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.
History of invasiveness is high. Arundo donax is established with measurable negative impacts on every continent except Antarctica. This species is already established, with negative impacts, in the southern half of the continental United States. The climate match is 0.885, high. The climate match was very high, as expected when A. donax is already established in a large portion of the country. The climate match does indicate that suitable conditions exist in many parts of the country without current populations of A. donax. The certainty of assessment is high. The overall risk assessment is high. A. donax is already present in the United States and has the potential to spread to the rest of the country. Control, eradication, and remediation efforts can be very costly and are not very effective; further spread of A. donax would have significant economic impacts as well as ecological ones.