How to calculate and interpret ecological footprints for long periods of time: the case of Austria 1926-1995

In this paper we present calculations of the ecological footprint (EF) for Austria 1926-1995, based upon three different methodological approaches. Ba sically, EF calculations convert the use of selected materials in a country into the area needed to sustain this material Row. Therefore, biological p roductivity essentially determines the outcome of EF calculations, given a certain pattern of socioeconomic metabolism In most EF calculations publish ed thus far. material and energy flows are converted to area (hectares) usi ng global yields of the respective year. In contrast, we analyze the effect different assumptions on yields have on the results of EF calculations by assuming: (1) constant global yields as of 1995; (2) variable global yields ; and (3) variable local yields for domestic extraction and variable global yields for imported biomass. Fossil-energy footprint is evaluated on the b asis of constant carbon sequestration rates published by Wackernagel. Accor ding to our results different assumptions on yields can influence the resul t of EF calculations by a factor of 2, at least. We conclude that further r esearch is necessary with respect to biomass yields assumed in EF calculati ons. The purpose for which EF calculations;Ire made, and the interpretation of their results, will determine future development of the EF methodology. (C) 2001 Elsevier Science B.V. All rights reserved.