Bryan Caplan suggests that the world could support a trillion people. I don’t disagree.
Another way to think of his point is to ask just how much of the earth’s land area would be taken up by people, if all of the people on earth lived like the folks in Manhattan do. Manhattan isn’t even nearly the most densely populated area in the world, but I use that example because many of us would not find it intolerable to live in such a place (as I write this from the comforts of a suburban mid-sized city …).
- Earth has 150 million square kilometers of land (this ignores the other 70% that is water).
- The Earth has about 7 billion people
- The population density in Manhattan is 27,257 people/km²
- So, to fit all 7 billion people in a city with the same density as Manhattan would require 7 billion / 27,257 people/km² = 256,815 km²
Taken together, if everyone on earth lived in modern American city, we would only require 0.17% of the total land area on earth! In other words, all of Asia would be empty, all of Africa would be empty, all of Australia would be empty, all of South America would be empty, all of Mexico would be empty, all of Canada would be empty, every island, isthmus, ocean, lake, etc. would be emtpy. All of these people would fit in a square area that is roughly 507 kilometers on each side (about 315 miles).
As a point of comparison, this is about the size of the entire state of Oregon. So if all of the world’s people lived in a Manhattan-like city, not only would every part of the globe be empty, but so would 49 of the 50 American states. Such a population not only would fit in Oregon, but of course could easily fit into Alaska, Texas, California, Montana, New Mexico, Arizona, Nevada or Colorado, and still leave plenty of room for parks and other amenities.
Let’s leave the talk of resources and producing for larger populations for another day, it is not the purpose of this post. But the one thing I would like to point out in addition to the above point that 7 billion people is really not any significant physical challenge in terms of living areas, something about the population discussion always confused me. When you ask people about the Black Plague, or the Spanish Flu, or the prospects of a Bird-Flue pandemic, or Mad Cow pandemic, they always paint horrible pictures of devastation and destruction … because that is true. Losing that many people is horrible in a huge variety of dimensions. If that is the case, then how can it also be true that increases in population are something we should worry about? The two stories just don’t fit together. Like the temperature, and like prices, there is not a “right” population … and just nashing teeth about a population that is too large does not make it a problem. It isn’t.
