Since Wackernagel and Rees introduced the idea of the ecological footprint in 1992 [28, 21, 27], it has been established as a concept of measuring the sustainability of nations, regions, cities, individuals, industrial goods, etc. Today, the ecological footprint is seen as a measure of demand of natural resources with respect to the regeneration capacity of the Earth. Since the findings of Rees [21], quite sophisticated calculation procedures have been defined [15]. They are based on the generic idea that every impact on earth—which is a closed system—can be converted to an amount of biologically productive area. To allow comparability, they are expressed in global hectares (gha), which represent the average spatial productivity worldwide.