Question: How much of our available land do we use in creating food?
Joel Cohen: Well, the ice-free land of the earth, you know, the world is mostly water, like about 71% water, and 29% is land. Now, some of that land is under ice, Antarctica and Greenland, so let's put that aside. If you're only dealing with the ice-free land, it's about 130 million square kilometers, okay? Of that, humans use 38% for agriculture. So almost two-fifths of the entire surface of the earth is now devoted to making food for you and me, and 6.8 billion other human beings. That's a huge chunk of the earth's surface for humans to be manipulating.
Of that 38%, I'm going to divide it into 2 pieces, 8% and 30%, okay? The 8% grows cereal grains for humans to eat, that go into human mouths—rice, wheat, corn, and then other grains also, okay? The 30% feeds our domestic animals. So the way we use the land, we're using 30% of the entire land area of the earth free of ice to feed our domestic animals. And of the cereals we grow, one-third goes into the mouths of animals and about half goes into human mouths, and about one-sixth goes into the mouths of the machines, our pets, for bio-fuels, and for starches and for other industrial uses.
So we can say that the production of food by humans has had a huge impact on the use of land on the earth, on the extinction of species due to burning of forests and change of grasslands by animals. And if you look at the amount of energy that the domestic animal populations consume, it's about twice that that all humans consume. So even though we consume a lot, our domestic animals consume about twice more.