1968+Paul+Ehrlich+(1968)

=Paul Ralph Ehlrich=

**__ WHAT DID HE DO? __**
Paul Ralph Ehlrich was famous for his warnings about exponential population growth and limited resources. However, Ehlrich was most famous for helping create the formula used to determine the human impact on a society, commonly expressed I=PAT, such that Human Impact (I) on environment equals the product of Population (P), Affluence (A) and Technology (T). This formula is very commonly used by environmental scientists all over the world to find the human impact.

**__WHEN DID HE DO IT?__**
The equation was developed in the 1970's during a debate between Barry Commoner, Paul R. Ehlrich and John Holdren regarding population growth. Commoner argued that human impact on the environment was caused primarily by changes in it production technology following World War II, while Ehlrich argued that all three elements, population, affluence and technology, were important and emphasized in particular the role of population growth.