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.
Egeria densa is an aquatic macrophyte that has spread from its native range in Brazil, Argentina and Uruguay through the aquarium trade. Like other invasive plants, this species is prolific with broad physiological tolerances. A number of U.S. states have restricted the species as a noxious weed. The history of invasiveness is high. It is now established in countries around the world. Invasive populations have had negative impacts on biodiversity, hydro energy infrastructure, and have even been implicated as contributing to a human death. Climate matching indicated the contiguous United States has a high climate match. There are established E. densa populations across most of the country but primarily concentrated along the coasts. The certainty of assessment is high. The overall risk assessment category is high.