Let’s imagine that we are going to build a new one-million-person city, and operate it using the new economic system described in this book. In addition, our new city will largely be independent and self-contained in terms of food, energy, industrial production, and so on. How much land does this city need?
It is certainly possible to build a big city quickly. It has happened in China multiple times. The city of Shenzhen grew from 30,000 to 10 million people over the course of 30 years [ref]. And Shenzhen produces the majority of the world’s electronics – just this one city produces 90% of all of the electronics used across the planet. There is no question that this can be done.
For the sake of this chapter, let’s assume that one million people is the right number, and understand that it is easy to extrapolate to larger sizes. And let’s assume that we are going to run at a steady-state population of one million (i.e. the population runs at replacement-rate fertility [ref][ref]). So we ask: How much land will a one million-person city require?
Let’s take it step by step…
We discussed housing in Chapter 18. The amount of space needed for housing really depends on how we choose to house people. At 10 people per acre for housing, we need 100,000 acres, or 160 square miles. At 25 people per acre, we need about 40,000 acres, or 62 square miles.
On the other hand, by building large, tall buildings, we could house everyone on much tinier amounts of land. Ten square miles could be sufficient to house the whole million-person population, depending on how much square footage each person is given for housing.
So there is a range. At its most spread out, with suburban-style single family dwellings and a picket fence around each one, maybe 200 square miles are necessary for housing one million people. This option also maximizes the infrastructure costs for things like water, sewer, electricity, Internet, transportation, and so on because everyone is so spread out. On the other end of the spectrum, at its most compact, the city takes ten square miles to house one million people. Let’s pick somewhere in the middle for now, and assume we will house everyone in 100 square miles.
How much space should we dedicate to parks and similar places of recreation? Our city’s residents would like to take a walk, hike a trail, play some softball, ride a bike, etc.
Central Park in New York City is one model to follow. Central Park is interesting because it has several different regions. In the southern part of the park, things tend to be manicured. In the northern part, things are more foresty and wild. Central Park receives about 40 million visitors a year and consumes 1.4 square miles of land.
If we assume that we 10X Central Park, so everyone in our city can visit a park every day, we would have far more park space than the average American city, but note that this park space only consumes15 square miles.
Think about where you are living right now. Chances are that your housing in intermixed in a residential zone that includes a lot of other stuff: retail stores, restaurants, gas stations, etc., along with all of their parking lots. This stuff can take up a lot of space. If the housing is taking up 100 square miles, it is easy to imagine another 10 square miles for retail, restaurants, schools, hospitals, etc. But it really depends. What if our new city has no need for retail space because everything comes via Internet shopping? And our new city will handle all transportation publicly (because private cars for every resident is an incredibly inefficient way to handle transportation), which eliminates the need for customer parking lots. For now, assume 10 square miles for retail and other civic structures.
We can use normal dirt farming for staples like wheat and potatoes, and then advanced greenhouses for vegetables. If we assume that there is a wide variety of food available for everyone, then perhaps we need a quarter of an acre per resident for farming. This means 250,000 acres, or 390 square miles, of farmland.
One thing that could change this estimate is meat. Livestock can consume a great deal of food to produce meat, and the number varies by the animal:
The efficiency with which various animals convert grain into protein varies widely. With cattle in feedlots, it takes roughly 7 kilograms of grain to produce a 1-kilogram gain in live weight. For pork, the figure is close to 4 kilograms of grain per kilogram of weight gain, for poultry it is just over 2, and for herbivorous species of farmed fish (such as carp, tilapia, and catfish), it is less than 2. [ref]
The point is that if everyone wants to eat a lot of beef, we need to grow a lot more grain to do it. Or we need to give animals space to graze, which requires even more land. In the case of beef, the conversion rate is quite inefficient. Assuming we stick mostly with chickens and fish, then the need for land in the farming sector might head toward 500 square miles. One future technology that will change this equation is cultured meat [ref].
Chances are that our new city will get its power from solar panels. Wind, or even nuclear power, is another option for green power generation.
If we assume solar, we can calculate the energy needs of the new city and determine the amount of land needed. It goes something like this:
- Assume the city needs 20 kilowatt-hours of electricity per person per day. This takes into account all usage – both home and industrial.
- Assume 1,000 watts/square meter of solar radiation [ref]
- Assume solar panels with 20% efficiency [ref]
- Assume 5 hours of usable sunlight per day. [Example: Colorado receives 5.5 kWh/SqMeter/day of sunlight][ref]
- Assume that there is some spacing between panels for maintenance. So a square meter of solar panel actually consumes 2 square meters of land.
- Adding this all up, for one million residents, we need about 20 square miles for solar panels.
Example calculation: If a person uses 20 kilowatt-hours of electricity per day, and a site in Colorado receives an average of 5.5 kWh/SqMeter/day, and solar cells are 20% efficient, then a square meter produces 1.1 kilowatt-hours of electricity per day on average. Each person needs 18 square meters of solar cells, and 36 square meters of land for those solar cells. Multiply by one million people, so 36 million square meters of land are needed. This works out to 13.9 square miles. Round up to 20 square miles to accommodate worst-case latitude possibilities.
The city is going to have a lot of factories because of everything the city needs to manufacture. And factories can tend to be large. Given the number of products we will have to produce, let’s assume about 100 square miles for factory space. See Appendix D for additional information on factories.
What will housing be made of? What about diapers and toilet paper? This is another way of asking: What will be the role of wood products in our new city? If we are using wood products, then our new city needs forest land.
For the sake of the calculation, assume that our new city wants to produce standardized wooden houses of the type found throughout America today. We need about 2,000 board feet of lumber for one 300 square foot house.
A mature pine tree (35 years old) is 15 inches in diameter and 72 feet long. It contains 500 board feet of lumber. If we let it grow 7 more years, it contains about twice that. So if we use trees that are 42 years old, we need 2 trees to build a house. Since we are assuming that houses are replaced every 15 years, and a stand of trees takes 45 years to grow (rounding 42 up to 45 years), we need 6 trees per stand to build a house (assuming no wood at all is recycled when a house is torn down) over the course of 45 years.
A stand might start with 500 trees per acre and get thinned down to 250 that are harvested at age 45. That means that each acre of trees yields approximately 40 houses worth of trees. There are one million houses, so we need 24,000 acres, or roughly 40 square miles of trees, just to handle housing construction.
If we round this up to 100 square miles of forest, there would be two advantages: 1) There would be plenty of wood for all kinds of common paper products like toilet paper and diapers, and 2) people who don’t like crowds would have a big, quiet place to go when they need a break.
Adding it all up
If we add all of this up, here is the total land needed for a one million person city:
- Housing: 100 square miles
- Recreation: 15 square miles
- Retail: 10 square miles
- Agriculture: 500 square miles
- Solar panels: 20 square miles
- Industrial: 100 square miles
- Forest: 100 square miles
Our new city therefore requires 845 square miles of land.
How big is 845 square miles? One way to think about it is that it is a piece of land that is 29 miles x 29 miles. Or try this visualization: If you look at the state of Rhode Island on a map, the state of Rhode Island is bigger than the space we need for our new city. Rhode Island covers 1,212 square miles. In other words, if Rhode Island were shaped like a square, Rhode Island would be 35 miles x 35 miles. Rhode Island is a good bit bigger than what we need. We can easily fit our new, stand-alone city for one million people into the state of Rhode Island. What does this look like on a map? Something like this:
Rhode Island is the tiny red square on the upper right. For perspective: The state of Texas could hold 315 or so of these cities. The continental United States, at 3.1 million square miles, could hold 3,600 of these cities (if all of America were flat). Roughly half of Africa could hold the entire world population, because Africa is four times larger than the continental United States.
If we want to minimize the land consumed per city, we could go with much more compact housing, saving 90 square miles. We could eliminate meat, saving 110 square miles or so. Compress a few other things, like the forest area. Now the city can fit in 500 square miles.
One million people fitting in 500 square miles means 2,000 people per square mile. One million people fitting in 1,000 square miles is 1,000 people per square mile.
There are not many places on Earth where a nation is completely independent in terms of food production, energy production, industrial production, etc. But if we want to compare the density of this new city with different places on Earth, several island nations like Puerto Rico, Bermuda and Taiwan have population densities similar to this. Puerto Rico, for example, has 3.4 million people living on 3,515 square miles, or roughly 1,000 people per square mile. [ref]
This analysis certainly prompts some thought. For example, is the idea of fitting one million people into 1,000 square miles of land sustainable? Can planet Earth support this? Here is one way to think about what we are proposing. On planet Earth today there are 57 million square miles of land. It breaks down like this:
“The total land surface area of Earth is about 57,308,738 square miles, of which about 33% is desert and about 24% is mountainous. Subtracting this uninhabitable 57% (32,665,981 mi2) from the total land area leaves 24,642,757 square miles or 15.77 billion acres of habitable land.” [ref]
If we create 7,500 new cities of 1,000 square miles each, this is only 7.5 million square miles of land consumed. This is enough new city space to house the entire human population. 7.5 million square miles is about one third of the available 24.6 million square miles of habitable land. Or it is about half of all the desert land of the planet. This desert land tends to be largely unused. If we can recycle the deserts, we can support every human being on the planet in half of the available desert land.
As soon as we mention “desert”, the immediate thing that pops to mind is “water”. People personally need water to drink, to bathe, to cook, and so on, and water tends to be scarce in a desert.
People also need water for agriculture. There are two possibilities with agricultural water use: An open system and a closed system:
- Either plants will be grown outside, probably with the help of some type of efficient irrigation system in order to conserve water. A great deal of water is lost to evaporation/transpiration and must be replenished [ref].
- Or plants will be grown inside in order to make maximum use of small amounts of water. A great example of what is possible can be seen at places like Thanet Earth [ref], where gigantic hydroponic greenhouses grow prodigious amounts of food: “A staggering 2.5 million tomatoes will be cropped every week of the year; 560,000 peppers and 700,000 cucumbers will be picked weekly… The scale of the £80 million project is mind-boggling. When complete, its seven greenhouses will sprawl across 220 acres of Kent countryside.” [ref] This sounds like a lot of money. But divided across a million people, this is only about $100 per person. And since human time will be abundant and easily allocated to the task in our new city, the construction cost will be even lower. Two or three of these facilities could completely cover all of the fresh produce needed for a million-person city, at a cost of only $300 or so per resident of the new city.
Water typically comes from one of seven sources depending on the location:
- A river
- A natural lake or a lake derived from a dammed river
- An aquifer
- Collected rainwater
- Desalination plants [ref] (the energy required for a reverse-osmosis water treatment plant is something on the order of 10 kilowatt-hours of electricity per cubic meter of water, or 38 watt-hours per gallon [ref])
- A tanker from another place that has plenty of fresh water (an oil tanker holds up to 84 million gallons of oil [ref] and costs just 2 or 3 cents per gallon for transport – the same kind of ship could easily transport water)
- Condensation from the atmosphere [ref]
A typical person in the United States uses about 100 gallons (378 liters) of water per day [ref], but nearly all of this water can be captured in the sewer system, treated and re-used over and over again.
Agriculture is a different story, because the amount of water needed can be immense using “traditional” farming techniques. This article [ref] points out that it takes 287 liters of water to produce 1 kilogram of potatoes (35 gallons per pound) [ref]. Wheat can consume 2 to 10 times more water depending on the growing conditions. Unless water and/or rainfall is plentiful, some sort of greenhouse water reclamation strategy may be needed to conserve water used for agriculture, or different farming practices will be necessary [ref]. See also these links on reviving desert land:
- The Al Baydha Project in Saudi Arabia [ref]
- The accomplishments in Israel [ref]
- The Great Green Wall [ref, ref]
- Prize-winning technology to make the desert bloom [ref]
Assuming that we can make agriculture relatively water-efficient for our city, we need 100 gallons of agricultural water per person per day. This means we need 100 million gallons of fresh water per day. If we derive this water via reverse-osmosis of seawater, it means we need 3.8 kilowatt-hours of electricity per person per day for water production. We have already allocated 20 kilowatt-hours of electricity per person per day (see above), so this is an incremental bump upward to 23.8 kilowatt-hours per day. Let’s round up to 25 kilowatt-hours. This means we need to increase the size of our solar panel farm by 25%, to 25 square miles. It is not a big deal.