Switching to numerical scale in marine environmental decision support systems: Fuzzy logic approach

Environmental decision support systems (EDSS) are usually based on environmental models, databases and assessment tools. However, EDSS requires lots of reliable data, which are not readily available, especially information on the distribution of species in marine environments and their dependencies on natural or human pressures. In these cases information is distributed among nominal categories (ranks) which are later used for the decision support. Rules used for assignment into the ranks usually are rough; some of them could be overlapping. But during the decision process the exact rank values are used ignoring the fact that they are derived from the incomplete knowledge. That complicates the comparison of results provided by different cases. In this study a fuzzy logic approach for merging rank and quantitative data with respect to initial accuracy is presented using the example of sensitivity assessment methodology provided by Marine Life Information Network. The proposed approach combines expert knowledge and fuzzy logic methods and provides a possibility to use numerical scales in marine environmental decision support systems, and is a flexible tool for explicit (numerically expressed) sensitivity assessment. This approach can be also applied to other environmental indicators and assessments.