It is rare that a book can be said to summarize the age in which it was written. It’s especially rare in our time, with millions of books being published every year, most of them quickly forgotten, leaving no trace. Such was not the case with The Limits to Growth, the 1972 book written by a group of researchers from the Massachusetts Institute of Technology (MIT) and commissioned by the Club of Rome. The book, which has sold some 30 million copies in some 30 languages, attempted to go to the heart of a fundamental question: What is the long-term destiny of our civilization? The book’s answer was, in brief, that if global economic growth was not stopped or slowed by certain policy interventions, the global economy would collapse within a century from the combined effects of resource depletion and pollution.
What is left of this thesis half a century later? What impact has it had on our own time? And are its conclusions still valid?
It’s easy to ridicule The Limits to Growth as nothing more than a series of wildly inaccurate predictions, the rumination of slightly feeble-minded savants who had been fooled by computer simulations into believing that the sky was falling. But this is an oversimplification, one that has dogged the book’s reputation since its release. The very fact that today, 50 years after publication, many people still vividly remember the book attests to its value as more than just a collection of questionable prophecies. Not only is the book still widely discussed, but a new report from the Club of Rome that reexamines the theory of the limits to economic growth, Limits and Beyond, was published earlier this year. (Full disclosure: I co-edited the volume.)
The Limits to Growth is best understood not as a novelty but as one of the many books written in the second half of the 20th century that attempted to grapple with the future of humanity. It was part of a reaction to ideas that had emerged after World War II, when, in the wake of Auschwitz and Hiroshima, millions of human beings had no choice but to put their faith in the possibilities of global peace and prosperity. In the Western world, the 1950s and 1960s were a time in which the popular imagination envisioned a car in every garage, a TV in every home, a refrigerator in every kitchen, and summer vacations for every family. It might strike us as absurd now, but back then, it wasn’t such a big psychological leap to go from living in that kind of world to imagining a near-future of flying cars, weekends on the moon, and friendly robot butlers mixing you margaritas after your four-hour workday. Fossil fuels appeared to be inexhaustible, pollution was not a concern, civilian nuclear energy was nothing short of a miracle, and the growth of food production was outpacing population growth. What could stop humankind from growing and expanding at increasing rates?
Yet this age of optimism lived in a dark shadow. Nuclear war threatened to wipe out civilization overnight. Growing prosperity and birthrates required an ever-increasing exploitation of necessarily finite natural resources. And although the existential threat of climate change was not yet perceived, ecological damage caused by industrial development was becoming more visible. So where, exactly, was humankind going? How far could it go down the path of continuous economic growth? What obstacles would it encounter? Could it be that 20th-century Western civilization would be the first in history to defy the fate of decline?
These questions were rarely asked in mainstream debates, but some of the most rigorous minds of the day became increasingly focused on them. Starting in the 1950s, those “minds” included early computers, which at the time were often referred to as “artificial brains.” The term “cybernetics,” the control of complex systems, was also invented in this period.
Mastering AI turned out to be much more difficult than originally assumed (and remains so today), but it seemed clear that applying at least primitive forms of it could be useful for understanding and perhaps even managing those systems we call “complex”: large corporations, whole cities, mass social groups, sophisticated economies, entire states, and even natural ecosystems. Each of these systems shares a common feature: They are composed of several independent factors that all interact with one another. When you change one of the factors, you change all the others in a cascade of effects that may lead to unexpected and uncontrollable results. It’s not for nothing that the field of biology observes a basic law of nature: “You can’t change one thing.” The literary equivalent of this principle was the English poet John Donne’s famous insight that “no man is an island.”
The human mind is not equipped to deal with these kinds of complex systems on its own. We evolved to focus on single elements within systems: Our hunter-gatherer ancestors profited by focusing on their prey and ignoring all other factors. If you are gathering mushrooms, you look down, not up or around, and you do it only in places where you know mushrooms can grow. But imagine you are the CEO of a multinational corporation: Focusing on a single factor in your company is not a very wise strategy. Maybe you think that a certain problem could be solved by firing a specific employee. But how will that affect the rest of the employees? Will others leave? How will customers react? A similar dynamic can be observed in politics, which is often a game of maximal simplification. Whatever the problem is, it is reduced to a single factor: a single enemy, a single bill, a single “act of God”—each is invoked to explain complex economic crises, epidemics, wars, revolutions, and the like. But things are never really this simple, and it is well known that “The best laid schemes o’ Mice an’ Men, Gang aft agley,” as Robert Burns said. “Pulling the levers in the wrong direction” is how it was put by the environmental scientist Donella Meadows, a lead author of The Limits to Growth.
“Intelligence” is a misnomer for what machines do when computing the evolution of complex systems. It is more accurately described as “brute force.” The computer is not affected by prejudices, scruples, ideologies, or moral feelings—it just goes on brutally computing. The job of real intelligence—of the human mind—is to evaluate the results.
So it happened that, in the late 1960s, a group of scientists who shared similar ideas about the world got together in the attempt to use the artificial intelligence that was available at the time to try to answer the question to end all questions: Where was humankind headed? The Italian industrialist and intellectual Aurelio Peccei had created an international think tank called the Club of Rome to examine what he called “the world problematique.” At the same time, the MIT computer engineer Jay Forrester had created a system dynamics model for computer simulation of interactions between multiple complex systems. The task of using Forrester’s creation to model future scenarios was entrusted to a group of young MIT researchers including Dennis Meadows, his wife, Donella, Jorgen Randers, and others. The Limits to Growth was the result of that study.
Despite the reputation that the resulting 1972 book generated in the course of being assessed, discussed, debated, criticized, reviewed, and demonized, The Limits to Growth was never a prophecy, nor a revelation, nor a political program. It was simply an attempt to assess what would happen to the world’s most complex systems if certain actions were taken or not taken. The main conclusion was that humankind would begin suffering the adverse consequences of its current trajectory before reaching the theoretical limits of available natural resources. In other words, the global economy would not need to “run out” of any particular resource before feeling the bite of resource depletion. Nor would it be necessary for societies to suffer mass death by pollution poisoning before succumbing to adverse effects of pollution. There would be no discrete “event horizon” or “singularity,” because complex systems typically change only gradually. As nonrenewable natural resources are exploited, they would likely become more expensive, and someone or something would have to pay the costs. The same process would apply to pollution. All this would put a growing strain on accumulated capital resources that are easier to expend than replenish. Eventually, economies would stop growing and start declining. Human population would follow a similar path.
It was, in the end, a simple theory: There is no such thing, in any system, as infinite growth. It didn’t take a computer to posit such a theory. But the computer used in the MIT study told a story that intuition alone never could. It seemed to demonstrate that economies would not just reach the limits of growth and remain there, as Thomas Malthus had suggested (compared to the results of Forrester’s model, Malthus was an optimist!). Instead, advanced economies would overcome the limits of growth for a while, running into a condition the researchers called “overshoot.” Eventually, they would have to return to rates of growth compatible with remaining resources, a process that would generate the collapse of the whole system. The combination of overshoot followed by collapse turns out to be a typical fate of complex systems, not just of modern economies. It occurs also in biology, politics, social systems, and other fields. It is a tendency first identified by the Roman philosopher Lucius Annaeus Seneca in the first century CE. Today, we tend to call it the “Seneca effect.”
That the MIT researchers and their computer simulation predicted collapse as a likely destiny should not have been much of a surprise. No civilization in human history has ever avoided collapse—why should ours be an exception? But in the heady atmosphere of the time (the decline in several measures of growth that began in 1971—in productivity, in wages, in income growth, etc.—was not yet obvious or palpable), many people believed that the thesis couldn’t possibly be true. It wasn’t just that The Limits to Growth was wrong on the specifics; the premise of the study itself was wicked.
Alas, 50 years after the publication of The Limits to Growth, the global economy has hewed rather closely to the scenario that, in 1972, was deemed most probable in the absence of significant policy interventions. The rate of economic growth has largely stalled among both advanced and middle-income economies. There is a sense that international trade and globalization itself may be receding from a high-water mark. There is increasing competition not only for traditional sources of energy but for the rare minerals needed to build sources of renewable energies. Pollution kills some 9 million people around the world every year. Extreme weather events are becoming more frequent and severe. Geopolitical chaos, including among nuclear-armed states, is rising. The probability of nuclear war remains low at any given point, but it is not and never can be zero—and it seems higher now than perhaps it did before Russia’s invasion of Ukraine. Let the clock tick for long enough, and the use of nuclear weapons somewhere in the world becomes all but inevitable.
The future is a set of possibilities, not the result of a prophecy. It is true that, as of now, there is no reason to think that The Limits of Growth was wrong in its most fundamental assumption: that even if it appears far-off, collapse remains our ultimate fate. But it’s also true that as we move through time, we learn new things, we adapt, and we change. Scientific and technological innovations have and will continue to lead to new possibilities that augment the rules of the system and help us delay or at least mitigate the consequences of collapse. If we at last decide to cut our dependence on fossil fuels and other nonrenewable resources, for example, and transition to truly sustainable ways of organizing society, then perhaps collapse can be avoided long enough for humankind to continue to flourish.
Ugo Bardi is professor emeritus of physical chemistry at the University of Florence, Italy. He is a full member of the Club of Rome, an international organization dedicated to promoting a clean and prosperous world for all humankind, and the author, among other books, of The Seneca Effect (2017), Before the Collapse (2019), and The Empty Sea (2021).