A possibilistic approach to diverse-stressor aquatic ecological risk estimation

A possibilistic approach to asses's the risk of co-occurring stressors in a n aquatic ecosystem based on the use of fuzzy sets is illustrated at the ha nd of a hypothetical case study. There are two aspects of importance: a fuz zy stressor response relationship where the may have reference to a lower l evel end-point, and a rule-based inference model relating the occurrence of low-level stressors to a high-level ecological goal such as sustainability . The stressor-response is expressed as a conditional possibility. The poss ibility and necessity measures of the disjunctive composition of the stress or-response with the possibility distribution of the stressors yield an est imate of the ecological risk. Such a possibilistic approach may well serve as a screening procedure in multiple stressor resource management when only qualitative risk assessments are needed.