1. Cities as Economic Engines
Nowhere is today’s economy more germane than within and among metropolitan areas. As the building blocks of nations, cities are sources of innovation and centers of trade fostering a vibrant society and its economic development. All across our planet, the undisputed engines of any nation’s economy are its cities, considered here to be networked social life focusing political power and actual power in cultural communities of at least 50,000 residents. Some experts regard the word “economy”—including efficient, conserving schemes—to infer a decline of cities’ energy needs. However, data suggest cities are instead more likely to show their wholes exceed their parts and so raise both their total energy budget and often their per-capita energy use (Φm), albeit slowly.
Urban systems are populous and dense, their structure and function organizationally intricate. Almost everything about most cities seems to be changing, growing, complexifying. Cities expand and proliferate as people not only multiply globally but also migrate from rural to urban locales. Although cities occupy hardly 2 percent of Earth’s land area, they now house about 55 percent of humanity and account for nearly 75 percent of all global energy used. By mid-century, the UN projects at least two-thirds of all people will reside in cities while using 85 percent of the world’s energy as total population nears 10 billion 
By contrast, in 1800 only a few percent of humanity lived in cities. By 1900 it was ~12 percent and about a dozen cities sheltered more than a million residents 
. Today, more than 400 cities each house that many people and a few dozen megacities have more than 10 million each. Most of the colossal ones are in Asia, which has 7 of the world’s 10 largest cities. Shanghai is currently the world’s biggest city proper with a single government (27 million) and is likely to be soon superseded by some other Asian city. Greater-Tokyo alone (38 million) has more residents than Canada and an annual economic output comparable to Australia.
By 2100, this growth trend will have likely shifted to Africa, which will then house at least half of the largest urban areas on the planet. Lagos, Nigeria, now the largest city on that continent, is already among the megacities—housing 7 million people two decades ago, more than double that now, and within a decade or two at least 20 million, topping that of New York and London combined. The center of world geography is shifting 
This massive movement of people toward cities—mostly to big ones in developing countries, not so much in already developed ones—is happening at the astounding rate of roughly a hundred million newcomers each year. By sheer numbers that makes it one of the most notable cultural changes of the 21st century. They are heading to cities, notably in China, India, and sub-Saharan Africa, mainly for economic opportunity since that is where jobs and energy abound. They are also coming because climate change is driving refugees away from some of the poorest and hottest parts of the world, forcing them to seek cleaner air and fresher water. Warfare, too, enhances the trend as city-bound people seek safety for themselves and their families.
Cities are complex, dynamical systems that enable healthcare, education, employment, and welfare, which make them among the best places in the world to improve one’s lot in life 
. Studies show the greener cities are, the happier their residents are, largely because sustainable cities give some urban space back to Nature when parks expand, rivers are restored and literally greener pedestrian pathways made safer for all 
. Cities need energy to function much like all complex, evolving systems, increasingly so from stars to plants, animals, and the human race. Many city energy budgets are trending upward, not downward, as cities grow when migrants adapt to new surroundings, select favorable options, tend to use more energy and evolve culturally. However, not all cities are succeeding; too many are failing. At issue, again, is energy—not enough of it and not the right kind.
Just as realistic efficiency or conservation tactics are unlikely to deter the growing energy needs of nations, energy budgets of vibrant cities are on the rise as well. Critics demur, especially the economists who, after all, are inclined to be economical. They often urge savings, for example advising as energy gets more expensive people will conserve it, reserve it or maybe use it more efficiently. However, energy is not becoming more expensive save nuclear energy that is declining precisely because it is so costly. Energy, especially solar energies, are becoming cheaper—and soon will cost even less than pumped oil and fracked gas that keep subsidized fossil-fuel prices artificially low and their companies afloat.
Urbanization as an example of human change now underway is profound, yet much as expected given the accelerating nature of cultural evolution. Cities have existed for thousands of years, yet city dwellers began outnumbering rural folks worldwide for the first time only a decade or so ago. Even in the expansive US where a third of its population lived on farms a century ago, hardly 1 percent does today. Human migration is a defining factor of this century, not just negatively owing to civil strife, bitter politics or climate change, but also positively since chances for personal advancement are better than ever in metropolitan areas, including cities per se as well as their surrounding suburbs.
Urban critics sometimes fuss over today’s heavy influx into the cities, some even calling for its end. Mitigate the migrators is what they urge. As many cities strive to make things work, their swelling populace outstrips their urban infrastructure—upward in bigger buildings, outward in sprawling suburbs. Some growing cities are among the most congested places on Earth, such as Delhi in India, Karachi in Pakistan, and Dhaka in Bangladesh. Throngs of people in some megacities are now choking on hazardous levels of air pollution. Others just arriving are thrust directly into harm’s way, rattled by heat-island effects or rising seas. The good news is that the oncoming solar revolution will enable cities to energize greatly without creating bad air, waste heat or increased trash, all desirable since cities are already the biggest producers of entropy on the planet 
Nowhere than in Earth’s most troubled cities is it clearer that humanity needs to abandon burning fossils and embrace the Sun. It is time to stop kidding ourselves or delaying yet again; one is the problem, the other the solution. Fortunately, some cities are not waiting for backward states or paralyzed nations to identify what can be realistically done now. In the US, at least half of all cities have strategic energy plans—retrofitting city-owned buildings and street lights, providing free energy audits for homes and businesses, revising building energy codes. Unfortunately, many of the action items in such plans are voluntary, encouraged by mayors who seldom require them 
Relocation is a common feature of biocultural adaptation and natural selection as evolution continues apace. Human migration under social (including socially induced climatic) pressure hardly differs from species migration now occurring throughout the plant and animal world. The former is a quick, Lamarckian accumulation of traits within a single generation; the latter a gradual, Darwinian passage of inherited traits over many generations. All life-forms, including ourselves, have renewed chances for better lives should they change their environs and access cleaner, safer, optimal energy.
None of these cultural developments is surprising when cities are surveyed “cosmologically” from afar. People quitting rural farmlands for city living are adapting to cultural change by selecting better lots in life. There is nothing wrong with that, however inconvenient changes might be in the short term—like now. Cities, built with energy and running on energy as much as anything, could be strained, their services stressed, their budgets stretched, as complex social systems for much of the 21st century. Those cities managing to acquire more quality energy will likely do well, and those that do not might well fail entirely. Still others might find the needed changes a hassle, worsening before improving, “muddling along” to use a frequently heard UN term. It is all part of evolution writ large.
Cities are as much a product of cosmic evolution as stars or galaxies, plants or animals. Among humanity’s greatest creations to date, cities comprise “organic organized complexity” according to the noted urban critic Jane Jacobs who likened cities to ecosystems, or “life at its most complex and intense” 
. City structure is largely its built infrastructure and its function is mainly its economic activity. Cities naturally emerge as people cluster for social contacts, job opportunities, higher wages, good education, and quality healthcare, as well as because that is where much of the energy is intentionally focused to help make it all go-round 
Historically, much of human progress has been closely linked to the origin and evolution of cities. Places like Uruk, Athens, Rome, Paris, among so many other famous settings, have often been at the forefront of humankind’s social and intellectual progress. Most enduring cities today are still evolving while hundreds of new ones are only now emerging, all of them trying by means of energy use, cultural adaptation, and natural selection—change and choice, adjustment and preference—to achieve productive and sustainable communities within Earth’s human ecology 
Like other complex systems, the form and function of cities, much as the larger states and even bigger nations housing them, can be analyzed in thermodynamic terms. Cities themselves are energy-centered, out of equilibrium, and dynamically stable 
. They acquire and consume resources as well as make and discard wastes while providing useful benefits: utilities, housing, transportation, communications, education, healthcare, and entertainment, among many maintenance and service tasks. Although built socially and not grown biologically, urban systems display a hustle and bustle resembling metabolisms with energy flows dependent on city size, location, culture, and history 
Cities are voracious users of energy, both to feed their many residents and to provide valued amenities offered by active city living. Compared to nearly everything else in Nature, Φm
values are high for people living in urban areas. For all citizens within all cities of all nations today, their Φm
averages 3.4 kW/per, or equivalently in proper metric units ~70 W/kg. That roughly matches UN and World Health Organization estimates that megacities typically use each year almost 1018
joules for transportation, electricity, heating, and cooling 
. Some cities in developed countries (notably in extravagant North America) have nearly double that city average Φm
, a per-capita power that many residents of developing cities might achieve later this century.
As a reminder, each adult human consumes as food only 2 W/kg or about 130 W/per. That is nearly the minimum energy needed to continue living—to barely sustain our bodily structure and function. So the just computed value of Φm means the average adult in an average city today uses a few dozen times more energy than the basic minimum. The extra energy used by each of us above and beyond what we actually eat provides many pleasantries of city living, including comfortable housing, bright lighting, convenient transport, and playful entertainment. Some 0.13 kW/per satisfies basic biology; 3.4 kW/per enables much value-added culture.
Some energy used in crowded urban centers might well be reduced if public transport reduces vehicle traffic or if people opt to live in small digs in high-rise buildings. With increasing numbers of people living in cities, buses and ubers would necessarily be selected and personal vehicles rejected. Since transportation leads all other energy sectors, energy savings could be real and substantial. However, greater urbanization also tends to raise productivity and income, which in turn builds up energy demand since it is more affordable and needed for other energy sectors, like heating, cooling, and lighting to support growing businesses. Rising numbers of middle-class households with discretionary money are often quick to take advantage of energy-intensive goods and services that also tend to increase, not decrease, energy use.
Big energy savings and carbon emission reductions in modern cities burning fossil fuels may well be urban myths. Cities built skyward and dense could abate some of their energy use compared to those built sprawling beyond—but not always. New York City, for instance, has more than a million buildings responsible for at least two-thirds of its carbon emissions and skyscrapers are the dirtiest of them all. Delivering heating and cooling, as well as people too, up and down tall, skinny buildings usually requires more energy per person than in smaller buildings.
Urban experts might have it wrong when claiming both energy use and carbon emissions are much less in cities than their suburbs. Data reported by several US cities suggest most urban systems are not notably energy efficient or much cleaner either, so not so economical besides 
. And the bigger cities get, the more energy they proportionately need, always totally and often per-capita. Carbon-dioxide levels are indeed rising in many cities, implying the snags of driving are rising even if vehicles are idling. Heating and cooling are also more in demand as new commercial buildings often grow in size. Cities packed with people and the things they do resemble networks of machines that might save energy individually, such as the Internet of Things connecting smart digital devices nationally and internationally, but they often use more energy per machine collectively.
As cities double in population, they typically use more
than twice the energy of their smaller selves. Not only does total energy usage increase with city size—after all, more people live in bigger cities—but also per-capita usage (i.e., Φm
) remains high and often increases as well. Residents of bigger cities use more energy than those living in smaller cities and they use it at a rate equal to or faster than their cities’ growth 
. For example, electricity use derived from utility bills sent to customers in several European, Asian, and American cities imply Φm
is neither level as cities grow nor dwindling as cities mature. That is only electricity, but since it often scales with total energy used it implies most energy budgets might well continue rising disproportionately as cities evolve, if only slightly and slowly. This should not surprise us since efficiency gains can hardly keep pace with energy demands for many cities reaping the benefits of booming economies 
New York City is a prominent example of a highly evolved, technologically savvy city, perhaps as atypical of world cities as the US is among nations. It might be at the vanguard of cities worldwide or merely an outlier, but it is telling us something since its per-capita energy usage has been roughly steady for decades and maybe even slowly declining in recent years. New York’s public transit system of trains, buses, and taxis works well—fast, frequent and reliable, the best in the US—keeping countless cars off its city streets. And its dense array of vertical buildings help limit the city’s total energy budget. Does a high yet nearly flat Φm mean America’s biggest city is beginning to fail, as its detractors flout? Or merely maturing while becoming more efficient, as supporters tout? Hard to know without better data; maybe a bit of both given the hustle and bustle amid its concrete canyons.
2. Measuring Cities
Theory is one thing, data quite another—a vital other. As people culturally gather into cities and society much like atoms physically cluster into stars and galaxies or cells biologically group into bodies and brains, all these complex systems are governed by the same general principles of thermodynamics guiding energy, adaptation, and selection. Unfortunately, reliable, consistent energy data are not well gathered by the municipalities where most people live. Accurate energy data for individual cities are hard to find in published reports or to compute from piecemeal statistics. Many cities tally their data differently or not at all, some counting energy used for electrical service mainly, others for transportation or buildings only. Some collect data for cities proper minus suburbs, others for metro areas of cities plus suburbs. Urban officials keep few records of their most vital diagnostic, total energy used, which is better compiled for nations and states whose boundaries are clearly drawn 
for a small sample of cities during the past half-century—not just electricity, but also energy used for heating, cooling, transport, as well as any commercial and industrial use within city limits 
. The graph is tentative pending better data from city governments, yet the cities plotted are not cherrypicked. They are selected for pedagogical insight. Rather than cluttering the graph with spotty values of many cities’ energy budgets over varied timespans, only a half-dozen prominent cities’ data are displayed for a range of places where people cluster internationally—some technologically young and only now developing, others older and more mature.
City Φm values are shown rising or plateauing over time for Washington, Toronto, and Sydney in the developed countries of the US, Canada, and Australia, which are among the highest per-capita energy users among all nations. These contrast with a rising then slowing curve for Hong Kong and a rapidly rising curve for Shanghai within the major developing country of China. Note that Shanghai’s data are plotted as a straight line on this graph’s semi-log scale, so its Φm is rising exponentially on a linear scale, which is not surprisingly given the industrial might that impressive city has recently achieved in modern China.
Figure 1. This graph shows energy usage rising (for adolescent cities) and then flattening (for mature cities) with Φm values plotted at left and equivalent per-capita energy use at right for a sampling of major cities around the world during the past half-century.
Each curve in Figure 1 suggests ways that Φm changes as urban areas evolve. During the past half-century graphed, Toronto proper has not grown much in size, scale or population (now about 3 million people); it is basically steady as is Washington though much smaller (about 700,000). Hong Kong (7.5 million today) and Sydney (5 million) are moderately growing cities, not quite doubling their population over the past 50 years. Shanghai has quadrupled to some 27 million people today. Their computed and plotted values of Φm, ranging from currently about 2.5 kW/per (50 W/kg) for Hong Kong and triple that for Washington, used the summed mass of all their residents living within city limits, not beyond in their greater metro areas that are not so steady and are still growing in size and scale.
Figure 1 is much as expected for any evolving complex system in the larger context of cosmic evolution. Energy used by urban residents generally rises as their cities evolve toward greater complexity and the plotted trends in Φm reflect those five cities’ ongoing development—Washington and Toronto not much, Sydney moderately, Hong Kong more so and Shanghai stunningly.
Washington has among the highest Φm for any city—nearly flat, maybe falling, and averaging 150 W/kg (7.5 kW/per). Think of all those government buildings, with high ceilings, huge volumes, and vast electrical needs to keep the lights on, the hot air controlled and the bureaucratic staffs pushing around bits and bytes, much of it inefficient and wasteful as for any publicly funded authority. Most nations’ capitals likely have thriftless energy budgets.
Limited data at hand for other developed North American cities show much the same trend, though more economical. In addition to Toronto’s plotted 120 W/kg, Boston, San Diego and Denver, for example, use 85, 90 and 110 W/kg, respectively, and all have remained roughly constant (level on the graph) over the past few decades. New York City, noted earlier as either an efficient trendsetter among big cities or perhaps one starting to slide, also displays a nearly constant value of about 80 W/kg, and even if slightly falling would hardly be noticeable on the scale of this figure.
Toronto has a moderately high Φm owing to its cold winters, warm summers, and heavy reliance on fossil fuels—slightly higher than most US cities and almost twice as high as most European cities. Its rapid rise in energy use, as for a few other Canadian and many US cities, occurred shortly after World War II, which is outside the timeframe of Figure 1. Their per-capita energy budgets then leveled off (or nearly so), which is why Toronto’s change during the time plotted in the graph is nil, its curve flat.
Sydney is a modern city though still complexifying, so has a steadily rising Φm
on its way perhaps to resembling Toronto eventually, owing to its serious cooling needs in summer. It is a city of developed Australia, but not yet as energy hungry as Toronto. However, Sydney’s plotted values of Φm
are still heading upward, with its citizens not yet easing up much on their per-capita energy demands 
Hong Kong is still an industrializing city (though light industries like finance and services) likely typical of thousands of cities throughout the developing world now showing a quick rise followed by a tendency to turn over yet still upping its Φm as each of its citizens uses more energy. Its energy needs grew rapidly under British rule until end of the 20th century, less so since rejoining China, though overall Hong Kong’s energy usage is still trending upward.
Shanghai, an historically old city yet one now rapidly modernizing, roughly doubled during just the past quarter-century both in population and Φm
, now nearing 30 million people and 100 W/kg 
. Among thousands of older revitalized and newer big cities of mostly Asian nations, Shanghai is widely considered the most western city in still-developing China and likely the most energy intensive megacity in the world. With names like Guangzhou (formerly Canton), Chongqing, Surat, and Chennai, energy budgets for hundreds of giant cities will likely balloon in the next decade.
Data plotted in Figure 1
help test a central idea inspired by cosmic-evolutionary cosmology as applied here to cities and their social organization: The up-and-to-the-right trend, in fact for all three figures of this article, supports the notion that growth and complexification of ordered systems usually have rising Φm
. Stars, for example, increase their Φm
while physically evolving, 
as do bodies and brains while biologically evolving, 
much as the data plotted here also show for cities culturally evolving. Numerically, however, city values exceed those for stars by orders of magnitude and even those for life-forms. Cities expend of order 100 W/kg (5 kW/per), which is roughly a million times more than for stars and even more than their individual residents, confirming intuition that cultured systems and their built products are among the most complex entities found anywhere.
Alas, not all cities’ Φm values are on the rise and some of them are not even flat, so are no longer complexifying. These are the cities that are failing, usually as their Φm values decline. Only an injection of renewed energy can help them, lest they collapse as viable places for humans to cluster and enjoy a life worth living.
3. Winning Cities, Losing Cities
Winners and losers populate the spectrum of complex systems across the Universe. Vibrant starburst galaxies among red-and-dead ellipticals. Blue stars ablaze among red giants and white dwarfs nearing death. Life aplenty all around us on Earth despite 99 percent of it once coping is now extinct. Organized society benefits humanity yet humanity is now so deeply threatened. Cities and economies, too, experience gains and loses while each provides both goods and bads throughout our lives.
Researchers have long noticed that big cities resemble massive stars, one attracting people and the other atoms, both seen brightly while evolving slightly. Useful lessons might lurk for cities despite their greater complexity and much higher Φm than for stars, if only because the thermodynamics guiding both is much the same. We do know that the biggest stars “live” fast and “die” young, usually imploding at “death.” What we do not know is whether big cities grow and densify at their own peril and if they too might someday collapse under their own weight.
Cities as well as nations and society itself are products of culture, each of them partly a progressive attempt to control energy. Each of these complex systems—and many do look and feel subjectively very complex even without numbers objectively confirming it—thrive when human actions accept favorable factors and decidedly reject the rest. As metropolitan areas culturally evolve, they change, adapt and often directly select their built infrastructure, consumer lifestyle and human behavior. Chance is somewhat eclipsed while necessity often prevails and intentionality ventures forth.
Cultural evolution differs from biological evolution in that culture is Lamarckian, biology Darwinian. Perhaps uniquely among life-forms on Earth, we humans can work to make change happen while actively striving to endure. Cultural adjustment and selection are mostly intentional, planned. In the ubiquitous mix of chance and necessity shaping every changeable outcome, determined actions (the necessary part) count more than random events (the chancy part). We are mostly in charge, so there are no excuses. The future is largely ours to make of it what we will. It is up to us to decide if and how cities’ success depends on thrifty economies and higher efficiencies reducing the energies that make them run, or on vigorous use of abundant energy driving cities forward without much limit provided it is clean and safe. Conserving energy and using it efficiently are always welcome since without them we would likely pay more for energy. However, frequent assertions that energy savings confer competitive advantages seem dubious and might even be dangerous.
Cities can profit economically in the 21st century when their residents take full advantage of richly available solar energies not only to power society copiously but also to better solve environmental impacts inevitably caused by any system’s evolution. Cities need not be places where more residents chase fewer resources. With the Sun, our prime resource is so plentiful—as well as cleaner and safer than any energy ever used by humanity—untold numbers of people could comfortably exist in cities and nations nearly anywhere on Earth.
Thermodynamics’ laws demand adherence. Cities able to manage their energy budgets optimally are most likely sustainable in the long run—or at least improve their odds of surviving with careful work and resolve. Other cities using too much or too little energy—beyond an optimal range of Φm, much like all complex systems—are naturally and non-randomly selected to abort. They fail, lose or otherwise terminate, for the underlying laws of Nature, unlike the systems obeying them, are unchanging and non-negotiable.
Cities, as for the nation-states housing them, rise or fall based on their energy budgets. War is too burly and famine too slight, both dreadful ways for cities to fail. Yet, urban collapse can also be subtle; cities can scrimp on energy while starving their economies or use too much energy while outrunning their infrastructure and overheating themselves with waste heat. Optimal energy, clean and safe too, is just right to sustain smart, successful cities.
Failing US cities such as Detroit, Buffalo, and New Orleans, among dozens of others officially or effectively gone bankrupt worldwide such as Damascus, Karachi, Pyongyang, and Port-au-Prince are not immune to thermodynamic consequences. Inability to optimize their energy budgets is one likely reason why these cities are good examples of bad outcomes, the main ones being living costs and job losses. Their economies are crashing, if not yet burning, though they might still recover with shrewd application of renewed energy.
Detroit is the epitome of a city having serious economic issues with, near the start of the 21st century, little industry, huge debt, social mismanagement, 20 percent unemployment, and less than half its population of nearly 2 million people a half-century ago. Today it is a naturally collapsing city on the brink of operational ruin, its demise understandable energetically. The Motor City’s S-shaped curve of Φm is neither rising nor flattening. After reaching a peak in the mid-20th century, its energy budget fell as the city devolved. At its lowest point about a decade ago, half of its street lights and a third of its public buses were not working and more than a million residents had fled the city.
Detroit is not the only economically challenged city, nor the only clearly troubled place where population has fallen for decades. Grand Rapids, also in Michigan, is largely boarded up among many cities in and around America’s Rust Belt. Buffalo began shrinking with a sinking energy budget starting a century ago. New Orleans is failing because it is literally sinking below rising seas, tanking financially and dying energetically. Baltimore, Philadelphia, Mexico City, Moscow among several once proud cities all seem tired, broken, lethargic—their sidewalks crumbling, lampposts leaning, roadways potholed, their people glum. Those cities’ values of Φm, to the extent data can be found to reliably compute that metric, are low, typically less than 60 W/kg and sagging.
All is not lost and aid is coming to many depressed cities. A few years ago, for example, downtown Detroit began what might be a turnaround, led by new home construction that raised its energy expended. JPMorgan Bank, which had reaped grand profits from a century of bankrolling the world’s leading automotive industry, poured money back into the community to help rescue old buildings for those folks willing to return. Abandoned Victorian mansions were offered for $1 to city workers able to repair them; rock-bottom rents allowed people to repopulate livable apartments; thousands of foreclosed homes were bought for a few hundred dollars each on credit cards.
Resurrecting any city creates jobs and needs supplies to fix up whole city blocks and deserted neighborhoods, which in turn requires energy. For Detroit, livening vacant buildings where little or no energy had been plied for decades is sure to raise its per-capita energy use. This once dying city has emerged from bankruptcy and restored basic services like streetlighting and road maintenance, giving it a chance to recover anew. Only time will tell if it can sustain this economic upturn even as builders complain about material and labor shortages—a demand for more energy in a city perhaps still unable to supply it. All the more reason for cities on the mend to look up and around at the golden solar energies raining down upon them and then act innovatively to grasp it.
Many cities around the world are struggling to lift themselves up by their own bootstraps or expecting handouts from others to bail them out besides those already mentioned: Baghdad, Juarez, Kinshasa, Barcelona, Genoa, Leipzig . . . . Ironically, some of them were once well run in developed countries, providing ample public services for their residents, yet are now mired in poverty, substance abuse and homelessness. Much the same also pertains to some post-industrial cities and towns of the US heartland in addition to those noted above: Cleveland, Memphis, Pittsburgh . . . . That said, help is on the way because with a solar revolution more energy is on the way.
Without government intervention, mostly as money handouts for energy-related tasks, cities with decreasing Φm could well abort. Unable or unwilling to adapt, they would likely be culturally deleted as viable urban entities. Nature would naturally select them out of existence. At best, the most troubled cities might be urban-renewed as smaller, less complex social systems. Razing, repurposing, revitalizing, rebuilding, much of it with sweat and tears (a kind of energy), yet none of it without applying real energy that can make a difference. Money alone cannot guarantee economic recovery; throwing dollars at any problem without a plan or purpose seldom works. Only energy influx (probably bought by money) has a chance—and only a chance if clean and safe—to rejuvenate failed cities.
Cities can indeed collapse, even great ones. Many have previously fallen, including Sumer’s Uruk and Ur, Egypt’s Memphis and Mohenjo-Daro, Persia’s Babylon, ancient Rome, Troy, Angkor, Teotihuacan, among others that came and went throughout recorded history. Most vanished via conquest, disease, or environmental disruption, forcing their urban energy metabolisms beyond the bounds of optimality. Warfare uses too much energy, famine too little, and sometimes not even economic revival can prevent failure 
. Modern world regions larger than cities yet hardly qualifying as nations can also fail and have. As megacities and city-states grow some of them will rival whole nations in size, scale, and energy budget. From those regions malfunctioning today we can learn how growing cities might avoid similar fates. Here are a few examples:
Puerto Rico was the first US territory (neither a state nor its own nation) to file for bankruptcy protection in 2017. This Caribbean island of 3 million people owes some $130 billion in public debt, dwarfing the nearly $20 billion bankruptcy filed by Detroit. Faced with an economic recession over decades, a “brain drain” to mainland US and several damaging hurricanes that destroyed much of its energy infrastructure, Puerto Rico has suffered a steady decline in Φm that has nearly caused its basic public services to collapse. Its energy use per capita (now about 65 W/kg and comparable to China’s) is half what it was decades ago and hardly a third that of the 50 US states averaged, dropping it to “developing” rather than “developed” status. The US government is now trying to prop up its energy flow by rebuilding its electricity grid—a smart move, especially if fed by the abundant sunshine and blustery winds for which most Caribbean islands are well known.
Venezuela, mentioned earlier and now hardly more than its capital of Caracas whose population is falling, is in full economic retreat despite its rich oil reserves. Not only have millions of people fled this once proud region in recent years, its falling Φm (now about 50 W/kg) has also devolved it out of developed status. Reason is, at least partly, Venezuela’s leaders cannot agree how to manage its energy budget optimally. The result is a humanitarian crisis with widespread hunger, malnutrition, armed groups roaming the countryside and a crumbling infrastructure. It has been teetering on the edge of failure for years, yet its revival is all around it. Its own energy supplies could bail itself out, dirty as oil is, then buy its way with the profits to build renewable solar technologies that could lead South America toward an auspicious future. Of course, local Marxist politics and crippling US sanctions are not much help.
Syria is a region in default and all but destroyed save its capital of Damascus, an excellent case of an insane state of modern affairs. More than a city, yet hardly a nation any more, it is a dysfunctional complex system whose energy budget has hit rock bottom. Its Φm (roughly 15 W/kg and diving, comparable to North Korea) is far too low and its economy broken, except during its ongoing civil war when its energy use is much too high. Either way, Syria is a failed nation-state, as is Somalia, Afghanistan and a few other countries having energy flows usually much less (during peacetime) and occasionally much more (during wartime) than optimal. A logical solution is for Syrians to leave their homeland, as they are already doing in droves. A better solution would be for Syria to use its vast, open lands (the size of Oklahoma) to build huge solar farms in its sunny interior and wind farms along its blustery Mediterranean coast to produce electricity for itself and its neighbors—creating jobs, regaining a quality of life and becoming a centerpiece for Middle East security.
All three of these weakened regions had been on the rise for many decades, their total energy consumed, per-capita energy usage and their economic wellbeing steadily strengthened—complex systems evolving nicely for the good of their citizens 
. Now, each is trending downward in people served and in Φm
. Instead of complexifying, they are simplifying, which is usually an adverse evolutionary trend. All three have recently lost some 20 percent of their population, swelling emigration from Puerto Rico and Venezuela toward the US and Latin America as well migrant caravans from Syria and other Mideast nations into Europe. Energy use gone bad can disrupt the world.
Even as some cities, nations and regions fail or flourish, others work to remake themselves. In an interesting development with great promise, some leading geopolitical centers seem to be evolving into huge and vibrant city-states. Regional clusters of cities not just surviving but also thriving could be among the biggest winners of the next great evolutionary advance—complex systems bigger than megacities that might someday replace nation-states. Fact is, no one knows how long our traditional cities might endure while culturally evolving or even what they become when they really grow up.
Emerging city-states might be opportune systems to actively tackle the energy crisis and its biggest victim, climate change. Some cities are already well ahead of nations in combating environmental pollution and global warming 
. When the US rashly pulled out of the Paris Accord in 2017, mayors of more than 400 cities formally pledged to remain and honor its goals. Now that the US is regaining good standing with much of the world, many more cities are doubling down and working together to forge ahead sensibly while ignoring those places crippled by climate conspiracies. Some US states, too, have joined in common cause, especially coastal regions like New England plus New York state along the eastern seaboard and California, Oregon plus Washington state along the west coast.
An example is the cities of Boston and nearby Cambridge where citizens have adopted a “fossil fuel free” standard to be achieved by 2050 and they fully expect companies, residences, universities and institutions to abide by it 
. Kudos to these progressive cities for even having a plan—bottom-up local actions that often trump top-down federal inertia—but nobody should hold their breath. Over the past two decades, hundreds of US cities have pledged to use clean energy to reduce carbon emissions by some future date yet a respected Brookings Institute report recently showed most of them struggling to meet their ambitions 
. Such a fine fossil-free goal, at least for electricity, might be doable for forward-looking cities and some nations, but not for the whole world, not in a single generation. Most nations are only beginning to develop technologically.
Jane Jacobs was right comparing cities to ecosystems and “… because of their complex interdependencies of components, both kinds of systems are vulnerable and fragile, easily disrupted or destroyed.” However, she foresaw dark days ahead as technologically challenged cities crumble and never recover, their decaying culture and degrading ecology simply unsustainable. She might have alluded to, as we now suspect scientifically, only few cities, like few species, long endure, but in her final master work she painted a much gloomier, Cassandra-like picture for cities on Earth 
Most of us do not want to accept a negative outcome, urging instead a chance Jacobs was wrong and history need not repeat—but only a chance on which we must act now. The likelihood of our cities, our society, and ourselves being winners might seem slim, yet a positive road forward also seems clear. Our future is surprisingly in our hands, with necessity and intentionality playing key roles. Cities that are rich in energy and optimally managed can be anything but dark, in fact quite bright in health, wealth, security, and social wellbeing.
The upshot of much of this unorthodox city analysis, however quickly urban experts might dismiss it, is this: As cities evolve, some efficiencies are naturally realized owing to city structures, but sizable savings from energy-driven functions are not likely among them. Total energy budgets rise for growing cities and so does per-capita energy usage (Φm) for many urban residents. Generally, the larger the city the hungrier it is in nearly every energy sector, transportation perhaps excepted if pedestrians eventually prevail. Successful cities, if nothing else, are growing—upward, outward, economically, and energetically, as well as in number and diversity of people.
To survive, cities of the future will not necessarily need to become more energy efficient, though it would be good if they do. Advancing cities procure (or produce) and use (or store) more energy—not only more total energy for their vibrant urban economies but also likely more per-capita energy for use by their individual residents. As advised, only the Sun and its renewable sources of shining light, blowing wind, falling water, and warming air can possibly provide humanity with the clean, safe, and abundant energy needed to endure without risking destroying our planetary home, which for most people in the foreseeable future will be cities. It is indeed time to stop digging up stuff on Earth and making a mess to boot, and time to start looking up at the solution staring us right in the face.
4. Whole Greater than Its Summed Parts
Anthropological evidence does imply simpler systems evolved into more complex ones as our forebears abandoned hunter-gatherer lifestyles and began cultivating the land. They first clustered into rural villages as long ago as 10,000 years, grouped into cities as agriculture grew, then into larger regions and eventually nations, even clusters of nations, or empires. Historically, cities led bottom-up, followed by states and nations, each using surely more total energy and likely more per-capita energy (Φm
) as each type of social system hierarchically complexified 
That today’s Φm values for states are greater than those for cities provides another example of wholes exceeding their summed parts. The city of Boston, for example, whose Φm noted earlier is ~85 W/kg (4.2 kW/per) is the capital of the state of Massachusetts, which has a higher value of 140 W/kg (7 kW/per). This inequality holds for many cities and states, at least in the US where data exist to make the comparison. A state is arguably more complex than cities within it, much as any state governor would admit when dealing with many varied city and town mayors. Ditto for New York City and Denver that reside in the states of New York and Colorado, whose Φm of 135 and 185 W/kg are each higher than their city values of 80 and 110 W/kg, respectively.
Most US cities for which data are available have Φm
between 70 and 120 W/kg 
, whereas most US states in which they are located have values somewhat higher, ranging from 130 to 200 W/kg (and even higher for some outlier mining and drilling states having few cities like Wyoming, Alaska and the Dakotas since to produce energy requires energy) 
In other words, major US cities average ~100 W/kg (5 kW/per) or about half that of the entire US nation. That is because not everyone lives in cities, not all cities fail to economize and not all energy used nationwide involves cities. Planes, trains, buses, and trucks crisscrossing the nation are not included in cities’ energy budgets. Nor do cities usually house food farms, power plants or shopping malls found in the countryside where energy production and consumption can be locally high.
An example is the huge amount of jet fuel used in 2019 to power US commercial airliners flying nationally and internationally—at a rate of 130 GW, which is a few percent of all energy used that year in the US—and none of it charged to the energy budgets of cities or states. Another example is the network of roads on which so much of America’s commerce depends. Energy is needed to build and maintain state highways that cities are not responsible for. Likewise, interstate highways get charged, both money and energy, against neither cities nor states, rather the whole US nation.
State and federal governments provide more structures and functions that benefit cities and added energy is needed to wed their many parts wholly to make it happen. That likely does make states more complex than cities and nations more complex than states, much as the Φm numbers imply. They also suggest cities are at the base of this social hierarchy, which again is not surprising.
The federal government does indeed consume huge amounts of energy across the US that is excluded from city or state energy accounts. Not just for post offices, court houses, and national parks, but also its many departments and agencies (State, Treasury, Defense, Justice, Commerce, NASA, etc.), each with bureaucracies and facilities using energy and costing money. The Defense Department is the biggest employer in the nation and the US government is the nation’s (indeed the world’s) largest single collection of workers, buildings, vehicles, ships, and aircraft, all of which consume energy paid for by faceless taxpayers—roughly 40 GW in 2019, which is another percent or so of the nation’s total energy budget (~3.5 TW) not counted by cities and states. Even during peacetime, the US military uses energy at the great rate of some 25 GW, equivalent to two dozen major nuclear reactors running full tilt, full time.
Many find it hard to believe that government could add so much to a nation’s energy budget above and beyond what is normally used by its citizens going about their daily routines. However, it is not a belief and two factual examples suffice. The US Postal Service, while headed in 2022 by a right-wing political appointee, ordered a whole new fleet of some 150,000 mail delivery trucks, hardly any of them electrically powered, almost all of them running on gasoline-fired internal combustion engines. At $11 billion for the total purchase, each vehicle cost nearly $75,000 and gets 30 L per 100 km (8 miles per gallon). Also, the US Army, always conservative while stressing reliability so using more expensive yet less explosive diesel fuel, has some 8000 battle tanks, each costing about $9 million and each using some 4 L per kilometer (0.5 mile per gallon).
So, nations likely have larger Φm values than municipalities comprising them, suggestive of wholes exceeding their summed parts. Likewise, states within nations often have Φm larger than the cities comprising them. In turn, cities have somewhat larger Φm than individuals or families housed in them. None of this should be unexpected since cities, too, have added energy needs above those of its single citizens or households, such as city government, public education, police and fire service, bus and subway transportation, among other urban infrastructure that makes cities attractive to many people.
Each level of increased complexity seems characterized, at least partially, by more energy used in total as well as, especially, more energy per capita., with people the essence of cities, which are the basic building blocks of nation-states everywhere. It will be important to check these trends and insights as cities, states, and nations develop, mature, and succeed or fail.
Though the US nation is not representative of the world on average, it is likely these trends (even if not the specific values quoted since all are changing with continued advancement) are much the same beyond the US, where new cities are sprouting, population is growing and energy use increasing. We cannot be sure that complexity rises for all cities, states, and nations until better data are in hand. However, of this we can be reasonably assured:
A big idea repeats in Nature and is worth repeating in words as well, which is good and useful if we are to gain a valid understanding, or at least a close approximation, of reality. At the heart of Earth’s global economy, many world cities grow and complexify, hungering for more, not less, energy—always totally and often per-capita. Energy rate density, Φm, generally holds as metric, or at least a proxy, for national and urban complexity, much as it does for so many other complex systems having emerged throughout cosmic history, from big bang to humankind. Like stars, galaxies, plants, and animals whose impressive wholes outperform their component parts, cities and the nations in which we live are also vibrantly and functionally more than the sum of our individual selves.
If the pace of life nowadays feels energetic, it is probably so. Nations and their cities are products of cultural evolution near its apex to date, differing much in degree yet little in kind of complexity from other physical, biological, and cultural creations of cosmic evolution. They use stunning amounts of energy controlled by us and do it in ways remarkably similar to so many other complex systems known anywhere in the Universe. Earth’s cities, in particular, perhaps our greatest cultural invention, and soon to be where three-quarters of all people live, are integral parts of Nature.