The International Handbook on Megacities and Megacity Regions. Cheltenham: Edward Elgar.

by William E Rees, PhD, FRSC Professor Emeritus UBC/SCARP

Establishing context Mainstream governments and organizations see the future as a technologically more advanced version of the recent past. They assume that advances in wind and solar electricity generation will enable a smooth transition to a zero-carbon economy and help avoid climate chaos; human population growth will continue uninterrupted before topping out at 11 billion by 2100; ongoing urbanization will add 2.5 billion people to the world’s cities by mid-century; we can readily meet an estimated 50-98% increase in the demand for food in coming decades; an ever-expanding economy will enable the world to eliminate poverty and achieve the rest of the UN’s Sustainable Development Goals, etc., etc. By contrast, this chapter argues that such a rosy, technologically-enhanced, mainly-urban future is by no means assured. Cities, particularly mega-cities, are increasing vulnerable to climate disruption, energy scarcity and resultant geopolitical instability. It is conceivable that the era of urbanization will end ignominiously before the end of the century. 

Mega-cities—indeed, all cities—are essentially path-dependent emergent phenomena. They are selforganizing entities that result from the sometimes unpredictable interactions of socio-cultural subsystems with the geological and ecological subsystems of particular biophysical ‘environments’. Certainly human agency is a key factor, but at least as much happens by chance and circumstance. No one anticipated or purposefully orchestrated the explosive growth of Shanghai, for example, as its population ballooned from one million in 1900 to 26 million people in 2019. Like other mega-cities, Shanghai emerged in its present form as a product of myriad interacting variables, potentials and circumstances. In other words, modern mega-cities like Shanghai exist because they can. 

And this raises interesting questions in an era of unprecedented economic, geopolitical and ecological uncertainty. What happens if the seminal factors and synergisms that enable modern cities are destabilized or disappear altogether? What if new combinations and antagonisms emerge that are aggressively hostile to the existence of mega-cities? How prepared is the world for an era of economic contraction and de-urbanization? These are not idle questions. Consider the effects of runaway climate change—rising sea levels, extreme heat waves, etc., etc.—on the livability of existing cities and on prospects for further urbanization. And what would be the fate of any megacity no longer able to access adequate food, water, energy or other resources essential to sustaining its population? While the official world generally avoids such questions, humanity’s urban future arguably depends more on the trajectory of green-house gas emissions, ecosystems dynamics and the nature of global energy supplies than it does on demographic and economic factors. 

Energy is key because no megacity could have ‘emerged’ in the absence of abundant cheap energy— indeed, all modern cities remain utterly dependent on fossil fuels. But the fossil-fueled technologies that empower mega-cities also emit the carbon dioxide that drives climate change—and despite ebullient hype 2 to the contrary, there are as yet no entirely suitable green alternatives to many uses of fossil fuel. The continued existence of urban civilization is therefore contingent upon not only whether we are able to stabilize the climate but also upon humanity’s ability to maintain the continuity of energy flows and support an expanding population, all without destroying the ecosphere (see Lang 2018). 

The unprecedented pace and scale of change 

The human brain evolved while H. sapiens lived in tribal groups occupying local territories or limited home ranges. Apart from seasonal cycles, ecological change was slow—nothing significant would transpire in most people’s entire lifetimes. In short, human perceptions and all our cognitive abilities evolved to cope with only a few dozen other people and simple, stable ecosystems over which we had little permanent influence. 

But all that has changed—and at a spectacularly accelerating pace. It took 99.9% of H. sapiens’ 200,000- year evolutionary history for our population to reach one billion in the early 19th century but only 200 years (1/1000th as much time!) to top an unsustainable 7.7 billion in 2018. Real global GDP has increased over 100-fold since 1800 and average incomes by a factor of 13 (rising to 25-fold in the richest countries) (Roser, 2018). Inevitably, energy/material consumption and attendant pollution more than kept pace (Steffen, et al. 2015)—driving an all-too-evident parallel degradation of ecosystems all over the planet. By the 20th Century, H. sapiens had become the major geological force changing the face of the earth. 

Meanwhile, tribal villages morphed into cities of millions and people daily engage an integrated globalscale macro-system of multiple interacting sub-systems. Many subsystems, including economies, the climate and ecosystems are characterized by lags, thresholds and other non-linear behaviours that render their responses to stress inherently unpredictable. Bottom line? The modern human mind—still basically Cro-Magnon—cannot wrap itself around the inherent complexities, emergent behaviours and possible trajectories of the global mega-system(s) that we ourselves have created. To think anyone is in control is sheer illusion. 

Biophysical dimensions of cities 

Few city dwellers—including urban planners—appreciate cities as meta-biological entities. Nevertheless, many urban infrastructural sub-systems—data centres; communication networks; transportation systems; water, solid waste and sewage disposal systems—are analogues, or even physical extensions of, human organ and sensory systems. It is therefore not much of a leap to see the modern city as a kind of superorganism.

From this perspective, mega-cities, like all living things, are governed by certain immutable physical laws. Among the most important—and least known—is the second law of thermodynamics, the ‘entropy law’. Entropy is a measure of the randomness or disorder in a system. The second law dictates that, with any change in an isolated system (one that cannot access energy or matter from its external environment) entropy increases. Each subsequent change increasingly disorders the system—gradients dissolve, concentrations disperse, structure breaks down. Eventually, the system descends to local ‘thermodynamic equilibrium’, an amorphously homogenous state in which nothing further can happen. 

What has this to do with urban sustainability? Everything, once we recognize that the forces of entropic decay also operate on open systems including mega-cities. The entropy law is as relentless as gravity; 3 there are no exemptions or exceptions. Entropy increases with every activity we or our machines perform. Every component of every subsystem of every megacity tends to wear, corrode, crumble and dissipate simply by serving its designated purpose. While they might not realize it is the second law at work, citydwellers see the evidence every day in the decrepit state of bridges, roads and other infrastructure in many poor or under-maintained cities. (Second-law corrosion can be dangerous. Forty people died in the collapse of the structurally-compromised Morandi Bridge in Genoa, Italy, on 14 August, 2018). With too many entropic failures, a city ceases to function as a coherently organized entity. 

This need not happen. The hallmark of living systems is the capacity to resist the persistent drag of the second law. A healthy super-organism is able to maintain itself in an optimal, high-functioning, low entropy, ‘far-from-equilibrium’ state, precisely because it is an open system able to exchange energy/matter with its ‘environment’ (Rees 2012). Thus, a primary goal of a well-managed megacity is to stay ahead of the second law. Wealthy cities in particular are able to import enormous quantities of energy and material as needed to repair, grow, complexify and otherwise elevate themselves ever-further from equilibrium. 

But resisting the second law does not negate it. The compound metabolism of cities (the bio-metabolism of its human inhabitants plus the industrial-metabolism of the economy and built environment) generates huge quantities of entropic waste—contaminated air, water and degraded energy/matter. Without defensive action, the megacity super-organism would suffocate in its own excreta. Any city that can afford to will therefore engineer elaborate waste disposal systems explicitly to export its metabolic dregs. Ironically, the wealthiest, best maintained (i.e., low-entropy) consumer cities impose a vastly greater destructive entropic load on the ecosphere than do their poorer relatively run-down (i.e., high-entropy) counterparts. 

Are mega-cities ‘ecosystems’? 

The term ‘ecosystem’ is frequently abused to mean just about any collection of interacting entities. Here we adhere to the original biophysical definition: an ecosystem is an integrated, community of living organisms that interact with each other and with their physical environment in ways that enable the continuous self-production of all living components. 

A complete ecosystem always includes three classes of organisms: producers (mostly green plants); macro-consumers (animals, including humans, that consume plants or other animals); and microconsumers (bacteria and fungi that decompose dead—sometimes living—plants and animals). Producers and micro-consumers are obviously essential to any self-perpetuating ecosystem while macro-consumers are more like free-riders. Through photosynthesis, plants use solar energy to recombine simple, dispersed, high-entropy compounds (water, carbon dioxide, nitrates, phosphates and a few trace minerals) into the plant biomass and oxygen from which the entire rest of the ecosphere produces itself. 2 Microbial decomposition ensures that essential nutrients embodied in dead matter are subsequently released for recycling. Thus, in thermodynamic terms, we can define ecosystems as complex, quasi-independent, selforganizing, far-from-equilibrium dissipative structures that can continuously (re)generate themselves. 

Cities may be humanity’s principal habitat, but the above definitions show unequivocally that they are not complete ecosystems. The producer and micro-consumer communities required to generate food, fibre and oxygen for the city’s human macro-consumers, and to recycle essential nutrients, are inadequately represented. At best, cities are ‘heterotrophic’ systems that depend for their existence on production and decomposition that takes place (or took place long ago) elsewhere on Earth. 4 4 

This highlights another crucial difference between ecosystems and cities. Both are exemplary negentropic, far-from-equilibrium ‘dissipative structures’. However, ecosystems self-produce and maintain themselves by ‘feeding’ on an extra-planetary source of high-grade energy, the sun, and by internally recycling the material basis of life. The degraded solar energy radiates into space as infrared (low-grade heat) radiation. By contrast, cities can self-produce and maintain themselves far-fromequilibrium only by ‘feeding’ on high-grade energy/matter imported from the ecosphere and exporting their entropic (and often toxic) wastes back into it. The local order represented by both ecosystems and cities is purchased at the expense of increased entropy ‘somewhere else’, but while ecosystems produce the ecosphere and disorder the universe, cities produce themselves and disorder the ecosphere (for a fuller explanation see Rees 2012). 

Urban eco-footprints 

If cities are incomplete human ecosystems, it seems essential to quantify the missing component. The first question of urban ecology should be: “How large a productive area elsewhere on Earth is committed to sustaining [any city] at its present material standard of living?” 

Ecological footprint analysis (EFA) provides an approximate answer to this question. EFA estimates the material and energy demands of any study population in terms of a corresponding ecosystem area (Rees 2013; Wackernagel and Rees 1996). Virtually all goods production can be traced back to ‘the land’ either as a growing area or carbon sink (see GFN 2018 for full details, examples, etc.). Thus, the ecological footprint (EF) of any specified population (individual, megacity, nation) is defined as:  

Multiple urban eco-footprint studies come to the same conclusion: high-income cities and mega-cities ecologically ‘occupy’ an extra-urban area, hundreds to more than a thousand times larger, than their political or built-up areas (e.g., Folke, et al., 1997; Warren-Rhodes and Koenig, 2001; Baabou et al., 2017). This has several immediate implications for urban sustainability that are largely ignored by urban planners and economists: 

• The complete urban human ecosystem comprises two distinct spatial components. The nominal megacity, e.g., ‘Shanghai’ or ‘Tokyo’ is a dense consumptive node but represents only a small fraction—typically less than one percent—of the whole. The complementary productive component is dispersed all over the planet (thanks to globalization and trade) and accounts for up to 99.9% of the total urban ecosystem; 

• The consumptive node cannot survive in isolation. Every modern city depends utterly on being able to maintain continuous intimate contact and exchange with the lands/waters that constitute its eco-footprint. A megacity imports many million kilograms of low-entropy energy and material daily and exports a nearly equivalent mass of degraded wastes. 

• The total human EF is about 20.6 billion ha while Earth has only 12.2 billion ha of productive ecosystems i.e., the human enterprise is in ‘overshoot’ by 69% (2014 data from GFN 2018). Since cities account for ~70% of global consumption and waste production, urban populations alone require the biocapacity equivalent of ~1.2 planet Earths to maintain their present lifestyles.5 

• Preventing ecosystemic collapse requires a massive reduction in the human ecological footprint (i.e., in populations and/or consumption). 5 

These facts underscore that cities—megacities in particular—are vulnerable to any global change that would isolate them from, or significantly reduce the area or productivity of, their supportive extra-urban ecosystems. 

Climate Change: An Existential Threat to Urban Civilization 

The Birds of Canada from 1966 lists Anna’s Hummingbird (Calypte anna) as a California breeder, merely ‘hypothethical’ in Canada. Yet, through winter of 2018-2019, three Anna’s jousted daily for position at my backyard feeder in Vancouver, Canada, and, by Spring were nesting somewhere in the neighbourhood. 

The climate change that has shifted birds’ ranges northward is real, but its effects not always so benign. In 2017 and 2018, British Columbia experienced two back-to-back ‘worst ever’ wildfire seasons; the deadliest wildfires on record torched California in 2018, destroying thousands of buildings and killing 85 people; droughts are becoming longer and more severe, storms more intensely energetic; record temperatures are destroying wildlife and livestock, property and people on every continent. Indeed, extreme weather events of all kinds are reflected in the economic costs of climate-related disasters globally—$895 billion (in 2017 dollars) between 1978 and 1997; $2.25 trillion between 1998 and 2017, a 151% increase (McCarthy 2018). 

The main anthropogenic driver of climate change is carbon dioxide, the greatest metabolic waste by weight of industrial economies and an inevitable entropic by-product of fossil fuel combustion. Atmospheric CO2 readings in April 2018 averaged over 410 ppm for the entire month for the first time on record (NOAA 2018). This is a human-induced increase of 46% above pre-industrial levels of ~280 parts per million and elevates atmospheric carbon to its highest levels in 800,000 years. CO2 is still climbing by 2-3 parts per million (ppm) annually and concentrations of other green house gases (GHGs) are increasing as fast or faster. 

One result is that mean global temperature has climbed by approximately 1.0 Celsius degree, mostly since 1980. A statistically improbable 17 of the 18 warmest years in the instrumental record have occurred in this young century (NASA 2017); 2016 was the warmest year; 2017 was second followed by 2015 and 2018—“the past five years are, collectively, the warmest years in the modern record” (NASA 2019). When the world was last this warm (the Eemian period 130,000-115,000 years ago) sea levels eventually rose 6–9 metres (20–30 feet), sufficient to inundate most of today’s coastal towns and megacities. (For an outstanding summary of climate change, likely outcomes and policy implications see Hansen [2018]). 

The Inadequate 2015 Paris Climate Agreement 

Our best science tells us that the world is currently on track to experience 3–5 C° warming. There is no dispute that five-degree warming would be catastrophic, likely fatal to civilized existence. Even a ‘modest’ three degrees implies disaster—enough to destroy economies, destabilize geopolitics and empty megacities. Parties to the United Nations Framework Convention on Climate Change therefore committed in the 2015 COP 21 Paris Agreement to hold the rise in global average temperatures to “well below 2°C above pre-industrial levels and pursue efforts to limit the temperature increase to 1.5°C above preindustrial levels.” 

Regrettably, the voluntary commitments (Nationally Determined Contributions or NDCs) made in Paris constitute only a third of the reductions needed to limit warming to two degrees; even if fully met, they put us on track for 3+ C°. System dynamics confounds the issue. There is a ~40-year lag between cause and effect because of ocean thermal inertia (the seas absorb 90% of accumulating heat but warm slowly). Present GHG concentrations if held constant commit the world to an additional .3 to .8 C°C degrees 6 warming, enough to overshoot the 1.5 degree limit (Marshall 2010; Hansen 2018). 6 Ominously, CO2 and other GHG emissions are still increasing. It is therefore particularly concerning that the parties to the Paris agreement discussed or endorsed mainly capital-intensive technological solutions from green energy (e.g., wind and solar), through unproved approaches to carbon capture and storage and even nuclear fission and fusion, i.e., any techno-solution that would contribute to investment and growth. Reductions in energy/resource use, fair income redistribution and population controls were not on the table. In short, the real commitment of the international community is to technological solutions that will sustain growth and not jeopardize the current social and economic system. This is the status quo by other means. Perversely, climate disaster policy is being designed to serve the capitalist growth economy “…so the latter becomes the solution to (not the cause of) the [problem]” (Spash 2016, p.931). 

There is another problem—recent analysis suggests that: 

Indeed, “....even if the Paris Accord target of a 1.5 C to 2.0 °C rise in temperature is met, we cannot exclude the risk that a cascade of feedbacks could push the Earth System irreversibly onto a “Hothouse Earth” pathway (Steffen et al. 2018, p.3).7 

To neutralize this risk, Rockström et al. (2017) assert that the world community must cut fossil fuel use in half each decade until 2050 as well as extract gigatonnes (Gt) of carbon out of the atmosphere all while shifting society to alternative green energy. Similarly, an IPCC Special Report on 1.5 degree warming and possible emissions pathways found that in “model pathways with no or limited overshoot of 1.5°C, global net anthropogenic CO2 emissions decline by about 45% from 2010 levels by 2030…, reaching net zero around 2050… (IPCC 2018, C1). All such pathways require “the use of carbon dioxide removal (CDR) on the order of 100–1000 Gt CO2 over the 21st century” (IPCC 2018, C3). 

Significantly for megacities, limiting warming to 1.5 C° would require “rapid and far-reaching transitions in energy, land, urban and infrastructure (including transport and buildings), and industrial systems….” The scale of the needed transition is unprecedented and implies “deep emissions reductions in all sectors, a wide portfolio of mitigation options and a significant upscaling of investments in those options” (IPCC 2018, C2). So far no city has taken up the IPCC challenge. 

Energy: The Achilles’ heel of every megacity 

The technological outlook for a transition to renewable ‘green’ energy is superficially encouraging. “Solar photovoltaic and wind power are rapidly getting cheaper and more abundant – so much so that they are on track to entirely supplant fossil fuels worldwide within two decades…” (Blakers and Stocks 2018); and don’t worry about solar arrays and wind-farms despoiling the countryside: “…if we cover an area of the Earth 335 kilometers by 335 kilometers with solar panels,… it will provide more than 17.4 TW power… That means 1.2% of the Sahara desert is sufficient to cover all of the energy needs of the world in solar energy” (Moahlem 2016); Jacobson et al. (2015) propose a set of “roadmaps for converting the energy infrastructures of each of the 50 United States to 100% wind, water, and sunlight (WWS) for all purposes (electricity, transportation, heating/cooling, and industry) by 2050”. This conversion, allegedly both technologically and economically feasible, would virtually eliminate energy-related pollution and GHG emissions while creating jobs, stabilizing energy prices, and minimizing land requirements. 7 

Such ebullient scenarios generate unwarranted confidence in human techno-prowess and have convinced many that the necessary energy transition is easy and already well underway. This is not so. The transition to renewables is a politically loaded, economically formidable and technologically daunting challenge framed in confusion and contradiction. Opposing narratives on prospects for a 100% green energy system by 2030/50 abound (e.g., EnergyWatch Group, 2018; Mills 2019). In a well-known dispute, Clack et al. (2017, p.1) condemn the buoyant Jacobson et al. (2015) study for significant errors, inappropriate modeling methods, and implausible, ill-documented assumptions that overpromise and potentially “[impede] the move to a cost-effective decarbonized energy system” (see also Bryce 2017). Germany’s much-lauded but faltering energy transition (‘Energiewende’) serves as a practical cautionary tale: investment in renewable reached 464 billion Euro by the end of 2015 without significantly reducing German carbon emissions or dependence on fossil fuels (Feronni et al. 2017; Shellenberger 2019). 

The reality is that in 2019 the world remains hooked on fossil fuels. Renewables (wind, solar, geothermal, biomass and waste) did see the highest rate of growth in 2017 but together supplied only a quarter of a 2.1% increase and only 3.6% of total energy demand, wind and solar just 2.2% (IEA 2018; BP 2018). Similarly, energy demand was up by 2.3% in 2018, with fossil fuels accounting for 70% of the increase (EIA 2019). (The corresponding numbers in BP [2019] are 2.9% and 66.5%.) The installed capacity of wind and solar electricity, particularly solar, is rising rapidly and in 2018 produced 1,270 TWh and 585 TWh respectively. However, the increase in global demand for electricity was 938 TWh, 70% more than the total generated by all existing solar photovoltaic installations. Just two years of global demand increase would swallow the entire contribution from more than three decades of wind and solar power development (data from BP 2019). Moreover, there is concern that green investment has been essentially flat since 2011. It actually fell substantially in several major countries in 2017 (36% in Europe overall) as subsidies were reduced. Only China’s 26% expansion helped bump global investment up by three percent in 2017 (FS 2018, Goreham 2018). Analysts agree that “the current level of investment [$300+ billion a year] is... too low to support a global transition to renewable electricity…” (Andrews 2018a).

In any case, green power generation “will not on its own deliver the emissions reductions demanded by the Paris climate agreement...” (REN21, Highlights, p.1). Electricity is not yet a viable substitute for fossil fuel in key areas accounting for 80% of urban society’s energy consumption including mining, various industrial processes, heavy construction, inter-city transportation (air or highway), and agriculture. Investment in green energy technologies will have to increase multi-fold if it is to keep up with growing demand and capture a greater share of the total energy market (CoR 2018). Securing that investment will become more difficult with reduced government subsidies, particularly if substantial subsidies remain for fossil fuels8 and global interest rates keep increasing. 

There are also significant systemic problems. Recent simulations show that, even if investment in renewables increased by 2030 to the present total investment in new energy (approximately $1.8 tn in 2017), fossil fuels would still be providing more than 50% of primary energy and emissions would be increasing again after 2035—and this assumes an optimistic non-declining ‘energy return on energy invested’ (ERoEI or EROI) for renewables of 15:1. “In this case, as renewables still require some fossil fuel energy to construct, it is essentially impossible for the economy to meet its energy demands and remain below the emissions ceiling” (Sers and Victor 2018, p.14). Sers and Victor call this ‘the energyemissions trap’. 

More realistically, the ERoEI of renewables is lower than 15:1 and likely declining so “…the long run consequence of transitioning to renewables... at sufficient pace to avoid transgressing cumulative emissions limits is a decline in the net energy available to society”. At 17% of GDP and an ERoEI of 3:1, “…the redirection of investment from the secondary productive sector to the primary energy sector leads 8 to a constraint on the productive capacity of the economy and a commensurate decline in output” (Sers and Victor 2018, p.17). I.e., the economy implodes—hardly the future anticipated by mainstream analysts. 

ERoEI and megacities 

The ERoEI concept is central to energy analysis yet remains mired in controversy. Most ERoEI studies estimate the ratio of the energy produced by a project divided by the sum of the direct (i.e. onsite) and indirect (i.e. offsite energy needed to make the products used onsite) energy used to generate that output. This measure gives a satisfying global average ERoEI for coal of 46:1; for important liquid and gaseous fossil fuels and wind, about 20:1, solar 10:1 (Hall et al, 2014). 

Controversy blooms when analysts ‘extend’ (ERoEIext) their assessments beyond on-site requirements. Ferroni and Hopkirk (2016, 2017) considered the energy expended on materials, labour, etc., for the manufacturing, transportation, installation, operation, decommissioning, integration of the intermittent PV generated electricity into the Swiss and German grids (including the energy demand for auxiliary storage capacity) and for obtaining and servicing the required capital. Result? An ERoEIext of only .82 (+/- 15%). This implies that an electrical supply system based on today’s PV technologies in cool northern countries may turn out to be an energy sink, not a source. 9 Spain—arguably Europe’s best insolated country— actually isn’t doing much better. Prieto and Hall (2013) found an ERoEIext of only 2.45:1 for that country’s extensive centralized PV system. 

What does all this mean for megacities? First, consider that the standard ERoEI of major fuels is steadily declining as source quality declines and extraction costs increase—it is only 5:1 to 4:1 for tar sands and less for shale oil, for example. Second, if the more dismal results of ERoEIext for solar PV prove correct, today’s green energy cannot substitute for fossil fuels. Question: At what point will it become impossible to sustain megacities? (Hall et al. [2014] suggest that ‘fuel’ requires an ERoEIext of 3:1 to be minimally useful to society.) Falling ERoEIs and rising energy costs are already being implicated in everything from the doubtful promise of electric vehicles (Goehring and Rozencwajg 2018) to Brexit and the so-called yellow-vest protests in France (Ahmed 2018). 

Can we make the transition? 

There are additional political and technical barriers to meeting even the two-degree warming limit. We need an unprecedented level of cooperation among major governments but in today’s fractious world, with major emitters like the US ‘dropping out’ and others like Canada bent on developing their fossil fuel reserves, this prerequisite will almost certainly not be met. 

Even if world governments were to align in common purpose, the sheer momentum of industrial society is formidable. Driven by exponential growth, half the fossil energy and other key resources ever consumed have been used in just the past 30-35 years (see graphs in Steffen et al., 2015). Thus, most of the infrastructure and equipment involved in electricity generation, manufacturing, transportation, communications, construction, space/water heating, food systems, etc., across the modern world is fueled by coal, oil or natural gas. And, as noted, the addiction persists. After flattening for three years, carbon emissions increased by almost 1.5% in 2017 and 1.7% in 2018 [Le Quéré 2018; IEA 2017, 2019]). In these circumstances, it stretches credulity to think the world can organize to reduce fossil fuel use by nearly 50% (~6% per year) in just 11 years. 10 

A full transition to green alternative energy—the 100% substitution of fossil fuels by renewable sources (wind, solar, biomass, hydro) while meeting a projected doubling of demand over the next several decades—implies at least a 50-fold increase in net renewable energy generation capacity, particularly of wind and solar electricity. Clearly this will not happen without global unity, universal commitment to the 9 Paris targets and massive redirection of investment and subsidies (all of which might still leave us energy poor and collapse the economy [Sers and Victor, 2018]) and cannot happen if the dismal ERoEIext results for solar electricity are confirmed. 

This last point is pivotal. Consider the ultimate extended net energy analysis (ERoEIult). To replace fossil fuels, green energy must be sufficiently intense and abundant to produce all the equipment and machinery used in the mining, refining, transportation, manufacturing etc., of the materials used to produce wind and solar installations plus all the roads, other supportive infrastructure and labour, needed to manufacture, install and operate those facilities, before it can address the bulk of society’s energy needs. So far, fossil fuel stands alone as the only energy source with the intensity both to produce itself, literally from the ground up, and provide the much larger surplus required to supply all the other energy needs of society (and keep in mind the anticipated 35% growth in energy demand by mid-century). Tellingly, fossil fuels currently provide most of the energy used to manufacture the materials, equipment and infrastructure for wind and solar electricity (and are these alternatives really ‘renewable’ if essential equipment must be replaced every 20-25 years, repeating the original energy investment?). 

A major technical barrier to wind and (particularly) solar energy is relatively low ‘density’ and intermittency compared to fossil fuels. Techno-optimists believe that these barriers can be surmounted through improved energy capture and storage technologies but this is energy intensive and expensive— today’s batteries, for example, can increase costs by a factor of 10 or more (Temple 2018, Andrews 2018b). Even modest fixes increase ‘integration costs’ and contribute to notably higher consumer prices for renewable electricity (Hirth et al., 2015). The added capital baggage also reduces the ERoEI of wind and solar below viable levels in many parts of the world. Even at low-but-viable ERoEIs, many countries would not have enough land for solar or wind installations sufficient to supply even their electricity needs (which are typically only 20% of all primary energy consumption). 

The climate-energy conundrum: 

The future is not what it used to be It has long been recognized that the Darwinian struggle for existence is, in effect, a competition for available energy. Building on Lotka (1922), ecologist Howard Odum formulated what is now known as the ‘maximum power principle’: Successful systems are those that evolve to maximize power—i.e., their use of available energy per unit time—in the performance of useful work (self-maintenance, growth and reproduction) (see Hall 1995). ‘Maximum power’ is a fundamental organizing force in living nature. 

Certainly by this measure, H. sapiens is the most successful vertebrate species ever to walk the earth. Modern industrial civilization is an emergent phenomenon birthed at the intersection of abundant cheap fossil energy and human ingenuity. Fossil fuels enable societies to acquire and transform all the other low-entropy resources they needs to grow and complexify. The megacity of ten or 20 million people is certainly the greatest far-from-(thermodynamic)-equilibrium dissipative mega-structure ever created by humans and arguably modernity’s most remarkable icon. 

The problem is that the enormous metabolic appetites of hundreds of city and megacity super-organisms can be satisfied only through the consumption (i.e., entropic dissipation) of prodigious quantities of energy, to date mostly fossil fuels. 11 Urban civilization therefore confronts a conundrum of its own making. If we are unable to replace fossil fuels with equivalent substitutes in the next couple of decades, our urbanizing world will remain substantially reliant on coal, oil and natural gas (at least while supplies last). Atmospheric CO2 and other GHG concentrations will increase and global warming will exceed the 2 C o limit. Our current trajectory implies 3 – 4 C o warming. 

Three-degree warming spells wide-spread disaster by late century—more and longer heat waves and droughts, accelerating desertification, melting permafrost, methane releases, water shortages, disrupted 10 agriculture, possible famine, rising sea levels, the flooding (and eventual loss) of many coastal cities, mass migrations, civil unrest, etc. Many cities would be cut off from food-lands and other essential resources with the breakdown of local and marine transportation networks (see Friedemann 2016); urban life would become untenable in the more vulnerable parts of the world; geopolitical conflict is almost inevitable. And this may be a best-case CO2 scenario. If the world warms by even 1.5-2.0 C o , we risk crossing tipping points (irreversible positive feedbacks) leading to runaway climate change and the end of anything passing for civilization. 

On the other hand, if the world attempts to avoid climate disaster through vastly increased investment in green energy or serious conservation (phasing out of fossil fuels) we could face energy shortages and shrinking economies even as global population and demand for everything increases. Reduced goods production, declining incomes, rising inequality, widespread unemployment, falling agricultural output, broken international supply lines, failing inter-city transportation, local famines, etc., are again a recipe for geopolitical chaos. 

In short, whichever way we turn, megacities in this century may well confront a destabilizing combination of climate change, eco-decay, deteriorating energy supplies and stalling economies. Absent abundant cheap energy and economically drained, megacities will succumb to the entropy law. No longer able to remain ‘far-from-equilibrium’ or even provision themselves, they can only contract or be abandoned. (What then of the 2.5 billion additional urban dwellers expected by mid century?) 

There is a modest upside. The world is already overpopulated—maintaining hundreds of city and megacity super-organisms far-from-equilibrium on a finite planet is the primary factor driving the entropic degradation of the ecosphere, including a precipitous loss of biodiversity (the ‘sixth extinction’). In short, the prevailing relationship of modern cities to their supportive ecosystems is that of malignant parasite to host. The contraction of the human enterprise, including megacities, would enable the recovery of nature—and might actually help ensure humanity’s long-term survival. 

Wages of self-deception