The Limits to Growth

Purpose

In commissioning the MIT team to undertake the project that resulted in LTG, the Club of Rome had three objectives:

Gain insights into the limits of our world system and the constraints it puts on human numbers and activity.

Identify and study the dominant elements, and their interactions, that influence the long-term behavior of world systems.

To warn of the likely outcome of contemporary economic and industrial policies, with a view to influencing changes to a sustainable lifestyle.

Method

The World3 model is based on five variables: "population, food production, industrialization, pollution, and consumption of nonrenewable natural resources." At the time of the study, all these variables were increasing and were assumed to continue to grow exponentially, while the ability of technology to increase resources grew only linearly. The authors intended to explore the possibility of a sustainable feedback pattern that would be achieved by altering growth trends among the five variables under three scenarios. They noted that their projections for the values of the variables in each scenario were predictions "only in the most limited sense of the word" and were only indications of the system's behavioral tendencies. Two of the scenarios saw "overshoot and collapse" of the global system by the mid- to latter part of the 21st century, while a third scenario resulted in a "stabilized world."

Exponential reserve index

A key idea in The Limits to Growth is the notion that if the rate of resource use is increasing, the number of reserves cannot be calculated by simply taking the current known reserves and dividing them by the current yearly usage, as is typically done to obtain a static index. For example, in 1972, the amount of chromium reserves was 775 million metric tons, of which 1.85 million metric tons were mined annually. The static index is 775/1.85=418 years, but the rate of chromium consumption was growing exponentially at 2.6 percent annually. If instead of assuming a constant rate of usage, the assumption of a constant rate of growth of 2.6 percent annually is made, the resource will instead last

ln

⁡

(

1

+

0.026

×

418

)

0.026

≈

95 years

{\displaystyle {\frac {\ln(1+0.026\times 418)}{0.026}}\approx {\text{95 years}}}

In general, the formula for calculating the amount of time left for a resource with constant consumption growth is:

y

=

ln

⁡

(

(

r

s

)

Conclusions

After reviewing their computer simulations, the research team came to the following conclusions:

If the present growth trends in world population, industrialization, pollution, food production, and resource depletion continue unchanged, the limits to growth on this planet will be reached sometime within the next one hundred years. The most probable result will be a rather sudden and uncontrollable decline in both population and industrial capacity.

It is possible to alter these growth trends and to establish a condition of ecological and economic stability that is sustainable far into the future. The state of global equilibrium could be designed so that the basic material needs of each person on earth are satisfied and each person has an equal opportunity to realize his individual human potential.

If the world's people decide to strive for this second outcome rather than the first, the sooner they begin working to attain it, the greater will be their chances of success.

The introduction goes on to say:

These conclusions are so far-reaching and raise so many questions for further study that we are quite frankly overwhelmed by the enormity of the job that must be done. We hope that this book will serve to interest other people, in many fields of study and in many countries of the world, to raise the space and time horizons of their concerns, and to join us in understanding and preparing for a period of great transition – the transition from growth to global equilibrium.

Criticism and responses

LTG provoked a wide range of responses, including immediate criticisms almost as soon as it was published.

Peter Passell and two co-authors published a 2 April 1972 article in the New York Times describing LTG as "an empty and misleading work ... best summarized ... as a rediscovery of the oldest maxim of computer science: Garbage In, Garbage Out." Passell considered the study's simulation simplistic and that it assigned little value to the role of technological progress in solving the problems of resource depletion, pollution, and food production. They charged that all LTG simulations ended in collapse, predicting the imminent end of irreplaceable resources. Passell also charged that the entire endeavour was motivated by a hidden agenda: to halt growth in its tracks.

In 1973, a group of researchers at the Science Policy Research Unit at the University of Sussex concluded that simulations in Limits to Growth were very sensitive to a few key assumptions and suggested that the MIT assumptions were unduly pessimistic and the MIT methodology, data, and projections were faulty. However, the LTG team, in a paper entitled "A Response to Sussex," described and analyzed five major areas of disagreement between themselves and the Sussex authors. The team asserted that the Sussex critics applied "micro reasoning to macro problems" and suggested that their own arguments had been either misunderstood or wilfully misrepresented. They pointed out that the critics had failed to suggest any alternative model for the interaction of growth processes and resource availability, and "nor had they described in precise terms the sort of social change and technological advances that they believe would accommodate current growth processes."

During that period, the very idea of any worldwide constraint, as indicated in the study, was met with scepticism and opposition by both businesses and the majority of economists. Critics declared that history proved the projections to be incorrect, such as the predicted resource depletion and associated economic collapse by the end of the 20th century. The methodology, the computer, the conclusions, the rhetoric, and the people behind the project were criticised. Yale economist Henry C. Wallich agreed that growth could not continue indefinitely; however, he believed that a natural end to growth was preferable to intervention. Wallich stated that technology could solve all the problems the report was concerned about, but only if growth continued apace. According to Wallich's cautionary statement, prematurely halting progress would result in the perpetual impoverishment of billions.

Latin American World Model (Bariloche Model)

In response to the physical limits and zero-growth recommendations proposed by the Limits to Growth model, a group of Latin American scientists at the Bariloche Foundation in Argentina developed the Latin American World Model (LAWM), also known as the Bariloche Model. The initiative emerged from a 1970 meeting in Rio de Janeiro sponsored by the Club of Rome, where Latin American researchers critiqued the Massachusetts Institute of Technology (MIT ) World3 model for reflecting the ideology and concerns of the developed world while ignoring the realities of the Global South.

Directed by geologist Amílcar O. Herrera, the LAWM project brought together an interdisciplinary team including mathematicians, economists, and sociologists such as Hugo D. Scolnik, Graciela Chichilnisky, and Gilberto C. Gallopín. Published in English in 1976 as Catastrophe or New Society? A Latin American World Model, the work challenged the MIT model's apparent premise that population growth and resource depletion would inevitably lead to global collapse.

The Bariloche researchers argued that the true limits to human development were sociopolitical rather than physical. They contended that the "catastrophe" predicted by the MIT model was not a future possibility but a present reality for the two-thirds of humanity living in poverty and underdevelopment. The LAWM was explicitly normative; instead of extrapolating current trends, it sought to demonstrate the material viability of an "ideal" egalitarian global society where production is oriented toward the satisfaction of basic human needs rather than consumerism and profit.

Methodologically, the LAWM introduced several innovations to global modeling. It utilized life expectancy at birth as the primary variable to be optimized, rather than economic indicators like Gross National Product (GNP), arguing that life expectancy is highly sensitive to socioeconomic equity and basic living conditions. Furthermore, the model treated population growth as an endogenous variable, demonstrating that the most effective way to control demographic expansion was by improving living conditions and satisfying basic needs, specifically nutrition, housing, health, and education, rather than imposing top-down population control measures.

The LAWM resonated strongly with the political climate of the 1970s, particularly the Non-Aligned Movement and the United Nations' calls for a New International Economic Order (NIEO ). It advocated for a radical restructuring of the international economy, proposing that developed nations reduce their economic growth to alleviate environmental pressure, while developing nations pursue autonomous development pathways rooted in regional solidarity and self-reliance.

Later responses

In 1997, the Italian economist Giorgio Nebbia observed that the negative reaction to the LTG study came from at least four sources: those who saw the book as a threat to their business or industry; professional economists, who saw LTG as an uncredentialed encroachment on their professional perquisites; the Catholic Church, which bridled at the suggestion that overpopulation was one of mankind's major problems; and finally, the political left, which saw the LTG study as a scam by the elites designed to trick workers into believing that a proletarian paradise was a pipe dream. A UK government report found that "In the 1990s, criticism tended to focus on the misconception that Limits to Growth predicted global resource depletion and social collapse by the end of the year 2000."

Peter Taylor and Frederick Buttle’s interpretation of the LTG study and the associated system dynamics (SD) models found that the original SD was created for firms and set the pattern for urban, global, and other SD models. These firm-based SDs relied on superintending managers to prevent undesirable cycling and feedback loops caused by separate common-sense decisions made by individual sectors. However, the later global model lacked superintending managers to enforce interrelated world-level changes, resulting in undesirable cycles that led to exponential growth and collapse in nearly all models, regardless of the parameter settings. There was no way for a few individuals in the model to override the structure of the system, even if they understood it as a whole. This meant there were only two solutions: convincing everyone in the system to change the basic structure of population growth and collapse (moral response) and having a superintending agency analyzing the system as a whole and directing changes (technocratic response). The LTG report combined these two approaches multiple times. System dynamists constructed interventions into the world model to demonstrate how their proposed interventions improved the system to prevent collapse. The SD model also aggregated the world’s population and resources, which meant that it demonstrated crises emerging with a strictly global logic or form at similar times and in similar ways less effectively because of the unequal distributions of populations and resources. These issues indicate that the local, national, and regional differentiation in politics and economics surrounding socioenvironmental change was excluded from the SD used by LTG, making it unable to accurately demonstrate real-world dynamics.

Positive reviews

In 1980, the Global 2000 Report to the President arrived at similar conclusions regarding expected global resource scarcity and the need for multilateral coordination to prepare for this situation.

Reading LTG for the first time in 2000, Matthew Simmons concluded his views on the report by saying, "In hindsight, The Club of Rome turned out to be right. We simply wasted 30 important years ignoring this work." In a 2008 blog post, Ugo Bardi commented that "Although, by the 1990s LTG had become everyone's laughing stock, among some the LTG ideas are becoming again popular".

Robert Solow, who had been a vocal critic of LTG, said in 2009 that "thirty years later, the situation may have changed... it will probably be more important in the future to deal intellectually, quantitatively, as well as practically, with the mutual interdependence of economic growth, natural resource availability, and environmental constraints."

In a study conducted in 2008, Graham Turner from CSIRO discovered a significant correlation between the observed historical data spanning from 1970 to 2000 and the simulated outcomes derived from the "standard run" limits of the growth model. This correlation was apparent across nearly all the reported outputs. The comparison falls comfortably within the range of uncertainty for almost all the available data, both in terms of magnitude and the patterns observed over time. Turner conducted an analysis of many studies, with a special focus on those authored by economists, that have consistently aimed to discredit the limits-to-growth concept over the course of several years. According to Turner, the aforementioned studies exhibit flaws and demonstrate a lack of comprehension regarding the model.

Turner reprised these observations in another opinion piece in The Guardian on 2 September 2014. Turner used data from the UN to claim that the graphs almost exactly matched the 'Standard Run' from 1972 (i.e., the worst-case scenario, assuming that a 'business as usual' attitude was adopted and there were no modifications of human behaviour in response to the warnings in the report). Birth rates and death rates were both slightly lower than projected, but these two effects cancelled each other out, leaving the growth in world population almost exactly as forecast.

Legacy

Updates and symposia

The Club of Rome has persisted after The Limits to Growth and has generally provided comprehensive updates to the book every five years.

An independent retrospective on the public debate over The Limits to Growth concluded in 1978 that optimistic attitudes had won out, causing a general loss of momentum in the environmental movement. While summarizing a large number of opposing arguments, the article concluded that "scientific arguments for and against each position ... have, it would seem, played only a small part in the general acceptance of alternative perspectives."

In 1989, a symposium was held in Hanover, entitled "Beyond the Limits to Growth: Global Industrial Society, Vision or Nightmare?" and in 1992, Beyond the Limits (BTL) was published as a 20-year update on the original material. It "concluded that two decades of history mainly supported the conclusions we had advanced 20 years earlier. But the 1992 book did offer one major new finding. We suggested in BTL that humanity had already overshot the limits of Earth's support capacity."

Limits to Growth: The 30-Year Update was published in 2004. The authors observed that "It is a sad fact that humanity has largely squandered the past 30 years in futile debates and well-intentioned, but halfhearted, responses to the global ecological challenge. We do not have another 30 years to dither. Much will have to change if the ongoing overshoot is not to be followed by collapse during the twenty-first century."

In 2012, the Smithsonian Institution held a symposium entitled "Perspectives on Limits to Growth". Another symposium was held in the same year by the Volkswagen Foundation, entitled "Already Beyond?"

Limits to Growth did not receive an official update in 2012, but one of its coauthors, Jørgen Randers, published a book, 2052: A Global Forecast for the Next Forty Years.

Comparisons and updated models

In 2008, physicist Graham Turner at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia published a paper called "A Comparison of 'The Limits to Growth' with Thirty Years of Reality." It compared the past thirty years of data with the eleven scenarios laid out in the 1972 book and found that changes in industrial production, food production, and pollution are all congruent with one of the book's eleven scenarios—that of "business as usual." This scenario in Limits points to economic and societal collapse in the 21st century. In 2010, Nørgård, Peet, and Ragnarsdóttir called the book a "pioneering report." They said that "its approach remains useful and that its conclusions are still surprisingly valid ... unfortunately the report has been largely dismissed by critics as a doomsday prophecy that has not held up to scrutiny."

Also in 2008, researcher Peter A. Victor wrote that even though the Limits team probably underestimated the price mechanism's role in adjusting outcomes, their critics have overestimated it. He states that Limits to Growth has had a significant impact on the conception of environmental issues and notes that (in his view) the models in the book were meant to be taken as predictions "only in the most limited sense of the word".

In a 2009 article published in American Scientist entitled Revisiting the Limits to Growth After Peak Oil, Hall and Day noted that "the values predicted by the limits-to-growth model and actual data for 2008 are very close." These findings are consistent with the 2008 CSIRO study, which concluded, "The analysis shows that 30 years of historical data compares favorably with key features ... [of the Limits to Growth] "standard run" scenario, which results in collapse of the global system midway through the 21st Century."

In 2011, Ugo Bardi published a book-length academic study of The Limits to Growth, its methods, and historical reception and concluded that "The warnings that we received in 1972 ... are becoming increasingly more worrisome as reality seems to be following closely the curves that the ... scenario had generated." A popular analysis of the accuracy of the report by science writer Richard Heinberg was also published.

In 2012, writing in American Scientist, Brian Hayes stated that the model is "more a polemical tool than a scientific instrument". He went on to say that the graphs generated by the computer program should not, as the authors note, be used as predictions.