Species that are considered high risk have a well-documented history of invasiveness in at least one location globally, and a high or medium climate match to the contiguous United States.
The history of invasiveness for Butomus umbellatus is high. B. umbellatus has been introduced in many parts of the world as an ornamental. Once established, the species can displace native plants forming dense aggregations that inhibit water flows which effects recreation, irrigation, and native plant growth. The climate match is high. Much of the contiguous United States has a climate that could support this species which is already present in many northern areas. The certainty of assessment is medium. The overall risk assessment category is high.
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High Risk
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