1. How to measure sustainability?
The impact on nature by mankind in a particular area can be defined by an indicator that is expressed in hectares (ha) or "number of planet earths" and is called the ecological footprint. In other words the ecological footprint helps to identify the frame in which you should produce the necessary goods (food, energy, ...) for your current lifestyle without causing damage to the environment.
Visit https://wiki.kidzsearch.com/wiki/Ecological_footprint and find out more about the ecological footprint.
What is biocapacity? Check on http://www.yourdictionary.com/biocapacity and/or http://www.greenfacts.org/glossary/abc/biocapacity.htm
Now answer the following questions:
1. What happens if the ecological footprint of a country or city gets bigger than the given biocapacity?
2. What might be consequences of a too large global ecological footprint?