Food & Water
According to Joel E. Cohen, there is enough grain grown on earth to feed 10 billion vegetarians. But much of it is being fed to cattle, which are eaten by the world’s wealthy.
There may be enough acreage already planted to keep the planet fed forever, because 10 billion humans is roughly where the UN predicts that the world population will plateau in 2060. (In the late 1980s, Brown University’s World Hunger Program calculated that the world then could sustain 5.5 billion vegetarians, 3.7 billion South Americans or 2.8 billion meat-loving North Americans.)
The world’s current population, with 1,000 square feet of living space each, could fit into Texas.
A water shortage that raised prices to around $150 would make it profitable to build pipes from the polar icecaps, or desalinate seawater, as the Saudis already do.