"Peak Civilization": The Fall of the Roman Empire

A silver mask that had belonged to a Roman cavalryman of imperial times. It was found on the site of the battle of Teutoburg, fought in September 9 a.d. This year, 2009, marks the 2000th anniversary of the battle that led to the annihilation of three Roman legions and changed forever the history of Europe. It was a tremendous shock for the Romans, who saw their mighty army destroyed by uncivilized barbarians. It was not yet the peak of the Roman Empire, but it was a first hint that something was deeply wrong with it.

This text describes the presentation that I gave at the "Peak Summit" in Alcatraz (Italy) on June 27, 2009 (the picture shows me speaking there). It is not a transcription, but something that I wrote from memory, mostly in a single stretch, while I had it still fresh in my mind. The result is that my 40 minutes talk became a text of more than 10,000 words, much longer than a typical internet document (but still less than Gibbon's six volumes on the same subject!) A talk, anyway, can be longer and more effective than a post, mostly because the people listening to you are not distracted by the infinite distractions of an internet connection. So, I wrote this post trying to maintain the style of an oral presentation. I don't know if it will turn out to be more easily readable than the usual style but, if you arrive to the end, you'll tell me what you think of it.

Ladies and gentlemen, first of all thank you for being here. This afternoon I'll try to say something about a subject that I am sure you are all interested in: the decline and the fall of the Roman Empire. It is something that has been discussed over and over; it is because we think that our civilization may follow the same destiny as the Roman one: decline and fall. So, the Roman Empire offers us some kind of a model. We can say it is the paradigm of collapsing societies. And, yet, we don't seem to be able to find an agreement on what caused the collapse of the Roman Empire.

Historians - and not just historians - have been debating this subject and they came up with literally dozens of explanations: barbarian invasions, epidemics, lead poisoning, moral decadence and what you have. Which is the right one? Or are all these explanations right? This is the point that I would like to discuss today. I'll be focusing on the interpretation of Joseph Tainter, based on the fact that empires and civilizations are "complex" systems and try to use system dynamics to describe collapse.

Before we go into this matter, however, let me add a disclaimer. I am not a historian and I don't pretend to be one. It is not my intention of criticizing or disparaging the work of historians. You see, there are several ways of making a fool of oneself: one which is very effective is to try teaching to people who know more than you. For some reasons, however, it happens all the time and not just with history; just look at the debate on climate change! So, what I am trying to do here is just to apply system dynamics on the history of the Roman Empire which - as far as I know - has not been done, so far. It is a qualitative version of system dynamics; making a complete model of the whole Roman Empire is beyond my means. But the results are very interesting; or so I believe.

The collapse seen from inside.

Let's start from the beginning and here the beginning is with the people who were contemporary to the collapse, the Romans themselves. Did they understand what was happening to them? This is a very important point: if a society, intended as its government, can understand that collapse is coming, can they do something to avoid it? It is relevant to our own situation, today.

Of course, the ancient Romans are long gone and they didn't leave us newspapers. Today we have huge amounts of documents but, from Roman times, we have very little. All what has survived from those times had to be slowly hand copied by a Medieval monk, and a lot has been lost. We have a lot of texts by Roman historians - none of them seemed to understand exactly what was going on. Historians of that time were more like chroniclers; they reported the facts they knew. Not that they didn't have their ideas on what they were describing, but they were not trying to make models, as we would say today. So, I think it may be interesting to give a look to documents written by people who were not historians; but who were living the collapse of the Roman Empire. What did they think of what was going on?

Let me start with Emperor Marcus Aurelius, who lived from 120 to 180 A.D. He was probably the last Emperor who ruled a strong empire. Yet, he spent most of his life fighting to keep the Empire together; fighting barbarians. Maybe you have seen the movie "The Gladiator": Marcus Aurelius appears in the first scenes. The movie is not historically accurate, of course, but it is true that Aurelius died in the field, while he was fighting invaders. He wasn't fighting for glory, he wasn't fighting to conquer new territories. He was just fighting to keep the Empire together, and he had a terribly hard time just doing that. Times had changed a lot from the times of Caesar and of Trajan.

Marcus Aurelius did what he could to keep the barbarians away but, a few decades after his death, the Empire had basically collapsed. That was what historians call "the third century crisis". It was really bad; a disaster. The empire managed to survive for a couple of centuries longer as a political entity, but it wasn't the same thing. It was not any longer the Empire of Marcus Aurelius; it was something that just tried to survive as best as it could, fighting barbarians, plagues, famines, warlords and all kinds of disasters falling on them one after the other. Eventually, the Empire disappeared also as a political entity. It did that with a whimper - at least in its Western part, in the 5th century a.d. The Eastern Empire lasted much longer, but it is another story.

Here is a piece of statuary from Roman times. We know what Marcus Aurelius looked like.

Now, if it is rare that we have the portrait of a man who lived so long ago, it is even rarer that we can also read his inner thoughts. But that we can do that with Marcus Aurelius. He was a "philosopher-emperor" who left us his "Meditations"; a book of philosophical thoughts. For instance, you can read such things as:

Though thou shouldst be going to live three thousand years, and as many times ten thousand years, still remember that no man loses any other life than this which he now lives, nor lives any other than this which he now loses.

That is the typical tune of the book - you may find it fascinating or perhaps boring; it depends on you. Personally, I find it fascinating. The "Meditations" is a statement from a man who was seeing his world crumbling down around him and who strove nevertheless to maintain a personal balance; to keep a moral stance. Aurelius surely understood that something was wrong with the Empire: during all their history, the Romans had been almost always on the offensive. Now, they were always defending themselves. That wasn't right; of course.

But you never find in the Meditations a single line that lets you suspect that the Emperor thought that there was something to be done other than simply fighting to keep the barbarians out. You never read that the Emperor was considering, say, things like social reform, or maybe something to redress the disastrous situation of the economy. He had no concern, apparently, that the Empire could actually fall one day or another.

Now, I'd like to show you an excerpt from another document; written perhaps by late 4th century. Probably after the battle of Adrianopolis; that was one of last important battles fought (and lost) by the Roman Empire. This is a curious document. It is called, normally, "Of matters of war" because the title and the name of the author have been lost. But we have the bulk of the text and we can say that the author was probably somebody high up in the imperial bureaucracy. Someone very creative - clearly - you can see that from the illustrations of the book. Of course what we see now are not the original illustrations, but copies made during the Middle Ages. But the fact that the book had these illustration was probably what made it survive: people liked these colorful illustrations and had the book copied. So it wasn't lost. The author described all sorts of curious weaponry. One that you can see here is a warship powered by oxen.

Of course, a ship like this one would never have worked. Think of how to feed the oxen. And think of how to manage the final results of feeding the oxen. Probably none of the curious weapons invented by our anonymous author would ever have worked. It all reminds me of Jeremy Rifkin and his hydrogen based economy. Rifkin understands what is the problem, but the solutions he proposes, well, are a little like the end result of feeding the oxen; but let me not go into that. The point is that our 4th century author does understand that the Roman Empire is in trouble. Actually, he seems to be scared to death because of what's happening. Read this sentence, I am showing it to you in the original Latin to give you a sense of the flavor of this text.

“In primis sciendum est quod imperium romanum circumlatrantium ubique nationum perstringat insania et omne latus limitum tecta naturalibus locis appetat dolosa barbaries."

Of course you may not be able to translate from Latin on the spot. For that, being Italian gives you a definite advantage. But let me just point out a word to you: "circumlatrantium" . which refers to barbarians who are, literally, "barking around" the empire's borders. They are like dogs barking and running around; and not just barking - they are trying hard to get in. It is almost a scene from a horror movie. A nightmare. So the author of "Of matters of war" is thinking of how to get rid of these monsters. But his solutions were not so good. Actually it was just wishful thinking. None of these strange weapons were ever built. Even our 4th century author, therefore, fails completely in understanding what were the real problems of the Empire.

Now, I would like to show you just another document from the time of the Roman Empire. It is "De Reditu suo", by Rutilius Namatianus. The title means "of his return". Namatianus was a patrician who lived in the early 5th century; he was a contemporary of St. Patrick, the Irish saint. He had some kind of job with the imperial administration in Rome. It was some decades before the "official" disappearance of the Western Roman Empire; that was in 476, when the last emperor, Romolus Augustulus, was deposed. You may have seen Romulus Augustulus as protagonist of the movie "The Last Legion". Of course that is not a movie that pretends to be historically accurate, but it is fun to think that after so many years we are still interested in the last years of the Roman Empire - it is a subject of endless fascination. Even the book by Namatianus has been transformed into a movie, as you can see in the figure. It is a work of fantasy, but they have tried to be faithful to the spirit of Namatianus' report. It must be an interesting movie, but it has been shown only in theaters in Italy, and even there for a very short time; so I missed it. But let's move on.

Namatianus lived at a time that was very close to the last gasp of the Empire. He found that, at some point, it wasn't possible to live in Rome any longer. Everything was collapsing around him and he decided to take a boat and leave. He was born in Gallia, that we call "France" today, and apparently he had some properties there. So, that is where he headed for. That is the reason for the title "of his return". He must have arrived there and survived for some time, because the document that he wrote about his travel has survived and we can still read it, even though the end is missing. So, Namatianus gives us this chilling report. Just read this excerpt:

"I have chosen the sea, since roads by land, if on the level, are flooded by rivers; if on higher ground, are beset with rocks. Since Tuscany and since the Aurelian highway, after suffering the outrages of Goths with fire or sword, can no longer control forest with homestead or river with bridge, it is better to entrust my sails to the wayward."

Can you believe that? If there was a thing that the Romans had always been proud of were their roads. These roads had a military purpose, of course, but everybody could use them. A Roman Empire without roads is not the Roman Empire, it is something else altogether. Think of Los Angeles without highways. "Sic transit gloria mundi" , as the Romans would say; there goes the glory of the world. Namatianus tells us also of silted harbors, deserted cities, a landscape of ruins that he sees as he moves north along the Italian coast.

But what does Namatianus think of all this? Well, he sees the collapse all around him, but he can't understand it. For him, the reasons of the fall of Rome are totally incomprehensible. He can only interpret what is going on as a temporary setback. Rome had hard times before but the Romans always rebounded and eventually triumphed over their enemies. It has always been like this, Rome will become powerful and rich again.

There would be much more to say on this matter, but I think it is enough to say that the Romans did not really understand what was happening to their Empire, except in terms of military setbacks that they always saw as temporary. They always seemed to think that these setbacks could be redressed by increasing the size of the army and building more fortifications. Also, it gives us an idea of what it is like living a collapse "from the inside". Most people just don't see it happening - it is like being a fish: you don't see the water.

The situation seems to be the same with us: talking about the collapse of our civilization is reserved to a small bunch of catastrophists; you know them; ASPO members, or members of The Oil Drum - that kind of people. Incidentally, we can't rule out that at some moment at the time of the Roman Empire there was something like a "Roman ASPO", maybe "ASPE," the "association for the study of peak empire". If it ever existed, it left no trace. That may also happen with our ASPO; actually it is very likely, but let's go on.

What destroyed the Roman Empire?

From our perspective we can see the cycle of the Roman Empire as one that is nicely complete. We can see it from start to end; from the initial expansion to the final collapse. As I said, a lot of documents and data have been lost but, still, we have plenty of information on the Empire - much more than for other past empires and civilizations that collapsed and disappeared as well. Yet, we don't seem to be able to find an agreement on the reasons of the collapse.

You have surely read Edward Gibbon's "Decline and Fall of the Roman Empire"; at least parts of it. Gibbon wrote a truly monumental account of the story of the Empire, but he doesn't really propose us a "theory" of the causes of the fall, as most historians would do, later on. On reading Gibbon's work, you understand that he thinks there was a sort of loss of moral fiber in the Romans. He attributes this loss to the negative effect of Christianity. That is, the noble virtues of the Ancient Romans - he says - had been corrupted by this sect of fanatics coming from the East. This had made the Romans unable to resist to the invading barbarians.

You'll probably agree that this explanation by Gibbon is a bit limited; just as are limited other interpretations by authors who came later. Spengler and Tonybee are two examples, but if we were to discuss their work in detail it would take - well - weeks; not hours. So, let me jump forward to the historian who - I think - has given a new and original interpretation of the decline of Rome: Joseph Tainter with his "The Collapse of Complex Societies". His book was published for the first time in 1990.

It is a great book. I suggest to you to read it and ponder it. It is truly a mine of information about collapses. It doesn't deal just with the Roman Empire, but with many other civilizations. Tainter goes well beyond the simplistic interpretation of many earlier authors and identifies a key point in the question of collapse. Societies are complex entities; he understands that. And, hence, their collapse must be related to complexity. Here is an excerpt of Tainter's way of thinking. It is a transcription of a interview that Tainter gave in the film "Blind Spot" (2008)

In ancient societies that I studied, for example the Roman Empire, the great problem that they faced was when they would have to incur very high costs just to maintain the status quo. Invest very high amounts in solving problems that don't yield a net positive return, but instead simply allowed them to maintain what they already got. This decreases the net benefit of being a complex society.

Here is how Tainter describes his view in graphical form; in his book.

So, you see that Tainter has one thing very clear: complexity gives a benefit, but it is also a cost. This cost is related to energy, as he makes clear in his book. And in emphasizing complexity, Tainter gives us a good definition of what we intend for collapse. Very often people have been discussing the collapse of ancient societies without specifying what they meant for "collapse". For a while, there has been a school of thought that maintained that the Roman Empire had never really "collapsed". It had simply transformed itself into something else. But if you take collapse defined as "a rapid reduction of complexity" then you have a good definition and that's surely what happened to the Roman Empire.

So, what was important with the collapse of the Roman Empire is not whether or not there was an emperor in Rome (or, as it was the case later, in Ravenna). We might well imagine that the line of the emperors could have continued well after Romulus Augustulus - the last emperor. And even after him there remained a legitimate Roman Emperor in Byzantium, in the Eastern Empire. You could very well say that the Empire didn't disappear as long as there were emperors in Byzantium, that is, until Costantinople fell, in the 15th cenntury. And since the Russian Czars saw themselves as Roman emperors (that is where "Czar" comes from, from "Caesar"), you could say that the Roman Empire didn't disappear until the last Czar was deposed, in 1917. But that is not the point. The point is that the Roman Empire had started undergoing a catastrophic loss of complexity already during the third century. So, that was the real collapse. What happened later on is another story.

After that Tainter has spoken of complexity, and of the energy cost of complexity, it is perhaps surprising for us that he doesn't consider resource depletion as a cause of collapse. Resource depletion, after all, is the main theme of Jared Diamond's book "Collapse". It is how he interprets the collapse of many societies. Tainter explicitly denies that in his book. He says that if such a thing as depletion appears, then society should react against it. After all, it is normal: society always reacts to all kinds of crisis, and why shouldn't it react to resource depletion? This point made by Tainter may appear surprising - actually unpalatable - to people who have made resource depletion the centerpiece of their thought. Peak oilers, for instance.

The disagreement between peak oilers (and Diamond) and Tainter may not be so strong as it appears. That we'll see as we go deeper into the details. But before we do that, let me say something general about these explanations that people give for collapse. It happens all the time that people discover something that they describe as if it was the only cause for collapse. That is, they sort of get enamored of a single cause for collapse. They say, "I have the solution; it is this and nothing else."

Consider the story that Roman Empire collapsed because the Romans used to drink wine in lead goblets; and so they died of lead poisoning. That has some truth: there is evidence of lead poisoning in ancient Roman skeletons; there are descriptions of lead poisoning in ancient Roman texts. Surely it was a problem, probably even a serious one. But you can't see this story of lead poisoning in isolation; otherwise you neglect everything else: the Roman Empire was not just people drinking wine in lead goblets. Think of a historian of the future who describes the fall of the American Empire as the result of Americans eating hamburgers. That would have some truth and for sure the kind of food that most Americans eat today is - well - we know that it is doing a lot of damage to Americans in general. But you wouldn't say that hamburgers can be the cause of the fall of the American Empire. There is much more to that.

The same kind of reasoning holds for other "causes" that have been singled out for the fall of Rome. Think, for instance, of climatic change. Also here, there is evidence that the fall of the Roman Empire was accompanied by droughts. That may surely have been a problem for the Romans. But, again, we might fall in the same mistake of a future historian who might attribute the fall of the American Empire - say - to the hurricane Katrina. (I have nothing special against the American Empire, it is just that it is the current empire)

The point that Tainter makes, quite correctly, in his book is that it is hard to see the fall of such a complex thing as an empire as due to a single cause. A complex entity should fall in a complex manner, and I think it is correct. In Tainter's view, societies always face crisis and challenges of various kinds. The answer to these crisis and challenges is to build up structures - say, bureaucratic or military - in response. Each time a crisis is faced and solved, society finds itself with an extra layer of complexity. Now, Tainter says, as complexity increases, the benefit of this extra complexity starts going down - he calls it "the marginal benefit of complexity". That is because complexity has a cost - it costs energy to maintain complex systems. As you keep increasing complexity, this benefit become negative. The cost of complexity overtakes its benefit. At some moment, the burden of these complex structures is so great that the whole society crashes down - it is collapse.

I think that Tainter has understood a fundamental point, here. Societies adapt to changes. Indeed, one characteristic of complex systems is of adapting to changing external conditions. It is called "homeostasis" and I tend to see it as the defining characteristic of a complex system (as opposed to simply complicated). So, in general, when you deal with complex systems, you should not think in terms of "cause and effect" but, rather, in terms of "forcing and feedback". A forcing is something that comes from outside the system. A feedback is how the system reacts to a forcing, usually attaining some kind of homeostasis. Homeostasis, is a fundamental concept in system dynamics. Something acts on something else, but also that something else reacts. It is feedback. It may be positive (reinforcing) or negative (damping) and we speak of "feedback loops" which normally stabilize systems - within limits, of course.

Homeostasis has to be understood for what it is. It is not at all the same thing as "equilibrium" as it is defined in thermodynamics. For example, a human being is a complex system. When you are alive, you are in homeostasis. If you are in equilibrium, it means that you are dead. Homeostasis is a dynamical equilibrium of forces.

Also, homeostasis cannot contradict the principles of physics. It can only adapt to physical laws. Think of yourself swimming in the sea. Physics says that you should float, but you need to expend some energy to maintain a homeostatic condition in which your head stays above the water. Now, suppose that your feet get entangled with something heavy. Then, physics says that you should sink. Yet, you can expend more energy, swim harder, and still keep your head above the water - again it is homeostasis. But, if nothing changes, at some moment you'll run out of energy, you get tired and you can't keep homeostasis any more. At this point, physics takes over and you sink, and you drown. It is the typical behavior of complex systems. They can maintain homeostasis for a while, as long as they have resources to expend for this purpose.

Something similar occurs for human societies. When there is a forcing, say, an epidemics that kills a lot of people, societies react by generating more children. Look at the demographic statistics for our societies: there is a dip in numbers for the world wars, but it is rapidly compensated by more births afterward. Also in Roman times there were epidemics and the eruption of the Vesuvius that killed a lot of people. But those were small forcings that the Roman society could compensate.

Not all forcings can be compensated, but we know that the Romans were not destroyed by an asteroid that fell into the Mediterranean Sea. It might have happened, and in that case there would have been no feedback able to keep the empire together. We would have a single cause for the disappearance of the Roman Empire and everybody would agree on that. But that has not happened, of course. Perhaps, something like that has happened to the Cretan civilization; destroyed by a volcanic eruption - but that's another story.

So, in Tainter's view there is this feedback relationship between complexity and energy. At least the way I interpret it. Complexity feeds on energy and also strains the availability of energy. It is feedback. And not just energy; resources in general. So, I think that Tainter is right in refusing a simple explanation like "resource depletion is the cause of the fall of the Roman Empire". But, clearly, resources are an important part of his model. I think Tainter had in mind the Roman Empire when he developed this model, but it is of quite general validity. If this is the way things stand, his model is not in contrast with the models we have that see resource depletion as the main factor that causes collapse. But not the only cause. We must see collapse as something dynamic, and now I'll try to explain just that.

Dynamic models of collapse

Once we start reasoning in terms of complexity, we immediately see the relationship of Tainter's model with other models. I can cite John Greer's theory of "catabolic collapse" but we can go directly to the mother of all theories based on feedback: the study called "The Limits to Growth" that appeared for the first time in 1972.

As we know, "The Limits to Growth" was not about the fall of the Roman Empire. The authors tried to describe our contemporary world, but the model they used is very general and perhaps we can apply it also to the Roman Empire. So, first of all, we need to understand how the model works. Let me show you a simplified graphic representation of the model

This image was made by Magne Myrtveit a few years ago and I think it nicely summarizes the main elements of the world model used for the Limits to Growth studies.

There is this problem with dynamic models; they are often very complex and difficult to understand. They use a graphical formalism, but if you look at one of these models made - for instance - using the "Stella" or "Vensim" software, all what you see is a jumble of boxes and arrows. If you are not trained in this kind of things, you can't understand what the model is about. Personally, often I find that the equations are clearer than all those boxes and arrows.

So, we need something more graphical, easier to understand, especially if we have to show these things to politicians. And, as I said, I think that Myrtveit has struck the right balance here: this graphic is "mind sized" (I am using a term from Seymour Paypert, who invented the "logo" programming language). It is mind sized because I think that you can make sense of this diagram in a few minutes. There remains a problem with politicians. Their attention span is more of the order of thirty seconds or less. But that is another problem.

So, Myrtveit's image shows us the major elements of the world model - the model of The Limits to Growth" - and their relationships. You see population, agriculture, natural resources, pollution and capital· Five main elements of the model; each one is rather intuitive to understand. What is important is the feedback relationship that exists among these elements. Perhaps the most important feedback loop is the one between capital and natural resources. Here is how the authors of "The Limits to Growth" have described this relationship:

The industrial capital stock grows to a level that requires an enormous input of resources. In the very process of that growth it depletes a large fraction of the resources available. As resource prices rise and mines are depleted, more and more capital must be used for obtaining resources, leaving less to be invested for future growth. Finally investment cannot keep up with depreciation, and the industrial base collapses, taking with it the service and agricultural systems, which have become dependent on industrial inputs.

Considering just two elements, instead of five, is not in contradiction with the more complex model. It makes sense especially when you are not considering a whole empire but something more limited, for instance the oil industry. Here are the results of this approach, this time with the equations written in clear.

You see that we obtain "bell shaped" curves. We do see bell shaped curves whenever a natural resource is exploited in a free market conditions. The "Hubbert curve" for oil production is just one case. There are many others. The curve is the result of a phenomenon called overexploitation or overshoot that leads to destroy even resources which are in principle renewable. The story of whaling in 19th centuries is typical and I wrote a paper on that - I am writing another one. It is a fascinating subject: whales are a renewable resource, of course, because they reproduce. But they were hunted so efficiently that, by end 19th century, it is estimated that in the Oceans there were only 50 females left of the species that was most hunted: the "right whale." ("right" is because it was easy to kill, of course nobody had asked the opinion of whales on this name).

If you consider all five elements, things become more complex, but the general approach doesn't change that much. You can play a game with the scheme in Myrtveit's figure and you can relate it to what Tainter said about human societies. You remember that Tainter says that if a crisis emerges, society will try to cope with it. From the scheme, you can see what happens as time goes by and as people do things to avoid collapse.

So, suppose that pollution becomes a serious problem. Let's imagine that fumes from smokestacks are killing people; then society will allocate some capital to reduce fumes. Say, they would place filters on smokestacks. But filters need energy and natural resources to be built and that will place some further strain on natural resources. That will put strain on capital - so, fighting pollution may accelerate collapse, but not fighting it may cause collapse as well, although for different reasons - because pollution kills people and that makes it more difficult to generate capital and so on. You see how it works.

Let's make another example. Suppose that population grows to the point that there is not enough food for everybody. In response, society will use a fraction of its natural resources to produce fertilizers which will increase the yield of agriculture. That, however, will create a further increase in population that will put further strain on population and generate more pollution. That, in turn, will put new strain on capital and resources, and so on... Within limits, society can always adapt in this way - it is homeostasis, as I said. But only within limits.

You can play this kind of game in various ways. The five elements figure by Magne Myrtveit is a good tool to gain a feeling of how society reacts to external interventions and how it evolves with the gradual depletion of natural resources. If these resources are non renewable, as it is the case of our mineral resources, eventually, the amount of capital that can be created and maintained must go down - it is one of the possible causes of collapse. Probably the most common. But in order to see how it is going to happen, you need to run the model in a computer and see what you get. Here are typical results, from the 2004 edition of "The Limits to Growth".

This is called the "standard run" or the "base case" scenario. It is a run of the model with the parameters most closely fitting the present situation. You see collapse occurring - it is when you see industrial and agricultural production crashing down. As you can see, the more complex model still produces bell shaped curves, although non symmetric ones.

Note that the model doesn't have a "complexity" parameter built in. However, it is clear that when the industrial and the agricultural system cease to function it is complexity going down (and population as well, of course). So, in a certain sense, the "Limits to Growth" model is compatible with Tainter's model - or so I tend to see things.

Of course, you don't have to take this scenario as a prophecy. It is just a mental tool designed to amplify your understanding of the system. You can change the parameters and the assumptions - collapse can be postponed, but the model is very robust. An important point is that these bell shaped curves are typical and are always the result, unless you use very specific assumptions in input, usually assuming human intervention to avoid collapse.

People are very good at optimizing exploitation. The problem is that they exaggerate and take out of the system more than what the system can replace. And that is the reason of the curve. First you go up because you are so good at exploiting the resource; then you go down because you have exploited it too much. In the middle, there has to be a peak -it is "peak-resource". In the case of crude oil, people speak of "peak oil". In the case of a whole civilization, we may speak of "peak civilization". And, as we said before, peak civilization also corresponds to "peak complexity", in the sense that Tainter described.

One last point, here. Collapse is not irreversible. Society goes in overshoot, then collapses, but the collapse gives time to the overexploited resource to reform, so growth can restart after a while. Homeostasis is like orbiting around an equilibrium point, without ever reaching it. It is a cycle that may keep going up and down, or may dampen out to reach an approximately stable state. That is, if the resource is renewable. If it is not, like oil or uranium, when it is used up, there is no more. In this case, there is no return from collapse. Also, from the viewpoint of a human being, even a reversible collapse that involves society as a whole tends to last much longer than a human lifetime. So, for what we are concerned, collapse is irreversible if we are caught by it and is something that we don't like, clearly. So we set up things like ASPO and TOD to see if we can convince politicians to do something to avoid collapse. Whether we'll succeed is another matter, but let's not go into that now.

The dynamic fall of the Roman Empire

Now we know that we should expect to see these bell curves in the behavior of a complex civilization or an empire. So, we can try to give a look to the Roman Empire in this perspective and see if it agrees with an interpretation based on system dynamics. So, first of all, let me propose a simplified model based on the same scheme that Magne Myrtveit proposed for our world as described in "The Limits to Growth".

Please do not take it as anything more than a sketch, but it may be helpful for us to understand the mechanism that lead the Empire to collapse.

Now, let me try to explain how this scheme could work. We know that the Roman Empire was based mainly on two kinds of resources: military and agricultural. I put the image of a legionnaire for "capital resources" because legions can be seen as the capital of the Roman Empire; military capital. This capital, legions, would be built on a natural resource that was mainly gold. The legions didn't mine gold, they took it from the people who had mined it (or had stolen it from somebody else).

This feedback between military capital and gold is a point that is very well described by Tainter in his book. You can read how military adventures played a fundamental role in the growth of the empire, and earlier on of the Roman Republic. There was a clear case of positive feedback. The Empire would defeat a nearby kingdom, rob it of gold and take part of the population as slaves. Gold could be used to pay for more legions and go on conquering more lands. Positive feedback: the more legions you have, the more gold you can rob; the more gold you have, the more legions you can create. And so on...

One of the inventions of the Roman was their capability of transforming gold into legions and legions into gold - as I said it is a very clear case of feedback. Still today we use the word "soldier", which comes from Latin, and it means "hired" or "salaried". It was not only gold, legionnaires were also paid in silver, but the concept remains the same. Legions paid for the salaries of the legionnaires using the profit they made from looting the conquered lands.

But, as conquest proceeded, soon the Romans found themselves without easy lands to conquer. It was a problem of EROEI; energy return on energy invested. In this case, GROGI (gold return on gold invested). After the easy conquests of the 1st century b.c., Gallia for instance, then things became difficult. The energy yield of conquering new lands went down. On the North East, the Germans were too poor - and also warlike. Conquering them was not only difficult, but didn't generate a profit. In the East, the Parthians were rich, but militarily powerful. Then on the West there was the Atlantic Ocean, the North was too cold, the south too dry. Negative feedback, you see?

With the legions not bringing any more gold, gold disappeared from the Empire for various reasons. In part it was to buy luxury items that the Empire couldn't manufacture inside its borders, silk for instance. In part, it disappeared because barbarian chieftains were paid not to invade the Empire or to fight alongside with the Romans. There were other reasons, but anyway gold was a dwindling resource for the Roman Empire, a little like our "black gold", petroleum. During the good times, the legions would bring back from foreign conquests more gold than what was spent but, with time, the balance had become negative.

Of course, military conquest was not the only source of gold for Rome. As I said, we are describing a complex system, and complex systems have many facets. So, the Romans had gold mines in Africa and in Spain. And they also had silver mines in Spain. There are no mines in the scheme; we could add mines to it, that wouldn't be a problem. But the problem here is that we don't have enough data to understand exactly the role of mines in the economy of the Roman Empire. We know, for instance, that silver mining declined in Spain with the decline of the empire. Did mining decline cause the collapse of the empire? Personally, I think not. At least, the Romans had started their expansion much earlier than they had conquered Spain and these mines. At the time of the wars with Carthage, it was the Carthaginians who held Spain and, I imagine, the silver mines. But this silver didn't help them much, since they lost the war and were wiped out by the Romans. So, we should be wary of single explanations for complex events. We can only say that mines are subjected to the same kind of negative feedback that affects military conquests. After you exploit the easy ores (or lands to be conquered) you are left with difficult ores (or lands) that don't yield the same profit. It is negative feedback, again.

Then, there was agriculture. Surely it was an important economic activity of the Roman Empire, as you can read, again, in Tainter's book. Agriculture is also subjected to positive and negative feedbacks as you can see in the scheme. With good agriculture, the population increases. With more population, you can have more farmers. In the case of the Roman Empire, as population grows, you can have also more legions which will bring back home slaves which can be put to work in the fields. But agriculture has also a negative feedback, and that is erosion.

You can see erosion in the scheme listed as "pollution". It affects agriculture negatively. It reduces population and sets everything backwards: negative feedback, again. The more you try to force agriculture to support a large populations (including the legions) the more strain you put on the fertile soil. Fertile soil is a non renewable resource; it takes centuries to reform the fertile soil, after that it has been lost. So, erosion destroys agriculture, population falls, you have a smaller number of legions and, in the end, you are invaded by barbarians. This is another negative feedback loop that is related to the fall of the Roman Empire.

The question of agriculture during Roman times is rather complex ad the data we have are contradictory; at least in some respects. There is clear evidence of erosion and deforestation, especially during the expansion period of the early Roman Empire. Then, during and after the third century, we have famines and plagues. These two things are related, plagues are often the result of poor nutrition. At the same time, we have evidence that the Romans of the late empire were unable to exploit in full the land they had. It is reported that plenty of land was not cultivated - apparently for lack of manpower. We also know that forests were returning with the 4th century a.d. So, there are various elements of the dynamic scheme which connect with each other. Apparently, the emphasis on military power took away resources from agriculture and ingenerated still another negative feedback: not enough people (or slaves) to cultivate the land. But it may also be that some areas of land were not cultivated because erosion had ruined them.

So, I have proposed to you a scheme and I described how it could work. But does it work? We should now compare the scheme with real data; fit the data to a model. The problem is that we don't have enough data to fit - we probably never will. So, I didn't try fitting anything; but I think I can show you some sets of data that are an impressive indication that there is something true in this dynamical model.

First of all, if the decline and fall of the Roman Empire has been a case of overexploitation of resources, we should expect to see bell curves for industrial and agricultural production, for population, and for other parameters. As I said, the historical data are scant, but we have archaeological data. So, let me show a plot that summarizes several industrial and agricultural indicators, together with a graph that shows how the extension of the Empire varied in time. It is taken from In search of Roman economic growth, di W. Scheidel, 2007" The other graph is taken from Tainter's book.

Especially the upper graph is impressive. There has been a "peak-empire", at least in terms of production and agriculture, somewhere around mid 1st century. Afterward, there was a clear decline - it was not just a political change. It was also a real reduction in complexity as Tainter defines collapse. The Roman Empire really collapsed in mid 3rd century. It had a sort of "Hubbert peak" at that time.

The other parameter shown in the figure, the extension of the empire, also shows an approximately bell shaped curve. The Empire continued to exist as a political entity even after it had been reduced to an empty shell in economic terms. If we think that the extension of the empire is proportional to the "capital" accumulated, then this relationship makes sense if we think of the dynamic model that we saw before. Capital, as we saw, should peak after production. This is a bit stretched as an interpretation, I admit. But at least we see also here a bell shaped curve.

There is more. Do you remember the curves that are calculated in the dynamic model for the relation Capital/resources? You expect the production curve to peak before the capital curve. Now, I proposed that this relation capital/resources exists between the Roman Army and the gold that they looted. So, do we have data that show this relationship? Yes, we do, although only approximately. Let's first see the data for gold. We don't have data for the amount of gold circulating within the Empire, but Tainter shows us the data for the devaluation of the Roman silver coin, which we would expect to follow the same path. Here are the data (the figure is taken from this site ):

Now, the amount of precious metal within a denarius is not a precise measurement of the total gold or silver in the Empire, but it is at least an indication that this amount was going down after the first century A.D. And, since the Romans had started poor, earlier on, there must have been a peak at some time, "peak gold", probably in the 1st century a.d.

About the size of the Roman Army, we have this figure from Wikipedia . As you see, the data are uncertain, but if we consider the Western Empire only, there was a peak around 3rd century a.d.

So, you see? Army and gold show the correct relationship that we expect to have between capital and resource. they both peak, but gold peaks before the army. The Romans kept increasing the size of their army even after the economic returns that they got from military activities went down, actually may have become negative. It is exactly the same behavior of whalers in 19th century who kept increasing the size of the whaling fleet even it was clear that there weren't enough whales to catch to justify that. I think this is an impressive result. At least, it convinced me.

There is more if we look at the Roman population curve, although for this we must rely on very uncertain data (see, e.g. the paper by Walter Schneidel . I can't show you a graph, here, too uncertain are the data. But it seems that, in any case, there was a population peak in the Roman Empire around mid 2nd century. If this is the case, the Roman population peak arrives after the production peak - just as shown in the "standard run" calculations for the world3 model.

So, I think we have enough data, here, to prove the validity of the model - at least in qualitative terms. Maybe somebody should collect good data, archaeological and historical, and made a complete dynamic model of the Roman Empire. That would be very interesting, but it is beyond my possibilities for now. Anyway, even from these qualitative data we should be able to understand why the Empire was in trouble. One of the main causes of the trouble was that it had this big military apparatus, the legions, that needed to be paid and didn't bring in any profit. It was the start of an hemorrhage of gold that couldn't be reversed. In addition, the Empire bled itself even more by building an extensive system of fortifications - the limes that had to be maintained and manned, besides being expensive in themselves.

The story of the fortifications is a good example of what we had said; the attempt of a complex system to maintain homeostasis. The Romans must have understood that legions were too expensive if you had to keep so many of them to keep the borders safe. So, they built these walls. I imagine that the walls were built by slaves; and a slave surely cost less than a legionnaire. Slaves, however, were not good as fighters - I suppose that if you gave a sword to a slave he might think to run away or to use it against you. You know the story of Spartacus, the leader of a slave revolt in Roman times. I am sure that the Romans didn't want to risk that again. But with walls the Romans had found a way to replace legionnaires with slaves. You needed less legionnaires to defend a fortification than to defend an open field. That was a way to save money, to keep homeostasis. But it wasn't enough - obviously. The Romans still needed to pay for the legions and - as a disadvantage - the walls were a rigid system of defense that couldn't be changed. The Romans were forced to man the walls all along their extension and that must have been awfully expensive. The Empire had locked itself in a cage from which it would never be able to escape. Negative feedback kills.

Military expenses were not the only cause of the fall. With erosion gnawing at agricultural yields and mine productivity going down, we should not be surprised if the empire collapsed. It simply couldn't do otherwise. So, you see that the collapse of the Roman Empire was a complex phenomenon where different negative factors reinforced each other. It was a cascade of negative feedbacks, not a single one, that brought down the empire. And this shows how closely related to the Romans we are. Surely there are differences: our society is more of a mining society and less of a military based society. We don't use slaves but, rather, machines. We also have plenty of gadgets that the Romans didn't have. But, in the end, the interactions of the various elements of our economy are not that much different. What brought down the Romans, and eventually will bring us down, is the overexploitation of the resources. If the Romans could have found a way to use their resources, agriculture for instance, in ways that didn't destroy them, erosion in this case, their society could have lasted for a longer time. But they never found an equilibrium point - they went down always using a bit too much of what they had.

Avoiding Collapse

From our viewpoint, we see what was the history of the Roman Empire. But, from inside, as we saw, it wasn't clear at all. But let's assume that someone had it clear, already at the time of Marcus Aurelius. I said that there might have been something like an ASPE; "association for the study of peak empire". Or let's imagine that a wise man, a Druid from foggy Britannia, an ancestor of Merlin the wise, was smart enough to figure out what was going on. You don't really need computers to make dynamical models, or maybe this druid made one using wooden cogs and wheels, the whole thing powered by slaves. So, let's say that this druid understood that the troubles of the Empire are caused by a combination of negative feedbacks and that these feedbacks come from the cost of the army and of the bureaucracy, the overexploitation of the fertile soil, the fact that Rome had exhausted the "easy" targets for conquest.

Now, it is a tradition of Druids (and also of ASPO) of alerting kings and rulers of the dangers ahead. After all, Merlin did that for King Arthur and we may imagine that the druid we are thinking of felt that it was his duty to do that with Emperor Marcus Aurelius. So, he decides to go to Rome and speak to the Emperor. Suppose you were that druid; what would you say to the Emperor?

Good question, right? I have asked it to myself many times. We could think of many ways of answering it. For instance, if gold is running out from the Empire's coffers, why not suggest to the Emperor to mount a naval expedition to the Americas? It is what Columbus would do, more than a millennium afterwards and the result was the Spanish empire - it was also based on gold and it didn't last for long. Maybe the Romans could have done something like that. But they didn't have the right technology to cross the oceans and, at the time of Marcus Aurelius, they had run out of the resources to develop it. So, they had to remain in Europe and to come to terms with the limits of the area they occupied. The Empire had to return its economy within these limits. So, there is only one thing that you, as the wise Druid from Britannia, can tell the Emperor: you have to return within the limits that the Empire's economy can sustain.

So you walk to Rome - kind of a long walk from Eburacum, in Britannia; a place that today we call "York". You are preceded by your fame of wise man and so the Emperor receives you in his palace. You face him, and you tell him what you have found:

"Emperor, the empire is doomed. If you don't do something now, it will collapse in a few decades"

The Emperor is perplexed, but he is a patient man. He is a philosopher after all. So he won't have your head chopped off right away, as other emperors would, but he asks you, "But why, wise druid, do you say that?"

"Emperor, " you say, "you are spending too much money for legions and fortifications. The gold accumulated in centuries of conquests is fast disappearing and you can't pay enough legionnaires to defend the borders. In addition, you are putting too much strain on agriculture: the fertile soil is being eroded and lost. Soon, there won't be enough food for the Romans. And, finally, you are oppressing people with too much bureaucracy, which is also too expensive."

Again, the Emperor considers having your head chopped off, but he doesn't order that. You have been very lucky in hitting on a philosopher-emperor. So he asks you, "Wise druid, there may be some truth in what you say, but what should I do?"

"Emperor, first you need to plant trees. the land needs rest. In time, trees will reform the fertile soil."
"But, druid, if we plant trees, we won't have enough food for the people."
"Nobody will starve if the patricians renounce to some of their luxuries!"
"Well, Druid, I see your point but it won't be easy....."
"And you must reduce the number of legions and abandon the walls!"
"But, but.... Druid, if we do that, the barbarians will invade us....."
"It is better now than later. Now you can still keep enough troops to defend the cities. Later on, it will be impossible. It is sustainable defense."
"Yes, it means defense that you can afford. You need to turn the legions into city militias and..."
"You must spend less for the Imperial Bureaucracy. The Imperial taxes are too heavy! You must work together with the people, not oppress them! Plant trees, disband the army, work together!"

Now, Emperor Marcus Aurelius seriously considers whether it is appropriate to have your head chopped off, after all. Then, since he is a good man, he sends to you back to Eburacum under heavy military escort, with strict orders that you should never come to Rome again.

This is a little story about something that never happened but that closely mirrors what happened to the modern druids who were the authors of "The Limits to Growth." They tried to tell to the world's rulers of their times something not unlike what our fictional druid tried to tell to Emperor Marcus Aurelius. The heads of the authors of "The Limits to Growth" weren't chopped off, but they were surely "academically decapitated" so to say. They were completely ignored. Not just ignored, ridiculed and vituperated. It is not easy to be a druid.

So, here we found another similarity between our times and the Roman ones. We are subjected to the "fish in the water" curse. We don't understand that we are surrounded by water. And we don't want to be told that water exists.

As things stands, we seem to be blithely following the same path that the Roman Empire followed. Our leaders are unable to understand complex systems and continue to implement solutions that worsen the problem. As the wise druid was trying to tell to Marcus Aurelius, building walls to keep the barbarians out was a loss of resources that was worse than useless. But I can see the politicians of the time running on a platform that said, "Keep the barbarians out! More walls to defend the empire". It is the same for us. Tell a politician that we are in trouble with crude oil and he/she will immediately say "drill deeper!" or "drill, baby, drill!" Negative feedback kills.

But I would like to point out to you something: let's go back to what our fictional druid was telling to Emperor Aurelius. He had this slogan "Plant trees, disband the army and work together". I had invented it in a post that I had written on the collapse of Tuscan society in 16th century; it is another story but one that shows how all societies follow similar paths. Anyway, can you see what kind of world the Druid was proposing to the Emperor? Think about that for a moment: a world of walled cities defended by city militias, no central authority or a weak one, an economy based on agriculture.

Do you see it.....? Sure, it is Middle Ages! Think about that for a moment and you'll see that you could define Middle Ages as a solution for the problems of the Roman Empire!

So, our Druid had seen the future and was describing it to Emperor Aurelius. He had seen the solution of the problems of Empire: Middle Ages. It was where the Empire was going and where it could not avoid going. What the Druid was proposing was to go there in a controlled way. Ease the transition, don't fight it! If you know where you are going, you can travel in style and comfort. If you don't, well, it will be a rough ride.

We may imagine a hypothetical "driven transition" in which the government of the Roman Empire at the time of Marcus Aurelius would have done exactly that: abandon the walls, reduce the number of legion and transform them into city militias, reduce bureaucracy and Imperial expenses, delocalize authority, reduce the strain on agriculture: reforest the land. The transition would not have been traumatic and would have involved a lower loss of complexity: books, skills, works of art and much more could have been saved and passed to future generations.

All that is, of course, pure fantasy. Even for a Roman Emperor, disbanding the legions couldn't be easy. After all, the name "Emperor" comes from the Latin word "imperator" that simply means "commander". The Roman Emperor was a military commander and the way to be Emperor was to please the legions that the Emperor commanded. A Roman Emperor who threatened to disband the legions wouldn't have been very popular and, most likely, he was to be a short lived Emperor. So, Emperors couldn't have done much even if they had understood system dynamics. In practice, they spent most of their time trying to reinforce the army by having as many legions as they could. Emperors, and the whole Roman world, fought as hard as they could to keep the status quo ante , to keep things as they had always been. After the 3rd century crisis, Emperor Diocletian resurrected the Empire transforming it into something that reminds us of the Soviet Union at the time of Breznev. An oppressive dictatorship that included a suffocating bureaucracy, heavy taxes for the citizens, and a heavy military apparatus. It was such a burden for the Empire that it destroyed it utterly in little more than a century.

Our Druids may be better than those of the times of the Roman Empire, at least they have digital computers. But our leaders are no better apt at understanding complex system than the military commanders who ruled the Roman Empire. Even our leaders were better, they would face the same problems: there are no structures that can gently lead society to where it is going. We have only structures that are there to keep society where it is - no matter how difficult and uncomfortable it is to be there. It is exactly what Tainter says: we react to problems by building structure that are more and more complex and that, in the end, produce a negative return. That's why societies collapse.

So, all our efforts are to keep the status quo ante . For this reason we are so desperately looking for something that can replace crude oil and leave everything else the same. It has to be something that is liquid, that burns and, if possible, even smells bad. Drill more, drill deeper, boil tar sands, make biofuels even if people will starve. We do everything we can to keep things as they are.

And, yet, we are going where the laws of physics are taking us. A world with less crude oil, or with no crude oil at all, cannot be the same world we are used to, but it doesn't need to be the Middle Ages again. If we manage to deploy new sources of energy, renewable or nuclear - fast enough to replace crude oil and the other fossil fuels, we can imagine that the transition would not involve a big loss of complexity, perhaps none at all. More likely, a reduced flux of energy and natural resources in the economic system will entail the kind of collapse described in the simulations of "The Limits to Growth." We can't avoid to go where the laws of physics are taking us.

Conclusion: showdown at Teutoburg

Two thousand years ago, three Roman legions were annihilated in the woods of Teutoburg by a coalition of tribes of the region that the Romans called "Germania". Today, after so many years, the woods of the region are quiet and peaceful places, as you can see in this picture

It is hard for us to imagine what the three days of folly of the battle of Teutoburg must have been. The legions surprised by the ambush of the Germans, their desperate attempt to retreat: under heavy rain and strong winds in the woods, they never were able to form a line and fight as they were trained to. One by one, almost all of them were killed; their general, Varus, committed suicide. The Germans left the bodies rotting in the woods as a sort of sacred memory to the battle. The ultimate disgrace for the legions was the loss of their sacred standards. It was such a disaster that it led to the legend that Emperor Augustus would wander at night in his palace screaming "Varus, give me back my legions!"

I think we could pause for a moment and remember these men, Germans and Romans, who fought so hard and died. We have seen so many similarity between our world and the Roman one that we may feel something that these men felt as well. Why did they fight, why did they die? I think that many of them fought because they were paid to fight. Others because their commander or their chieftain told them so. But, I am sure, a good number of them had some idea that they were fighting for (or against) the abstract concept that was the Roman Empire. Some of them must have felt that they stood for defending civilization against barbarians, others for defending their land against evil invaders.

Two millennia after the battle of Teutoburg, we can see how useless it was that confrontation in the woods soaked with rain. A few years later, the Roman general Germanicus, nephew of Emperor Tiberius, went back to Teutoburg with no less than eight legions. He defeated the Germans, recovered the standards of the defeated legions, and buried the bodies of the Roman dead. Arminius, the German leader who had defeated Varus, suffered a great loss of prestige and, eventually, he was killed by his own people. But all that changed nothing. The Roman Empire had exhausted its resources and couldn't expand any more. Germanicus couldn't conquer Germany any more than Varus could bring back his legions from the realm of the dead.

Civilizations and empires, in the end, are just ripples in the ocean of time. They come and go, leaving little except carved stones proclaiming their eternal greatness. But, from the human viewpoint, Empires are vast and long standing and, for some of us, worth fighting for or against. But those who fought in Teutoburg couldn't change the course of history, nor can we. All that we can say - today as at the time of the battle of Teutoburg - is that we are going towards a future world that we can only dimly perceive. If we could see clearly where we are going, maybe we wouldn't like to go there; but we are going anyway. In the end, perhaps it was Emperor Marcus Aurelius who had seen the future most clearly:

Nature which governs the whole will soon change all things which thou seest, and out of their substance will make other things, and again other things from the substance of them, in order that the world may be ever new.

Marcus Aurelius Verus - "Meditations" ca. 167 A.D.

Good post about fascinating topic. It may be worhwile to mention here two books that deal with the subject of fall of Roman Empire (among many other issues)

"Collapse: How Societies Choose to Fail or Succeed" by Jared Diamond
"The ecological basis of revolutionay change" by William Catton

After these two there is very little that can be said about the subject what has not been said before in one way or another.

Are you sure that Jared Diamond's book talks about the Roman Empire? My copy of "Collapse" discusses the Mayans, the Vikings, Easter Island and so on but Rome just gets one single solitary mention in passing... there's no chapter about Rome at all... perhaps you have a new edition... :-)

Thanks for an interesting essay
It's easy to forget that during the entire Greek/Roman empire period there was a much larger civilization that did not collapse, the Chinese civilization, and many smaller empires that lasted longer.
A question: Why was not Northern Europe, UK cleared and farmed allowing continued agricultural expansion?

"So, all our efforts are to keep the status quo ante . For this reason we are so desperately looking for something that can replace crude oil and leave everything else the same."
We have had it for 110 years, it's just that for the first 100 oil was too cheap for electric vehicles to be considered as a viable alternative. They are now!

Neil, thanks for this comment. About your question, as I say in the text, agriculture was not an isolated element in the Roman economic system. So, it was not just a question of "not enough land; let's get more". (just like for us it is not just a question of "not enough oil, let's drill for more"). So, I think the explanation is that the Romans lacked the economic resources to develop new lands because they had concentrated all they had into the military. And I hope you are right about electric cars, what I see now is a tremendous resistance against all novelties.

Ah.... also, about the Chinese civilization, All the time as I was writing, I had in mind that I should have mentioned the parallel Chinese empire; but the essay was already too long and the matter too difficult. It would be interesting to explore the concept that the Chinese didn't collapse as the Romans did because their society was less based on military fortunes than the Roman one. But I don't know enough about China to go into this in any depth

Terrific article! I know this may sound far-fetched to some, but perhaps China's long-standing civilization is due to their use of "night soil" or human waste as a fertilizer. When I read about ancient ruins, I find it odd that the existence of sewer pipes is considered a sign of an advanced society. Looked at another way, they are highly efficient devices for moving valuable nutrients into the ocean. Grain, vegetables, and meat are moved from rural areas into urban centers, where they are flushed into the nearest river and washed into the ocean. Over centuries, this will almost certainly reduce agricultural productivity, because ancient farmers couldn't economically borrow nutrients from distant places, as we have done by mining guano or producing fertilizers from natural gas. In contrast, China and Japan had efficient systems for moving feces and urine back into the fields. I heard a radio interview with William McDonough in which he described growing up in Japan in the 50s, hearing farm carts rolling into the city full of produce in the mornings and rolling out full of sewage in the evenings. I have also read that in 1880s Japan, people were paid for the contents of their privy barrels, and five or six people living in an apartment could pay the rent with the proceeds. Apparently farmers in China still build outhouses next to highways to collect night soil from passing truckers. I believe attaching this kind of value to human "waste" is a sign of a long-term agriculture that can sustain dense populations like those of China and Japan. Yes, I know they had periodic outbreaks of cholera, but there are other ways to cultivate rice without so much standing water (see Masanobu Fukuoka) and other ways to process the manure (see The Humanure Handbook).

All ancient civilizations depended almost completely on agriculture for their energy needs, and their EROEI was based mostly on fertility which determined how many people a single farmer could feed. Legionnaires, bureaucrats, miners, and craftsmen did not have time to farm, so they had to be fed on the agricultural surplus, and the gold may have served largely as a marker for the basic value unit of food. An influx of gold would then only cause inflation, and perhaps the more important aspect of conquest was obtaining fertile land, previously inhabited by "barbarians" too uncivilized to have removed the soil nutrients efficiently.

Yes, I have lived in Japan for 6 months, back in the 1980s, and they had stopped doing the humanure trade long before. Too bad!

China is an interesting case. It actually collapsed very frequently, in cycles of around 300 years.

Chinese dynasties (central government) regularly change.

However, the bureaucracy tend to remain largely intact, as with local authorities and villages.


On the same, abridged, post on the main TOD page, there is a comment from Hoekomsa (http://www.theoildrum.com/node/5594/521745) where he refers to a book by Peter Turchin, called Secular Cycles. I'm reading it right now and it's fascinating. He describes how many agricultural societies go through cycles lasting about 200-300 years. The emphasis is on Europe, but I assume the same happens for other societies as well. The 300 year cycles of China are very similar in duraction to the European cycles. I don't know enough about China, but I guess the same principles apply.

On this topic, another very intriguing (and more mathematical) book is Introduction to Social Macrodynamics: Secular Cycles and Millennial Trends. In particular see the chapter "Historical Population Dynamics in China". Basically, yes, the reason for the 300-year cycles is almost entirely Malthusian.

Thanks for the tip. I'm reading it right now (on Google Books) and it's fascinating. I just finished the introduction. It makes me wonder if the world will continue on it's hyperbolic course after the coming collapse or that this could be the last collapse and we descend into Olduvai.

As has been noted, China collapsed frequently.
Philosophers like Confucius, Moh Tze and Lao Tze were products of the collapse of the Han empire.
Confucius is very much about 'how things were done in the good old days'. Moh Tze proposes tactics for communities to defend themselves. And Lao Tzu has a clear 'return to nature and downsize' message (Chuang Tze, a pupil of Lao Tze, speaks of the drunken contemplation of one's leek garden in the moonlight...).
The Ch'in dynasty that gave China it's name, for whom the famous pottery army was built,
was a rather short-lived attempt at restarting the empire militarily from the collection of warring statelets that China had become after the collapse of the Han.
The Tang dissolved into chaos.

China is actually an interesting case history, of repeated collapses, and the repeated attempts at homeostasis.

I don't think you are aware but the Chinese empire has risen and fell at least a half dozen times in its history. Specifically as the Roman empire was in the process of falling apart, the Chin dynasty was also breaking up at the same time. The resulting break up of the Chin Dynasty made China look very much like mideval Europe. Similarly the Indian subcontinent was also starting to fragment at the same time. The only large empire to survive this period of disintegration was the Persian empire.

The main reason that the Chinese empire is seen to have never fallen is that the people in the area all spoke variants of the same language and held almost entirely the same religious beliefs. The rise and fall of the central organization didn't affect the culture, unlike the Roman culture that was completely wiped out by Christianity. Also a little known fact about the Barbarians was that they were Christian as Christianity had spread into the areas outside of the Roman empire much quicker than inside the empire.

Excellent post, Ugo.

1) Link to my site broken (the graph on Roman era inflation) - http://europe.theoildrum.com/node/www.sublimeoblivion.com/2009/04/09/not... , first part should be removed.

2) I think you over-emphasize the importance of gold. The major thing it allows you to do is efficiently monetize the economy so as to make the extraction of surplus easier (a very hard thing to do in pre-industrial subsistence economies). "Running out" of gold would have made this more difficult and may partly explain the transition to barter and payments in kind in the later empire.

That said, it was nowhere near as critical as our natural resources towards sustaining industrial civilization. Gold on the other hand has no energy or productive value, except as a way of better rationalizing the economy. I think the main cause of Roman collapse was simply too many pressures; a response in the way of a metastasized state, which worked previously; further over-exploitation of its human resources --> collapse inevitable.

3) Excellent point about the tragedy of those who realize what is happening, but whom society or politicians are bound to ignore if not suppress. The Roman Empire was based on the Idea of the imperial state; our Megalopolis is based on the Idea of ever more industrial growth. To question either is either lunacy or heresy.

4) The other excellent point is about how Tainter and the peakists are not mutually exclusive. The way I look at it is that Tainter's theory of collapse is very general; whereas peakists concentrate on just one factor, the declining EROEI (or even just oil production).

Thanks, historian. Sorry about the link: it should work, now. About overemphasizing the importance of gold; of course it is possible. But the beauty of dynamic modeling is that it is flexible. If you think dynamic, you don't say "the Roman Empire collapsed because they ran out of gold". You say something like: "running out of gold was a negative feedback in the economy of the Roman Empire". Then, we might be able to quantify that one day.

But you are right in saying that gold was not so important for the Empire as our natural resources for us. Without gold, the Roman Empire could still have survived as a political entity, had it not made the mistake of over-exploiting their human resources so badly.

There is more if we look at the Roman population curve, although for this we must rely on very uncertain data (see, e.g. the paper by Walter Schneidel . I can't show you a graph, here, too uncertain are the data. But it seems that, in any case, there was a population peak in the Roman Empire around mid 2nd century. If this is the case, the Roman population peak arrives after the production peak - just as shown in the "standard run" calculations for the world3 model.

copy of my post at TOD

Archaeology... I want to reach for a pistol and place it at the back of the head of archaeological academia.

I apologize in advance for my poor use and poverty of language

I take these Roman collapse arguments with a very large pinch of salt. Especially graphs deduced from statistical analysis of archaeological data. I do not dismiss Tainter's arguments out of hand but the validity of the supposed Hubbert like graphs and "what not" are often premised on some pretty loose analysis of what is in hindsight badly collated data.

The archaeological evidence of Roman London (londinium) is a case in point. The current model is that Londinium expanded in size to a peak population in the early 2nd cent then declined. This of course fits this peak empire model we see here. The evidence for this population profile is myriad but mainly taken from pottery data. The economic and cultural artifact assemblage mostly represented by pottery in London shows a distinct concentration in the early part of the city's life with a peak circa 120AD followed by a dramatic decline with a long tail extending in the late 4th cent.


this pottery vs time profile has been reinforced over the last 60 years with every site excavated in Roman London and seems to be a slam dunk for those advocates of peak late 1st early 2nd cent Roman London (and forms part of the wider roman empire argument)

Naysayers tried to argue that the later Roman assemblage had been truncated out the archaeological record by the action of later eras.. the closest in phase being the extensive pitting activity in the medieval era... since broadly speaking the assemblage is arranged in chronological strata (simplification) the later romman assemblage is more vulnerable to truncation by physical activity from above.

however Marsden and West did a study of residual roman pottery in medieval pits. The thinking was that if the latter roman assemblage was removed by later activity the Roman pottery profile of this residual Roman pottery in medieval layers would show a opposite or different shape to the un-truncated Roman profile....

well it doesn't. The Roman profile is preserved in the later Medieval features. This seemingly confirms without a shadow of doubt that the Roman assemblage is some sort of genuine parallel analogue of Roman demographic and economic activity.

case closed. and has been for 60 years (and some)


all of this has two big assumptions

1) the first of which is a genuine general failing of archaeology in general. the assumption is that the entirety of activity above ground is always represented by what is left below ground in proportion across time. IE if we find a decline in pottery density over time it represents a decline in pottery use above ground.... this is the "know unknowns" and "unknown unknowns" point that "what's his face" made in that book The Black Swan. the problem is we are not aware or even looking for what it is that is missing from the data set.

2) the second is more specific to the case study of Roman London in that the idea the Roman assemblage has to be an un-truncated distribution because we can not find any post roman process that could have truncated it.. this assumption is quite stupid in hindsight and should have been scrutinized a lot earlier especially given some of anomalous evidence. Virtually nobody bar one dismissed and forgotten observer in 1933 realised that the assemblage may have been truncated by the Romans themselves!

The data left by the Romans was modified by themselves.. any civilisation will modify its physical remains with in the time period of its on existence.

In the case of Roman London (and no doubt other centers of Roman civilisation) it is now coming to light that the Romans MUST HAVE done this extensively.

to be keep a long story short the Romans changed the way they disposed of roman pottery detritus in the latter roman period and therefore it does not show up in the archaeological record

One of the salient facts of many london sites is the domination of the Roman pottery assemblage by material in backfilled Roman quarries. My first thought was that since these quarries are concentrated in the first part of Roman London’s history do they represent a special case of disposal of Roman sherd detritus. Roman quarry activity declines at about the same time as the pottery assemblage appears to decline furthermore since quarry activity is a one time deal the ability to keep quarrying will be limited by spatial and geological limits rather than disposal practices. If the Romans had built the city from stone rather than clay and timber buildings from the outset would they have dug large pits for rubbish disposal? What we do know is in the latter Roman period when more stone buildings are being constructed there is a cessation of intensive quarry activity and the pottery assemblage is not concentrated as often for disposal. Could it be the early pre 160AD Roman pottery assemblage only survived in the record because the opportunity to dispose of it was presented by the existence of open areas peppered with large quarry pits that required backfilling? The problem with this argument is that it is circular in nature. The decline in pottery and quarries may be due to a genuine decline in activity rather a change in activity. How do you resolve such a circle?

what we did was divide the roman assemblage on a few test sites into two components. casual and mass disposal... casual disposal represents small quantities of potery scatter left kicking around and mass disposal represents the deliberate disposal of waste material.. the idea being casual disposal should still mirror mass disposal of the period. The results were sobering.

There is nearly twice as much casual pottery in the last 150 yrs of roman occupation as in the first 150 years. This is diametrical opposed to the current view of Roman economic activity. But it is not just the amount of material that is the problem it’s the realisation that almost all the late material in the profile is not actually the result of deliberate disposal activities. There is no large assemblages of late pottery concentrated in dumps or features It was hard to find any mass disposal mechanism for late roman pottery and the casual assemblage grew in time. that is to say that the part of the assemblage that didn't make it to the bin and was left kicking around pavements and backyards grows while the location or mechanism for waste disposal disappears!... what is worse we can calculate the rate the casual pottery assemblage is being created and its pretty absurd to suggest that the latter roman waste disposal mechanism is the wide scatter of potery sherds at the rate of one sherd per hectere every 2-3 days.

if you are arguing that the roman pottery vs time distribution is a genuine representation of declining roman economic activity you have to assume the mass disposal mechanism is in the record for us to see.

even more enlightening During the assessment stage of analysis was terracing activity observed that could be responsible for the removal of late 2nd cent stratigraphy thus a reason for why late 2nd century material was absent on some sites. We had a look for a possible destination of this missing strat and the first port of call we thought of (as did many other observers) is the Roman waterfronts which require large backfilling deposits. Since the dating evidence for these truncation events is they took place in the 3rd cent an investigation of the residual assemblages in waterfronts may throw up a mismatch between the dendrochronological dates of the late waterfronts and the material behind them. Basically we were hoping that 3rd century waterfronts had residual mid-late 2nd century pottery. It was on reflection a rather naive notion from the look and learn book of archaeological deductive reasoning. The pottery assemblages in the roman waterfront are pretty tight to the dendrochronolgical dating evidence and there is no obvious smoking gun. But this investigation again raises a very serious problem concerning the pottery profile

The notion that waterfront dump pottery is contemporary with the waterfront is rather problematic when we view the nature of the later Roman assemblage as a whole. The largest concentrations of later Roman pottery of the 3rd century are in the waterfronts deposits they are pretty much the only concentrations of 3rd century pottery deliberately disposed of on mass. Yet they must have been generated in a short period with in the time frame of the waterfront construction. How long does a waterfront take to construct. Canvassing opinion from peers returned estimates unanimously of less than a year. Even if we say that pottery wastage was stockpiled for a year because the waterfronts were going to be a known opportunity for waste disposal we are still left with a major headache. Where is the large assemblage of pottery for the year after or the year before? It doesn’t appear in the record yet we know when a waterfront is built one suddenly appears! The implication is that this waste assemblage is constantly being created but not surviving in the sequence because it is disposed of outside the city. Even more telling is the amount of pottery in waterfront deposits increases in time. The early waterfronts have little pottery in them compared to the later. In other words we again have a similar process to compare like casual disposal across time and the later waterfronts produce more pottery than the earlier despite they must have taken roughly equivalent times to build per unit length. The more this issue is investigated the more the roof starts to fall in on the house of cards we have built for ourselves

the answer is the romans probably threw there rubbish into the river... its not rocket science.

I could go on but I'm starting to Rant..and I'm off to watch the tour de france on tv..there is a lot more to this but the failing has been the constant generalizing from specific example school of thought and is in part a systemic failing of how archaeology is managed...

Basically the Roman city got big and remained big

from our perspective the worrying thing that all doomers are going to love is the decline was probably VERY rapid and there was in fact large amounts of economic activity prior to collapse..... this is a tentative as we are in the early stages of re-writing the story.



Boris, thanks for this interesting comment. If I understand your point correctly, there are some systematic biases in the archaeological record that imply that the collapse was much more rapid and abrupt than it would seem. It is very interesting, because if you look at the graph by Schneidel in my post, it does seem that the collapse may have been very rapid. And, for such things as shipwrecks, the Romans had no possibility of altering the record themselves.

In some respects, there is a parallel with the extinction of the dinosaurs: there may have been a systematic bias in the paleontological record that seems to make the extinction less abrupt than it actually was. That, however, is simply a sampling bias, and the dinosaurs had no chance to alter the distribution of their own bones!

cheers for responding...

I am more arguing that there is systemic bias in the record that hides the fact!

the problem is this

what is in the archaeological record (in the ground) be it a relative abundance or lack of certain types of evidence does not equate to a mirrored lack of or abundance of activity above ground...

the example I gave in Londinium (I'm a professional archaeologist there) is that the supposed peak in 2nd population is mirrored by a total orgy of pottery detritus that has been interpreted as some sort of economic and demographic maximum...

this has been the accepted truth for over 60 years

over the last 3 years (this is cutting edge) we have suddenly become aware that the negative evidence of a lack of late pottery actually represents an INCREASE in population and economic activity...

IE we didn't have an unfinished picture of Roman urban history we had THE COMPLETELY WRONG ANSWER the population did not peak mid 2nd cent.... it in fact went into some sort inflexion upwards to a new steady state that was preserved pretty much until the end... if there was some sort of overshoot it took a long time to manifest itself as societal collapse.

we do not know is the short answer and we need to review everything in the record based on understanding how it ended up in the ground. there is a new more objective archaeology based more on deduced mechanisms that created the sequence rather than cultural top down thinking.

some of these mechanisims can only be seen in very large sample sets.

example from above..

currently we look a site one at the time aiming to answer peer group designed research questions.

a common one in London is

"what is the evidence if any for late 2nd cent decline?"

most of this decline is predicated on a lack of artifact assemblage of certain date ranges... if that's your criteria you will always see the decline because there is a dearth of late Roman artifacts on London sites.. however when we look at ALL the sites we can see that the mechanism for rubbish disposal is not preserved in the record all of a sudden the meaning of what the dearth of finds represents suddenly changes..yes?

the light goes on and the penny drops.... this surprising simple insight answered several problems we had with cemetery data and anomalous assemblages of late dates in Roman waterfronts

to understand the past the contradictory pieces of the puzzle must reconciled together so as to explains EVERYTHING. you mention this in part about the contradictory evidence for agricultural activity...

the holy grail we came up with is that no evidence must be ignored or marginalized. there has to be a reason why two contradictory pieces of information can sit side by side.

if you can't explain everything you can't explain anything. (exaggeration but you get my drift)

what we often have had is the superimposition of current economic thinking onto models of the past. This is fraught with problems not least being the presumptions in the current data base are probably an utter load of bollocks

hard pill to swallow for the Romanist urban archaeologists

we got it BADLY wrong

.... in the current economic environment and with the end of the world and everything this new understanding hasn't as of yet gained much traction.. mainly because the funding for publication and research has dried up... there is also a massive problem with archaeology being funded on a site by site basis which actual impedes our ability to merge data from numerous sites..

we are not allowed to spend time combining sites as its a matter of budgetary restrain imposed top down

it doesn't work

I had to go outside the system to make the case. very frustrating

in a rush



Boris, thanks for these fascinating notes from a field archaeologist. I understand how difficult it must be to reconstruct the past from pottery shreds. Of course, I have no competence in this field, what I tried to do in my essay was just the following:

1. Build a qualitative system dynamics model of how the Roman Empire could have worked
2. Compare the model results with the archaeological or historical evidence as available in the literature.

Qualitatively the comparison appears to be good, so I think the model supports a certain interpretation of the archaeological data, and also the archaeological data support the model. But only qualitatively!! There is plenty of "slack" both in the data and the model, so that we can accommodate new archaeological data and new interpretations of the data. So, as you say, the population drop in Londinium may have been abrupt - that is not in contrast with the dynamical model. You could say, actually, that an abrupt collapse is more in agreement with the model than a gradual one.

One thing that I would like to do, one day or another, is to interpret by system dynamics the collapse of the Mayan civilization; which is also discussed in Tainter's book. You look at the archaeological data reported in some papers and they are smack on target: perfect lotka-volterra relationship of resources and population. But are the data valid? Other archaeologists contest these results and I - not being an archaeologist - don't know what to do. Difficult life.......

intuitively I suspect the Mayan collapse is a better/easier to use example of resource stress though I do not rule it out in the case the western Empire.

The Collapse in the west is seductive because we view it as a complex society sharing characteristics with our own...

The issue of slack needs some thought. Population collapse may not have occurred. The opposite may have occurred in Britain.

our understanding of the end times for Londinium is not understood well

things we know and the things we know we do not know

the collapse, it wasn't recorded! this fact is the biggest piece of evidence we have it was relatively quick. And again its a piece of negative evidence. We do believe abandonment of urban centers (in the UK at least) was not simultaneous by a meaningful margin of years.

I know of no real historical record of abandonment?

which I find slightly odd given we have some records of municipal meetings for boarderline sub-roman towns

we do not know if it represents a collapse in general population... as an aside we should note Somalia's population still grew even though the place went to hell. though food aid wasn' around in 410AD

from your perspective on which data to believe? I suspect that the carpet is going to pulled out from underneath a lot of long term holy cows in the Roman world.

but I suspect and I must re-iterate suspect the picture that could form may well be one that is far more catastrophic than is currently fashionable. which may agree with the points you raise.

whether collapse of social organisation in the late Roman era produces the same effects we could expect from other collapses is a very large unknown..

did complexity decline...

well my guess is yes.. because plumbing seems to have disappeared for a good few hundred yrs and you had to go and crap in a hole in the ground ;-)

complex societies=plumbing in my book

whether resource depletion was a cause....?

the gold argument is strong... as is the repeated hammer blows of increasing frequency (of all crisis types)

I think the wood depletion and carrying capacity arguments are far far more suspect..

we know that the largest wooden structures surviving in Londinium built in the late roman era are still using timbers of equivalent maturity as earlier structures. it appears to be a well managed resource.. wood is also removed and recycled constantly in a very though manner throughout the roman sequence starting from when the first buildings are demolished.. it was never a new activity occurring in later roman periods suggesting some remedial measure.

I think it is too tempting a target for sustainable warrior types to pick on these issues and go "see look what happened to them"

I am not sure whether the Roman empire was active enough to produce ALL of these resource depletion effects attributed to it.. I'm open minded about it...

the money/gold/inflation problem along with a degree of political social inflexibility strikes me as likely

there is better evidence of the problems it caused and we can see it as a common problem throughout history including today..

whats this website about?

I would argue the problem isn't fossil fuel depletion or population(though it obviously is) its persuading everyone to accept a paradigm shift in living. which is what your trying to do..yes?

an inability to change direction.

I think the problem is people carry on being stupid when its apparent the underlying problems one has aren't being fixed..

that appears to be true of the Western roman empire.. what exactly was the problem(s) is where I have my doubts when it comes to statistical presentations of all this stuff and served up as analogs

In a way I am very much on board your line of thinking despite disagreeing with almost all of it...

Great article. Thanks!

I learnt all (nearly!) I know about economics and the rise and fall of civilizations from playing "Age of Empires", an excellent computer game which many might have come across. Basically it is a computer model - steered by the player - of system dynamics, as per your essay. If you create too many soldiers then there are not enough peasants working in the fields to feed them, so they are weak in battle. If you want to build walled cities you need to put your plebs to work in the mines, which might be far from the garrisons so you need to build a garrison near the mines....

It really is a fascinating and educational game. One that all politicians should have to play.

Thanks for the post

Yes, of course; I have played that game, too! And at the actual presentation of my talk in Alcatraz, I showed a slide with one of the many strategic games that have the Roman empire as background. Wargames are, after all, a kind of simulation. Boardgames are a bit simplified, but still they can very well catch the essence of the development of an Empire. By the way, even Dennis Meadows - of "The Limits to Growth" - teaches system dynamics using boardgames.

Great article! Was prepared for the occasion to scan one of my favorite documents about Rome's decline, a page from a modern German text that lists all the potential culprits postulated to date; but I see who else but TOD member Asebius did the honors a couple of years ago, for Stoneleigh's post "Entropy and Empire":

Published in Bryan Ward-Perkins' book The fall of Rome and the end of civilization. Note "Impotenz" - aw honey, you'll do better next time...or "Hyperthermia" - drafty houses?

Would be great if someone fluent in German could translate some more of these. Perhaps one of them is "Hamburgers." ;)

I should also mention that Ward-Perkin's book is an outstanding catalog of the decrease in Roman complexity, sourced from the latest finds in archaeology. An example is the gradual decline in pottery, both in the finesse of its manufacture and the extant of its distribution.

Absolutely great, Dude. I can understand many of the terms of this list, although I am not fluent enough in German to translate the whole thing in English. Anyway, it makes me think - again - of the similarity of the way people deal with abrupt collapses: looking for a single cause that explains everything. Tt is true for the fall of the Roman Empire and for the extinction of the dinosaurs as well.

Let me cite from Benton's "When Life Nearly Died" (2003), p 85.

"In the time from 1920 to 1990, at least one hundred of theories for the extinction of the dinosaurs were proposed, although clearly at the low rate of only one or two per year. No stone or fossil was left unturned in the search for ideas, and these ranged from the purely biological to interactions among species, to changes in environments, to extraterrestrial causes <..> According to the varied list of reasons for dinosaurian extinction, anything is possible: climates become too wet, too dry, too hot, too cold: you can take your pick. Evidently, something is wrong here <..> I have labelled this phase of speculation as the "dilettante" approach", meaning that it was beset by dabblers, by people who thought about the topic for a while, published their pet idea, then moved to another subject. <..> a large number of the theories <..> show a remarkable relaxation of scientific standards."

Perhaps someone has examined this in depth - which would be apropos. Puts me in mind of the character in Foundation who is juggling various theories as to the veracity of the theory concerning a single planet whence humanity sprang to populate the Galaxy; he scoffs at the notion of actually going out and conducting research himself, too, preferring to contemplate what those before him have concluded. Rather memorable demonstration of intellectual sloth.

Got as far as "aberglaube" - superstition. Moving on to searching for "ackersklaverei," I see someone fed the list through OCR software and obtained these results. And from there: 210 Reasons for the decline of the Roman Empire.

Blockage of land by large landholders
Blood poisoning

What, they had unruly worker collectives back then?

These lists would make excellent T Shirts!

Though covering a different era, this might be of interest to the readers of this post: Guy Bois, La grande dépression médiévale XIVe et XVe siècle, 2000.
It's subtitled "Le précédent d'une crise systémique". I don't think you need to be fluent in French to get the meaning.

I discussed a similar point a few years ago on my blog (which died thanks to intransigence on Google's part, but I won't go there right now).

The post is here:


but I will reprint here a section on Rome that I think is relevant:

As I said, I don't think it's relevant. Also, I am uncertain as to whether it is actual or reasonable to think of a Western Roman "collapse", as much as it was a strategic withdrawal by the elite to more profitable places. Constantine could see, from his heinously expensive wars in Gaul, that Western Europe was a dud - a money pit, a black hole where wealth gets poured and little else comes back. In energistic terms, it had a negative ER/EI - Energy Return divided by Energy Invested. He went broke chasing the barbarian army around France, and converted to Christianity to loosen up the funds in a dominantly Christian run Treasury. This insight ran a hundred years earlier than Constantine - to Emperor Diocletian who initiated the divided between eastern and western Roman Empires.

And every rich family in Rome with any sense at all invested in the east. West of Roman Power? Celts. Illiterate pagan "savages". To the north? Picts. Nutty people from Scotland who painted themselves blue, which gets them all hopped up and crazy. And the Northeast was populated by Huns and Goths and other unsavoury groups. To the South? The Sea, and beyond the sea? Excellent farms hard up against the largest desert on the planet. To the East? All The Money In The World. Big Rivers, and the ancient civilisations of what is now Palestine, Egypt, Greece, Turkey, Iran, India, China, and the Silk Road through Afghanistan... Let's see, Celts vs. Greeks. Picts vs. India. Goths vs. Persians. Hmmmm. Not a hard choice to make there!

Within 200 years, Rome was done, but the Empire lived on: a few hundred years later it was still enough of a potent social notion that Charlemagne crowned himself the Holy Roman Emperor....

From a post in a Bay Area Energy group, by Dave Fridley, primary author of the SF City Council Depletion Protocol Study Proclamation (who deserves a medal, IMHO):

"In Roman times, 85-90% of the population were the energy producers--that is, the farmers--whose surplus energy supported the 10-15% of the population (including the emperor, army, musicians, artists, vagabonds, merchants and so forth) who were not directly involved in energy production. In the US today, 3% of the population (and vast amounts of fossil fuels) provides the surplus to support the 97% of the population not directly involved in energy production. In that regard, only the "elite" of the empire would have even noticed a material change with "collapse"."

Today, North Americans and Europeans are the elites. Again: Fridley writes:

"Although some Roman historians lamented the passing of the Republic (which lasted for about 400 years--longer than ours--til about 40 BC), I've never read anything of a self-aware group that looked at the material conditions of the empire and predicted collapse over some centuries in the future. That, I think,would be pretty much unlikely at the time, since in Western civilizations, at least, it wasn't until the publication of Thomas More's Utopia in 1516 that we ever viewed the future as a better place than the past, and thus see decline as something odd. Before then, the "Golden Age" of man--what civilizations aspired to, were always those of the past, and history was considered a process of degeneration. With this kind of world view, what exactly would "collapse" mean to one of the elite Romans and how exactly would it have mattered to the 90% of the population who lived in stasis?"

It's also important to remember why the Romans would even bother invading England and Wales in the first place... Why? Tin. the Phoenicians were in Wales 1500bce. At the time, there was so much tin in Wales, it came up out of the ground in extremely rich ores of black, almost purely metallic, material. It was harvested and sent back to Phoenicia to make bronze. The Romans were Iron Age people, but bronze was still a vital metal, and tin had many other purposes. The production of tin peaked during Roman times and went into depletion. England became worth less to the Romans, and yet another reason to abandon Western Europe.

So, to talk of a "collapse" of the Roman empire, as Fridley notes, is an act of 20/20 hindsight. After Constantine gave up on it, it took centuries for Rome to be sacked and leveled by the people it had violently oppressed. The Romans had no sense of a "utopian future", so calamity was always the word of the day.

Again Fridley:

"Compare this as well to the worldview of the Chinese, who developed a sophisticated view of rise and fall that came from thousands of years of dynasties rising then collapsing. To a Chinese, this was a natural phenomenon, and they created a whole phenomenology around it, including the concept of "mandate of heaven" (tianming) that gave the emperor his right to rule, and the withdrawal of the mandate that led to the collapse of the dynasty, usually indicated by natural disasters. It survived to the 20th century even...the massive Tangshan earthquake of July 1976 was commonly seen as the event that withdrew the mandate of heaven from Chairman Mao, and indeed, he died 2 months later and his regime overthrown."

And a few years later the post-punk music combo The Gang of Four would sing:

Out on the street: assassinate all of them
look so desperate
declare blood war on the bourgeois state too!
Watch new blood on the 18 inch screen
The corpse is a new personality
Ionic charge brings immortality
Guerrilla war struggle is the new entertainment!!!
Guerrilla war struggle is the new entertainment!!!
Guerrilla war struggle is the new entertainment!!!
Guerrilla war struggle is the new entertainment!!!

Fridley continues:

"...Kunstler (I believe) had a good insight into this as well. He remarked on the phenomenon of "temporal amnesia"--the fact that we forget how things were after a period of change, such as living in the same place for a long time. This building is replaced. Those trees are planted. Social security benefits are reduced. Copays go up. Food prices creep up. After 10 years, things are materially different, but do you really remember how it used to be? Over several hundred years of collapse, who in Rome or Mesopotamia or any of the other major civilizations that collapsed have had the historical context to talk about "collapse"?"

What we have, and the romans didn't have, is the knowledge of the basic laws of physics that govern all energetic systems. One big rule is: you can't get more energy out of a system than what is already there (or supplied). There is no energy fairy. When most work is done by hand, your farmers are the energy producers. When most work is done by hand, most work is in energy production.


So, I would submit that Rome didn't collapse. By our standards, perhaps, but to the Romans - the rich abandoned Rome and moved East where all the money was anyway, and the rest were left to fend. This is not a collapse: this is adaptation to changed circumstances.

WE have the tools to see it as "collapse". They didn't, so in that sense, it DIDN'T COLLAPSE. I would submit that much the same will characterise our own "collapse". The plagues, starvation, battles for resources, ecocide, etc. won't be seen as the logical conclusion of complexity, overpopulation, and resources depletion against thermodynamic limits. These will be seen as: a failure of the health care systems, political manipulation of food distribution, wars over ideological differences and social preferences, and the necessary sacrifice of nature for the economic needs of humanity.

It won't be a "Collapse". The collapse, which will easily take a century or more to complete, will likely be masked by these ideological human scaled reframings, as these are much more understandable, especially in a narrative driven media framework.

Tainter is brilliant, as is Diamond and the Club of Rome. I would add some other voices to the mix who don't have an iron in the depletion fire, but who provide important understandings as to how this ugly mess keeps afloat, especially Adorno, Althusser, and (to a certain extent) Stuart Hall and his notion of contested media.

Agreed: it is a point that Kunstler has made, and that I make, too, in my essay on the Roman Empire. Collapse is invisible from inside - just as water for the fish.

the result was the Spanish empire - it was also based on gold and it didn't last for long.

Not for long? If we take its duration from the year of Discovery by the Spanish Admiral Cristobal Colón [1492] to the defeat in the war of aggression by the USA [1898] where Spain lost Cuba, the Philippines, Puerto Rico, Guam and some islands in the Pacific, the Spanish Empire lasted four centuries, although much reduced in size from 1810.

In contrast, the British Empire started after the defeat of Napoleon (it had lost its colonies in North America in the 18th Century) say from 1825 and lasted to 1946 when it was forced to grant independence to the Indian subcontinent.
That's a scant century and a half.

As to the American Empire (whatever we want to mean by that) from its triumph in 1946 it is going on for some sixty years and there must be a reason why intimations of the mortality of empires and societies are so much the rage today.

You are right, Santalucia, my sentence was imprecise. Of course, "Long" or "short" depend on what you take as standard. I wanted to say that the Spanish empire had a relatively short phase of brilliance; which coincided with the arrival of gold from the Americas. Then went through a long tail of decadence in which it remained alive, but little more than that.

Anyway, as for short lived empires, I think the shortest lived one was the Italian Empire at the time of Mussolini, when the king of Italy declared himself emperor of Ethiopia. It lasted only 5 years, from 1936 to 1941!

I hope you aren't serious!

From wikipedia:
The British Empire began to take shape during the early 17th century, with the English settlement of North America and the smaller islands of the Caribbean, and the establishment of a private company, the English East India Company, to trade with Asia.

Why would you take the Spanish empire from the year of discovery, but ignore The Battle of Plassey in 1757, which saw the British, led by Robert Clive, defeat the French and their Indian allies, leaving them in control of Bengal?

Why ignore the fact that Maryland was founded as a haven for Roman Catholics (1634), Rhode Island (1636) as a colony tolerant of all religions and Connecticut (1639) for Congregationalists?

Why not point out that the British Cabot landed at Newfoundland only five years after Cristobal (Columbus)?

[Edit: Because he didn't start a colony, that's why...]

I will date the british empire from that Cabot landing, as you date the Spanish empire from Columbus' landing.

You are not making your claim in good faith, when you give the Spanish a start date of discovery but define the British empire as beginning long after they controlled land on 3.2 Continents (India is a 0.2!). Furthermore, the battle of Waterloo, commonly taken as Napoleon's defeat, was in 1815, so you've brazenly snipped another ten years off there.

Nor is it valid to define the end of the British empire so soon. The war with Argentina to retain the Falkland Islands was not so long ago, and Hong Kong was still controlled and (probably?) taxed by Britain until 1997.

To prove the point, I also observer that today, Elizabeth II is the queen regnant of sixteen independent states known informally as the Commonwealth realms: the United Kingdom of Great Britain and Northern Ireland, Canada, Australia, New Zealand, Jamaica, Barbados, the Bahamas, Grenada, Papua New Guinea, the Solomon Islands, Tuvalu, Saint Lucia, Saint Vincent and the Grenadines, Belize, Antigua and Barbuda, and Saint Kitts and Nevis.

She's not called an Emperor; but neither is Obama, and noone bats an eyelid at the mention of the American Empire. Queen Elizabeth II, in total, is the head of state of 32 various states and territories, and is the legal owner of about 6,600 million acres of land, one sixth of the earth’s non ocean surface. (http://www.whoownstheworld.com/about-the-book/largest-landowner/)(is this source reputable? That seems a lot...)

I'm not directly making the claim here that the British Empire still stands, rather I'd point out that it's by no means the flash in the pan that you indicate, and that whatever you call it, it's bigger today than the Spanish Empire ever was, and if we accept the 6.6 billion acres figure (which could be dodgy..) the it's three times bigger today than the US Empire is.

So! Having got that off my chest, if we are going to discuss empires in general, we need a better definition. Back to wikipedia again, we have a good one: "An empire is a State with politico-military dominion of populations who are culturally and ethnically distinct from the ruling ethnic group". Works for me; but it means that we are both wrong about our start dates, but I claim 1997 as an end date for the British Empire. I give you the permanent Hispanola colony in 1493, and claim... Ireland, drawing on precedents dating back to the Norman invasion in 1171. (Just kidding) If we only count successful colonies, we get St. Kitts in 1624!

So that's 1492 to 1898, 406 years for Spain.
And it's 1624 to 1997, 373 years for Britain.

So even though you were wrong, you still win! Congratulations, this has been fun.

Negative feedback kills.

This is a common misconception and should be corrected. It is positive feedback loops that most often lead to "negative" effects. It's confusing, I know, but positive feedback is self-reinforcing and results in the kind exponential curves that exhibit overshoot and collapse behavior. Negative feedback loops are self-dampening and result in the kind of curves that exhibit goal seeking behavior.

Complex systems have a balance of both self-reinforcing and self-dampening loops that tend to cancel each other out. It is when you introduce a forcing that tips the balance in favor of a positive, or self-reinforcing feedback that you set the stage for potentially catastrophic results.

Positive feedback kills.


Yes, you have a good point. But note also that my sentence "negative feedback kills" was just a way to emphasize the concept that the negative feedback determined by - for instance - running out of mineral resources, will eventually destroy that society. But, it is true that without a positive feedback, you can't have the negative feedback that kills!

The many subtleties of system dynamics.....

Thanks for the reply, and for an excellent article on the dynamics of collapse.

But, it is true that without a positive feedback, you can't have the negative feedback that kills!

I won't belabor the point anymore except to point out that you seem to be confusing the words "feedback" and "consequences" which in the context of an article on system dynamics have two totally different definitions. I thought I described it simply enough in my original comment: Positive feedback has negative consequences. Perhaps the subtlety is being lost in translation, but if you want your meaning to be clear then your article should be rephrased in several places.


Just wondering if anyone here has read "When Histories Collide" by Raymond Crotty. He has some very interesting ideas in the early chapters on both the growth and collapse of societies and empires.

I read Collapse of Complex Societies several years ago. Tainter says that certain civilizations, notably the Mayans and some MesoAmerican civilizations failed due to overfarming and environmental degradation. He does not say that this is the cause of the collapse of the Romans or many other civilizations.

One example that stands out is that Britain almost collapsed in the early 19th century after it was almost entirely deforested for fuel. In order to keep warm the British were forced to mine coal in horrible conditions. Tainter viewed this as a collapse process. Where more and more effort is required to maintain a lower standard of living. Tainter credits the invention of the steam engine, which was invented out of necessity to drain flooded mines, as being the fundamental invention that saved British civilization from collapse.

IMHO, Diamond is fixated on the Malthusian ideology and instead of letting the data tell him things he mearely picks examples that conveniently reinforce his ideology. Easter Island and the Greenlandic Norwegian civilization are pathetic examples in that they were very small groups of people that didn't last for very long. Tainter on the other hand focuses a lot on Rome, and especially the Eastern Roman Empire (Byzantium) which lasted longer than any civilization in the history of the world except for the Egyptians.

Most interesting, thank you!

Michel Bauwens has proposed an analogy; the fall of the Roman Empire necessitated a relocalisation of production, which an "open design community" caled the Catholic Church helped propagate throughout Europe (think of monasteries as capacity-building centres). In the same way, the collapse of the Consumer Empire will need a relocalisation of production propelled by the Internet driven p2p open design communities. See, e.g.,

Bauwens' idea seems to tally well with the Druid's proposal.

However, I'm wondering about the concept of complexity here. Couldn't one argue that the transition from Roman times to Middle Ages also, in a sense and eventually, also increased complexity? Wasn't the Catholic church with its different orders also a very complex thing? How do we measure, even qualitatitely, the complexity of a society? Does "lower complexity" equal "less hierarchy" and, therefore, "classic anarchism"?

Astroboy, you are making a good point. The problem is, as you have noticed, is that we are talking of "complexity" in qualitative terms. I tried to equate it to such parameters as industrial capital and population in the "Limits to Growth" model, and that quantifies it a little bit - at least it defines it.

Now, perhaps we could measure complexity as "number of people employed in non food producing activities" or as "relative complexity" as the "ratio of the number of people employed in non food producing activity to the number of people employed in food producing activities"

Now, the Catholic church is - surely - a complex structure and it was at its beginnings. But how do we quantify its complexity? My impression is that in the late Roman Empire the Catholic Church was a far smaller structure than it is today. Read the story of the life of St. Patrick to have some idea of what the early Church was like. So, I think the presence of a Church and of a minimal hierarchy within it didn't make the late Roman society more complex than it was at the height of the imperial times.

But the point you are raising is interesting in the sense that we could define a "cultural complexity" that is not the same as "social complexity". Since I mentioned St. Patrick, think of Ireland at his times. For what we know, it was not a complex society: low population, no central administration, no structured hierarchies. But it was the land of the Bards who developed a very complex and structured form of poetry. Thinking complex things in one's head may not require so much energy as building up a formal hierarchy with friars, deacons, priests, bishops, archbishops, cardinals and a Pope.

Another point that maybe many of us have noticed is that modern language seems to be gradually losing complexity as society becomes more complex. Maybe our brain can treat just so much complexity and no more.

Hmm ... and it all gets even more complicated if not "complex" if we believe the recent anthropological findings that suggest that primitive gatherer-hunters use much less time in "food producing activities" compared to agriculturalists. Would this mean that gatherer-hunter communities are more complex than agricultural communities? Certainly they are less hierarchical and more equalitarian. Maybe there are two different axes at work, here.

The distinction between cultural and social complexity may be important here. At the very least, I think, we could argue that the type of multi-generational knowledge implicit in oral traditions – Bards, druids, the shamanistic practices of nomadic and gatherer-hunter cultures – is qualitatively of a different type compared to the implicit knowledge of cultures included in eras like the Middle Ages or Modern West. One possible "primitivist" hypothesis could even be that the amount of environmental sustainability increases with the amount of "cultural complexity" and decreases with "social complexity", if these types of complexity are linked to these different types of knowledge. Again, at the very least, we can empirically observe that all sustainable civilizations/cultures (sustainable for millenia) have been oral civilizations with a different type of knowledge.

On the other hand, it might be relatively simple to argue that Ancient Greece, for example, was culturally much more complex than contemporary societies. And that was not very sustainable, or aware of its own conditions of existence.

Even for the level of depth we are used to here on TOD this essay is a milestone.

Prof. Bardi will probably remembered as a true "renaissance man" for this feat of presenting a complex line of thinking with such power of language that you just can't stop reading page after page. When I read his final chapter I thought of the poem "Ozymandias" by Percy Shelley. (It describes something very different from the Teutoburg forest, but makes the same point.)

I have a question (to Prof Bardi, but also to whatever druid who wants to answer):
Such a fundamental point as the inability of decision-makers to stop the frantic clinging to the status quo ante (which would allow us to at least travel in style and comfort instead of having a rough ride to the dimly percieved future) should that not be discussed also by those people who are paid for such things? Philosophers? Sociologists? Even Theologians?

I understand that mainstream media and politics may be limited by phenomena not unlike the reasons that prevented Mark Aurel to disband his legions. But are there no academic circles that would profit from a discussion about this excellent essay?

Or is the continental divide too big between those who (at least sometimes) use the yardstick of mathematics to assess an idea and those who are purely discussing ideas in the context of what sounds good or does not sound good according to the currently prevalent paradigm?


Not quite a druid here, but I'll take a stab at your question:

People inclined to question the current paradigm are unlikely to find themselves in positions where they will be heard by the leaders, let alone paid to provide advice to them, regardless of their training.

This is one of the feedback loops that supports continuation of a social paradigm even after it passes its usefulness.

Thank you, Polydeukes, but, really, I am not doing anything special. I am just applying principles that were developed by the real masters of this way of thinking; Jay Forrester, first of all, and then the team of "The Limits to Growth", Dennis and Donella Meadows, Jorgen Randers and others. Actually, the true giant of dynamic thinking is - I believe - Charles Darwin. He was - probably - the first in modern history to tackle what we call today "complex systems" (to be sure, also Darwin's contemporary, Stanley Jevons, was a first class dynamic thinker)

But you can see that dynamic thought has tremendous problems in being accepted - that is true for both "The Limits to Growth" and "The Origins of Species": Maybe we can find an explanation within Darwin's thought: thinking dynamic, in itself, doesn't give one a great evolutionary or reproductive advantage.

So, what to say? For one thing, it is true that we have these intellectual tools that no society before us ever had: dynamic modeling, computing, etc. On the other hand, our leaders don't show any willingness in using these methods. And even in academic circles things are not better. For an academic career, interdisciplinarity is not only useless, it is a definite disadvantage.

At this point, I think that Nate Hagens (another dynamic thinker) would say that the solution to diffuse dynamic consciousness is in having women choosing men who think dynamic. I would completely agree!!!

Sorry, Prof. Bardi, I did not realize that you are so profound a pessimist with respect to interdisciplinarity and even w.r.t. the procreation abilities of dynamic thinkers.

I did not ask why druids are such a small group at the fringe that nobody wants to listen to. The reasons are obvious and you give a good example in your essay yourself.

We all know that doomers are per se not very attractive to women. Even less if they paint a picture of the future like J. H. Kunstler in "World Made By Hand" where women are basically only there to cater to the needs of the male heroes. (Otherwise this novel is quite worth reading btw.)

So let me ask my question again: Is there no interdisciplinarity at all? Would not philosophers, sociologists, theologians etc. need some new food for their thoughts now and then? Especially in times like these where the global crisis shows that something may be changing at a fundamental level and we do not understand it very well?

I can understand that it is nice and cosy in the ivory tower and the view is great. Such is human nature. But do we really have to lock ourselves up there forever?

Polydeukes, I don't think I am especially pessimistic. It is the way academy works. You know, it is curious how often structures claim most loudly the things they are not. The Old Soviet Union claimed to be working for the "proletarian paradise", here in Italy we suffer under the dictatorship of a party claiming to be "the party of freedom"; there are many more examples. Now, academics always claim that interdisciplinarity is a good thing - just like the old soviet union did with workers being in charge....

But, if Academia as a formal structure is so innovation-averse, that doesn't mean that individuals in it can't be innovative. In fact, there is a good tradition about "academic freedom". It is mostly talk, but there is something in it and in Academia they - normally - leave you free to do the things you like at least for a fraction of your time. It is like that for me. My work is mainly with high temperature materials for the aerospace industry. What I can do with modeling the Roman Empire or Peak Oil, I can do in my free time. I am sure it would be more difficult for me if I were employed in a company. And, if I were a freelance writer or like that life would be much more difficult; for sure. So, I think academia is a good compromise: you give away some of your freedom, but not all of it.

I'm afraid it will be the opposite. Societies under stress - which we are likely to become in the next decades - tend to repress thought and insist on conformity. Talking of "limits to growth" may well come to be regarded as "sabotage" or "terrorism" by the powers that be.

Of course. Actually,all that has already been said about "The Limits to Growth"

Of course. Actually,all that has already been said about "The Limits to Growth"

where's my comment gone ?

From a modeling perspective I am surprised at the ease with which a model is applied out of the context of its development. Force fitting rarely leads to valid results, even they might be in line with the preconceived notions of the audience.

This paper would have benefitted greatly from taking recent publications on the fall of Rome by historians into account.

Just because there is system dynamics model about limits to growth and there was a Roman empire which frist grew and then declined does not prove that the variables in the generic world model are sufficient to explain the fall of Rome. For example parts of the Empire which were governed by East Rome and were not raided by the invaders showed no sign of decline in the fifth and sixth century, on the contrary some areas were getting richer. Lots of the decline in complexity has to be attributed to the loss of provinces to the Germanic tribes which caused parts of the highly integrated and specialized Roman production system to collapse, also the loss of revenue generating provinces could not be dealt with in the established governing system (this is a relevant learning from the fall of West Rome for us today: Elites which do not adjust in their spending might well ruin the empire).

This is the first explanation of the decline of Rome without mentioning Alans and Huns. The Roman borders were relatively quiet before the advent of these folks. The unrest of the Germanic tribes was most likely caused by pressure from the east, and even began to unite to large scale military operations and settlements, not simple border raids. Rome had to defeat itself against constant military threat; in addition the Persian border was never really safe. Military innovation further helped the attackers - especially when comparing the organisational complexity of the tribes defeating Varus with for instance the Goths, trained in long years of service in the Roman army, thus accumulating Roman military know-how. Rome lost its military edge - quite of a few of its military leaders were not of Roman origin. It took until well into the fifth century until the marauding tribes could successfully lay siege to a fortified town. I have not yet seen any mentioning of invaders in the world model. The dynamics change imo completely when one is not dealing with external invaders - I do not see that threat currently for Europe or the U.S.A - but with limiting ourselves to resource constraints we have to impose on our selves. More fitting to our situation is the observation that Rome's demise was largely helped by internal fighting which again and again prevented efforts to drive back the invaders.

Just because the wind did follow the usual seasonal pattern the Vandals escaped annihilation by the combined East and West Roman attack in the June of 468. Had the wind blown in another direction, the ensuing military push of the Romans and the state of the Gothic states at that time could well have been brought North Africa, Spain and France back under West Roman leadership within a year or two. This would have given West Rome a sufficient tax base back and as the Huns were defeated in 451 probably some hundred years more of existence. East Rome - which almost went bankrupt because of the failed investment in the fleet of 468 - was so close to collapse that it continued to exist for 1000 more years. The proposed model cannot explain why East Rome survived West Rome.

Suggested reading: The Fall of Rome, Bryan Ward-Perkins, 2005; The Fall of the Roman Empire, Peter Heather, 2005

While your points are all very valid (as are many others from other commentators e.g.: that the elites just moved east and abandoned the west) I do not see them disproving the basic model of food supply, money supply and inner workings of the empire. (Who is doing the work, who is doing the administration, who is doing the fighting.)

As far as I can see, you just put your emphasis on different facets of the same story. (Internal fighting instead of buerocracy, loss of military knowledge instead of the cost to pay the fighters to fight on your side)

Hmm, apologies for not making myself clear when typing this down in the middle of the night... I'm coming from an different angle: I just don't see that implosion was a necessary outcome for the Roman empire, more importantly half of it did not implode at all. Limits to growth postulates decline without external forces (eg Martians or whom ever from space to stay in the picture), whereas Rome got under external threat and could not change its internal workings to adapt to the changes, like the governors and fugitives from lost provinces didn't lose their entitlements thus overburdening the state without adding value (this I think is the interesting part for us today - as no one can lose an entitlement but resources decline).

The elites didn't went eastward and left a vacuum in the west. The empire got split up and each part looked after its own benefit (first and foremost). There were always close contacts but the surplus to help the others was often missing as each one was fighting different wars. The tragedy of 469 is that the final joint effort failed because of bad luck. The tone of the article implies at that stage decline would have been inevitable. It wasn't as especially eastern Rome had a millennium to go. We cannot devide an empire in two parts and only look at the part which went under to claim food, money supply and internal workings to be the culprits for the demise. Both parts of the one empire did not collapse at about the same time. Or the author should prove that in last hundered years the western and eastern culture deviated that much to make his point.

The loss of military knowledge was a built-up of military knowledge on behalf of the attacker. The tribes at Varus time could lure the Roman army into an ambush but they could not build own Reichs. The Goths three to four centuries later could, Rome had lost its organisational and military edge over the attackers. And it lost large parts of its tax base after the invasions of 406. An empire in fatal decline - but even the west survived 70 shorts years thereafter.

Also, Rome did never document its most remarkable achievements well. Most of its economic power is not understood yet. For instance I read a book by a member of the Vorstand of the Bundesbank describing Ceasar's Aureus as an unsurpassed model for monetary stability over a very long period of time. Of course, after some 300 years it lost its touch but I don't know many currencies which survived such a long time without substantial debasement. In comparison in the short period since 1913 the dollar lost more than 90% of its value.

None of the factors I'm mentioning here is reflected in the world model. It is an interesting thought to apply it to a different setting but we should not do force fitting just because we like the idea. Glass bead games do not help system dynamics. The models due to their power cause enough anxiety on their own - read Forrester's recent interview in the Sloan Journal. Misapplying them dilutes the clarity of the message.

Quite telling which posts get a comment from the professor and which not. Reminds me why I shunned a career at the university.

I'm not sure if I understand what distinguishes the articles that get a comment from the professor from those that do not. I would definitely like an answer to your arguments from professor Bardi.

That said, if you agree to discuss your point with a complete amateur like me, I still do not see how your points disprove the model that has been adapted from the club-of-Rome model. It always depends, what you consider variables and what you consider boundary conditions. The fact that military edge is lost after some time is treated as a fact of life here i.e.: as a boundary condition.

The Romans were still vastly superior to the Gauls in military technology when Caesar fenced in Vercingetorix and fenced out the Celtic tribes that would have come to his rescue. The Roman empire had lost this edge already some time later but was able to incorporate (at least some of) the Goths into the empire by using enough of its resources (gold, agricultural land for retired soldiers). But even this strategy did not work any more with the Huns and the other "strong opponents" that you seem to prefer as the leading cause of the fall of the Roman empire.

Your point about the Vandals in North Africa is also very worth of discussion. It reminds me of the cause why the "limits of growth" druids met with such ridicule soon after the oil crisis was just a bad dream the world had woken up from. It was the new oil fields in the north sea and an Alaska that for a short time created a world "drowning in oil". That would have been the equivalent of the Romans discovering a really big gold mine somewhere or if the winds would have blown differently so the Romans and Goths would have recaptured North Africa from the Vandals. But as we all know, the reprieve from the oil crisis lasted only a few decades and in the same way even a recaptured North Africa would only have extended the resources of ancient Rome for one or two centuries. Then the same phenomena linked to "using up more than what can grow back" would have taken effect wouldn't they?

And the military edge of the Roman empire when Caesar defeated the Gauls needed a lot of trees to build those walls. In addition to soldiers that really work together putting the last ounce of strength behind the wheel so to say to ensure victory. (As opposed to soldiers that need to be paid decently and don't trust their superiors so much any more.)

Therefore I think your points don't disprove Bardi's model any more than the "years of cheap oil" disproved the "limits of growth" model.

Of course I agree with you that we can (an should!) always argue what are primary variables, what are secondary variables (consequences) and what are boundary conditions (facts of life) in any model.

apologies, but I cannot follow you as you take that which has to be proven as an assumption and base your argumentation on it.

If resource constraints were the reason for the collapse then the whole empire would have collapsed. The Roman empire does not equal Rome. The internal dynamics were the same in East and West Rome. If internal constraints were the main driver for its demise, the Eastern and the Western part of the empire would have collapsed at about the same time. Any model has to explain why after the formal separation in 395 (or maybe take Diocletian in 286) Rome fell in 476, Constantinople in 1453 (and do not underestimate the blow it took when the crusaders took it out in 1204). Your argument about additional "cheap oil" does not cover an extension in time of 10:1 (or 5:1).

Or it has to be shown which fundamental internal differences must have developed between both parts of the empire after 395 (or 286). Justinian unopposedly took over the claims over the western part after the fall of Rome so West and East Rome were not considered separate entities. They were parts of one entity.

Marc Aurelius headed an unified Roman empire. Could anyone here please explain using only the variables pollution, capital investments, population, agriculture, and natural resources why West Rome fell 1000 years earlier than East Rome? If not, the whole exercise is futile.

What I am seeing is that a model is taken out of context and its conclusions are applied in a new context. This is always tricky and calls at least for recalibration. Otherwise it is just guesswork. SD has a clear quantitative base and I don't see any of that applied here. Bardo's claim "to apply system dynamics on the history of the Roman Empire" does not hold true, as he only applies qualitative system thinking. Worse, he takes a model from someplace else and claims - but not proves - that it is applicable. I'm not arguing that LtG is wrong, it just doesn't explain the fall of the Rome as it does not explain the fall of the Roman empire.

Very good point, Yerk. I think I finally understood your line of reasoning.

Egregio Professore Bardi, could you enlighten us on this issue?

(I.e.: What distinguished the two parts of the Roman empire so that one part collapsed so much faster than the other?)

We do see bell shaped curves whenever a natural resource is exploited in a free market conditions.

I'm puzzled by this. Surely wind and solar power are natural resources, which are effectively undepletable?

Correct, Nick. That sentence should have read "Whenever a non renewable or slowly renewable resource....."


Well, the Limits to Growth model assumes that there is a hard limit to all resources. We know that's not true of energy, right? In fact, we know that with enough energy there are very few resources that have practical limits.

Doesn't that invalidate the LTG model?

Nick, take it from a physicist: If you consider earth and sun as a closed system, you do have (for all practical purposes) a hard limit on the energy that is available per unit of time. Everything except geothermal energy and nuclear energy is direct (wind, water, sun, biomass, etc.) or stored (coal, oil etc.) solar energy and there are definitely also hard limits on nuclear or geothermal energy.

True, there seems to be a lot of solar energy available to anybody on earth. But in essence, you need to own land to make use of this portion of energy. In the olden days it was fertile land that was most precious. Soon it may be deserts for CSP plants or areas of water where you can grow algae. But in the end you need to defend your land (or portions of the sea) against intruders that want a slice of your energy cake in the same way as in the olden days, don't you?

If you consider earth and sun as a closed system, you do have (for all practical purposes) a hard limit on the energy that is available per unit of time

We also have to worry about the Sun dying in 5 billion years. But that's not a concern for practical purposes.

True, there seems to be a lot of solar energy available to anybody on earth.

Yes, about 100,000 terawatts, vs our current consumption of about 10!

you need to own land to make use of this portion of energy.

Sure. There's more than enough farmland in the US with good wind resource to supply all we need. The rooftops in the US provide enough area for our current electrical needs as supplied by PV. I think we have the land. The rest of the world varies, but there's an enormous excess of renewable energy just about anywhere.

you need to defend your land (or portions of the sea) against intruders that want a slice of your energy cake in the same way as in the olden days, don't you?

Who would the US be worried about? Canada?

Nick, I congratulate you on your optimistic attitude. albeit your viewpoint seems to be very limited to the USA. (Your comment about Canada reminds me of the joke what distinguishes an American rucksack tourist from a Canadian one: The dude from the US has a BIG Canadian flag on his rucksack :-)

But you should consider that the US model of land use (suburbia) needs a lot of energy because things are so far apart and you have to drive everywhere. Therefore the amount of available land for PV and wind is mostly theoretical and I don't think it will ensure the role of the USA as the ruling elite of the world for very much longer.

optimistic attitude

Not really anything optimistic about it. I'm questioning the validity of the LTG model. That's a basic question.

viewpoint seems to be very limited to the USA.

Not at all. The US is clearly the country most relevant to this discussion: it has the largest new wind-build, it's the largest consumer of oil, etc.

US model of land use (suburbia) needs a lot of energy

It doesn't need a lot of energy (think Aptera), and it certainly doesn't require oil, but it does currently use a lot of both, I'll agree.

I don't think it will ensure the role of the USA as the ruling elite

Well, China, India and Japan are going to be hurt by Peak Oil quite as much as the US. Russia will do well. Brazil will be ok. Then all of these relationships will change after the transition away from oil.

But, let's get back to the question: doesn't the lack of practical limits to energy supplies make the LTG model invalid??

Hey Bardi;
Our man Marcus Aurelius was just spouting the standard observation based philosophy of the ancient world.
He was one of the old guard nothing futuristic about your quote given at the end of the article.
See this quote from Nietzche I posted on my blog:
For the Greeks the sexual symbol was therefore the venerable symbol par excellence,the real profundity in the whole of ancient piety.
Every single element in the act of procreation,
of pregnancy, and of birth aroused the highest and
most solemn feelings.
In the doctrine of the mysteries,
pain is pronounced holy: the pangs of the woman
giving birth hallow all pain; all becoming and growing
-all that guarantees a future-involves pain.
That there may be the eternal joy of creating, that the will to life may eternally affirm itself, the agony of the
woman giving birth must also be there eternally.
All this is meant by the word Dionysus: I know no
higher symbolism than this Greek symbolism of the
Dionysian festivals.
Here the most profound instinct of life, that directed toward the future of life, the eternity
of life, is experienced religiously-and the way to life, procreation, as the holy way.

The end of empire was implicitly recognised by the entire belief system and the iconography of empire.

For example the corner stone of Roman myth - Romulus and Remus came from nothing to found Rome.

I imagine the elite maintained the sang froid of the old philosophy.
Being enlightened they realised that for them concentrating wealth even when you can see the inevitable outcome has been proven to be a winning strategy in the long run and results in a comfortable life.

My perspective is that warfare has its own logic look at the longevity and wide distribution of Genghis Khans DNA a good return on investment.

More efficient forms of warfare allow quick conquest of others concentrated resources i.e. women.

Look at other DNA profiles, the Welsh – only the Y chromosome is Welsh.

Look at any modern ethnic cleansing action Bosnia, Sudan – all the men are killed.

You seem to have missed the prime directive as the cause of the rise and fall of the Roman Empire.

The Y chromosome drives us to warfare.

Typically if your family have not the basic surplus of resources to buy a bride or get you a marketable education the only option is to sell your labour as a soldier gambling on gaining a greater share of resources.

Either directly or by “service guaranteeing citizenship”

All your exposition about gold is just plop ;¬)

Once you have conquered territory and your soldiers have married locals there can be no retreat - you can not settle them on lands already occupied and to not fight often results in male genocide.

Here is some hard evidence


Well, as for Marcus Aurelius, he surely was within the established stoic tradition. He was not especially original, he amply drew, for instance, from Seneca. The curious fact about him is that he was both a stoic philosopher and the Emperor!

About the Y chromosome and the drive to fight; you are basically right. All these models imply that individuals try to improve their lot in the way which is best for them. In some societies, it is fighting in the army. For the Romans, it was surely one of the few ways for commoners to gain money, a bride, and some land.

Are you really getting the picture from my perspective all of the models you mention are rather like theories for how phrenology can be best interpreted ;¬)
That is the basic premise is just wrong: the Romans orbit was described by their form of warfare all societies collapse as part of the sexual selection process.
Core 'culture' survives the process depending on its then proven generic usefulness and the proportion of the population which are strongly genetically / culturally identified for example the Han Chinese.
Chinese empires come and go Han culture resurfaces.
Another example are the Anglo-Saxons they wiped out the native and Romano British, when invaded by the Normans the Normans ended up speaking Anglo-Saxon after a couple of centuries.
Perhaps the most telling example is the Roman state itself composed of genetic sub-groups.
An good friend a daughter of an old Campanian elite family was adamant that her family were Etruscan not Roman or Italian and had maintained that knowledge since antiquity.
Members of her family were pivotal in the rise of modern “Italian” nationalism.
The heartland of the Etruscan people just happens to be the current population centres of central and northern Italy.
Emperors were effectively civil servants by the time of Marcus Aurelius (MA) therefore it is predictable that an appointee of the elite would be a stoic philosopher.
The way I see the situation is that the centre was well aware of the long term outlook.
It is implicit in their philosophy just because they chose not to explicitly state the obvious in the few records that exist does not imply lack of comprehension.
MA seems to be a man of good taste to state the obvious would be the mark of an under educated man.
You mention the example of land grants to time served soldiers, land grants can only happen once. They are also a good example of how dry facts from one era in an ancient society become incorporated into a holistic model of a society and trotted out without analysis.
So looking at land grants: once made what other options do you have given the case I made in my previous post that withdrawal is not actually an option after the first generation.
Debasing of the currency was inevitable given that gold is a finite resource even if being mined its rate of extraction after the initial find will be constant.
Meanwhile the proportion of the population tied to Rome by blood and so entitled will be growing...

Regarding the Y chromosone driving us to war, two thoughts:

- the demographic transition that certainly has a lot to do with current economic problems is in part due to an increase in the power of women to make their own decisions regarding childbearing. Not surprisingly, we're ending up with less kids. This rather new phenomenon not observed in history previously to my knowledge seems to indicate a change in the balance of power away from the Y chromosone, which seems like a positive development.

- secondly, large scale war is no longer a good employer of men. Industry has gotten to the point where it needs less and less human input - consequently interest rates have descended to a 315 year low. Future wars are most likely to be decided by biological and nuclear means, and further, the ROI of a war of conquest will not be what it has been in the past. So I suspect (hope) that this avenue of collapse may be closed off.

It is nice to think that we have entered a completely new era where "war does not pay" and where women take leadership because now we have birth control. (Creating a more just and peaceful world, if I understand your post correctly.)

However this may be a fallacy as has been noted by Philip Longman in his seminal essay in 2006:


Longman also discusses ancient Rome and how patriarchy seemed to disappear at the end of the empire. He notes that it may become unpopular among some people, but these people are soon replaced by others:

"Eventually, for example, the sterile, secular, noble families of imperial Rome died off, and with them, their ancestors' idea of Rome. But what was once the Roman Empire remained populated. Only the composition of the population changed. Nearly by default, it became composed of new, highly patriarchal family units, hostile to the secular world and enjoined by faith either to go forth and multiply or join a monastery. With these changes came a feudal Europe, but not the end of Europe, nor the end of Western Civilization."

Falling birth rates are pretty universal - they're not limited to a small elite.

Sure, much of Africa and the Middle East are still growing pretty fast, but they're a distinct minority.

Nick makes the key point. If we consider the anglo-saxon west as the current elite, it is easy to show the fertility decline extends well beyond this domain. In particular china has a huge aging problem coming down the pike, and nations such as iran are having big problems with replacement.

The causes are not always the same but are often linked within the bigger picture. I'm not an expert on Iran but I suspect their problems have much to do with the attitudes towards women, which they share to some extent with places like italy and japan - all these nations have serious fertility problems. The issues with anglo-saxon population growth in places like the US, UK and germany I think has more to do with the simple economics of child rearing.

I broadly agree, but here's one quibble: I don't think Iran is having problems. On the contrary, their fertility decline is the result of deliberate public policy, like China's.

That's related to a key point, which many on TOD don't understand: humanity, to a great extent, has taken conscious control of it's fertility and population growth. That makes us very, very different from any animal model of growth, overshoot and collapse.

Great article! This my first post here, hopefully with some thoughts that add to the debate.

Firstly, I'll challenge the suggestion that permanent growth is the fundamental idea of our society. Rather I think the aim is the homeostatic one of maintaining stability and perpetuation of the civilisational organism. Why does this homeostatic impulse work better during persiods of expansion rather than contraction?

If we consider that the surplus at any given time cannot be stored in any appreciable amount or over long periods, then the only way for individual entities whether they be persons, corporations or nations to store surplus is in the form of buying debt. Consequently civilisation as a whole does not save anything although some parts can do.

The ability for individuals to save in this manner is vital to increasing technological specialisation since increasing specialisation implies increasing vulnerability. In general as long as such savings are always spent by someone else civilisation is maintained (or in keynesian terms, output is maintained). On the way up the surplus storage expresses itself as a +ve interest rate, however on the way down it would be expressed as a -ve interest rate.

If the correct homeostatic reaction to negative external drivers like energy costs is to contract, then what is required to accomodate this process gracefully an appropriate rate of negative interest on the medium of exchange, such that a reasonable level of employment and social stability is maintained. This is standard keynsian stuff, with the exception of the negative interest rate, which now seems to be required, and finally within our technological reach now we have a society based largely on electronic money.

Welcome to the meat grinder, scepticus, and thank you for this comment. Just a comment to your comment, it is that homeostasis is not stability, it is completely different. Homeostasis may mean oscillating between two widely different states: during the growth phase, it means keeping growth; and this is the present paradigm. Indeed, I think that the system will evolve towards a contracting phase, which may mean de-facto negative interest rates. We may already be there, actually

well bardi, it seems to me we certainly have negative real rates, that is a +ve rate made negative through inflation. The body of financial engineering we've accumulated seems to have been a way to try and deny the reality as ever widening real losses were hidden in a fantasy of risk management.

Now the shadow banking system is gone, and while the 0% bound remains intact, there's nowhere left to go. While it remains in place we'll get deflation which IMO will never result in the kind of eventual market clearance and recovery that the various flavours of liquidationists think will happen if we wait long enough.

I guess the best outcome that can be expected is a long period of stagnation during which losses are monetised and people get their heads round the idea of negative rates. What then needs to be instituted is a workable system of the economics of loss, which if properly done will allow free markets (really the only way we know) to ensure that capitalism can continue as people compete to lose the least money. That would be a true homeostatic system response - in which rates can go +ve or -ve as required in response to external shocks while maintaining social stability through employment. Its a big change though.