Cassandra has moved. Ugo Bardi publishes now on a new site called "The Seneca Effect."

Monday, January 21, 2019

Why do Societies Collapse? Diminishing Returns are a key Factor, a new Study Says

In 1988, Joseph Tainter published a fundamental study on the collapse of societies, proposing the existence of a common cause, diminishing returns, for the fact that all past empires and civilizations had eventually collapsed. Recently, myself and my coworkers Sara Falsini and Ilaria Perissi performed a system dynamics study that confirms Tainter's ideas and goes deeper into the origins of the diminishing returns of civilizations. It was published now on "Biophysical Economics and Resource Quality"

Why do civilizations collapse? It is a question that has been haunting the nebulous entity we call "The West" from the time when Edward Gibbon published his "Decline and Fall of the Roman Empire," in 1776. The underlying question in Gibbon's massive study was 'are we heading for the same destiny as the Romans?' A question that generations of historians have tried to answer, so far without arriving to answer on which everyone would agree.

There are, literally, hundreds of "explanations" for the decline and fall of empires, and the same confusion reigns for the fall of the past civilizations rising to glory and then biting the dust, becoming little more than ruins and footnotes in history books. Is there a single cause for these collapses? Or is collapse the result of many small effects that, somehow, gang up together to push the great beast down the Seneca Cliff?

One of the most fascinating interpretations of the collapse of civilization is Joseph Tainter's idea that it is due to "diminishing returns." It is a well-known concept in economics that Tainter adapts to the historical cycle of civilizations, focusing on the control structures designed to keep together the whole system, the bureaucracy for instance. Tainter attributes these diminishing returns to an intrinsic property of control structures to become less efficient as they become larger.  Below, you can see a rather well-known graph taken for Tainter's book "The Collapse of Complex societies." (1988)

Tainter's idea is fascinating for several reasons, one is that it generates some order in the incredible confusion of hypotheses and counter-hypotheses of the debate on societal collapse. If Tainter is right, then the many phenomena we observe during the collapse are just a reflection of an inner sickness of the society undergoing it. Barbaric invasions, for instance, are not the reason that led the Roman Empire to fall, the Barbarians just exploited the chance they saw to invade a weakened empire.

A problem with Tainter's idea is that it is qualitative: it is based on the available historical data, for instance, the debasing of the Roman currency, but the curve of the diminishing returns is just drawn by hand. One question you might want to ask is: fine, there are diminishing returns, but where is the collapse in the curve? Another one could be: if the system experiences diminishing returns, why doesn't it just retrace the curve to go back to where it was before?

These and other questions are examined in a system dynamics study that myself and my coworkers, Ilaria Perissi and Sara Falsini, performed. The idea is that if a civilization is a complex system, then it should be possible to model it using system dynamics, a tool specifically designed for this purpose. So, we built a series of models inspired by the concept of "mind-sized" models. That is, models that don't pretend to be a detailed description of the system but try to catch the basic mechanisms that make the system move and, sometimes, go through tipping points and collapse. We found that on the basis of some simple assumption, it is possible to produce a curve that qualitatively looks like Tainter's one

The system dynamics model tells us that the origin of the diminishing returns lies in the gradual depletion of the resources that flow through the system. It is not so much an effect of increasing complexity in itself, the problem is sustaining that complexity.

Then, the model also tells us what happens on "the other side" of the curve. That is, what happens if the system continues its trajectory beyond the point where Tainter's curve stop. The curve shows a clear hysteresis, that is, it doesn't follow the earlier path, but it remains always on a low-benefit trajectory. It means that cutting on bureaucracy doesn't make the system more efficient.

These results are not the final word on the question of societal collapse. But they do provide some fundamental insight, I think. It is the fact that the system is "alive" as long as its resources provide good returns -- in terms of energy resources, it means they have a good EROEI (energy returned on energy invested). If the EROEI goes down, then the system falls into the Seneca Cliff.

Of course, since our society depends on fossil fuels, we are bound to go that way because the depletion of the best resources is progressively lowering the EROEI of the system. If we want to keep alive some kind of complex society, we can't do that by scraping the bottom of the barrel, desperately trying to burn what we can still burn. But, unfortunately, it is exactly what most governments in the world are trying to do. It is a good way to speed up toward the impending cliff.

What we should do, instead, would be to move as fast as possible toward a renewable-based society. We are lucky that we have energy technologies efficient enough in term of EROEI that they could support a transition to a better, cleaner, and more prosperous world. Too bad that nobody seems to want them.

There has to be something in the concept of "BAU" that makes it one of the most powerful attractors you can simulate in a system dynamics model. And so we are moving toward an uncertain future, but one thing that we can be sure of is that fossil fuels will not accompany us there.


Our complete paper can be found here. You can also find an abridged version on ArXiv.

And here are the authors

Ugo Bardi

Sara Falsini

Ilaria Perissi

Note: an earlier version of this post was destroyed by the evil minions of the Great Satan -- that is by Google Blogger.


  1. ////So, the only hope to maintain a complex society alive is to switch to new sources with higher EROEI.//////---end quote

    surely if some new kind of Aladdin's lamp existed, we would have rubbed it long ago?

    As it is, we leverage our muscle power through the explosive forces of carbon based fuels. We know the usable properties of every other element in the periodic table. so If another element existed that could help us gain traction to reach our imagined future, surely we would have begun to use in by now?

    All other elements at our disposal seem to require a carbon dependent ''funnel' to enable us to exploit them. (if I've missed something, feel free to point it out)

    Wind and solar are not ''new'' they are merely extenders of what we have. They are not going to power us into some imaginary utopia of unlimited power

    so, this being the case, we are left with the reality of depending on some new ''energy concept'' that has not got beyond the fantasy stage yet, let alone been built and tested for feasibility

  2. A high EROEI is a necessary but insufficient condition for avoiding the Seneca Cliff. Society needs its energy as power, which the EROEI calculation doesn't adequately address. Solar and wind need to be concentrated to provide power, and only some of this concentration is captured in EROEI calculations.

  3. Thanks for this, Ugo! One minor factual question: In your second para you state, "...hundreds of past civilizations..." It seems to me that "dozens" would be more accurate, yes? If you still mean "hundreds", how are you defining "civilizations"?

    1. Yeah, sorry, it is all part of the crash.... writing in a hurry.

    2. Too damn cute!
      Keep up the great writing!

  4. I'd also love to know what you think of John Michael Greer's model of "catabolic collapse" as articulated in the first part of his book, The Long Descent? I found this version of his paper online: "How Civilizations Fall: A Theory of Catabolic Collapse", which is also included as an Appendix in his book:

    1. Have to read more of the stuffy that the Archdruid writes. We had been discussing about the catabolic collapse, a few years ago. I'll try to get back to that.

  5. Interesting lecture.

    Why do civilizations collapse?

    Since industrial revolution started, mankind had to manage collapse as we intend, for one case only. It was a pre-industrial civilization and despite that, I think Easter Island example is an excellent case of study, to foresee the future dynamic phases during collapsing. Other cases of study about collapsing, they happened many century ago, all before the industrial revolution, and only a couple of collapsing are about industrial society.

    In any case, history tells us many interesting stuffs, even if it is a very small sample.

    476DC: Roman Empire collapsed for invasion.
    800DC: Maya State Cities destroyed them self in civil wars.
    1400DC: Eastern Island culture collapsed for over population and scarcity of local resourse.
    1521DC Incas Empire collapsed for invasion.
    1521DC: Aztec Empire collapsed for invasion.
    1917DC: Russian Empire collapsed for WWI stress and national famine
    1989DC: Soviet Empire collapsed for cold war stress and national famine

    So on the one hand, history tells us that complex societies usually collapses for:

    .first of all for invasion: 3/7=43%
    .second for war stress and famine: 2/7=29%
    .third reason of collapsing is civil war: 1/7=14%
    .last but not least, there are over population and scarcity: 1/7=14%

    On the other hand, that's true on Earth there is in overpopulation situation and in the future things will turn from bad to worse, because climate change damages will over push scarcity. History tells us that overpopulation and scarcity always bring collapsing, so, there's no doubt in my mind: mankind culture will collapse for over population and climate change damages and scarcity

  6. Will mankind collapse everywhere on earth in the same way?!

    I don't think so, because countries on Earth are in different phase of socioeconomic and nations have different level of hard military power.

    I°world countries: all nations with a powerfull military power will avoid a collapse.
    II°world countries: the bigger part of those nations will collapse, only the military stronger will survive at XXI century.
    III°world countries: all nations will collapse.

    So in terms of continents, which continents will survive ar XXI century?

    Africa: overpopulation and climate change damages will over push scarcity, so Africa I think will collapse for over population and scarcity, and civil war and war stress and national famine.

    Europe: the european military power is weak, but it is stronger then africa, so the most part of the Europe will survive at the collapsing, on stopping african invasion.

    North America: I think they will surivive.

    South America: a larger part will collapse for civil war and over population and scarcity.

    Asia: the most part of the Asia nations will collapse for invasion, civil war collapsing, over population and climate change damages and scarcity, and for war stress and national famine.

    1. South America over population and civil war? I think this is incorrect.
      they are 422 millions and a lot of natural resources, in Europe we are 741 millions in half of South America territory and virtually no natural resources left. Plus most of America Latina population just do well with 1/5 of what we consume. Same situation in Africa. There is no overpopulation in Africa. In Africa there are 1.216 millions people in 30 millions km2, that means that Europe population density is more than double! Compared to Europe and Asia they are empty continents and they are much more resilient than us in the North. In case of "scarcity" it's much more likely they will survive and we won't.

      I read Tainter's book and one of its key message is that complex civilisations collapse, not gather/hunters societies or small farming communities. Since what you call with an obsolete term " III world" is usually less complex and dependent on global markets they will have less chances to collapse.

    2. @ Mario Pansera January 23, 2019 at 12:51 AM

      ROTFL, are you kidding me?

      About South America, check it out

      Nobody wants Venezuela's migrants in south america.
      What if amazon forest will gets dry?
      Do you really think South America lay on iperuranio in a safe space, totally climate change free?!

      About Africa:
      Have you never ever heard about some areas in Africa named Sahara and Kalahari?
      Do you know that Sahara and Kalahari are desert and nobody can live there?
      Have you never ever heard something about desertification?
      Do you really think Africa lay on iperuranio in a safe space, totally climate change free?!

      In Africa there is 1.2BLN of people, too many people for Africa.
      In 2050s african people will be 2.4BLN and the most part of overpopulation on earth on 2050s, it will be by African people.

  7. Thank you, Dr. Bardi.
    If I may, I think Dr. Bardi is talking about systems? We need to change our systems or behavior in order to meet this challenge. E.g., we first cut consumption and, thus, energy use and contamination. We change how we do things or we change our process and system.

  8. I've added this excellent analysis to the comments section on the collapse of complex societies.
    Thank you for your continued seminal work on this aspect of the unfolding collapse.

  9. Tainter's most important conclusion is that civilization is not energy efficient machine. Therefore, the real question is does it make sense at all to maintain and run such machine. The machine makes much misery, frustration, dissatisfaction and mental and physical illness for the people. If you calculate all negative effects (environmental and other) and subtract it from positive effects you may see that net effect is negative. It is difficult to see that from the perspective of a person living in civilization, but people can (and do) live without it. Person inside civilization is brainwashed and subject to much propaganda which teaches them that civilization is mostly positive thing, but the truth is that it is mostly negative. If you calculate all the losses in IC engine you will see that it is not really clever idea. In the same way, if you calculate all the losses in Mega Machine (to borrow Lewis Mumford's words) you will see that it is not really clever idea. If it is not, than it's irrelevant which kind of energy it uses, renewable or non-renewable.

    Don't get me wrong, I enjoy living in civilization because I am mostly spared from the worst of it's vices, and frankly I do not know anything else. I only know that it is not worth running and maintaining.

  10. Most complex systems are quite similar to each other in most abstract senses. The global ecology and the global economy mimic each other to an astounding degree. [The main difference there -- again, in the most abstract sense -- seems to be time scales; transitions that happen in the economy take months, while the ecosystem takes millions of years.]

    The human body is one of these complex systems, and as we approach death, we too fall off a Seneca Cliff. Most of the health care expenses for the average human are incurred in the last 3 months of life, and that's not just the medical sector taking advantage of the desperate. At a certain point, we pass a tipping point where recovery is simply not going to happen.

    The same goes for species, galaxies, climate systems... and civilizations. Rome wasn't built in a day, but it damn near collapsed in one.

    A side note: Tainter doesn't seem to take into account the fact that our civilization is the first one with computers and networks, and they eat complexity for breakfast. Of course, they also produce complexity as well (as well as making complexity far more tolerable than it would be otherwise), so it would be interesting to see what comes out in the wash.

  11. Thank you for sharing the paper Prof Ugo, it is well explained and clear.
    I am wondering what the curve for Production vs Economy for 4 stock model looks like, whether it differs from the 2 stock one?

  12. One recent example that proves my point:

  13. "What we should do, instead, would be to move as fast as possible toward a renewable-based society."

    I have to wonder whether this sentiment is overly simplistic in the current iteration of it that dominates the main narratives regarding energy and its transition to a 'sustainable' global civilization. There is certainly is a convincing argument to be made that there are not enough resources remaining to accomplish this, certainly not for the current world population (although the 'advanced' economies certainly do waste a lot of the reserves)--let alone the 'capital' necessary to fund this given the absurd levels of debt already accumulated. Also, as long as we use and depend upon a monetary/financial/economic system that is debt/credit-based and requires perpetual growth to avoid implosion, we seem destined to chase the infinite growth chalice. I read so many simplistic, hopium-filled solutions to our dilemmas (e.g. if everyone just adopts electric vehicles, the world will be saved) that ignore the complexities and roadblocks to such utopias. Is there a solution (or solutions)? I don't think so. Non-linear feedback loops and emergent phenomena make complex systems impossible to predict and therefore control. I think that like any other species we will consume the really important resources that support us and experience the classic overshoot and collapse scenario. How it all plays out, though, is excellent fodder for fictional narratives; like those that litter the Internet.

    1. Yes, no matter how noble the end destination, change that is too rapid has significant risks of instability and highly unpredictable unexpected consequences.

      Too many times I see these type of articles dress themselves up in some kind of scientism to support a pre-supposed dogma in the form of a lofty goal, but with little consideration of the road map and journey risks to get there.

  14. IMHO Rome collapsed for two reasons
    1 it debased its currency
    2 it ran out of places and people to steal from so it did not have to debase its currency .
    EROEI only in silver and gold .

  15. I think you are missing and forgeting the main point: the military dimension. During West Roman Empire collapsing, the Roman military power loose the battles. There are clear military reasons:

    .west roman infantry weren't the roman infantry soldiers of the roman repubblic or those the first decades of the roman empire. The West Roman infantry soldiers were barbarian people (french, and german people, not sufficient trained, not enough motivatd to stop an invasion, not sufficient well armed to face off the barbarian forces).

    .roman military power had always a light cavalry: the roman tactics during time never ever developed an heavy cavalry, instead the hun troops had a much heavier cavalry than roman forces, and a new mobile force on the field.

    .hun bow was a letal weapon: roman archery and roman cavalry never hadn't this military weapon.

    So the weak military force caused the collapse of the West Roman Empire.
    Until the military forces were just sufficient to stop invasion, the west roman collapsing have been stopped.

    It's not matter of Return on Investiments rate or decreasing productivity of the factors, it's a matter of war: less effective weapons, older tactics, bad roman infantry troops.

  16. Ugo, your model exactly shows Tainters qualitative argument. The resources in your model are homogenous, and do not decrease in quality over time. As you state in the paper, it is the time delays that cause the hysteresis, not any EROEI. The Limits to Growth research team must have understood this quite well, because in the detailed 1974 manual, they repeatedly emphasized the importance of delays to model behaviour.

    It is really interesting that even the two-stock model shows this, so getting rid of the bureaucracy wouldn't solve the problem.

    If only our ability to build models that project future consequences had allowed us to decrease delays in action.

  17. Complex interconnect dynamic systems exhibit counter intuitive behaviours due to feedback loops.

    There is actually a branch of engineering where the level of understanding of both the math and the practical applications (and limitations) is fairly well understood for practical use - control systems engineering.

    Most control systems utilise negative feedback to stabilise various flows, levels, temperatures etc, but rely on tuning the controllers to suit the dynamic behaviour of the subsystem involved.

    Practitioners in the field understand the general behaviours of underdamped and overdamped systems is well understood, as well as systems that are interconnected and become unstable due to similar time constants, sympathetic perturbations out of phase (often related to transport lag) etc etc.

    In light of the above comments and as a controls systems engineer of over 30 years theoretical and practical experience I find this discussion of system dynamics/behaviour disturbingly simplistic, incomplete and naive and have always considered the original LTG paper not much better.

    To get a feel for system dynamics in real world applications generally takes a minimum of several years of theory study followed by significant field experience where over time the counter intuitive system behaviours resulting from variation of the various inputs, levers, transfer characteristics and tuning parameters become apparent and learned to the point of being able to understand and eventually predict general system behaviour, if it is engineered, arranged and configured suitably, fairly narrow constraints usually in practical applications.

    Unfortunately the real and unconstrained complex world at large is a very messy place, with lots of non linearaties (think butterfly effect) and unexpected adaptive behaviours by the fauna in it, creating feedback loops that pop in and out of existence unexpectedly, yielding short and long lived emergent global and localised stabilities and unstabilities.

    The relatively excessive simplicity of effectively decomposing the world into a poor grade second order system effectively analysed in an open loop mode, makes this whole exercise smell heavily of Dunning-Kruger.

    1. First of all, thanks for the insults, Gareth -- which I will not reciprocate. Then, as a control engineer, would you tell me where you could find the equivalent of - say - a steam governor in an ecosystem or an economic system? This is a serious question, the key of the whole problem



Ugo Bardi is a member of the Club of Rome, faculty member of the University of Florence, and the author of "Extracted" (Chelsea Green 2014), "The Seneca Effect" (Springer 2017), and Before the Collapse (Springer 2019)