% of the earth covered by man-made

How much of the earth’s surface is covered by man-made features?

This should go in our General Questions forum so I will move it.

After flying from Denver to NYC recently, I’d say that almost the entire Midwest is. At least, every single acre had been dramatically altered by farming. Rather disturbing.

To that I say Feh.

To the OP, how close do you want to get?

The world pop is about 6.2 billion. The percentage of that population which lives in urban areas is around 50%. An average space per person in big US cities looks to be about .2 acres. (An acre is 640x640 feet.)

So, half of 6.2 billion is 3.1 billion. 3.1 billion times .2 is 620 million. So, using my somewhat guessish numbers, that’s 620 million acres for all the cities of the world.

Do you think of everything in cities as a man made features, like lawns? How about agricultural fields?

To that iffy number we need to add non-city man made features, like rural housing and roads. I don’t even want to guess how to take those into account.

A few sources:
http://www.census.gov/cgi-bin/ipc/popclockw
http://www.prb.org/Content/NavigationMenu/PRB/Educators/Human_Population/Urbanization2/Patterns_of_World_Urbanization1.htm

As a way of understanding how little of the earth is covered by man made features one can look at bombing campaigns. The Japanese had the bright idea of dropping bombs tied to weather balloons over the Western US. None of them came close to hitting anything.

An astronomy buff can also help me out with this, but I know that matter from space enters the earth’s atmosphere on a regular basis, but only a tiny fraction of those rocks etc… hit anything of notice.

Depending on who you ask, of the total surface of the Earth:

1 - 2.5% is urban or developed
7 - 10% is arable

Type “percent of the Earth’s surface” into google to get various descriptions and metrics.

Umm not quite. This was actually a very clever idea. Although only 6 people were killed by Japaense balloon bombs and in the end caused only minor damage, this was a successful diversionary tactic. The balloon bombs posed a threat of germ warfare or the possibility of forest fires in the Northwest. Men were staioned to combat fires and fighters were dispatched to shoot down incoming ballons. More on the Japanese Ballon Bombs