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No. 2673:
Population Density

Today, twenty people per square mile. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

I was born on a planet with two billion other people. Now I share Earth with almost sevenbillion others. Together, we occupy about four hundred million square miles of dry land. That means fewer than twenty people (on average) occupy each square mile. That sounds like a lot of room until we realize that life in many huge areas, like the Sahara or Antarctica, has its drawbacks.

1/2 person per foot
Roughly 1/2 person per linear foot

So let's see how all these people are distributed. Look at, say, arid Nevada here in the US. It has over two and a half million people and a population density of 24 people per square mile. That's close to the world average; but 78 percent of those people live in Las Vegas.

Elsewhere, Nevada's density is only five people per square mile; and they almost all live in a few small cities. Take White Pine County. It's seven times the size of Rhode Island. Discounting those who live the county seat of Ely, the rest live on about two square miles each. (Imagine only ten total people living on Manhattan instead of the actual density -- 71,000 per square mile.) 

Our big agricultural states tend to be near the world average or fewer. Nebraska has 23 people per square mile, but South Dakota has only around ten. And the population density in Saskatchewan, Canada's bread basket, is fewer than two people per square mile.

Now, compare those farmlands with our crowded East Coast. Massachusetts and New Jersey hold about a thousand people per square mile. The population densities of England, Korea and Japan, each with a great deal of coastline, are all high -- around 400. 

So what does this tell us? First of all, that inland life becomes less hospitable. Life is hard in Russia, with eight people per square mile, or landlocked Tibet with only two. Of course, the very desirability of coastal regions makes life hard in another way. They become populated beyond the capacity of their adjacent land to sustain them. Bangladesh, with almost three thousand people per square mile, suffers constant food shortages. 

All this evokes the huge question hovering over us. What's Earth's real capacity for housing us? How many people can our environment survive in the long run? The answer depends on the quality of life the population enjoys. For our standard of living the number would probably be a lot fewer than now live. Those conversations carry vast political baggage, and I won't try to argue them here. But I do notice something: Where population density is low, so too is the tendency to worry about such matters.

For the moment, I only ask you to consider the odd way we distribute ourselves on our planet. It's like a cocktail party: Fifty out of sixty people in a large house may always be found in one room or another at any moment. By the same token, I never cease to wonder at the empty vastness of Texas whenever I leave Houston's close-knit camaraderie. 

I'm John Lienhard at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)

The statistical information herein can easily be found in Wikipedia. Simply Google the name of the town or country followed by Wiki to get the data. A sidebar on the right will almost always give the area, population, and population density.

Photos by J. Lienhard. UN population information courtesy of Wikimedia Commons.


World Population
Past world population along with three UN estimates of future population.

dense flight of white pelicans
How many white pelicans per cubic foot of sky?