By Ugo Bardi (a similar version has appeared in 2017 on “The Journal of Population and Sustainability“)
1. Introduction
“The world has enough for every man’s need, but not enough for every man’s greed.” Gandhi [1]
While Gandhi’s observation about greed remains true even today, it may not be so for the ability of the world to meet every man’s need. Gandhi is reported to have said that in 1947 when the world population was under 2.5 billion, about one-third of the current figure of 7.5 billion. And it keeps growing. Does the world still have enough for every man’s need?
It is a tautology that if there are 7.5 billion people alive on planet earth today there must exist sufficient resources to keep them alive. The problem is for how long: a question rarely taken into account in estimates purportedly aimed at determining the maximum human population that the Earth can support.
The problem of long-term support of a population can be expressed in terms of the concept of “overshoot,” applied first by Jay Forrester in 1972 [2] to social systems. The innovative aspect of Forrester’s idea is that it takes the future into consideration: if there is enough food for 7.5 billion people today, that doesn’t mean that the situation will remain the same in the future.
