A Hungry World
The human brain, so frail, so perishable, so full of inexhaustible dreams and hungers, burns by the power of the leaf.
-- Loren Eiseley, The Unexpected Universe, 1969
Photographs of Earth taken from the moon make the finite nature of our planet apparent in a way that no writing can. But knowing a vehicle is finite and knowing how many passengers it can carry are not the same thing. What is the actual capacity of Earth to support people? Unfortunately, there is no simple answer to this question, although certain theoretical limits may be calculated. Justus von Liebig's principle, known as the "law of the minimum," says, in essence, that the size of a population or the life of an individual will be limited by whatever requisite of life is in the shortest supply. It is not yet entirely clear what that requisite will be for the human population, which, as we have seen, is growing at an extraordinary rate. But the likeliest factor to limit Earth's capacity to support Homo sapiens is the supply of food, since this supply depends on the availability of so many other essential resources: land, water, nutrients, and energy.
Apart from the limits that may ultimately be posed by Earth's absolute capacity to support human beings, there are gross differences between groups of people with regard to their food supplies. The rich are abundantly, even wastefully fed; the poorest live perpetually on the brink of famine.
This chapter describes the present nutritional status of the human population and the outlook for meeting future