A Many-Faceted Problem

by William E Rees, PhD, FRSC

Setting the conceptual stage

Let’s start with a thought experiment. Suppose you and your close family and friends, perhaps 150 people in all, were confined to an isolated island – let’s call it Esperanza – characterized by landscapes and soils that were representative of average arable land in the United States and that, henceforth, you would have to be food self-sufficient – you have no access to trade goods. Let’s also assume that you had ‘just enough’ of the usual inputs to modern agriculture including adequate water and fertilizers (e.g., ammonia-nitrate and super phosphate), etc., to maintain current productivity.
Esperanza isn’t a large island – it has only about two km2 (200 hectares or ~494 acres) of arable land. Now, knowing that this was all the land to which your little band will ever have access, it might occur to you to ask: Just how many people could the island support at a specified material and dietary standard? In other words, what is the human carrying capacity (CC) of the island?
For the sake of illustration, we’ll also assume there is presently sufficient land and resources for other purposes (buildings, community infrastructure, etc.) so that we can answer the CC question based solely on food requirements. Studies suggest that it takes ~.2 ha (.5 ac) of cropland to support one person on a meat-free diet; this number increases to at least .4 ha (1 ac) should our little band opt for a diet that includes 190 gm meat per day, the average US level of consumption. So, the answer to our question is that Esperanza might ultimately support about 988 vegetarians or 494 people on the average US diet. Of course, these data depend on exquisite attention to land/soils management. The land requirement per capita would increase markedly, and the carrying capacity of the island would decline proportionately, should soils be depleted or exogenous inputs dry up (at least until the inhabitants got up to speed in applying agro-ecological farming methods).
It should already be apparent that life on our hypothetical island would raise questions that rarely come up in average North American settlements today. For example, suppose our little village was able to prosper and multiply and, on average, favored the average US diet. As the village approached 500 people, some concerned individuals might point out that if the population were to grow any further it would have serious implications for land use and food availability. There would undoubtedly be calls to limit birth rates and family size to maintain the island’s quality of life, including the prevailing moderate level of animal protein in the diet. Others would probably protest that family size was a matter of personal preference and that ‘the community’ had no right to interfere.
Meanwhile, certain community members who had done well as ‘developers’ in the settlement’s early days now propose a new subdivision to accommodate both future growth and perhaps a few existing families that simply wanted bigger houses. Their plan would involve assembling just 10 contiguous acres of easily buildable arable land to provide 80 single-family houses (for ~200 people) on typical urban-sized lots. This is ‘only’ two percent of the island’s arable land, but that two percent would be permanently lost to agriculture. Would the ‘cost of groceries’ rise for everyone? Would this impose significant dietary changes on the relatively poor? And wouldn’t more astute folks ask whether such ‘development’ was in any way sustainable? What about the next proposal? Where would it all end?
Whatever the responses to these obvious questions, the community would likely be in an uproar. Some would protest that given climate change and other uncertainties inherent in complex ecosystems behavior, not a square inch of agricultural land should fall to other purposes. Others would argue that the community would surely be able to find some technological breakthrough (intellectual capital) to increase productivity so that the loss of arable land (natural capital) would be of little consequence. The crucial point is that the islanders, living in intimate proximity to, and being utterly dependent on, a finite area of productive landscape, would be forced to confront the consequence of converting even an acre of farmland to other uses. What would they decide?

Meanwhile, back in the real world

Now consider yet another isolated island, planet Earth. On a cosmic scale, Earth is an infinitesimal speck orbiting a middling star on the edge of an ordinary galaxy, one of many billion galaxies populating the known universe. For all its cosmic insignificance, Earth is crucial to the existence and survival of H. sapiens. This planet is the only home humans have ever known; we evolved with millions of other species on Earth, effectively co-creating the ecosphere – i.e., Gaia – as it unfolded in all its complex magnificence over the past four billion years. We and all our contemporaries are therefore exquisitely adapted to the (pre-industrial) environment of this, and only this, singularly unique planetary island profoundly isolated in deepest space.

We have a long history on Earth. Anatomically modern humans have been around for at least 250,000 thousand years, but it has only been during the past 50,000 or so that we dispersed over the entire planet (reaching Tikopia only three millennia ago). It is a hallmark of H. sapiens’ expansionist tendencies and evolutionary success that every significant habitable space on Earth is now occupied by H. sapiens.

Human reproductive behavior marks us as typical of ‘K’-strategic species. We are large, long-lived, highly adaptable, energy-demanding mammals that exhibit extended parental care and relatively high infant survival rates. Populations of H. sapiens therefore tend to press up against the carrying capacity (‘K’) of their local habitats (this was Malthus’ controversial insight). In fact, like all other species, humans are actually capable of exponential population growth – positive feedback – under favorable conditions. Conditions are rarely favorable for long, however. Drought or other climate factors frequently reduced food/resource availability; disease and inter-group competition for habitable space further increased mortality. Indeed, during most of human evolutionary history, such ‘negative feedback’ has kept our populations in check, fluctuating in the vicinity of local carrying capacities. There were probably no more than one to a few million people on Earth during most of the Paleolithic or Old Stone Age.

Everything changed with the adoption of agriculture about 10,000 years ago. Humans could finally increase food production and even generate surpluses for storage; local populations began to creep up; large settlements and ultimately urban civilization had become possible. Nevertheless it took 99.9% of H.sapiens’ 250,000 year evolutionary history for the global population to reach its first billion in the early 1800s. Then, in just ~200 years (1/1250th as much time!), human numbers ballooned to eight billion, real gross world product increased 100-fold, and per capita consumption expanded by a factor of 13. This explosive growth was facilitated by improving population health – i.e., plummeting mortality rates – and a 1000-fold increase in the use of fossil fuels (with its associated CO2 emissions). The latter enabled production of the food and other resources necessary to sustain the growing human population. Modern medicine and an ‘exosomatic’ (outside the body) source of abundant cheap energy had reduced or eliminated the negative feedbacks on population enabling H. sapiens to realize, for the first time, our species’ full potential for exponential growth over an extended period.

California Oil Field - Rees

Humanity’s Parasitic Relationship with the Earth: Oilfields, Belridge, CA, 2003

Photo: © Edward Burtynsky, courtesy Nicholas Metivier Gallery, Toronto”.

Meanwhile, the planet didn’t get any larger

Which is why H. sapiens is now in a state of advanced ecological overshoot. Overshoot means that human consumption of resources greatly exceeds ecosystems’ regenerative capacity and that waste production exceeds than the ecosphere’s assimilation/processing abilities. More simply, H. sapiens has exceeded the long-term carrying capacity of Earth; we are consuming and polluting the biophysical basis of our own existence (and that of countless other species). It should be clear from this definition that, left untreated, overshoot is a terminal condition.
Overshoot is a meta-crisis. Few people ‘get’ this reality because humans tend to think simplistically, one issue at a time. For example, the world community is presently fixated on CO2 emissions and the specter of climate change (aka ‘global warming’), but this is only one of many important co symptoms of eco-overshoot. Overshoot is the overriding cause of anthropogenic climate change, but also of plunging biodiversity, ocean acidification, tropical deforestation, land/soil degradation, falling sperm counts, the contamination of food supplies, energy and resource shortages, the pollution of everything, etc., etc. Rarely do alarm calls about an increasingly erratic climate ‘connect the dots’ among such systemically related issues.
This perceptual error is crucially important because we cannot solve any major symptom of overshoot in isolation from the others. For example, the present, politically acceptable, approaches to reducing CO2 emissions – e.g., substituting wind/solar/hydrogen electricity for fossil energy (FF) and deploying (unproved) carbon capture and storage technologies – assumes we can maintain growth-based ‘business-as-usual-by-alternative-means.’ But business-as-usual is at the heart of overshoot and, if that were not enough: a) all current climate ‘solutions,’ from solar panels to electric vehicles, are highly on FF dependent for mining, refining, manufacturing, installation and maintenance and: b) it will be decades, if ever, before electricity can substitute for FF in key applications (e.g., high-heat manufacturing, bulk transportation). This is why the US Energy Information Administration expects US energy-related CO2 emissions to remain around 80% of 2022 levels right through 2050.
In short, despite 50 years since publication of Limits to Growth, several scientists’ warnings to humanity, twenty-seven COP climate conferences and a half-dozen international agreements to reduce CO2 emissions, atmospheric CO2 and other greenhouse gas concentrations are still increasing. Indeed, it is actually no longer possible to limit mean global warming to 1.5 Celsius degrees as required by the 2015 Paris Accord. Simplistic solutions to climate change/global warming are not only failing to cool the climate but, by maintaining the growth-oriented status quo, are actually exacerbating overshoot.

What the world refuses to accept

The only way to reverse overshoot is to address it directly. The material cause of overshoot is excess economic throughput; humans are extracting resources from nature at unsustainable rates (consumption) and all this energy and matter ultimately returns to the ecosphere as degraded, sometimes toxic, waste (pollution). Clearly fixing the overshoot meta-problem will require significant absolute global reductions in energy/material consumption and waste generation. On the plus side, this would address all major symptoms of overshoot simultaneously
But we have a problem – modern techno-industrial (MTI) societies are addicted to a socially-constructed, growth-oriented economic narrative (neoliberal economics) based on the assumptions that: 1) the economy is a self-producing system not significantly connected to ‘the environment’ and therefore essentially unconstrained by biophysical limits; 2) the efficiency gains from globalization and trade can only increase material well-being for everyone and; 3) human ingenuity (technology) can find substitutes for any product of nature that might run out. Once politicians and ordinary people buy into these constructs, it is a small additional step to believe in perpetual economic expansion. With MTI societies hooked on growth, overshoot was inevitable.
Both rising incomes and growing populations contribute to increasing economic throughput. Historically, the world’s wealthy, particularly North Americans and Europeans, have been responsible for the bulk of consumption and waste. US citizens, for example, consume about four times as much energy as world average citizens, 12 times as much as average East Indians. However, in recent years, population growth has been a greater contributor to overshoot than rising GDP/capita in all income quadrants. Population growth is also a major factor behind increasing CO2 emissions. Avid pro-natalists, and others who deny the contribution of sheer human numbers to the overshoot meta-crisis, are wrong-headed, even anti-human to the extent that delay in confronting the population factor will increase human misery with the inevitable population correction.

Now what? Learning to live on an island planet

To eliminate overshoot we need a personal to civilization-level transformation, a transition to a different cultural narrative and way of being on Earth. An essential first step is for society to acknowledge that, far from floating free of the natural world, the economy is a fully embedded, physically dependent sub-system of the non-growing ecosphere. In short, the growing human enterprise is positioned to be a malignant parasite on the living ecosphere.
It follows that the world must renounce the concept of perpetual growth/capital accumulation and acknowledge the folly of unfettered globalization on a finite planet. With ever-freer trade, most countries and regions have been temporarily able to exceed their domestic carrying capacities by drawing upon resource stocks from ‘elsewhere.’ Result? Accelerated depletion ‘everywhere’ so that we all blow through global carrying capacity simultaneously.
Globally we have dropped close to the critical .2 ha of cropland/capita needed to feed just the existing population adequately (again unrealistically assuming continuous supplies of all artificial inputs). The emphasis in both national and global planning should therefore shift from efficiency and quantitative growth (getting bigger) toward controlled contraction with a focus on qualitative improvement (getting better) and greater social equity. (This option would most likely emerge by agreement among the small colony of settlers on our imaginary island of Esperanza.)
A related conceptual shift is a formal recognition that overshoot is a collective problem requiring collective solutions. Humanity needs an era of unprecedented international cooperation if we are to implement a global economic system compatible with the operating principles of the ecosphere.
It is not difficult to envisage the end-goal: a global system of national and regional subsystems operating in an aggregate sustainable ‘steady-state’ (i.e., involving a more or less constant, sustainable level of energy and material throughput) within the capacities of the Earth system. Achieving this ideal is another matter. Economic compatibility with biophysical limits will require a 40-50% global reduction from present levels of energy and material consumption rising to 75-90% in high-income countries. Perhaps surprisingly, such politically daunting targets may actually be technically achievable even while improving human well-being.
For sustainability with justice, the contraction of economic activity would also have to be accompanied by income, taxation, and related social policies to address today’s egregious inequality. Additionally, a global program of population planning beginning with improved education and economic freedom for women would be required along with free contraception. The world should be planning for a smooth, decades-long transition to the one to two billion people that could to thrive more equitably in relative comfort within the ecological means of Nature.
As I have written elsewhere, “the political and economic mainstream – and many ordinary citizens – will see these principles and actions as impossibly radical. …however, they are consistent with basic theory and empirical evidence. On its current trajectory, the present system will crash…” The point here is that, hubris aside, humans remain bound by the basic laws of nature including those of population dynamics: the recent two centuries of explosive growth that MTI societies take to be the norm is actually the most anomalous period in human history, possible only because of a one-time endowment of abundant cheap energy. Humanity’s resulting population curve resembles the boom phase of the (one-off) population boom-bust cycle common in nature, i.e., bust will follow.
In theory, we can still choose between a chaotic, painful crash or a planned, controlled descent. Thus, it remains to be seen whether our increasingly fractious polyglot world community can unite in: 1) abandoning what has become a destructive economic myth and; in 2) articulating a compelling new narrative for survival on our tiny – and shrinking – island planet. Regrettably on a human scale, Earth seems less a calmly united island than a raucously divided archipelago.
Some will argue that there is no need for radical change, that pessimists and doomsayers are simply wrong. To techno-optimists, modern humans have forever escaped the Malthusian trap, and the future resides in unwavering confidence in maintaining technological progress. Others recognize that such complacent optimism can be fatal, that we need to be optimistic but dissatisfied if we wish to work effectively to make the world a better place.
Pessimism and optimism are mere states of mind that may or may not be tethered to reality. Either – along with giddy ‘hopium’ – can be debilitating. What we really need is stimulative realism that springs from a grasp of both history and the current state of the world. It is only from a clear-eyed understanding of both the biological and cultural roots of our eco-predicament that we can identify the programs and policies that might actually work in managing the descent.
What is there to do but work diligently, both individually and collectively, toward that end as if billions of lives depend on it – because they do?

William Rees is a population ecologist, ecological economist, Professor Emeritus and former Director of the University of British Columbia’s School of Community and Regional Planning in Vancouver, Canada. He researches the implications of global ecological trends for the longevity of civilization, with special foci on urban (un)sustainability and cultural/cognitive barriers to rational public policy.


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