Human appropriation of natural capital: A comparison of ecological footprint and water footprint analysis

The water footprint concept introduced in 2002 is an analogue of the ecological footprint concept originating from the 1990s. Whereas the ecological footprint (EF) denotes the bioproductive area (hectares) needed to sustain a population, the water footprint (WF) represents the freshwater volume (cubic metres per year) required. In elaborating the WF concept into a well-defined quantifiable indicator, a number of methodological issues have been addressed, with many similarities to the methodological concerns in EF analysis. The methodology followed in WF studies is in most cases analogous to the methodology taken in EF studies, but deviates at some points. Well-reasoned it has been chosen for instance to specifically take into account the source and production circumstances of products and assess the actual water use involved, thus not taking global averages. As a result one can exactly localise the spatial distribution of a water footprint of a country. With respect to the outcome of the footprint estimates, one can see both similarities and striking differences. Food consumption for instance contributes significantly to both the EF and the WF, but mobility (and associated energy use) is very important only for the EF. From a sustainability perspective, the WF of a country tells another story and thus at times will put particular development strategies in a different perspective. The paper reviews and compares the methodologies in EF and WF studies, compares nation's footprint estimates and suggests how the two concepts can be interpreted in relation to one another. The key conclusion is that the two concepts are to be regarded as complementary in the sustainability debate.