Mathematical risk assessment models for invasive alien plant species: Fuzzy symmetric and asymmetric linguistic scale approach

The main aim of this research is to develop mathematical models to assess the invasive potential of alien plant species. The parameters used to define this potential are expressed as linguistic variables, which are often imprecise and uncertain. To handle this, the fuzzy 2-tuple linguistic technique was applied. Two approaches were introduced: Approach I, based on a symmetrically distributed linguistic term set, and Approach II, based on an asymmetrically distributed term set. In each approach, two models were developed, one assuming all parameters are equally important, and the other assuming unequal importance based on expert opinions. In Model I (Symmetric) and Model III (Asymmetric), all parameters were treated as equally important. In contrast, Model II (Symmetric) and Model IV (Asymmetric) assigned different weights to parameters according to expert input. Among these, Model II (Symmetric with weighted parameters) produced the most significant results: out of 33 invasive species, the predicted risk levels of 17 species matched the expected outcomes. This shows that the Model II (Symmetric with weighted parameters) is a more effective tool for tracking invasive alien plant species than conventional risk assessment methods.