in world history that has the ability to learn from all the experiments being carried out elsewhere in the world today, and all the experiments that have succeeded and failed in the past. And so at least we have the choice of what we want to do about it.
Published 17 July 2003
