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Mother Pelican
A Journal of Solidarity and Sustainability

Vol. 21, No. 12, December 2025
Luis T. Gutiérrez, Editor
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Homo Sapiens: Inherently Unsustainable,
But Do We Have to Be that Way?

William E. Rees

This article was originally published by
William E. Rees' Substack, 24 November 2025
REPUBLISHED WITH PERMISSION



Illustration provided by the author. Click on the image to enlarge.


The embarrassing pattern

It’s pretty obvious when you think about it: humanity is inherently unsustainable (though all governments and international institutions – virtually everyone, actually – are in denial about the obvious). There’s plenty of recent and ancient evidence to back up these assertions but let’s start with just a few well-known warnings that modern humanity in particular is on a fatal tack:

  • Rachel Carson’s Silent Spring warned about the hazards of broadcast pesticides biocides (especially DDT) use in 1962. Sixty-three years later, biocide residues pollute everything, including commercial foods, and are implicated in various health problems such as plunging human sperm counts. (What logically reflective species would poison its own food?) Meanwhile, the global application of chemical ‘pesticides’ is steadily increasing, 20% by volume in just the decade to 2023.
  • The Club of Rome’s/MIT’s (in)famous landmark computer simulation study, Limits to Growth, (LtG) dates from 1972, also more than half a century ago. LtG’s so-called ‘standard run’ or ‘business-as-usual’ (BaU) scenario suggested that, driven by excess demand, energy and resource scarcity would begin to undermine industrial society generating reductions in GDP, major services, food production, and population. The most likely outcome would be “sudden and uncontrollable decline” toward the middle to end of the 21st Century. Several subsequent analyses of real-world trends show that the industrial world is, in fact, approximately tracking LtG’s BaU collapse scenario. (Well, why wouldn’t it? This is a finite planet, after all.)
    This obviously “puts into question” the suitability of continuous economic growth as humanity’s ‘development’ mantra in for coming decades. Yet, perpetual growth, propelled by technology, remains the dominant cultural narrative for all the world’s major governments and international institutions with many economist expecting gross world product to more than double by 2050.

    (We probably should note that the human enterprise is already in unsustainable – meaning ‘potentially terminal’ overshoot?)

  • Responding to repeated climate scientists’ warnings, the United Nations Framework Convention on Climate Change (UNFCCC) was drafted in 1992 – that’s 33 years ago – with the overriding goal of stabilizing atmospheric carbon dioxide (CO2) concentrations and reducing carbon emissions. The convention established a dedicated decision-making body, the so-called Conference of the Parties (COP), to facilitate a global approach to reversing anthropogenic climate disruption. More than three decades and 30 COP conferences later, carbon dioxide emissions have actually increased from 22.3 giga-tons (Gt) in 1992 to a record 37.4 Gt in 2024 and are still tracking upward; extreme weather events ravage every continent and the more stringent COP Paris 2015 goal of limiting mean global warming to 1.5 Celsius degrees is probably as ‘dead as a doornail’. Meanwhile, atmospheric concentrations of carbon dioxide have reached have a record 427 parts per million ~53% above preindustrial levels, and show no sign of leveling off. In the circumstances, it seems fair to ask the world’s climate-concerned: “How’s the UNFCCC working out for you?”

    Now ponder humanity’s sorry treatment of a just small sample of non-human vertebrate species with whom we share the planet, beginning with the

  • Passenger pigeon: Before European colonization, Eastern North America was habitat for what may well have been the most abundant bird species on Earth, Ectopistes migratorius, better known as the passenger pigeon. The peak population of passenger pigeons – three to five billion birds – comprised as much as 40% of the total avian population of North America. Various accounts state that migrating flocks darkened the day-time sky for hours on end. That’s bloody miraculous!! So, naturally, Euro-Americans hunted the birds relentlessly for subsistence, sport, and by the barrel-full for urban markets. The massive flocks had noticeably declined by the mid-late 18th Century and dropped precipitously between 1850 and 1890 – not coincidently while the US population ballooned from 23 to 63 million (by 174%). As flock size shrank, breeding success plunged – the passenger pigeon had evolved to thrive only with the social stimulation and protection afforded by large flocks. The last known wild passenger pigeon was shot in Ohio in 1900; the species winked out forever with the passing of a captive female, Martha, in the Cincinnati Zoo in 1914.
    Not too sustainable.

    Human depredation has also extended to various marine birds including the

  • Great auk: Pinguinus impennis was a large, flightless bird that once thrived by the millions in the cold coastal waters on both sides of the Atlantic Ocean. Intensive human exploitation of great auk colonies got underway in the early 16th Century. The unwary birds were easy prey. They became highly valued for their meat, excellent down and oil in Europe where growing demand drove the extermination of eastern Atlantic auk populations before 1700. European explorers and settlers to the Americas took the birds for fish-bait as well as food, accelerating extirpation from the western range. The last known breeding pair were killed on the rocky islet of Eldey – still host to one of the world’s largest colonies of northern gannets – off the south-west coast of Iceland in June, 1844. The final demise of the great auk is one of the best-known examples of human-induced extinctions in modern times.

    But don’t think for a moment that human-induced extinction is strictly a modern product of gunpowder and firearms. Consider the fate of the nine species of

  • Moa: The moa (order Dinornithiformes) were large flightless birds, the tallest of which apparently towered to 3.7 meters (12 ft) and weighed up to 250 kg (550 lbs). These natural wonders evolved on New Zealand, two large islands devoid of large mammals. Since moa had acquired no fear of terrestrial threats, they were easy prey for the earliest human settlers, the Māori, who colonized at least the north island as early as 1250. The Māori exploited the moa intensely for meat, feathers, bones and egg-shell pottery. Over-hunting and habitat loss to humans, possibly combined with predation by dogs and rats introduced by the Māori, drove the moa to extinction in the 1300’s perhaps less than 100 years after human settlement. A related, indirect human-caused extinction was the demise of Haast’s eagle. This native raptor relied almost exclusively on moa for food, so its ‘departure’ quickly followed that of its primary prey.

    Even earlier, a similar human-induced fate befell several species of

  • Elephant birds: These large, flightless birds were among the largest feathered creatures ever to walk the Earth. Some species were three meters (10 ft) tall and remarkably heavy – estimates for Aepyornis maximus range from 700 to 1000 kg (1,500 –2,200 lbs). Native to Madagascar, elephant birds went extinct around 1000 CE along with the Malagasy hippopotamus, a dozen species of giant lemurs, and several other vertebrates species, due to increasing human activity including hunting and habitat destruction.

    The passenger pigeon, great auk, moa and elephant birds join a large and varied flock of extinguished birds. Humans have driven the extinction of at least 216 avian species since 1500 (though recent data suggests the total number may be as high as 1430).

    The story is little different when the focus shifts to mammals. One stunning example concerns the

  • American bison: Various estimates put the population of American or plains bison (Bison bison bison) at between 30 and 60 million – the largest ungulate population on the planet – at the time of European colonization of North America. Intensive hunting and purposeful destruction of the vast herds (the latter to hasten the subjugation of Native Americans, aka ‘Indians’) took off in the early-mid 19th Century and accelerated with the westward extension of the railway (~1860). Near the peak of the slaughter, in 1872-1874, an average of 5000 bison were killed every day. (This was about the time the passenger pigeon was suffering its precipitous decline back East.) By 1884 only about 350 wild plains bison – .0006% to .001% of the original population – remained in the United States; none were left in Canada.[1] The good news is that conservation efforts beginning in the early 20th Century rescued the bison from extinction. Estimates vary, but about 30,000 animals now roam free on public lands and parks in the US and Canada. Private meat-producing herds in the US contain ~190,000 bison; Canadian ranches run another ~150,000 animals.

    Like valuable marine birds, economically-worthy marine mammals attracted excess human attention. Among the best-known magnets was the

  • Sea otter: The largest of the weasel family, sea otters (Enhydra lutris) thrived in the hundreds of thousands along much of the Pacific rim from northern Japan, along the Kamchatka Peninsula and Aleutian Islands, and down the coast of North America to the Mexican state of Baja California. Unfortunately for the animals, sea otters have exceedingly fine fur, the densest of any mammal, cursing them with high market value and triggering the (human) profit motive. Between 1740 and 1912, intensely competitive commercial ‘harvesting’ of the otters’ valuable pelts by Russian, American, British and European trades was relentless, devastating local populations and pushing the species to the brink of extinction across its entire range. By the early 20th Century, the global population had collapsed to only a few scattered remnants totaling less than 2000 animals. However, as with the bison, there is good news – intensive conservation efforts have since enabled a spotty, fluctuating recovery of some local sea otter populations. The global population is currently estimated at ~125,000 animals.

    Not all marine mammal stories have an upbeat ending. Among the most intriguingly regrettable is that of

  • Stellar’s sea cow: A member of the Dugong family, Stellars’ sea cow (Hydrodamalis gigas) was a docile herbivorous shallow water giant that ranged up to 7.5 m (25 ft) in length and weighed up to 11,000 kg (28,000 lbs). When ‘discovered’ by Georg Wilhelm Stellar in 1741, it inhabited the waters near fresh water stream mouths around only a few islands in the Bering Sea, but the fossil record shows its prehistoric range was similar to that of the sea otter. Stellar’s sea cow was exterminated by 1768, a mere 27 years after discovery! Wasteful over-hunting for meat and blubber is probably the primary cause, but the sea cow’s final demise may have been accelerated by the near extirpation of sea otters (life is a complex system, see above). Sea urchins are among the otter’s prime food source so, with the human-caused local extinction of otters, urchin populations bloomed to become competition for the sea cow’s diet of sea grass and algae. Whether direct or indirect, human exploitation caused the sea cow’s extinction. Arguably, hunter-gatherers may even have been responsible for the sea cow’s earlier ‘withdrawal’ from most of its prehistoric range millennia ago, as aboriginal peoples colonized the Pacific coasts of both Asia and North America.

    Stellar’s sea cow is just one of the growing herd of ~80 mammal species humans have driven to extinction since 1500.

  • What could all this possibly mean?

    Several common threads run through all these examples. First, whether talking chemical pollution, climate disruption, bloated economies, potential societal collapse or the incipient ‘sixth extinction’, humans are at cause. In every case, growth of the human enterprise or human greed or both are the direct drivers. Second, none of the issues considered should have come as a surprise. In some cases, as with Silent Spring, Limits to Growth and climate change/global heating, the world community had explicit warnings for decades that something was seriously amiss. As for extinctions or near-extinctions, it would have been obvious to the perpetrators themselves, again many years before collapse, that the end was nigh. Most importantly, however, the warnings – whether documented scientific studies or participant observation – had virtually no significant impact on human behaviour, the overall trend or final outcome.

    To be clear:

  • Silent Spring did contribute to the banning of DDT in agriculture in much of the world (albeit decades of push-back later), and is credited with kick-starting the ‘environmental movement’. However, pesticide use in general is rampant and rising, still remains controversial, (i.e., dangerous) and the environmental movement has been stifled or, at best, conflated with climate angst.
  • Limits to Growth was crushed under the weight of economists’ contrary assessments and swept away by political ‘reality’. Young people today have never heard of it. Subsequent affirmations of LtG’s more dire scenario notwithstanding, the human enterprise marches undeterred toward ignominious collapse.
  • The UNFCCC has failed utterly to achieve its primary goal; [2] the COP process is increasingly a creature of the corporate (including fossil fuel) sector and the butt of rude jokes. Fossil fuel use and emissions continue to grow, while dangerous weather events are worsening in frequency and intensity.

  • Meanwhile, it’s not looking good for non-human species. Humans plus our domestic livestock now comprise ~96% of the mammalian biomass on Earth (up from <1% at the dawn of agriculture) and the proportion keeps growing. We are ‘competitively displacing’ other animals from their food niches and habitats. The populations of wild monitored vertebrates have fallen by more than 70% in just the past half century; invertebrates (insects, mollusks, etc.) are not far behind as uninhibited human exuberance continues to shred the fabric of life.

    It’s an old story

    For every area of the world that paleontologists have studied and that humans first reached within the last fifty thousand years, human arrival approximately coincided with massive prehistoric extinctions (Diamond 1992, 355)

    While human-induced extinction has accelerated with population growth and technology, it is actually an ancient phenomenon. The paleo-ecological, anthropological, and archaeological literature is replete with examples of local extirpations and total extinctions of large mammals and (particularly flightless) birds after the invasion of their habitats by Homo sapiens over the past 50,000 years. Humans hunted large animals such as mammoths, mastodons, and giant sloths as we expanded our range across the planet (much like bacteria on a Petrie dish of nutrient broth); extinctions occurred at varying rates, quickly in some places but taking millennia in others. Diamond reports that In North America, South America, and Australia, about 72%, 80%, and 86% respectively of large mammalian genera became extinct in the decades and centuries after human arrival. Another study estimates “that with only Stone Age technology, the Polynesians exterminated >2000 bird species, some ~15% of the world total.”

    The human nature of unsustainability

    What this overall picture suggests is that human-caused species extinction is mostly a natural phenomenon. Homo sapiens, like all other species, evolved in ways the enabled successful survival and reproduction. Natural selection favoured behaviours that maximized early humans’ ability to secure essential resources, often in the face of competition. So it is that humans, like other species, evolved an innate tendency to use up all scare resources.

    Arguably, members of small, relatively isolated bands of hunter-gatherers would be able to agree to exercise some self-restraint out of mutual concern for their future[3] but, when faced with unconstrained competition, the advantage would fall to those individuals and groups who were inclined to take it all now before someone else did.[4] Note too that competition would be a strong driver of technological innovation and that every increase in technological competence has been shown to increase the likelihood of resource depletion, even among non-human primates.

    So far, we have a base case that even paleolithic Homo sapiens was potentially unsustainable by nature. Humans are genetically predisposed to use up available resources and are better at it than other creatures.[5] We are a large energy-demanding patch-disturbance species, and like all such species, have always significantly altered, and sometimes overwhelmed (read ‘destroyed’), our habitats.

    But wait, it gets worse

    Then there’s the modernity factor. Even simple technological advances can significantly increase what is ‘available’ to humans while modest social changes can alter the internal dynamics of social groups to the detriment of nature. New relational properties ‘emerge’ as the system complexifies.

    For example, the adoption of agriculture was huge; it created food surpluses that enabled the development of permanent settlements, social hierarchies, excess accumulation by some (leading to extreme necrocapitalism in colonial/modern times) and all the related emergent trappings of ‘civilization’. Jump ahead 10,000 years. With the industrial revolution, technology and social change go into warp drive abetted by another innate human behaviour – the tendency to ‘socially construct’ lived reality.

    This last is a crucial factor. Post-enlightenment society, particularly modern techno-industrial (MTI) culture, is partially founded on the notion of human exceptionalism, the idea that Homo sapiens stands uniquely outside of nature. Exceptionalism posits that humans are not subject to natural laws and that our social behaviour is entirely the product of social learning untainted by evolutionary history or genetic predisposition. Mainstream economics, particularly the neoliberal version, reflects the exceptionalist perspective. Textbooks depict the economy and ‘the environment’ as separate, essentially independent systems; economists consider human ingenuity to the greatest resource; technology can find substitutes for any good or service provided by nature. With material growth unconstrained by biophysical limits, everyone everywhere can have as much as they want. And since globalization and freer markets can be shown to maximize productive efficiency, an integrating world marketplace becomes the arbiter of social values.

    These few beliefs and assumptions alone are enough to sustain faith in perpetual economic growth facilitated by continuous efficiency gains and technological progress. And let’s face it – the fantasy has worked spectacularly well – at least in material terms – for about 20% of the world’s people. Gross world product has increased >100-fold in the two centuries since 1820 so even average GWP per capita has increased by a factor of ~13. Little wonder a conceptual fabrication has become the developmental algorithm for all the world’s major nations and international institutions. The ecosphere, of course, is much diminished reeling from biodiversity loss, incipient climate chaos, collapsed ecosystems, ubiquitous pollution and even rising human death tolls, the costs of which either go unrecorded, or perversely, contribute to the illusion by adding to GDP.

    Stop to think about this for a moment. A quasi-religious human social construct (which the accelerated loss of global life support functions shows to be a shared delusion) is all MTI culture needs to abstract humans from finite reality and reduce the living world to little more than passive backdrop to human affairs.

    We say we are a rational scientific culture, but unfolding events suggest that subconscious belief in human exceptionalism and technological invulnerability, combined with market dynamics and faulty accounting – all reinforced by the comfortable lifestyles of decision-makers and the well-to-do generally – overrides real-world science on the fraying of global life-support systems. This goes a long way toward explaining the world’s non-response to major symptoms of ecological overshoot (e.g., pesticide contamination, global heating, plunging biodiversity, pollution of everything, etc.). We can safely conclude that Homo sapiens is also potentially unsustainable by nurture.

    Tying the threads together

    So, lets summarize humanity’s modern eco-predicament. Natural selection shaped the evolution of Homo sapiens in ways that made us unmatched in the inter-species competition for scarce resources and habitat. Humanity was able gradually to expand, occupy the entire planet and consume vastly more than any ecologically ‘normal’ species. This early competitive ‘advantage’ made us potentially unsustainable and, with modernization, things really got out of hand. Virtually the whole global community now adheres to a mythic, perpetual-growth-based, eco-destructive cultural narrative that reinforces our natural expansionist tendencies.

    Is this not a regrettable combination on a finite planet? Consumption/pollution has exploded and shows every sign of ramping up. Our dominant cultural narrative has rendered Homo sapiens unsustainable by nurture as well as by nature and propelled the human enterprise far into ecological overshoot.

    And remember, overshoot is a terminal condition.

    Let’s be clear about the systemic implications of these assertions. Contrary to exceptionalist mantra, Homo sapiens has evolved as an integral part of nature and is therefore subject to natural law, particularly the entropy law. From this perspective, unsustainability, as manifested in overshoot, is an inevitable emergent phenomenon resulting from the interaction of MTI culture and the ecosphere. Inevitable because the modern human enterprise is a growing energy- and resource-consuming subsystem of the living but non-growing ecosphere that obtains its energy and material resources from, and dumps depleted wastes back into, into that same ecosphere. In short, the human sub-system has always been potentially parasitic on the ecosphere and this means that there is a point, long passed, beyond which the growth and maintenance of that sub-system can be maintained only at the expense of the entropic degradation and dissipation of its host system, the ecosphere. No configuration of MTI values and norms can produce a sustainable state.

    Let me repeat that in simpler language. Modern human societies live and grow by depleting and polluting the only habitat they have even had or will ever know (sorry, Elon). And we can hardly plead: “Who knew?”

    There’s no easy way out

    Conceivably, a century or even half a century ago, if this were a more conscious and logically reflective society, we might have crafted a completely different cultural narrative. This would still be an act of social construction, but one based on reality. It would begin by: acknowledging humanity’s evolutionary heritage and the intractability of natural law; taking seriously the mounting data on depletion and pollution, including its manifestation in global heating; formally acknowledging biophysical limits to material growth; committing to basic notions of equality and social justice; recognizing in current affairs the symptoms that led to societal collapse in multiple previous civilizations; and, most importantly, working cooperatively to fashion a smaller global economy that would support fewer people generously and more equitably within the productive and assimilative capacities of the ecosphere.[6] The final product would be a biophysically realistic cultural mindset that would enable human thriving while counteracting, rather than reinforcing, Homo sapiens’ natural expansionist tendencies.

    Such a deliberate act of global sustainable culture-building may no longer be possible (if it ever were). The sheer momentum of MTI culture has pushed so far beyond biophysical limits – seven of nine crucial Earth systems boundaries have been breached – that a graceful controlled contraction would be difficult in the best of circumstances.

    And these are anything but the best of circumstances. Contemporary geopolitics puts anything like the required cooperative dynamic far outside the realm of political feasibility. Remember our innate competitive bent? The global community is an unruly, belligerent, fractious collection of self-interested tribes with no uniting vision of the future, that often can’t abide by its own agreements (e.g. the COP Paris Accord, Biodiversity Convention, etc.) and that is already fighting over territory and scarce resources. Moreover, despite the contrary evidence, all major nations remain addicted to continuous material growth; many are even actively pronatalist, trying to pump up their populations. How likely, then, are these governments to sit around a table to negotiate an agreement that would reduce gross world product by, say, 50% (80% in rich countries) and bring the world population down to one or two billion over the next century?

    Current events show that most decision-makers remain oblivious to our collective eco-predicament. Politicians and corporate leaders are the hard-wired exemplars of the expansionist techno-mindset and the former are increasingly in the pockets of the latter.

    And the latter have all the power that money can buy. This should be worrisome because (with apologies to Margaret Mead) we should:

    Never doubt that a small group of thoughtless, committed billionaires can change the world; indeed, it’s the only thing likely to do so.

    Our political and monied elites are so utterly convinced of their correctness (and invulnerability) that they are unable seriously to entertain the thought that their MIT cool-aid is laced with slow-acting soporific poison. Half the population, similarly sedated, cheers them on from the bleachers; the rest – even elected oppositions – wait passively as if simply wondering how things will all turn out.[7]

    If there is to be any movement at all, ‘we the people’ need to wake up and tip the poison bottle. Until ordinary citizens understand that we have been conned and medicated, and act accordingly, there is little chance that anything resembling ‘civilization’ can survive the coming implosion.

    Any bets on the probability of this happening (or are we irrevocably inherently unsustainable)?

    References

    [1] Though a few hundred wood bison, a separate sub-species (Bison bison athabascae), survived in north-eastern Alberta.

    [2] Some argue that climate change would be more extreme in the absence of UNFCCC/COP but if the goal is to reduce something, and 33 years later that something is 60% higher and rising, then… well, failure is failure. At best we’ve delayed the onset of climate feedbacks so that as they do come on, they will impact a larger economy/population proportionately harder.

    [3] Elinor Ostrom was awarded the ‘Nobel’ prize in economics for specifying the conditions under which ordinary people can organize cooperatively to manage their local ‘common property’ resources sustainably, even today.

    [4] Some argue that the emphasis on competition ignores or diminishes the importance of cooperation. Fair enough, but cooperation largely serves to increase the competitive advantage (and ‘fitness’) of cooperators over non-cooperators.

    [5] This holds for both self-producing and non-renewable resources. MTI society is burning through economically accessible supplies of petroleum and natural gas, scouring the bottom of the barrel for many commercially valuable metals and ramping up exploitation of rare-earth elements to enable the (as yet) non-existent energy transition.

    [6] Think of a steady-state economy, one with a more or less constant rate of material throughput (consumption and pollution) sized so that there would be no net depletion of essential self-producing natural capital nor cumulative toxic pollution. Total quantitative growth would cease, but there need be no limit on qualitative improvement.

    [7] How’s the local experiment in the US going?


    ABOUT THE AUTHOR

    William E. Rees is a population ecologist and ecological economist. He is Professor Emeritus and former Director of the University of British Columbia's School of Community and Regional Planning; a founding member and former President of the Canadian Society for Ecological Economics; a founding Director of the One Earth Initiative; and a Fellow of the Post-Carbon Institute. Professor Rees' research focuses on the biophysical requirements for sustainability and the policy implications of global ecological trends. He is perhaps best known as the originator, and co-developer with his graduate students, of Ecological Footprint Analysis (EFA). EFA shows that the human enterprise is already in ecological 'overshoot' and that we would need 4.4 Earth-like planets to support just the present world population at Canadian material standards. Such findings led to a special focus on cities as particularly vulnerable components of the human ecosystem and on psycho-cognitive barriers to ecologically rational behaviour and policy. Professor Rees has authored hundreds of peer-reviewed and popular articles on these and related topics.


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