Time to revisit Ehrlich's formula

May 20, 2026

In Julian Cribb’s article, he mentions “…a billion farmers in a billion fields…”. Had there been a mere million farmers in a million fields the story might have been different. Groundwater would have been replenished at a rate faster than it was extracted and the global axis would not have shifted by 78 centimetres.

It is worth revisiting the formula developed by Paul Ehrlich and John Holdren in the early 70s: I=PAT. It says that total environmental impact (I) equals the number of people (P) multiplied by how much each person consumes (A) multiplied by the environmental damage caused per unit of consumption (T).

Thus, numbers aren’t the whole picture when it comes to human impact on the Earth, but they do matter. Were there only two billion people on the Earth, rather than eight billion, we might be living within our means, that is, using the natural resources of the planet at a rate below which they can be regenerated, and producing wastes at a rate below which they can be absorbed.

We urgently need to reduce the size of our population to a quarter of what it is now by voluntary means, before nature does it for us.