Modern urban centers around the world now have neighborhoods that house well over 100,000 people per square mile. The Choa Chu Kang district in Singapore, defined by boulevards lined with 10 to 12 story mid-rise residential buildings, has a population density of over 125,000 per square mile. The entire borough of Manhattan has an average population density of over 70,000 per square mile, with far higher densities in areas of midtown and lower Manhattan.
According to a 2018 report released by the United Nations, today 55 percent of the world’s population lives in urban areas, a proportion that is estimated to increase to 68 percent by 2050. At the same time, the United Nations projects global population to increase from 7.8 billion today to 9.7 billion by 2050. These projections lead to a surprising calculation: the absolute number of people living in rural areas is expected to decline, from 3.5 billion today to only 3.1 billion in 2050.
What should not be surprising by now is that people around the world are voluntarily and inexorably migrating from rural areas to cities. But the corollary effect is relatively unheralded; that around the world, open land is slowly depopulating. For the most part, this is happening absent government coercion. It flies in the face of the conventional wisdom – heard endlessly in the United States – that we are running out of open space.
The sustainability challenge that matters is not preserving open space, not only because the world’s population is already moving into cities faster than the world’s population is increasing, but because the absolute urban footprint on the planet is relatively insignificant.
This reality was explored in great depth in an earlier article, The Density Delusion, and can be distilled down to this: If ten billion people were all to live in four person households that were each on quarter-acre lots, everyone, with an equivalent amount of space allotted for commercial and industrial use, that would equate to a population density of 5,210 people per square mile, and at that density would only consume 3.8 percent of all land area on earth. Actual estimates of worldwide urbanization as of 2018 are only 2.7 percent of global land area excluding Antarctica, and some analysts believe this estimate is grossly overstated.
But everyone does not want to live in a home with a yard that big. Most people would be content living on a smaller lot, and a large proportion of the population prefers to live in homes with no yard at all. Billions of people, for that matter, apparently prefer to live in high rise apartments. It is not suburban sprawl that constitutes the prevailing sustainability challenge to humanity, it is building megacities that are resilient to environmental and economic threats, and constitute an inviting destination for migrants from rural areas.
Cheap Energy is the Prerequisite for Viable Mega Cities AND Population Stabilization
The consequences of environmentalists making “climate change” their central focus instead of population growth are epic. Two factors, more than anything else, induce people to voluntarily limit the size of their families: prosperity and urbanization. Both of these require cheap and abundant energy.
It is estimated that as of 2020 there are 38 “megacities” on earth, defined as a metropolitan area with over 10 million inhabitants. Of these, only six – Tokyo, Seoul, New York, Los Angeles, Paris and London – are located within high income nations. Moreover, nearly all the forecast growth of megacities will be in developing nations, in places like Jakarta, Dhaka, Mumbai, Kolkata, Karachi, Lahore, Lagos and Kinshasa.
So what innovations being pioneered today will enable megacities in the future to provide a high quality of life, and how will cities of such size and density reduce their vulnerability to economic or physical disruptions?
The biggest variable governing the success or failure of megacities is energy. Abundant, affordable and reliable energy is not only a nonnegotiable prerequisite for prosperity around the world, it is the only way megacities are feasible. Environmentalists typically observe, correctly, that per capita energy consumption is lower in cities, but they ignore the converse – if you make energy too expensive by curtailing use of fossil fuels, you prevent people from vacating rural areas where they can forage for energy – unsustainable, dirty, and free – by stripping the biosphere.
Therefore if the energy challenge is addressed responsibly, meaning an “all of the above” energy strategy is adopted worldwide, all the other building blocks of megacities can be assembled. But this means that the legal and financial obstacles that are preventing developing nations from exploiting their oil and gas reserves and building nuclear power plants will have to be lifted.
With abundant energy, for example, the challenge of creating water abundance is manageable. This is because for nearly every type of water infrastructure, the biggest single operating cost is energy. Investing in 100 percent reuse of wastewater, augmented by desalination of seawater, offers nearly every megacity on earth the opportunity to never experience water scarcity. Closely related to this is the rapidly maturing technology for indoor agriculture, including high rise agriculture.
Making Cities Self Sufficient Food Producers
Since a megacity is by definition an epicenter of human habitation, by definition it is antithetical to the notion of being “off-grid.” But on the other hand, the megacity needs to be as self sufficient as possible, since having 50,000 or even 100,000 people per square mile means that any resource that needs to be imported, stored or removed is going to have to be handled in very high volumes. Therefore energy efficiency, waste management, as well as energy and water harvesting and treatment are technologies that are extremely important to the megacity – along with smart systems to interconnect all of them. Fortunately, water supply and treatment can be synergistic with indoor agriculture.
Indoor urban agriculture makes a lot of sense. It is possible that using hydroponics, aeroponics, and aquaponics, industrial agriculture operations sited within urban areas can produce enough food to feed the inhabitants, reducing the need to import food from farming regions. These facilities would also be able process waste water from elsewhere on the utility grid – using it to water the plants AND to reuse as drinking water.
Here’s how: The grey water extracted from sewage would be subjected to biological and mechanical filtration, then it would be used to water the plants. The plants, in turn, would transpirate heavily in the indoor environment, and dehumidifiers would harvest this water – this transpirated water would be pristine drinking water, able to be pumped back upstairs or into the utility grid for reuse.
This concept of using transpiration from plants in a commercial high-rise agricultural operation to provide the last mile of grey water purification in the urban environment is revolutionary. Along with the surprisingly low, and dropping, cost of desalination, and advances being made in primary sewage treatment, this innovation could help solve the issues of potential water scarcity in the urban environment.
The quantity of food that a high-rise farm might produce is also surprising. Because the plants are grown in optimal conditions – optimized light and water, and no pests – they can yield 3-4 crops per year instead of one, and each crop may require only a few vertical feet of space. This means each story of high-rise space occupying an area of one acre, for example, can literally produce several times as much food per year as an acre of ordinary farmland.
This multiple order-of-magnitude increase in potential productivity per unit of land, combined with the proximity to market, means high-rise farming is merely waiting for economic and political conditions to align in its favor. The technology for high-rise farming continues to commercialize, and it will be available when we need it to feed the burgeoning megacities of this world.
Building Up, Out and Down
It is common for the smart growth crowd to say “build up, not out,” but this ignores the fact that building out as well as up increases the overall supply of dwellings, making them more affordable, and reduces the pressure to increase density in suburban areas where the people living there want to preserve their way of life. But what about building down as well?
It isn’t as if building down hasn’t been tried with success already. The New York City subway system. The London Underground. The Paris Metro. What about Boston’s “Big Dig?” Mistakes were made, to put it mildly. But today, anyone who tries to get to Logan Airport from downtown Boston during rush hour will have nothing but good things to say about the much maligned “Big Dig.” It’s too bad we don’t have more big digs – in the heart of urban centers we could put freeways and rail underground, our cities could reach for the sky, and there would never be traffic jams.
Tunneling on a grand scale may seem mundane, but the industry is rapidly innovating, incorporating new technology across multiple disciplines as fast as it becomes available. From GPS systems that allow a tunneling machine to always know precisely where it is beneath the earth, to better cutting bits, to debris removal conveyances, to mechanical conveyances that simultaneously bring forward shoring material, to worker shelter and control rooms, modern tunneling machines can exceed a mile in length and cost billions to acquire and operate. The global leader in tunneling systems is Herrenknecht AG. An emerging and very disruptive new competitor is Elon Musk’s The Boring Company.
Tunneling, like blasting payloads into low earth orbit, is extremely expensive. But The Boring Company claims tunneling costs can be dramatically reduced. On The Boring Company’s FAQ page, the following innovations are proposed: (1) Triple the power output of the tunnel boring machine’s cutting unit, (2) Continuously tunnel instead of alternating between boring and installing supporting walls, (3) Automate the tunnel boring machine, eliminating most human operators, (4) Go electric, and (5) Engage in tunneling R&D, “the construction industry is one of the only sectors in our economy that has not improved its productivity in the last 50 years.”
Skeptics may consider the fact that Musk’s Space X brought the price of delivering cargo into orbit down from $26,000 per kilogram in 1995 to $1,800 per kilogram in 2017, courtesy of the 100 percent reusable Falcon 9 rocket. The Falcon Heavy promises to drop that cost by another 50 percent within the next few years.
As the megacities of the future are built, tunneling machines will play an integral part in endowing these cities with efficient transportation systems. Tunneling underground to create upgraded, higher capacity, smarter utility conduits to transport water and energy will also be necessary in cities of ultra-high density. Using the volume of underground space to host much of the physical plant of megacities will make the surface areas less congested and more pleasant.
The implications of building upwards and downwards, employing novel technologies ranging from enhanced geothermal systems to high-rise farming, hold forth not only the oft-wished for promise of attracting humanity’s billions off the land and into densely populated megacities, but also the promise of cities that live nearly off the grid, cities that may, despite their magnitude, require very little from the rest of the world.
This is the optimistic scenario that is altogether feasible. A planet of megacities that might actually export power and food, along with culture and technology, in exchange for raw materials. There are many paths from here to there, but none of them are easy even with abundant and clean fossil fuel remaining an unhindered and major part of global energy supply until replacement energy technologies are fully competitive at scale.
Global prosperity and peace, glorious destination megacities, abundant water and food, voluntary population stabilization, asteroid mining, restored wilderness, and plenty of open land for those who still want to live under a big sky – all of this could be just around the corner.
Edward Ring is a co-founder of the California Policy Center and served as its first president.