ABSTRACT
WBGU derives a sustainable corridor for bioenergy use primarily from its own guard rail concept (WBGU, 1995b). The Council uses the term ‘guard rail’ to refer to quantitatively defined damage limits, exceedance of which is intolerable or would have catastrophic consequences. An example of such a limit is an increase in global mean temperature by more than 2°C from pre-industrial levels. Sustainable development pathways follow trajectories that lie within the range delimited by the guard rails. This approach is based on the realization that it is virtually impossible to define a desirable, sustainable future in positive terms – that is, in terms of a goal or state to be achieved. It is, however, possible to agree on the boundaries of a range that is acknowledged to be unacceptable and that society seeks to avoid. If the system is on course for collision with a guard rail, steps should be taken to change direction.
