Can we build a world-wide city?


Doug Kastinen

By the year 2050, it is estimated that two-thirds of the world’s population will live in an urban environment. This will in fact be the end product of a process that has been ongoing for more than the last half-century–the explosive growth of the size and scope of the world’s cities.

Even though modern cities are not megastructures by the strict definition of the word, the need for ever-more careful planning, fully coordinated large-scale construction, and long-range integration of new technologies as these urban centers grow will slowly transform them from haphazard collections of commercial and residential zones into complex, unified structures on a grand scale.

A Megacity is currently defined as any urban center that has a population exceeding ten million inhabitants. This includes not only what’s within the city’s borders proper, but all its closely associated suburbs and urban development zones. These are often described as the city’s ‘greater’ area in popular usage, such as the Greater New York Area or Greater Tokyo Metropolitan Area or similar. As of this writing, there are between 22 and 25 megacities worldwide, depending on the source, and this number is sure to grow substantially in the decades ahead.

Challenges of the Megacity

As urban centers become ever larger, the challenge of the upkeep of their infrastructure as well as maintaining a decent standard of living for its many millions of inhabitants presents a number of technological and logistic hurdles. Prudent long-range planning and a recognition of projected growth would seem to be the major key to both, but in many of these megacities such efforts often fall short. As a result, megacities are often hodge-podges not only of different cultural and economic neighborhoods, but also of uneven zones of decay and urban renewal.

These zones are not always the same from Megacity to Megacity. One Megacity may have a decaying downtown but a thriving rim of suburbs; Another may be seeing a large investment in their central commercial sections while the outlying townships are gripped by overpopulation and decay. Still another may invest most of its building budget in its ports or highway offramps, and let the rest rot.

Waste disposal is often a major issue in these modern megalopolises. The larger the city, the more sewers and sewage treatment plants and landfills are needed to handle the mountains of waste and garbage the city will produce everyday. Today, this is a serious issue with no easy answer; some megacities, especially in the developing world, are beginning to be choked by their own waste. As urban centers keep getting larger, new methods for dealing with this problem will have to be developed.

Also, even though it struck a merely “large” city, the Hurricane Katrina disaster in New Orleans in 2005 shows just how vulnerable modern metropolises can be to unexpected disasters. Megacities, being so much larger and with much higher populations, would be far more vulnerable to an unexpected disaster such as Katrina, especially if they have large percentages of poor inhabitants without the means to evacuate easily. Imagine if the Indian Ocean Tsunami of 2006 had hit a megacity area such as New York or Hong Kong with no warning.

Cities who grow together, stay together

The next step up from today’s megacities are the urban ‘Sprawls’, which assume that the trend toward ever larger megacities continues and even accelerates in the next few decades.

Urban growth reaches a point where megacities relatively nearby to each other begin to merge, so that you could drive from one city center to the other without ever leaving a developed urban environment. For example, Los Angeles, San Francisco, and San Diego would all expand to the point where they become one single megalopolis sprawling for hundreds of miles along the southern California coast. On the east coast of the US, another megalopolis would stretch from Boston to Washington DC and subsume the existing megacities of New York and Philadelphia, resulting in a Sprawl that would be home to over a hundred million inhabitants.

However, it is also assumed that some necessities, such as food, power, clothing and the like, undergo a dramatic downturn in price and uptick in general availability, making life in the Sprawl at least tolerable for the average citizen. These benefits are generally attributed to new technologies creating consumer goods in ever greater quantity, driving the prices down just through sheer volume.

There is some precedence for this trend, as all one has to do is look at how Wal-Mart and its contemporaries have made a number of consumer products dirt-cheap just through its broad distribution and ready availability. Whether this trend will continue into the future remains to be seen.

Tech and food in a Sprawl

The production and distribution of food to the masses of a Sprawl would also have to utilize many new technologies in order to keep up with demand by the megacity’s tens of millions of inhabitants. Fully-automated factory farms, undersea cultivation, and the extreme high prevalence of artificial, pre-processed foods have all been mentioned in various sources. With mere contemporary technology and techniques, the Sprawl would by all rights should be stripping the surrounding farmland bare for hundreds of miles in all directions just in its sheer ravenous demand.

Neighborhoods in any city go through cycles where they decay, revitalize, decay, and revitalize again from decade to decade. Super cities such as a Sprawl will also feel this effect, but on a much larger scale. Entire townships may go through the cycle from decade to decade, affecting tens of millions of citizens. The arcologies that had once been gleaming corporate showcases may become slums twenty years later. Slum areas may be revitalized by corporate and government investment, and undergo renovation that soon turns it into a commercial or industrial center.

Technically, there is no limit to how large cities can grow, as long as basic needs of its population can be met and its infrastructure can be maintained. The next step up from a Sprawl would be urban centers that stretch across entire continents, from one coast to another. There may still be large swaths of wilderness or farmland, but compared to the size of the city itself they at best could be considered parkland.

Cities on such a scale would need many new technologies to keep them viable. They would for example generate enormous amounts of waste and garbage, to the point that it could bury the remaining arable land and even surrounding oceans, dooming the city if not managed prudently. Recycling of every material capable of such would be a necessity, as would renewable and non-polluting sources of energy, such as solar, geothermal, and wind. A city of such a size would take every opportunity conserve its resources without generating potentially hazardous mountains of waste that could choke it and the surrounding ecosystem to death.

Feeding such a huge megalopolis would also be very problematic. Its possible only one such continent city could exist, and the rest of the planet’s landmass could be converted into farmland to support it. For multiple continent cities, however, alternative means of food production would be necessary, many of which were already outlined above for Sprawls.

Continent-sized cities need not necessarily fill up an entire continent. They may have other configurations and geometries that would add up to a continent-sized urban area.

So the question beckons

Can we build a world-wide city?

The surprising answer is maybe, and it would sort of be like Hong Kong spread all over the world. If we assume continued food production improvements as seen over the last 50 years, we could carry around 73 billion people on Earth in 100 years and 640 billion in 200 years. Calculations below.

Note the following:

  • Earth has a land area of 148 million km22.
  • Hong Kong has an area of 1104 km2. Of this total, about 70% (773 km22) is not used by humans (woodlands, farms), and 331 km22 is used by humans or otherwise unusable. The large majority of Hong Kong’s land area is steep tropical vegetation prone to flash flooding and landslides, making it historically difficult to build on. This is why it has not been completely built over, and it is now strictly protected.
  • Hong Kong has a population of 7.188 million. The overall population density is 6510 people per km22, or 21716 people per km22 if you only count the land used by humans.

If Hong Kong was scaled up to the Earth’s total land area, the world would have a population of 970 billion people

Hong Kong is pretty packed, but most people there do have a reasonable quality of life by global standards. But we’re obviously going to run out of food really fast unless we get some magical new farming technologies. So what would be feasible in the reasonable future?

  • About 10.8% of the world’s land area is arable; i.e. 16 million km22.
  • Right now, we have about 0.25 Ha of arable land per capita, worldwide. The world produces around 10% more food than it needs, so in a decade or so we might really need only 0.2 Ha per person using near-future farming technology. Food production efficiency has improved by around 2/3 over the past 50 years – if this trend continues, we might need 0.022 Ha per person in 100 years. In 200 years, it might be down to 0.0025 Ha/person.

This means that if we use all available arable land and assume continued improvements in food production capacity for another century, we could feed around 73 billion people in 100 years and 640 billion people in 200 years.

How much space would we need to house the people? Around 3% of the Earth’s land area is currently used for human infrastructure. If all of this area was converted into Hong Kong, we would have a global population of 29 billion people. If we convert non-arable land into human habitat, we will still have enough land left. And that’s before we start looking to the oceans for large-scale food production and living space, which happens quite a bit in Hong Kong via land reclamation. Some parts of the world’s land mass would be unpopular for humans (extreme altitude or cold or desert), so it is quite likely that extensive land reclamation would occur in desirable climate zones.

In my opinion, this shows that we have massive untapped resources, and that we are not necessarily fucked because more people come along, and our species expands.

We can actually make this work and here is how:

How the Megacity would work

Providing for that many people in terms of just raw food is going to be a serious under-taking – According to FAO, it’s a bare minimum of 0.0002 sq. mile per person to support them. Put another way, to support 531 Billion People, you’d need 106,200,000 square miles of farm land.

Now, you might say “alright, deth, but what about a vertical farm? Surely a vertical farm could help this situation!”. To put it into perspective, the world trade center complex was about 0.538051 square miles of usable floor space. So you’d need around 197,397,769 world trade center-size structures, to produce the bare minimum food assuming fully optimal production and distribution, and a bare-naked standard of living (like, “borderline starvation” standard).

So that’s your baseline for food.

Now, you could assume that technology makes food production more efficient (or take less space, or that all the food production is done in a vast underground area, etc etc). But that’s just the first hurdle to get over.

The main problem isn’t the “durable” stuff (steel, etc) – that’s recyclable and easy to produce. it’s the consumables, the fuels, the foods, the stuff that can’t be recycled or at least not effectively.

The key is that either you need really good waste processing and recycling, or you need really good sources of raw materials. Really good waste processing implies super-science like nanotechnology (or something), while really good sources of raw materials implies super-science spaceships.

some ideas:

  1. Mohovic mines – tapping into the mantle would provide tremendous power and resources, and might be perfectly viable with only mildly advanced technology.
  2. Solar reflectors and beamed power – Perhaps it’s the case that power is beamed in from giant solar reflectors (perhaps with a bigger surface area then the planet!). this would solve many issues.
  3. perhaps they have some kind of hyper-efficient recycling, to the point where every bit of waste is reduced to it’s elemental components, and then remade as needed. If so this solves many, many problems.
  4. Off-world support. this isn’t a panacea, but it’d help lighten the load. In particular, if they had a solid off-world source of fuel or chemicals, it would make the burden on recycling much easier.
  5. Massive use of genetic engineering, with plants being part of the infrastructure of the city (filtering the air, making lots of food, etc).

Overall though, having a huge city that spans the planet is a significant challenge to make believable and realistic.

Editor’s note: 

This article was synthesized from writing found here, here and here.

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