Advantages and Dangers of the Ranking Approach

A major advantage of the categorization and ranking approach described above is the intrinsic simplicity of the approach. Few assumptions are needed, 

In a properly constructed ranking analysis, each assumption has to be documented. A sensitivity analysis can be performed, investigating the impacts of ranking decisions upon the final outcome. Uncertainties can also be quantified and data gathered to make the ranking more based upon data-derived rules. 

Another advantage of this technique is that it is consistent with methods that rely upon the formation of rules derived from data that may lead to more consistent and accurate rank predictions. In this manner it is a direct descended of the nonmetric clustering approach described in Chapter 11. 

Another drawback is the reliance upon a ranking system without at least some confirmation of the risks projected. The rankings are effectively hypotheses that are testable. There cannot be a substitute for testing the reality of an analysis using a variety of techniques. These methods can include comparison of field concentrations of stressors to benchmark concentrations, analysis of biomonitoring data, and the use of field collections to examine community structure and dynamics. 

There has been progress in establishing protocols for confirming risks or at least the likelihood that a cause-effect relationship may exist. Two of the methods are the use of specific criteria for the establishment of causation, and the other is the weight of evidence (WoE) approach. 

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