Population Matters

Ehrlich equation

Ehrlich equation

Real sustainability means that activity can continue indefinitely. This was theorised in 1968 by American biologist and educator Paul R. Ehrlich.in his book, The Population Bomb.

The impact of humanity on the environment and the demands that people place on the resources available on the planet can be summarised by what is known as the Ehrlich or IPAT Equation, I=PAT.

I = impact on the environment or demand for resources.

P = population size, A = affluence and T = technology.

Though this isn’t an exact equation in a mathematical sense, it does give an insight into how these factors combine together to define the limits of sustainability.

The two most important conclusions deriving from this relationship are that:

  • the Earth can support only a limited number of people in a sustainable manner; and
  • humanity has a clear choice: between more people with poorer lifestyles and fewer people with a better quality of life.

Read more about sustainability and the Ehrlich Equation.