Ecological footprint

Ecological footprint:
Ecological footprint (EF) analysis measures human demand on nature. It compares human consumption of natural resources with planet Earth's ecological capacity to regenerate them.
It is an estimate of the amount of biologically productive land and sea area needed to regenerate (if possible) the resources a human population consumes and to absorb and render harmless the corresponding waste, given prevailing technology and current understanding.
Using this assessment, it is possible to estimate how many planet Earths it would take to support humanity if everybody lived a given lifestyle.
While the measure is widely used, some also criticize the approach.

From: wikipedia