Modelling invasive alien plant species : fuzzy based uncertainty Modelling Invasive Alien Plant Species: Fuzzy Based Uncertainty presents applications of different fuzzy theory techniques in developing risk assessment models for invasive alien plant species whose introduction and spread outside their natural range threatens biodiversity. Invasion risk of species is expressed by biological traits which would be considered as the risk factors accompanied with uncertainty and imprecision. It considers both quantitative and qualitative input in modelling the invasive risk by incorporating different mathematical models based on fuzzy set theory operators interval methods and fuzzy linguistic operators. The proposed models can be applied for investigating risk of invasive alien plant species in different regions