13 Limits to Growth?

Are human societies able to continue growing forever, or are there limits to the Earth’s carrying capacity?


One of the most basic but often overlooked aspects of human interactions with the environment that has come to the attention of historians and more recently the public is the impact of population growth and resource scarcity. There are a number of reasons society prefers to avoid thinking about the danger of having too many humans around. We like people. Especially those who are close to us. And historically, the growth of our own particular group has been important for our survival and therefore has been desirable. In the past, people haven’t always been too concerned if the success of their particular community came at the expense of their neighbors. But recently that neighborhood has expanded to cover the whole globe.


Portrait of Malthus
Thomas Robert Malthus, one of the first philosophers to concern himself with the question of overpopulation

There’s an economic concept called the zero sum game which says that in many situations, for every winner there has to be a loser. Especially when societies face scarcity, attention focuses on how a shrinking or too-small pie is divided up. Since the industrial revolution though, Westerners have been able to live outside of the constrictions of zero sum logic. To a great extent, this abundance and sense that the pie was growing was based first on the increase in staple foods made available throughout the world by the Columbian Exchange and the Green Revolution, and also by the harnessing of fossil fuels such as coal and oil. But that doesn’t mean Westerners have been unaware of the question. At the very beginning of the modern age, an English economist named Thomas Robert Malthus (1766-1834) published a short book called An Essay on the Principle of Population. Malthus’s theory, published in 1798, became instantly controversial on both sides of the Atlantic. Thomas Jefferson sent a copy of the book to his favorite economist (Jean-Baptiste Say) and asked for an opinion.

Malthus stated his basic idea like this: “The increase in population is necessarily limited by the means of subsistence…the population does invariably increase when the means of subsistence increase, and …the superior power of population is repressed and the actual population is kept equal to the means of subsistence only by misery and vice.” Another way of saying that is, population grows as long as there is food and water to support it, and when these resources run out, population is brought back down through famine, disease, and war. These three causes of depopulation are often termed “Malthusian disasters.”


Malthusian catastrophe graph
The Malthusian catastrophe simplistically illustrated

Malthus went on to observe that populations tend to increase geometrically: two people become four, four become eight, eight become sixteen, etc. In contrast, he said, food supplies at best increase only arithmetically: two bushels of wheat become four, which become six, which become eight. By this logic it is easy to see that a society can easily outrun its ability to feed itself if the population is not kept down by reducing births or increasing deaths, and to understand why early modern Europeans were so obsessed with acquiring new territories to improve their food production abilities.

The famines, diseases, and wars of European history gave Malthus the examples he needed of the types of crises that tended to reduce populations. If society was going to avoid these periodic disasters, he argued, then it would need to find some way of limiting the birthrate to avoid starving. The Malthusian theory, as it is called, was intensely controversial right from the start. One of the reasons was that it advocated birth control. Malthus himself only called for what he termed “moral restraint” to help reduce the birth rate, but many Malthusians had more active contraceptive measures in mind. The idea of limiting reproduction was seen by most religious people as a violation of the injunction to “be fruitful and multiply,” and eliminating the risk of pregnancy was seen as an encouragement of vice and an invitation to sin. Over two centuries later, we have not left these arguments behind.


Global Deaths chart

The other big controversy surrounding Malthusian thought was that it was used by some members of the British upper classes to argue that the conditions of the poor should not be improved. If poor people had higher wages and more to eat, they argued, they would have more children and more of their children would survive, which would put unnecessary stress on the social system and in the long run lead to mass starvation. The poor simply had to suffer, they said, or society was doomed. Some critics accused these upper-class Malthusians of simply wanting to hoard more of everything for themselves. But some of them sincerely believed that there just wasn’t enough to go around, and that adding more hungry mouths wasn’t good for the poor or the rich.

It turns out, however, that the assumption held by Malthus and those members of the British upper class (and by many people today) that feeding the poor would lead to a population explosion is actually untrue. Population scientists today agree, after studying societies all over the world, that as economic security increases, a “demographic shift” occurs and birth rates decline. In other words, if the poor have enough to eat, infant mortality rates and people’s fear of starving in their old age decrease. Death rates of children decline and as a result parents needing to insure that someone will survive to take care of them in their old age have fewer children. Educating women is the other major factor demographers have credited with reducing birthrates. Both factors have contributed to a demographic shift in the developed world where family sizes have decreased from an average of six children per family in the early nineteenth century to 1.6 in the twentieth. Many developed nations now face decreased growth or even shrinkage in their native populations.

In spite of the developed world’s success limiting population growth by providing education for women and a social safety net, the argument is still raging regarding the “developing world.” The Gates Foundation recently started a campaign called #StopTheMyth. A few years ago Melinda Gates made a short video titled “You Decide: Save the People or Save the Planet,” claiming that the issue is still very poorly understood. Gates compared two nations, Afghanistan and Thailand, which currently have populations of similar size. She pointed out that in Afghanistan, where 10% of children die before the age of five, population is expected to nearly double by 2050. In Thailand, on the other hand, the number of children dying has decreased substantially. And so has the birthrate. “Clearly,” Gates concluded, “letting children die now so they don’t strain the planet later doesn’t really work. It’s a myth.”



The other assumption you may have noticed in the Malthusian theory was that food production is expected to increase much more slowly than population. As we have already seen,  this has not been the experience of the nineteenth and twentieth centuries. New staple crops from the Americas, abundant land, fertilizers, and technology created a global Green Revolution that has allowed us to continually outrun Malthus for the last two centuries. But an agricultural scientist named Karl Sprengel noticed in 1828 that plant growth was limited by the availability of the essential nutrient with the lowest concentration. Sprengel’s contemporary, biologist Justus von Liebig, realized this idea had wider applications and popularized it as Liebig’s Law, which became a key idea in ecology. The Law states that growth is dictated not by the total resources available, but by the scarcest resource, which he called the limiting factor. So the question is, will we be able to keep outrunning Malthus forever, or will a limiting factor end our exponential growth?

Questions for Discussion

  • Why did Malthus worry that overpopulation would lead to chaos?
  • What has prevented a Malthusian catastrophe so far?
  • Why do you think Melinda Gates felt she needed to set the record straight on population?


Until very recently in human history, the Earth has been so big and the total human population relatively so small, that the resources available to us have often seemed infinite. In 1800 there were fewer than a billion people on the planet. In 1900 there were still less than two billion. By 1960 there were three billion, and in 1999 there were six billion. Current world population is about 7.7 billion people. During this dramatic increase, there were periods like the early industrial revolution when worriers like Malthus and his followers expressed doubts and anxiety.

Malthus had no idea that his nation was about to expand its empire into Africa and Asia, or that emigration to the Americas and Australia would continue to reduce populations at home. And of course he couldn’t anticipate advances in technology or the demographic effects of increasing economic security we have just considered. But sometimes even these advances proved temporary or subject to disruption.

The population of Ireland boomed in the first decades of the nineteenth century, as potatoes increased the calories available to poor people and seemed to eliminate the threat of famine. The Irish population peaked at over 8 million in 1841, based on the potato. About a third of all Irish people ate no other solid food, and lived on a diet of milk and potatoes. Worse, the entire nation (indeed all of Europe) grew just a single variety of potato, called the Irish Lumper. The blight that attacked this monoculture and destroyed potato harvests for several years in Ireland and throughout Europe killed over a million people and forced a million more to flee to America. The Irish population is about 4.8 million today, a little more than half its peak 175 years ago. As the science of ecology developed in the second half of the twentieth century and we began to distinguish between renewable and nonrenewable resources, and to worry about the dangers of depending on monoculture food supplies. Malthusian anxiety has returned.


In 1968 Stanford University Biology professor Paul R. Ehrlich published a sensational book called The Population Bomb, that was an instant bestseller. It began with the statement, “The battle to feed all of humanity is over. In the 1970s, hundreds of millions of people will starve to death in spite of any crash programs embarked upon now. At this late date, nothing can prevent a substantial increase in the world death rate.” Ehrlich became an instant celebrity and publicized his theories of social collapse on popular media like Johnny Carson’s Tonight Show. Ehrlich’s scenarios inspired some great dystopian science fiction, but luckily they did not happen in the way Ehrlich had predicted. Actually, a couple hundred million people did die of hunger in the decades after The Population Bomb  was published. It’s hard to tell exactly because when the United Nations reported worldwide deaths in the 1970s and 80s, it specifically omitted deaths from hunger. But these deaths did not reduce world population overall or result in the social chaos that Ehrlich had prophesied.

The Population Bomb may have done more harm than good in the long run, by making worry over the population issue an easy target for critics. But people remained concerned about the rapid increase of the world’s human population. In 1972 an international organization called The Club of Rome published a study titled The Limits to Growth. Unlike Ehrlich’s sensational predictions of doom, The Limits to Growth applied mathematical systems modeling to five particular variables: world population, industrialization, pollution, food production, and natural resource depletion. The researchers used newly-available computer technology to produce a study that illustrated the complex interactions of these variables by showing three potential future outcomes. In two of these scenarios, the global system experiences what the researchers called “overshoot and collapse” in either the middle or toward the end of the twenty-first century. In the third scenario the computer models arrived at what the researchers called a stabilized world system.


World Model Standard Run as shown in The Limits to Growth, which the authors claim has been validated by the data from the last thirty years.

In 2008, the original authors of The Limits to Growth returned to their models and published a 30-year review of how accurate their predictions had been. They found that measurements of all the variables they had identified were tracking with the predictions the computer models had made for an “overshoot and collapse” scenario. The accuracy of the predictions the study had made for the short term does not prove their longer-term predictions were accurate, of course. However, the findings do suggest that further study might be in order.

Questions for Discussion

  • What monocultures do we depend on today that might make us vulnerable, similar to the Irish potato situation in the 19th century?
  • Why did Paul Ehrlich’s book possibly do more harm than good?
  • Do you think the possibility of social collapse, even if uncertain, is something we should study more closely?



Hubbert peak oil curve
A bell-shaped production curve, as originally suggested by M. King Hubbert in 1956

Not all the warnings that humanity is reaching resource limits have come from university academics or international think-tanks that are naturally distrusted by regular people and corporate leaders. Marion King Hubbert was an American geophysicist working for Shell Oil in 1956 when he presented a research paper to an oil industry trade group The American Petroleum Institute, where he showed that for any geographical area (and by implication, for the planet as a whole), petroleum production follows a predictable bell-shaped curve. Hubbert’s theory, which became known as Peak Oil, correctly predicted that oil production in the continental US would peak between 1965 and 1970, and then begin to decline. Hubbert also predicted that world oil production would peak “in about fifty years.” Although the data and especially its interpretation are very controversial, several credible sources suggest that the peak in world production happened between 2003 and 2004, right on Hubbert’s schedule.

Petrochemical prices can be expected to rise as supplies diminish. Currently, new technologies such as fracking and converting tar sands have added some new sources to the supply we now designate as “petroleum.” These new additions do not refute the logic of Hubbert’s predictions, although they do potentially push back the timing of the supply crunch that we would expect to raise prices. Two elements of The Limits to Growth‘s computer mode, industrial production and food supplies, depend heavily on the price of energy, and a third (pollution) is an issue for both fracking and tar sands processing. A reduction of the supply of oil, an increase in its cost, or an increase in pollution could all have a significant negative impacts on those variables.

Hubbert’s words actually echoed Malthus. “Our principal constraints,” he said, “are cultural. During the last two centuries we have known nothing but exponential growth, and in parallel we have evolved what amounts to an exponential growth culture. Hubbert said our growth culture is “so dependent on the continuation of exponential growth for its stability that it is incapable of reckoning with problems of non-growth.” These are not the words of some dewy-eyed environmentalist or crazy academic or sensationalist. Hubbert was an oil industry analyst. Some have argued that possible future discoveries of more oil could postpone society’s shift to a non-fossil fuel energy economy. But even the oil industry for the most part agrees that production will decline. So the question we are left with is, how quickly will we use up what remains? And, given what we have learned in the last decade about the effect of burning fossil fuels on the global climate, should we?

Question for Discussion

  • What did Hubbert mean by an “exponential growth culture”?



Global warming chart
Global surface temperature reconstruction over the last millennia using proxy data from tree rings, corals, and ice cores in blue. Observational data is from 1880 to 2019.

Some climate activists have begun to suggest that for the sake of the environment, we ought to switch from fossil fuels to other energy sources as soon as possible and leave as much as possible of what is left in the ground. The argument against burning the rest of the oil (and coal) is that fossil fuels are one of the biggest contributors of atmospheric carbon that leads to global warming. While this is true, other factors such as deforestation and even agribusiness release comparable amounts of carbon. Simply stopping the use of oil will not solve the whole climate change problem, although it is a key element of the change society needs to make to stabilize the global climate.


But because energy is such a large part of the economies of developed nations, any change is heavily contested. Global energy corporations have an incredible ability to influence politics. A few years ago BP (British Petroleum, established in 1908 as the Anglo-Persian Oil Company and now operating in 72 countries) issued an “Energy Outlook” report for the year 2035. BP claimed that Hubbert’s Peak Oil scenario was actually incorrect and announced the company’s intention to burn just as much as possible over the next two decades. BP’s claim that oil production hasn’t peaked, however, depended on redefining the word oil to include both tar sands and biofuels such as ethanol. Ethanol production depends not only on the energy-intensive production of surplus corn and cane sugar (used in Brazil as the primary plant source), but in government subsidies that keep the prices of these commodities below their cost of production. So it’s hard to see how biofuels could legitimately be called a new source of “oil.”

Climate change, more than any other environmental concern, has dominated the attention of Americans in recent years (and has in many cases pushed pollution off the table, which is unfortunate). Although the idea that the planet’s climate has been adversely affected by human activity is very controversial in the media, politics, and popular culture, it is almost universally accepted by scientists. According to NASA, at least 97% of climate scientists agree that global warming over the past couple of centuries is due to human activities, or anthropogenic. American and international science organizations like the American Geophysical Union, the American Meteorological Society, and the American Medical Association, in addition to the Intergovernmental Panel on Climate Change, have all gone a step further, agreeing with the American Physical Society, “We must reduce emissions of greenhouse gases beginning now.”


per capita carbon
Per capita carbon emissions by country. Height = per capita emission; width = size of population. Color = rate of change.

Of course who they mean by “we” is unclear, and the penalties for heeding their warnings are really hard to specify. We often hear that “The forecasts show that it is China, India, and the other emerging economies that are increasing their carbon dioxide emissions at a speed that will cause dangerous climate change. In fact, China already emits more CO2 than the USA, and India already emits more than Germany.” This objection came from a European Union environment minster, speaking at the World Economic Forum at Davos in 2007. The population of China is 1.386 billion. India is 1.339 billion, USA 327 million, Germany 82.79 million. That means that although China emits more total CO2 than the US, on a per person basis, we still emit twice as much (15.7 tons per person to China’s 7.7 tone). Similarly, on a per capita basis, Germany emits more (9.7 tons) than China, and five times more than India (1.8 tons per capita). While it’s important for China and India to get their carbon emissions under control, it is unacceptable for Europe and America to try to shift the blame when we still outproduce them on a per capita basis. Especially since most of the carbon now in the atmosphere was put there by us.

Questions for Discussion

  • Why is atmospheric carbon a global rather than a regional or national problem?
  • Why is it misleading to compare current total carbon emissions between countries in trying to assess “blame”?



Climate science is complicated and it can be difficult for some people to understand. And to make matters worse, most Americans share a belief system that distrusts science and scientists, because science seems to contradict their most cherished religious doctrines about the nature of the world and their place in it. To make matters even worse, concern over climate change has been identified with a particular political orientation, with people like former Vice President Al Gore seeming to suggest that if people aren’t alarmed by climate change, they’re monsters who don’t love their children. The claim that only liberals care about the environment is not only absurd, but it ignores the traditional meaning of the word conservative. In reality, this is not a liberal vs. conservative issue. However, in addition to the negative reaction many people had to the tone of messages like the trailer above, the argument against recognizing climate change and doing something about it has also been carefully managed and funded by political action committees and foundations representing corporations that oppose changes in fossil fuel energy policy.


scientific consensus graphicAlthough 97% of climate scientists agree on anthropogenic climate change, when Americans are asked by pollsters, “Do most scientists believe that the Earth is getting warmer because of human activity?” 55% say either “No” or that they don’t know. Less than half of Americans are aware that scientists are basically unanimous on this issue, and thinking that scientists are unsure affects their own opinions about climate change and the the government policies they are willing to support to mitigate it. A recent study found that most of the public statements against climate change made from 2003 to 2010 could be traced to about 91 organizations which received $558,000,000 in funding during that period. From 2003 to 2007 this money was easily traceable to sources such as Exxon-Mobil and Koch Industries, two corporations opposed to any changes in energy policy.

With the changes in foundation funding that followed the 2008 Citizens United Supreme Court decision that allowed corporations to hide their political spending, the sources of money paying for climate change denial have been more difficult to trace. Ultra-free market foundations and even a few religious organizations like the John Templeton Foundation pay the bills of websites like Climatedepot.com that go out of their way to label any scientist endorsing climate change a “Warmist” who is probably working for Al Gore in an effort to regulate every aspect of our lives in some big global prison state. Climate deniers warn of the “command economies” they claim environmentalists wish to impose, using language designed to rile up libertarians and free market enthusiasts and mobilize them against changing the economy in ways that although they would be very bad for big oil companies, would almost certainly create millions of new jobs.

A Recent study found that conservative think tanks funded by energy corporations play a central role in “denying the reality and significance of anthropogenic global warming (AGW), especially by manufacturing uncertainty over climate science.” The conservative think tanks sponsored the publication of 108 books denying climate change through 2010. American think tanks have also recently begun funding publishing in foreign countries to spread their message.

The study also examined the credentials of the authors and editors of these climate change denial books and found that “an increasing portion of denial books are produced by individuals with no scientific training. It appears that at least 90% of denial books do not undergo peer review, allowing authors or editors to recycle scientifically unfounded claims that are then amplified by the conservative movement, media, and political elites.”


One deceptive approach is cherry picking data from short time periods to falsely assert that global average temperatures are not rising. Blue trend lines show short-term countertrends that mask longer-term warming trends (red trend lines). Blue dots show the so-called global warming hiatus.


German solar energy
The Solar Settlement, a sustainable housing community project in Freiburg, Germany.

This is unfortunate, to say the least. While Germany is becoming a world leader in solar energy deployment, in spite of receiving only as much sunlight as Alaska, and while Britain is mapping its shift to a post-oil based economy with its “transition towns,” many Americans continue wasting their time arguing over the make-believe issue of climate change denial. Most economists agree that there are currently more jobs in the renewable energy sector than in the fossil fuel sector, and that trend is going to increase. The overall economy would be better off, if we shifted to sustainable energy sources and reduced carbon emissions. Of course, the global petroleum industry would be decimated, so they’re spending their money trying to slow the transition.

Of nearly 14,000 peer-reviewed climate articles published between 1991 and 2012, only 24 reject global warming. There really isn’t any doubt that the Earth’s climate is changing in ways that are going to cause serious social disruption in the future. When political leaders say there is still doubt about the need to address climate change, we should follow the money to discover why. Our unwillingness or inability to understand the situation causes us to continue being manipulated by organizations interested in maintaining the status quo, and may mean that our choices in the future will be much more limited than they need to be.

Questions for Discussion

  • How does politicizing the climate debate make it more difficult to find solutions?
  • What motivates some organizations to resist the idea that humans have caused global warming?
  • Would addressing climate change more rapidly hurt or help the global economy?



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Modern World History Copyright © 2021 by Dan Allosso and Tom Williford is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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