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Why a major 'population correction' is inevitable

Professor Bill Rees, one of Stable Planet Alliance's most famous and determined patrons, published this paper this week in the journal World, and an excerpt is reprinted here with permission. You can read the original article in full here.

Bill wrote to us:

"In this article, I try to draw together various biophysical factors that are rarely invoked in discussions of the human population contribution to 'overshoot'... I propose no solutions. As some of you know, from where I sit our present global crisis is a macro-variation on an historically familiar theme -- human societies/cultures seem to follow a repeating cycle of birth, development and decay/collapse. This cycle has been well studied in dozens of human societies (and is common elsewhere in nature), yet we seem incapable of organizing so that we do not repeat the pattern. Moreover, even if the mechanisms were understood by governments, and they took appropriate action, the ecosphere is in such a state of disrepair that, whether the global community is prepared for it or not, I reckon that the economy will contract accompanied by a major population 'correction' (and this is without nuclear war or other exogenous event such as an alien invasion)."

The Human Ecology of Overshoot: Why a Major ‘Population Correction’ Is Inevitable


Abstract: Homo sapiens has evolved to reproduce exponentially, expand geographically, and consume all available resources. For most of humanity’s evolutionary history, such expansionist tendencies have been countered by negative feedback. However, the scientific revolution and the use of fossil fuels reduced many forms of negative feedback, enabling us to realize our full potential for exponential growth. This natural capacity is being reinforced by growth-oriented neoliberal economics—nurture complements nature. Problem: the human enterprise is a ‘dissipative structure’ and sub-system of the ecosphere—it can grow and maintain itself only by consuming and dissipating available energy and resources extracted from its host system, the ecosphere, and discharging waste back into its host. The population increase from one to eight billion, and >100-fold expansion of real GWP in just two centuries on a finite planet, has thus propelled modern techno-industrial society into a state of advanced overshoot. We are consuming and polluting the biophysical basis of our own existence. Climate change is the best-known symptom of overshoot, but mainstream ‘solutions’ will actually accelerate climate disruption and worsen overshoot. Humanity is exhibiting the characteristic dynamics of a one-off population boom–bust cycle. The global economy will inevitably contract and humanity will suffer a major population ‘correction’ in this century.

Keywords: overshoot; exceptionalism; human nature; cognitive obsolescence; exponential growth; ‘K’ strategist; over population; over consumption; climate change; energy transition; dissipative structure; civilizational collapse; population correction

1. Introduction and Purpose

This paper examines the human population conundrum through the lens of human evolutionary ecology and the role of available energy. My starting premises are as follows:

(1) Modern techo-industrial (MTI) society is in a state of advanced ecological overshoot (for an excellent introduction to overshoot see William Catton’s classic, Overshoot [1]). Overshoot means that even at current global average (inadequate) material standards, the human population is consuming even replenishable and self-producing resources faster than ecosystems can regenerate and is producing entropic waste in excess of the ecosphere’s assimilative capacity [2,3]. In short, humanity has already exceeded the longterm human carrying capacity of the earth.

(2) The fossil-fuelled eight-fold increase in human numbers and >100-fold expansion of real gross world product in the past two centuries are anomalies; they also constitute the most globally-significant ecological phenomena in 250,000 years of human evolutionary history, with major implications for life on Earth.

(3) H. sapiens is an evolving species, a product of natural selection and still subject to the same natural laws and forces affecting the evolution of all living organisms [4,5].

(4) Efforts to address the human demographic anomaly and resulting eco-crisis without attempting to override innate human behaviours that have become maladaptive are woefully incomplete and doomed to fail.

Within this framing, the overall objective of the paper is to make the case that, on its present trajectory and regardless of the much-lauded demographic and so-called renewable energy transitions, the sheer number of humans and scale of economic activity are undermining the functional integrity of the ecosphere and compromising essential lifesupport functions. Unaddressed, these trends may well precipitate both global economic contraction and a significant human population ‘correction’—i.e., civilizational collapse— later in this century.




It Would Not Be the First Time

The prospect of societal collapse, however horrific it sounds to MTI ears, is perfectly consistent with history and the systems dynamics characterizing the rise and fall of previous human civilizations [94,95]. In particular, many MTI nations are exhibiting the diminishing returns and socio-political pathologies—egregious and increasing inequality, government and institutional incompetence and corruption, currency debasement, popular loss of confidence in the state, increasing civil unrest, etc.—of an overly complex society on the verge of collapse [96] as well as the potentially avoidable symptoms—ecological destruction, climate change, breakdown of trade and international relationships, and inability or unwillingness to adapt to changing circumstances—of a society apparently ‘choosing’ to fail [97]. More generally, the stages of civilizational development and decay catalogued by Toynbee [94] (genesis, growth, time of troubles, universal state, and disintegration) are markedly similar to the phases of the repetitive cycles common to living systems (initiation and exploitation, maturation and conservation, rigidification and release (i.e., collapse)). Gunderson and Holling advance the ‘panarchy’ theory to explore such cyclical change as a mechanism for adaptation common to complex ecosystems and social systems. They argue that each iteration of a naturally-repeating cycle (e.g., the cyclical fire regime of certain forest ecosystems) theoretically provides opportunities for innovation and evolutionary adaptation [98]. One is forced to wonder why modern H. sapiens stubbornly fail to apply lessons from well-studied historic collapses to develop the foresight and the policy actions needed to head off the next. On the contrary, many analysts reject historical precedents as guides to contemporary policy.

Perhaps they should take warning from the aforementioned infamous 1972 Club of Rome/MIT study, Limits to Growth (LTG) [99], which showed that, on a businessas-usual track, global society would face collapse by mid-21st century. As might be expected, many economists and techno-optimists roundly rejected this assessment—economists ignore overshoot and even grossly underestimate the damage from climate change; their concepts and models are divorced from biophysical reality [100]. However, subsequent studies show that the real world is behaving with disturbing fidelity to LTG modelling, particularly the two (of four) scenarios that indicate a halt in growth over the next decade or so, followed by subsequent declines and collapse [101].

6. Summary and Conclusions: It’s Really Quite Simple

“Without a biosphere in a good shape, there is no life on the planet. It’s very simple. That’s all you need to know. The economists will tell you we can decouple growth from material consumption, but that is total nonsense… If you don’t manage decline, then you succumb to it and you are gone” (Vaclav Smil, [102]).

H. sapiens, like all other species, are naturally predisposed to grow, reproduce, and expand into all suitable accessible habitat. Physical growth is natural, but is only an early phase in the development of individual organisms; growth in sheer scale, including population growth, is characteristic of early phases of complex living systems, including human societies. However, both material and population growth in finite habitats are ultimately limited by the availability of essential ‘inputs’, by the capacity of the system’s environment to assimilate (often toxic) outputs, or by various forms of negative feedback as previously listed. Growth will cease, either by “design or disaster” [103].

For most of H. sapiens’ evolutionary history, local population growth has, in fact, been constrained by negative feedback. However, improved population health (lower death rates) and the use of fossil fuels. particularly since the early 19th century, enabled a period of unprecedented food and resource abundance. In nature, any ‘K’-strategic species population enjoying such favourable conditions will expand exponentially. Growth will generally continue until excess consumption and habitat degradation once again lead to food shortages and starvation, or disease and predation take their toll. The population then falls back below the long-term carrying capacity of the habitat and negative feedback eases off. Some species repeatedly exhibit this cycle of population boom and bust.

Humanity is only a partial exception. The abundance generated by fossil fuels enabled H. sapiens, for the first time, to experience a one-off global population boom−bust cycle (Figure 1). It is a ‘one-off’ cycle because it was enabled by vast stocks of both potentially renewable self-producing resources and finite non-renewable resources, including fossil fuels, which have been greatly depleted. No repetition is possible. As Clugston argues, by choosing to industrialize, Homo sapiens unwittingly made a commitment to impermanence [77]. We adopted a self-terminating way of life, in which the finite resources that enable our industrial existence would inevitably become insufficient to do so.

The physical mechanisms are simple. Living systems, from individual cells through whole organisms to populations and ecosystems, exist in nested hierarchies and function as far-from-equilibrium dissipative structures [104]. Each level in the hierarchy depends on the next level up both as a source for useful resources (negentropy) and as a sink for degraded wastes (entropy). As Daly [8, 9] reminds us, the human enterprise is a whollydependent subsystem of the ecosphere; it produces and maintains itself by extracting negentropic resources from its host system, the ecosphere, and dumping degraded entropic wastes back into its host. It follows that the increasing structural and functional complexity of the human sub-system as a far-from equilibrium-dissipative structure (a node of negentropy) can occur only at the expense of the accelerated disordering (increasing entropy) of the non-growing ecosphere. Indeed, humanity is in overshoot—global heating, plunging biodiversity, soil/land degradation, tropical deforestation, ocean acidification, fossil fuel and mineral depletion, the pollution of everything, etc., are indicative of the increasing disordering of the biosphere/ecosphere. We are at risk of a chaotic breakdown of essential life-support functions [105].

Little of this is reflected in contemporary development debates or in discussions of the population conundrum. The international community’s response to incipient biospheric collapse is doubly disastrous. MTI culture’s commitment to material growth, including continued FF use (Track 1), condemns humanity to the predictably dangerous impacts of accelerating climate change; at the same time, our pursuit of alternative energy sources (themselves FF dependent) in order to maintain the growth-based status quo (Track 2) would, if successful, assure the continued depletion and dissipation of both selfproducing and non-renewable resources essential for the existence of civilization.

The mainstream view of population asserts that the growth rate is declining so “not to worry”—or worry that population decline is bad for the economy! Even the base assertion is controversial. Jane O’Sullivan points out that the rate of decline has itself declined in this century. She argues that UN demographers have thus ‘persistently underestimated recent global population, due to their over-anticipation of fertility declines in high-fertility countries’ [106]. The human population continues to grow at about 80 million per year— O’Sullivan argues that the number is closer to 90 million—and its ultimate peak is highly uncertain. Renewed negative feedback may well end growth well before the population reaches the UN’s expected 10.4 billion in the late 2080s.

It is crucial to remember that, right or wrong, conventional projections ignore the fact that the ecosphere is not actually now ‘supporting’ even the present eight billion people. The human enterprise is growing and maintaining itself by liquidating and polluting essential ecosystems and material assets. In short, even average material living standards are corrosively excessive, yet, in 2019, ‘almost a quarter of the global population… lived below the US$3.65 per day poverty line, and almost half, 47 percent, lived below the US$6.85 poverty line’ [107] and the world considers sheer material growth as the means to address this problem. Following this path, eco-destruction will ramp up, increasing the probability of a self-induced simplification and contraction of the human enterprise.

Barring a nuclear holocaust, it is unlikely that H. sapiens will go extinct. Wealthy, technologically advanced nations potentially have more resilience and may be insulated, at least temporarily, from the worst consequences of global simplification [108]. That said, rebounding negative feedbacks—climate chaos, food and other resource shortages, civil disorder, resource wars, etc.—may well eliminate prospects for an advanced world-wide civilization. In the event of a seemingly inevitable global population ‘correction’, human numbers will fall to the point where survivors can once again hope to thrive within the (much reduced) carrying capacity of the Earth. Informed estimates put the long-term carrying capacity at as few as 100 million [109] to as many as three billion people [110].

It is uncertain whether much or any of industrial high-tech can persist in the absence of abundant cheap energy and rich resource reserves, most of which will have been extracted, used, and dissipated. It may well be that the best-case future will, in fact, be powered by renewable energy, but in the form of human muscle, draft horses, mules, and oxen supplemented by mechanical water-wheels and wind-mills. In the worst case, the billion (?) or so survivors will face a return to stone-age life-styles. Should this be humanity’s World 2023, 4 523 future, it will not be urban sophisticates that survive but rather the pre-adapted rural poor and remaining pockets of indigenous peoples.

Bottom line: Any reasonable interpretation of previous histories, current trends, and complex systems dynamics would hold that global MTI culture is beginning to unravel and that the one-off human population boom is destined to bust. H. sapiens’ innate expansionist tendencies have become maladaptive. However, far from acknowledging and overriding our disadvantageous natural predispositions, contemporary cultural norms reinforce them. Arguably, in these circumstances, wide-spread societal collapse cannot be averted—collapse is not a problem to be solved, but rather the final stage of a cycle to be endured. Global civilizational collapse will almost certainly be accompanied by a major human population ‘correction’. In the best of all possible worlds, the whole transition might actually be managed in ways that prevent unnecessary suffering of millions (billions?) of people, but this is not happening—and cannot happen—in a world blind to its own predicament.

Read the full article here. Professor William E. Rees, School of Community and Regional Planning, Faculty of Applied Science, The University of British Columbia, Vancouver, BC V6T 1Z2, Canada;

We also appreciate the editorial work of Dr Jane O'Sullivan and Céline Delacroix on the original article.


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18 août 2023
Noté 5 étoiles sur 5.

It's sad that even on this site arithmetically-impaired commenters will propose "abundant" energy, of any form. The simple reality is that our human footprint on the planet is deeply destructive _precisely_ because we've had "abundant" energy for far too long. Sometimes, you can't see the cliff ahead. It helps to put on the blinders of common innumeracy.


14 août 2023
Noté 2 étoiles sur 5.

Good point on the entropic / dissipative nature of life.

Generally an extremely pessimistic Malthusian view of the world. A “renewable” world powered by oxen & human farm labor implies that 90% of people will go back to farming. What a shit quality of life, spending all of your precious life energy just struggling to scrounge up organic potatoes.

as another commenter posted — Abundant Nuclear Energy is possible but is a complete deal breaker for the malthusians who either prefer global depopulation to widespread energy availability, or unknowingly conflate Nuclear energy with warfare.

The only mention of nuclear power was as a threat of global nuclear war/disaster. Tells you all you need to know about this…


13 août 2023

So, why is abundant nuclear energy not recognized as a possibility? Until recently, no significant progress has been made to generate heat and electricity from the safest, most capable and least material intensive energy source that mankind has ever had. Bill Rees did not recognize this, either, in this paper.


Pam Pence
Pam Pence
13 août 2023
Noté 5 étoiles sur 5.

Thanks Bill for pulling all these sources of knowledge together to serve us up reality so that we can, if we choose, deal with it--as opposed to denying, burying our heads, or numbing ourselves. May those who survive through this be wiser, more courageous than this era of humanity has been. And, as I do my part, I hang onto the awareness that complex systems can "turn on a dime" and that the long arc of evolution (including human love, wisdom and compassion) will continue.

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