Carrying Capacity and Overshoot
Iterating towards an objective view
“For the first time in history a conviction has developed among those who can actually think more than a decade ahead [and would rather know than believe] that we are playing a global endgame. Humanity’s grasp on the planet is not strong. It is growing weaker. Our population is too large….”— Edward O. Wilson, Half Earth: Our Planet’s Fight for Life 2016
“The carrying capacity concept has become essential for understanding what is now happening to human societies, and consequences to follow later…. To appreciate the relevance of carrying capacity to human lives and humanity’s future, we need to acknowledge some neglected (but obvious) facts.”— William R. Catton, Jr., 2013
Catton summarized concerns/understanding of the human predicament in Overshoot: The Ecological Basis of Revolutionary Change 1980. Catton continues with some obvious and neglected facts:
I. Human beings are organisms. [“The first thing you have to realize is that you are an animal.”— David Suzuki]
II. Every organism, whether plant or animal or whatever — as a bounded bundle of living substance — is distinct from its surroundings. But life’s processes involve interaction of that bounded bundle with those surroundings. To live, an organism has to use its environment in three ways.
1. To maintain its life, any organism must take in substances (and energy) from outside its body. [E.g. water as substance and food as energy.]
2. Living bodies, as physical entities, occupy space; their lives depend on having sufficient room for their existence and normal activities. [E.g. a habitat that provides water and food within limits.]
3. The organism’s biochemical processes necessarily transform the substances taken in from the environment. The transformed products of such metabolism differ not only from the original environmental components but some also differ to some extent from the tissues of the organism. Being harmful (toxic) if retained within the organism, these products have to go somewhere. So they are excreted — returned to an environment (as eventually also the dead remains of the organism will be returned).
In short, any living thing requires an environment from which to obtain sustenance materials, including energy, in which to exist and do whatever it does, and into which to discard stuff. A novel but useful way to express this is to note that organisms inevitably use their surroundings in three kinds of ways: All living beings do some “from-whiching,” some “in-whiching,” and some “into-whiching.”… The term carrying capacity simply means, therefore, the maximum amount or intensity of a given kind of use, or the maximum use-load, an environment can endure while retaining its future suitability for that use….
The intensified misery and competition for dwindling supplies the carrying capacity deficit will entail is likely to encourage a kind of paranoid imputation of culpability. “Others” will be vilified and blamed; overt conflict on various scales will be likely, contributing to a period of population reduction, unplanned, merciless, deplored, self-reinforcing. Societies will fall into disarray. Historians will discover clues that “should have been recognized” but were not. Only ecologists, some of them, will truly understand the rise and decline of human carrying capacity and the rise to dominance and fall therefrom by Homo colossus.
— William R. Catton, Jr. Carrying Capacity: What Is It? How Have We Misunderstood It? And Why Is It Important? 2013
George Mobus, former ISSS (International Society for the Systems Sciences) president, notes the obvious: that carrying capacity/overshoot are Reality 101 concepts that modern humans who would persist on the planet (who would be sapient) by becoming evolvable (non-metastatic) animals need to understand.
Following a depopulation event, a K-selected (K from the German for carrying capacity limit) species is able to increase their population exponentially, but as the lower limits of carrying capacity are approached, negative feedbacks (e.g. more time/effort needed to find food) in the form of stress (GAS, General Adaptation Syndrome) are experienced and the species’ fertility rate, as evolved to, declines to avoid overshoot which always does long term harm to K-selected species despite short-term prospering.
Rule #1: Avoid exceeding the upper limit of carrying capacity (the condition of overshoot) by any means.
The success of modern humans (EMH/MMH/LMM, Early, Mid, Late Modern Humans) has been by exceeding carrying capacity and then moving on, expanding by conquest of unoccupied land (e.g. New Zealand by Māori) and human occupied habitat, e.g. New Zealand by Indo-Europeans). Post conquest, a remnant population may partially adapt, for a time, to limits, but to expand, each would-be expansionist population must await an accident arising from the weakness of others to again prosper.
Special cases vary, e.g. the celebrated masters of living sustainably on the small island of Tikopia. The first Tikopians, Melanesian expansionists, were forced to live like renormalized humans, due to lack of trees to build voyaging canoes, for 2k years until conquered (kill males, breed females) by Polynesian expansionists 1k years ago who were in turn forced to renormalize or die, and did renormalize minimally, but not in a conscious, intentional, and determined way with a clear aim of never becoming expansionists again.
To maximize the human population, the Tikopians exploited all parts of the island surface (sustainably of course, but without intentionally leaving room for nature) and eventually killed all the pigs about 1600 CE, which they had brought with them centuries before, that were competing for food humans could eat. And so when they could, when Indo-Europeans provided transportation, they expanded off island (off Tikopia to surrounding islands, leaving 1,200 on Tikopia) to increase their population six fold just as us other expansionists did before being denormalized in urban habitats.
Conjecture: Earth is viewed by expansionists as an illimitable plane, a flat planet of infinite extent in all directions for the taking. Human centrality is presumed. Ideology (zero-order humanism) became modern human’s “superpower” allowing them to deny limits (for a time). The last 300 years of turning fossil fuels into food (and stuff) has allowed metastatic modernity to take the planet. When a metastatic r-selected cell in a soma is as successful as late modern humans in the 18th to 21st centuries, degradation and death are the outcome.
The simply delivered argument: a species that causes other species to go extinct has exceeded its carrying capacity (causing damage/degradation/reduced environmental productivity of habitat), therefore modern humans have exceeded long term carrying capacity for millennia.
The baseline rate of species extinction is about one species per million species per year. The current rate of anthropogenic species extinction is about 8,000 times baseline, rapidly increasing to 10,000 times higher this century. Human population growth and the fossil fueled agriculture needed to turn ecosystems into agroecosystems that for a time divert all environmental productivity, insofar as possible, to human consumable products (e.g. wood, fiber, meat, plants using all exploitable terrestrial and aquatic habitats) is the primary driver of the Anthropocene mass extinction event.
Modern humans, in the form of Early Modern Humans (EMH) became an invasive species expansionists about 75k years ago. A likely story (science is the endeavor to tell the most likely story) is that humans (homininans who evolved for over six million years) where first able to live in groups larger than those of nomadic hunter-gatherers (20–50, range 5–85, mean 28) about 160k years ago.
Behavioral modernity and the modern form of human may have been a mutation among those who lived on the southern tip of Africa 160k to 70k years ago associated with coastal shellfish beds providing a steady, dependable supply of seafood along with seasonal land foods that supported a large population of sedentary humans able to live in larger than Dunbar’s number (150) of individuals in a group (a condition that selected for hyperprosociality).
About 76k years ago (per archaeogenetic data) one community (memetically and/or genetically) mutated, came to overexploit environmental resources unto overshoot (in violation of six million years of homininan K-culture norms and hundreds of millions of years of K-selected genetic evolution, as inferred by their persistence, hence a mutant form arose).
Overshooting their shellfish beds, they persisted by conquering other coastal groups (doing so requires an ability to justify doing do, i.e. ideology), then they began expanding inland, repeating the pattern, until they were able to spread throughout and then leave Africa about 55k years ago to rapidly expand into Eurasia. Those who expanded along the southern Asian coast reached Australia within a few thousand years.
Somewhere (if not the southern tip of Africa) some humans were able to socially construct reality as a consensus narrative to thereby create an ideological worldview and then mis-take that worldview for the world, which is today’s precondition for the ideology of zero-order humanism (human exceptionalism).
A paradigm shift had to arise somewhere in Africa where living in small 20 to 50 trusted others in nomadic bands was not the norm, e.g. at Blombos Cave and Pinnacle Point where conditions for a mutant r-selected culture had existed for up to 85,000 years prior to the within Africa beginning of the Great Expansion of 76 kyo (thousand years ago) leading to the out of Africa Great Expansion of about 55 kyo per interpretation of archaeogenetic data.
We modern humans are now presiding over the greatest mass extinction event since the late Cretaceous (one that did not begin in 1970), one that could rival that of the Permian, and we are nearing the climax of our one-off global overshoot event.
For eons our ancestors were K-selected species whose populations fluctuated at or near the lower carrying capacity (K) of the environment in which they resided. We modern techno-industrialized humans are a one-off plaque-phase population of an r-selected form of human that has been regionally repeating the pattern of overshoot and collapse as EMH and as agro-empowered empire building MMH (Mid Modern Humans).
Unlike some locusts, for example, we are not adapted to overshooting carrying capacity, so there will be no evolved viable outcome, merely a dissipative one (e.g. hurricanes are dissipative structures/systems that adapt to terrain/atmospheric conditions but do not evolve) that always end. Few public intellectuals, including eminent ecologists, argue (in public) that a human population of more than 2 billion is not remotely sustainable long term (any ‘thought leaders’ saying much less than 2 billion would not remain thought leaders).
If humans are to understand the planet and learn to live with it properly long term, we need to become K-strategists (who intentionally endeavor to become K-selected animals) again. This means our population would, were we to endeavor to think objectively, likely need to be in the 7–35 million range globally given that to persist we must via systemic management, limit ourselves so as to leave significant room for the Gaian system (Nature) to function to both end anthropogenic species extinction and allow for new species to evolve — a much tighter constraint on human populations.
Our overcomplex monetary growth culture is adaptive but not evolvable (like cancer it selects for its own failure), and our collective inability (so far) to understand this may have extinction as outcome (or worse, we make fusion work and become Borg-like expansionists and assimilate all worlds for the taking in the Milky Way before spreading to other galaxies).
Defining Terms
Carrying capacity
The population of a given species that can be supported indefinitely in a changing habitat without permanently damaging/degrading the ecosystem (reducing the maximum empower, MEP, of the overall system) upon which it is dependent; the number of people, other living organisms, or crops that a region can support without environmental degradation including species mass and diversity, i.e. not the maximum number of humans a habitat can support by diverting all environmental productivity to supporting humans and mutualists.
When a species exceeds carrying capacity (the upper limit) it causes permanent damage to the biotic community (habitat) it depends upon, whether a small watershed area or planet Earth. When a species’ footprint causes the extinction of other species, that impact is permanent and involves environmental degradation, a loss of function. So one measure of ‘degradation’ is ‘causing species extinction’ which is objectively measurable.
We are currently causing the greatest mass extinction event since the late Cretaceous. When did excessive impact begin? We regionally exceeded carrying capacity, one valley at a time, when we became a technology-using, invasive ideology dominated species spreading within Africa in which we evolved (as megafauna in Africa co-evolved with us, most did not go extinct). The rate of anthropogenic species extinction is now over 8,000 times baseline (1 species per million per year), heading towards 10,000 times higher by the end of this century.
Humans exceeded carrying capacity when the population of our Anthropocene enthusiast ancestors (regionally causing megafauna extinctions on five continents before the development of agriculture pre-mass extinction during megafauna extinctions of the paleolithic) exceeded a few million r-selected takers. We moderns, evidently, are far more enthusiastic now (8k times and counting) than they were.
Overcarry
The upper level of carrying capacity.
Overshoot
The condition of a population that has exceeded overcarry, the upper level of carrying capacity, the overcarry limit as measurable by envirnmental degradation.
Overpulsing
The population level associated with bumping against the lower limit of carrying capacity and occasionally exceeding it before corrective feedbacks reduce population to avoid overshoot.
Examples of Overshoot: The Tale of St. Matthew, St. Paul and St. George Islands
If the maximum sustainable number of reindeer St. Matthew Island could support was 1,200 and the 29 reindeer introduced in 1944 exceeded this number in 1957, then they could have continued to degrade the stored primary productivity in the form of lichens and grasses of the island for a time until they couldn’t. Reindeer evolved to depend on wolves to manage their population as one part of a predator-prey dynamic (homininans did not).
If when the population had reached 600, wolves were introduced to the island and the reindeer population had leveled off to pulse between 500 and 700 over the centuries, then the carrying capacity for reindeer would not have been exceeded. Voles, foxes, reindeer and wolves would be able to continue living on the island, though the vole and fox populations would be smaller (due to sharing environmental productivity with reindeer/wolves). Biodiversity maximizes empower, and is selected for by complex systems. The reindeer’s one-off overshoot event on a predator-free island did not.
Assume lower carrying capacity was 600 and overcarry was 1,200. Exceeding overcarry implies plague-phase overshoot, while exceeding the lower limits of carrying capacity, for a time, does not. A wildlife biologist managing the island would avoid both exceeding the lower carrying capacity boundary and the overcarry limit to maximize productivity/diversity (MPP/MEP). They would have either not brought reindeer to the island, or brought wolves when the reindeer population reached 200–400. [Figure average wolf pack is six, needs 50 sq. mi (130 sq. km), so two packs of 4–8 wolves and a non-food-stressed population of 600 reindeer.]
But that didn’t happen.
[Note: If you think Earth can support 2 billion humans as the millennia pass, then you think we went into overshoot in 1927. If you think 500 million humans can be supported without fossil fuel inputs into their agricultural system or economy, with most people working in agriculture as serfs/peasant-slaves serving elites, then you think we went into overshoot in 1650. If you think the human footprint, when it started causing species extinctions, permanently degrades the environment, then you might guess we exceed carrying capacity about 3.6 thousand years ago when our population exceeded about 35 million. This was also when maybe half of humans lived in an empire (overcomplex society) and served empire builders from chiefdom to state level complex societies, all of whom collapsed or ‘faded away’.]
Species that overexploit environmental productivity incur an ‘ extinction debt’, a future die-off debt, that their descendants have to pay. For twenty years the reindeer prospered until they didn’t. Those alive in 1964 paid the debt: they experienced a 99.99% die-off event. If the winter season had been less severe, the die-off would have taken longer. There were foxes and voles on the island. If only voles, they would have overexploited island resources like humans on a planet for the taking.
Exceeding carrying capacity caused environmental degradation and when the population exceeded overcarry, descent and extensive environmental degradation was locked into the dynamic. Because exceeding carrying capacity is often not far from exceeding the overpulsing level (the maximum long-term population) the two concepts are often conflated.
The argument for not exceeding the maximum overshoot limit (overcarry) is to avoid harm to the species doing the overshoot during the descent that follows (which also harms the environment). The main argument for modern humans avoiding overshoot is to avoid harm to Gaia, the planetary life-support system, aka Nature (by reducing maximum empower of the biosphere). But modern humans are well into overshoot and our descent is locked in.
Specifying ‘long-term carrying capacity’, however, implies an overcarry limit, which is mostly what ‘carrying capacity’ commonly means when applied to humans. But we should also consider transitioning to a low enough population/footprint that we do not cause species extinction, nor by over-occupying niches, prevent the evolution of new species to make up for those we have already caused the extinction of. Maximizing human population implies pushing the overcarry limit, which may be well above the optimal population that maximizes empower of the global biosphere.
Environmental degradation (reduced carrying capacity) occurs prior to overshoot. Humans could kill all pigeons in North America (passenger pigeons were a good start) or whales in the sea (causing environmental degradation), but not have reached the climax of their overshoot.
Humans can preside over vast environmental degradation, e.g. deforest continents and cause megafauna extinctions on five continents before going on to cause the greatest mass extinction event since the late Cretaceous, and not degrade the environment’s short-term ability to support them by converting forests into tree farms and everything else that can be into farms/aquafarms and pasture/rangeland apart from the megacities most would live in. The view that technology has permanently increased the planet’s carrying capacity is an illusion enabled by error and ignorance.
Humans could preside over the above and if the end state of converting all the planet’s environmental productivity into humans, livestock, crops and pets (and some zoo animals to amuse) was sustainable and limits not exceeded, if we actually avoid overshoot as techno-optimists insist we will, then no descent is implied. If modern techno-industrial society never descends/collapses, then by definition we were never in overshoot.
If we actually turn Earth into a Trantor, then overpulsing never happened and from a humancentric point of view there was never any environmental degradation as the planet’s ability to support humans was enhanced, maximized, and so not at all degraded in any way. From the point of view of all life except perhaps our crops, livestock and pets/wildlife display inhabitants, a Trantor Earth would look like the Borg won.
Isaac Asimov, by the way, Anthropocene enthusiast and urbanite that he was, once admitted he envisioned Trantor as the place he would want to live — one planet, center of the universe’s control system, with one global ultratechno megacity covering the entire surface, with no thought given to the millions of species that once had made Trantor their home.
Oh, but if “we are the environment” [David Suzuki], if we are well into overshoot (served for a time by a global, mostly fossil-fueled extractive economy that is not remotely sustainable), then, well, different outcome — the Collective fails. That’s where ‘sustainability’ comes in.
Note: Most of the following graphics were created primarily using data from the research of Vaclav Smil and is published in this 24 page PDF file: Harvesting the Biosphere: The Human Impact. Paul Chefurka, Alice Friedemann, Garvin Boyle, and other Cassandras (Jay Hanson, Jack Alpert, Gail Tverberg) are not scientists nor academics (not scientists/academics like William Rees, Jay Forester, Donella Meadows, E.O. Wilson, David Suzuki, James Lovelock, M. King Hubbert, Garrett Hardin, John B. Calhoun, Rex Weyler, Howard T. Odum, Nate Hagens, Charles Hall, William R. Catton, Jr….). The 65 experts deemed credible enough to be included in the UN range of guesses as to Earth’s carrying capacity for humans above, had a low cut-off of 2 billion, perhaps because the consensus view is that any less is to be dismissed as doomer extremism.
When the reindeer population on St. Matthew Island (137.9 mi²) reached 5–6 thousand, perhaps any reindeer that suggested (if they could have) that no more than 2 thousand reindeer could have been supported would likely have been dismissed as the consensus of 65 expert reindeer was that the island could easily support 26 thousand prosperous reindeer (if reindeer were as smart as humans). Unfortunately, with the exception of Jack Alpert and H.T. Odum (who offered a vision of a prosperous way down), no one mentioned above, none of the UN’s experts, nor any scientists/academics/activists I know of (except Muzuki), seem to be thinking in terms of ‘real solutions’ that might actually work long-term as a belief in political solutions seems a near universal at this time.
And the experiment has been done elsewhere with similar outcome;
The greater the overshoot, the greater the environmental degradation.
We are about 8 billion humans too many. The bigger we get, the harder we fall.
So far, we are following the St. Paul Island (40.3 mi²) trajectory.
Human society is vastly more complex, so loss of functional behaviors on the downslope may be more likely to preclude recovery.
Humans on prehistoric Malta collapsed to island extinction, climaxing about 2500 BCE followed by 3–5 centuries of decline to extinction. All cultures involved in the Late Bronze Age collapse failed to persist. The larger of the three ancient civilizations: Egyptian, Mesopotamian, and Indus Valley civilization failed to persist, i.e. climaxed about 1900 BCE followed by 600 years of decline to regional extinction (their existence became known to archaeologists int the 1920s). Collapse to extinction happens (about 80% of time).
If you are not a failed modern human, “your salary” (social approbation) depends upon your not understanding that you have a predicament that has an outcome (no solution). Two outcomes: mutate back into a viable form of human or as hyperprosocial metastatic storytelling moderns to go extinct.
Modern humans cannot choose to mutate nor to not go extinct. Human agency, ensouled and wrapped in free will cannot select for a viable outcome, but only sleepwalk into futurity telling stories of how to solve the mess of multiplying fine messes so as to make one’s identity group great again. The way out of our Wittgensteinian fly bottle is choiceless understanding by “throwing yourself into the humility of not-knowing” [Donella Meadows] by understand human limits and limitations, a condition that may be mutagenic.