© Eric R. Pianka
Humans cannot live without food and water. One third of Earth's surface is desert which supports very few people. People can visit deserts but long-term survival in desert regions is very tenuous. Cities built in deserts like Los Angeles, Las Vegas, Phoenix, and Tuscon, cannot exist without importing water or pumping groundwater out of deep aquifers. Indeed, they all face serious water shortages. Similarly, humans cannot sustain themselves for very long in mountains, though we often visit these regions on a temporary basis. Humans have occupied almost all of Earth's habitable lands.
Some like to assert that everybody on Earth could be fit into the State of Texas, using logic as follows. The area of Texas is about 262,000 mi2. Dividing this figure by the current human population of 7 billion leaves each person with less than 100 square meters, a small plot the size of a big room about 10 m x 10 m. Sounds plausible enough, right? Without going into the fact that almost half the State is desert, notice we have not allowed for any roads, shopping malls, schools, hospitals, football stadiums, prisons, sewage plants, rivers, lakes, reservoirs, golf courses, parks, and what else? How much land does it take to support a human being?
Let's do the math again, but this time for the entire planet. The total land surface area of Earth is about 57,308,738 square miles, of which about 24% is mountainous and about 33% is desert. Subtracting this uninhabitable 57% (32,665,981 mi2) from the total land area leaves 24,642,757 square miles or 15.77 billion acres of habitable land.
Divide this figure by the current human population of 7 billion (that's 7,000 million people!) and you get just under one hectare (2.3 acres) per person. If all the habitable land on Earth were equally distributed among all human beings present on Earth, this is the per capita share of good land per person. Again, however, we have not allowed for any nice amenities such as roads, schools, hospitals, shopping malls, rivers, lakes, reservoirs, parks, golf courses, etc. Even so, could you live on 2.3 acres?
Efforts have been made to estimate the amount of land needed to sustain an average individual human (link). A person living the lifestyle of an average American requires almost 24 acres, ten times the world per capita share. The Shrinking Planet
Bottom Line: For everyone presently on this planet to enjoy the lifestyle of an average American, we would need about ten planet Earths. We have only one. For everyone to live like an American, Earth can only support about one-tenth as many people. To increase the average quality of life, the number of people on Earth must be reduced.
Let's Concentrate the World Population into the USA
Population Impacts on Land, Water, and Food
Diamond: The Worst Mistake Humans Ever Made