Ecological Risk Screening Summary - Nuttall’s Waterweed (Elodea nuttallii) - High Risk

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.

Nuttall’s waterweed (Elodea nuttallii) is a freshwater aquatic plant native to North America, including much of the contiguous United States. The plant grows fully submerged except for the flowers and may create large, dense beds. There is some trade in this plant in the aquarium industry. The history of invasiveness for E. nuttallii is high. It has been introduced around the world and in Alaska. Established populations have had impacts such as changes in species richness, altering invertebrate species composition, out-competing native plants, changes to sediment nutrients, and dense beds can impact flooding and recreational uses of waterways. It may have displaced a population of native fish in Alaska. There are regulations to control the trade of this species in Belgium, Switzerland, Japan, and Australia. The climate match is high for most of the United States, where the plant is native. There were few areas, mainly in the Deep South that did not have a high climate match. The certainty of assessment is high. Quality information is available and the history of invasiveness is documented in peer-reviewed and grey literature. The overall risk assessment category is high.