In general, a carrying capacity oriented index like the EF or the
SPI is calculated by identifying certain consumption and multiplying
it with a specified land need index. The land need index
represents the amount of land needed to provide for the respective
consumption per year, e.g. in biomass energy consumption the
amount of land needed to produce 1 MJ of energy per year [m2.a/
MJ] (Stöglehner, 2003). The overall footprint of the population
within a given region is calculated by summing up the eco-land
equivalent material or energy consumption for each major
consumption type. By introducing a carrying capacity oriented
calculation method, value judgements have to be made to implement
land need indices. In order to guarantee transparency in our
methodological approach, we lay out the underlying values that are
derived from the concept of sustainable development (United
Nations, 1992) following the interpretation of “strong sustainability”
(Mayer, 2008) acknowledging that the economy is
a subsystem of society and society is a subsystem of the environment.
The subsystems cannot “grow bigger” than the overall
system without damaging the whole system (Birkmann, 2000).