Speaker:
Martin Sers is Adjunct Professor at York University and Fellow of the Centre for Sustainable Prosperity.

Limits to Growth was published in 1972. It was the first use of systems dynamics to model a growing economy on a finite planet. Systems Dynamics has become an indispensable tool in science and engineering but not in economics. The report was vilified – criticized as either too simple or too complex – because it challenged the idea that free markets could supply our needs endlessly.

Event Notes:

Martin Sers gave a brilliant presentation on ‘Limits to Growth’ – now 52 years old – to a spell bound audience at St. Andrews and across Ontario, by zoom.

Limits To Growth exploded into the world in 1972. I know because I was there. 

It was a time of immense optimism. We were still in what the French called, ‘Les Trente Glorieuses’ – the decades of full employment after WW2. And the 1960s revolution had been an incredible party. The Vietnam war was coming to a close. ‘Mutually Assured Destruction’ had contained the threat of nuclear oblivion. We were going to the moon and on shiny new jets to Europe and around the world. Every day we turned on our colour TVs and saw our bright futures in front of our own eyes. It was time to seize the day – there would be no end to our happiness and prosperity.

And LTG had everything going its way. It was American – from one of its most celebrated schools – MIT – wrapped in a sophisticated European patina, ‘The Club of Rome’. It used ‘computers’ – we had hardly heard of them – and a ‘program’ called World3. It seemed like magic, a bit like today’s AI but without even a hint of cynical suspicion. It was full of graphs and charts – all new stuff. It seemed to reflect the hope, power and brilliance of its time.

Then shock! That there could be limits?? It insulted our newfound notions of freedom – that we were free to do and dream whatever we pleased and that markets were free to bring us whatever we wanted. And anyway, it was all so far in the future and ‘they’ wouldn’t let any of this happen, would they?

Martin recounted how, with time, shock became wariness, which became hostility. LTG was criticized as being both too complex and too simple. It was damned by economists like William Nordhaus – subsequently a Nobel laureate and climate denier – and by the media and by other academics. By the 1990s it had been eerily forgotten. It was a topic not to be mentioned in serious company. 

LTG was written by Donella and Dennis Meadows, Jørgen Randers and William Behrens and the book jacket shows a tidy price of $2.75. It had its origin in Jay Forrester’s work on system dynamics, which was Martin’s first port of call. 

Even today, we talk of the economy, population and environment as separate things. But 52 years ago, World3 pulled them together into a single model comprising five key elements: population, agriculture, industry, capital and the environment (pollution) – all of them interacting through feedback loops – positive feedback amplifying changes and negative feedback diminishing them. The way an entire system changes over time is called its system dynamics. And the purpose of modeling it is not to make exact predictions but to see, broadly, how the system behaves under different circumstances. Systems dynamics is widely used, today, in science, engineering, and ecological economics – climate models are an example. Unfortunately, it is still not used in conventional economics or for business planning or to assess the likely outcome of government policy.

Martin’s next port of call was exponential growth and how we, humans, are just not wired to understand it. Exponential growth is straightforward – it doubles every fixed period of time – the ‘doubling time’. But at one end, tiny doublings are still tiny so are not noticeable, while at the other, large doublings appear overwhelming. So we tend to see exponential growth as nothing much happening followed by sudden, disruptive change. 

The authors of LTG found exponential behaviors everywhere – in population growth, fertilizer consumption, uses of non-renewable resources, eg, metals, fossil-fuels and arable land – and, of course, CO2 concentrations in the atmosphere.

As a member of the audience said during the Q&A, “anyone who believes you can have exponential growth in a finite world is either a fool or an economist”. I always think the saying is a bit unfair to fools who come by it honestly while economists have to study hard to not understand it.

Given the growing human enterprise and the fact that limits will ultimately be reached, the purpose of World3 was to determine how the human system would behave when it reached its limits. Martin showed three examples. Maturing is one way – exponential growth is common in the natural world and most living things grow exponentially before slowing down and stopping (maturing) as they reach their ‘carrying capacity’. A tree is a great example of something that grows and stops. A second is overshoot – things grow beyond their carrying capacity then fall back, perhaps cycling up and down. But a third – collapse – occurs when overshoot is so high that it destroys carrying capacity – think of Easter Island with all the trees gone. 

World3 was “calibrated” – a term that means adjusting the interactions in the model – using 70 years of previous data. If World3 could be made to accurately describe previous data, then its predictions for the next 70 years might be reasonable and the following 70 years plausible. Martin then presented some of the results:

• The ‘standard run’ of World3 showed human population collapsing around 2050, caused by running out of resources.
• The next run doubled resources on the basis we might get better at finding them. This time population collapsed because of pollution, ie, environmental degradation.
• The next run tried unlimited resources and pollution controls. This time the collapse was caused by running out of arable land and food.
  
  

The authors tried hard to find a stable solution but it was highly constrained – it required no population growth and no economic growth. Of course, this is not what has happened. 

Martin emphasized the authors were very cautious in presenting their findings, “These are not exact predictions… only indications of the system’s behavioral tendencies” and their question, “Can anything be learned from such a highly aggregated model? Can its output be considered meaningful?”

Martin’s final port of call was a comparison of World3’s predictions with what has actually happened – the comparison was made by Graham Turner, in 2012:

• Actual population is very close to World3 predictions, although birth and death rates are somewhat different.
• Industrial output and food production are in reasonable agreement.
• Ditto non-renewable resources and pollution.
  
  

But a caution! These comparisons are prior to any collapse. Therefore they do not prove our world and economy will collapse or even what a collapse might really look like. All that can be said is that predictions, so far, look uncomfortably close to what World3 predicted, 52 years ago.

And again, the authors’ words were of cautious hope:

“We are convinced that… the tragic consequences of overshoot require new forms of thinking that will lead to a fundamental revision of human behavior.” I think it is fair to say that, so far, this has not happened.

And, “Our present situation is so complex and so much a reflection of man’s multiple activities… that no combination of purely technical, economic, or legal measures… can bring substantial improvement. Entirely new approaches are required to redirect society towards goals of equilibrium rather than growth.” It is also fair to say that no such new approaches have been embraced either.

At the beginning of his presentation, Martin showed the current assessment of ecological overshoot – not just climate change but the poly-crisis. In 2009, seven boundaries were assessed with three in overshoot (one of them climate) and in 2023, nine boundaries were assessed with six in overshoot. Similar work has been done by Kate Raworth (Doughnut Economics) and Julia Steinberger, although not using systems dynamics. 

Canada’s William Rees has also developed the concept of Ecological Footprint; Jason Hickel has written extensively on climate change and ecological economics; and Fadhel Kaboub on sustainable prosperity. Nate Hagens also runs a popular blog called, ‘The Great Simplification’.

Finally, Martin’s professor and one of our past presenters, Peter Victor, recently published a book, ‘Escape from Overshoot – Economics for a Planet in Peril’, which was the genesis of this Speaker Series event. I met Peter at his book launch and asked him whether he had heard of World3. Not only had he heard of it he used it extensively. And when I asked if he knew of a potential speaker, he smiled and mentioned a remarkable student, Martin Sers, who graciously joined us to share his knowledge.

World3 is still being updated – what was a colossal computational undertaking in 1972 is now a fast and routine application on a personal computer – it has become a workhorse. And, importantly, it has been responsible for the widespread adoption of systems dynamics into the field of ecological economics.

French Translation
translation provided by Chat GPT

Martin Sers a fait une brillante présentation sur les “Limits To Growth”, qui a maintenant 52 ans, devant un public captivé à St. Andrews et dans tout l’Ontario, via Zoom. “Limits To Growth” a explosé dans le monde en 1972. Je le sais car j’étais là. C’était une époque d’optimisme immense. Nous étions toujours dans ce que les Français appelaient “Les Trente Glorieuses” – les décennies de plein emploi après la Seconde Guerre mondiale. Et la révolution des années 1960 avait été une fête incroyable. La guerre du Vietnam touchait à sa fin. La “Destruction Mutuelle Assurée” avait contenu la menace d’oblivion nucléaire. Nous allions sur la lune et en avion vers l’Europe et le monde entier. Chaque jour, nous allumions nos téléviseurs couleur et voyions notre avenir radieux devant nos propres yeux. C’était le moment de saisir le jour – il n’y aurait pas de fin à notre bonheur et à notre prospérité.

Et LTG avait tout en sa faveur. C’était américain – issu de l’une de ses écoles les plus célèbres – le MIT – enveloppé dans une patine européenne sophistiquée, “Le Club de Rome”. Il utilisait des “ordinateurs” – dont nous avions à peine entendu parler – et un “programme” appelé World3. Cela semblait magique, un peu comme l’IA d’aujourd’hui mais sans la moindre pointe de suspicion cynique. Il était rempli de graphiques et de diagrammes – tout du nouveau matériel. Il semblait refléter l’espoir, la puissance et la brillance de son époque.

Puis le choc! Qu’il puisse y avoir des limites?? Cela insultait nos nouvelles notions de liberté – que nous étions libres de faire et de rêver tout ce que nous voulions et que les marchés étaient libres de nous apporter tout ce que nous désirions. Et de toute façon, c’était tellement loin dans le futur et “ils” ne laisseraient pas que cela se produise, n’est-ce pas?

Martin a raconté comment, avec le temps, le choc est devenu de la méfiance, qui est devenue de l’hostilité. LTG a été critiqué comme étant à la fois trop complexe et trop simple. Il a été condamné par des économistes comme William Nordhaus – ultérieurement lauréat du prix Nobel et négationniste du climat – et par les médias et d’autres universitaires. Dans les années 1990, il avait été étrangement oublié. C’était un sujet à ne pas mentionner en société sérieuse.

LTG a été écrit par Donella et Dennis Meadows, Jørgen Randers et William Behrens, et la jaquette du livre affiche un prix soigné de 2,75 $. Il avait son origine dans le travail de Jay Forrester sur la dynamique des systèmes, qui était le premier point d’appel de Martin.

Même aujourd’hui, nous parlons de l’économie, de la population et de l’environnement comme de choses séparées. Mais il y a 52 ans, World3 les a regroupés dans un modèle unique comprenant cinq éléments clés: la population, l’agriculture, l’industrie, le capital et l’environnement (la pollution) – tous interagissant à travers des boucles de rétroaction – les rétroactions positives amplifiant les changements et les rétroactions négatives les diminuant. La façon dont un système entier évolue au fil du temps est appelée sa dynamique de système. Et l’objectif de le modéliser n’est pas de faire des prédictions exactes, mais de voir, globalement, comment le système se comporte dans différentes circonstances. La dynamique des systèmes est largement utilisée aujourd’hui dans les sciences, l’ingénierie et l’économie écologique – les modèles climatiques en sont un exemple. Malheureusement, elle n’est toujours pas utilisée en économie conventionnelle ou pour la planification commerciale ou pour évaluer les résultats probables des politiques gouvernementales.

Le prochain point d’appel de Martin était la croissance exponentielle et comment nous, les humains, ne sommes tout simplement pas câblés pour la comprendre. La croissance exponentielle est simple – elle double à chaque période fixe de temps – le “temps de doublement”. Mais d’un côté, de petites duplications sont encore petites et ne sont pas remarquables, tandis que de l’autre, de grandes duplications semblent écrasantes. Nous avons donc tendance à voir la croissance exponentielle comme peu de choses suivies d’un changement soudain et perturbateur.

Les auteurs de LTG ont trouvé des comportements exponentiels partout – dans la croissance de la population, la consommation d’engrais, l’utilisation de ressources non renouvelables, par exemple, les métaux, les combustibles fossiles et les terres arables – et bien sûr, les concentrations de CO2 dans l’atmosphère.

Comme un membre du public l’a dit lors de la séance de questions-réponses, “quiconque croit que l’on peut avoir une croissance exponentielle dans un monde fini est soit un idiot, soit un économiste”. Je pense toujours que cette phrase est un peu injuste envers les idiots qui l’ont honnêtement méritée, tandis que les économistes doivent étudier dur pour ne pas la comprendre.

Compte tenu de l’expansion croissante de l’entreprise humaine et du fait que des limites seront finalement atteintes, l’objectif de World3 était de déterminer comment le système humain se comporterait lorsqu’il atteindrait ses limites. Martin a montré trois exemples. La maturation est une façon – la croissance exponentielle est courante dans le monde naturel et la plupart des êtres vivants croissent exponentiellement avant de ralentir et de s’arrêter (maturité) lorsqu’ils atteignent leur “capacité de charge”. Un arbre est un excellent exemple de quelque chose qui pousse et s’arrête. Une deuxième est le dépassement – les choses dépassent leur capacité de charge puis retombent, peut-être en faisant des cycles ascendants et descendants. Mais un troisième – l’effondrement – se produit lorsque le dépassement est si élevé qu’il détruit la capacité de charge.