The most frequently heard objection to using science to make people live longer is the issue of overpopulation. Our world is totally filled up as it is, right? Well, maybe. Let’s take pause for a moment, and look at a few numbers.
The United States has about 10,000,000 km² of land. The average population density is 30/km². The earth as a whole has about 150,000,000 km² of land and 350,000,000 km² of water, for a total area of roughly 500,000,000 km². The average population density on land is 40/km².
My hometown of Burlingame, CA, a typical suburb, including some very large houses, has an average population density of 2,000/km². The housing unit density is about 1,000/km². It is a calm suburban town, and certainly isn’t overcrowded.
New York City has an average population density of about 10,000/km². While it could be considered somewhat crowded, many people love living there, staying for the entirety of their busy and urban lives. Hong Kong has a population density of about 6,000/km², but despite this, is considered one of the greenest cities in Asia and has devoted 40% of its land to Country Parks and Nature Reserves. The population density of San Francisco is also about 6,000/km², and it is very pleasant to live here.
Population density by country:
So it turns out that if 5% of the United States were converted into urban area with a population density of 6,000/km², and 45% were converted into suburban area with a population density of 2,000/km², with the remaining 50% left for rural area, parks, and farms, there would be enough room for 3 billion in the urban areas, and 9 billion in the suburban areas, for a total population of 12 billion. This is in the US alone. This scheme could be extended to the other countries and continents for a total population of around 100 billion. Everything between the Arctic and Antarctic circles are potential targets for colonization. This is about 130,000,000 km² of land area (the circumpolar regions have about 20,000,000 km² of land).
Five primary obstacles to this 100 billion-person population scheme are colonizing the deserts, colonizing the highlands, providing energy, food, and disposal of waste.
colonizing the deserts: primarily a matter of air conditioning/heating and water sources, which can also be used to grow abundant plant life. To decrease the intensity of sunlight, dozen-square-kilometer sunshades can be deployed a few km above the ground in urban areas, held aloft with solar-powered airships. For heating during the night, grilles placed beneath the streets could radiate energy gathered during the day, warm enough to create a temperate atmosphere but not so hot as to create a fire hazard. Desalinization plants can produce fresh water in gigantic quantities, to serve the needs of billions of desert-dwellers. Including agricultural and industrial uses, the average person needs about 120,000 litres of water per year, which is 12 cubic meters of water. The world’s largest desalinization plant in Ashkelon, Israel, is capable of producing 100 million cubic meters of water per year, enough for over 8,000,000 people. Drilling down to the water table could provide similarly abundant sources of fresh water. The only problem remaining would be the sandstorms, which people could endure either by wearing adequate masks or going inside when they occur.
colonizing the highlands: people assume this is impossible, because there aren’t many roads there already. But the reason there aren’t many people living there is because few roads go there, and few roads go there because few people live there. Chicken and egg problem. To eliminate this, we switch to personal flying machines, on their way to general affordability by the late-10s. Terraces can be created with simple dynamite. For altitude problems, you get injected with respirocytes, which we may see by the 2030s. As artificial red bloods cells, these simple diamond spheres will be capable of holding 236 times the oxygen per unit volume as their biological equivalents. Not only will you will able to breathe at very high altitudes, you’ll be able to sprint at high altitudes and hold your breath for minutes at a time without incident. Abundant tunneling through the mountains could also make them very fun and spacious place to live. Think of the part during Lord of the Rings when they’re wandering through the mountain caverns, but well-lit and filled with plants and animals that thrive under artificial light. Modern-day drilling techniques can remove ~50,000 tonnes of earth per day.
providing energy for 100 billion people requires different technology than our current fossil-fuel-based regime. The thorium fuel cycle, which could be implemented with current reactors, eliminates both nuclear proliferation and waste dangers, while costing much less than a uranium fuel cycle. Nuclear fusion, while it could take a few more decades to go commercial, will provide energy dozens or hundreds of times more abundant than fission reactors for less cost, using deutrium extracted from water for fuel. A kilogram of deutrium can produce a hundred million kilowatt hours of power. In the longer term, Helium-3 can be harvested from the moon, which provides much greater power output than deutrium. Chemist Ouyang Ziyuan from the Chinese Academy of Sciences, leader of the Chinese Lunar Exploration Program, is making the mining of Helium-3 a major goal. He is quoted as saying, “each year three space shuttle missions could bring enough fuel for all human beings across the world.” The efficiency of photovoltaic panels is increasing, year by year, while manufacturing costs are steadily decreasing. Arrays of hundred-kilometer-wide solar panels put in geosynchronous orbit will give us enough energy to boil all the oceans in the world, if we wanted to.
to provide food, we can exploit all of the world’s arable land, about 21% of all land mass, or 31,000,000 km². We should also start thinking in three dimensions rather than just two. Vertical farming will provide us with more food than we could possibly eat, even if there were a trillion of us. Terraforming Mars and Venus into farming planets will be entirely unnecessary. We can build oceanic cities that manufacture all types of seafood cheaply, including the super-nutritional algae spirulina, which we can process into a variety of textures. Marshall T. Savage describes this process in detail in his book The Millenial Project. Dr. Martin Schreibman of Brooklyn College has been in national media in the past few months for his efforts to encourage urban fish farming, where fish are kept in carefully-regulated tanks.
disposal of waste: we will genetically engineer bacteria to break down anything organic into mineral constituents. The “principle of microbial infallability“, commonly accepted across university biology departments, asserts that there is truly no biomatter that some microbe cannot consume. It’s just a matter of diligently determining which microbes can break down which compounds, and setting them to work. For artificial compounds such as plastics, we can incinerate them in gigantic sealed autoclaves, burying the ash in km-deep caverns carved out for the purpose, or, more simply, only produce recyclable plastics and ensure that the recycling process is as efficient and waste-free as possible. For manufacturing pollution, we’ll need to employ nanotechnology and bottom-up manufacturing techniques to ensure that our products are created without releasing waste into the environment. It can be done – chemists regularly oversee reactions with no byproducts, and with positional control over our atoms in our manufacturing economy, we will make certain that none go to waste.
The above is just an outline to buy us some time before we really do fill things up. But current trends are hopeful: when women are educated and contraceptives are made available to them, the birth rate plummets. The Vatican cannot hold back the pill for long.
The above image shows that in many developed countries, the birth rate is less than 1%/year and is sometimes even negative. As the death rate decreases, the birth rate will need to decrease in synch to preserve minimal population growth. I think this is doable, and we will probably be able to decrease the world population doubling rate from once every 25 years to about once every 50 years, and then possibly once every 100 years. For those who want to breed prodigously, there is always the rest of the solar system, which has the resources to support approximately 10^25 humans, by my estimate. Nick Bostrom points out that our local supercluster could support around 10^38 individuals.
In summary, there is plenty of room for everybody.