Ecological Risk Screening Summary - Water Soldiers (Stratiotes aloides) - 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.

Stratiotes aloides, Water Soldiers, is a rooted, flowering aquatic plant native to Eurasia. The precise native range of this species is unclear because of its long history of ornamental
cultivation in Europe. S. aloides is still in trade today, including in Canada and possibly the United States. In Canada, it has escaped into the wild and has formed nonnative populations in the Trent and Black rivers in Ontario. An introduction was also reported from New York in 2024, with population status unknown. Introductions and establishment of nonnative populations have resulted in loss of native plant diversity and abundance. S. aloides is regulated in 12 U.S. States. The history of invasiveness for this species is High. The climate matching analysis for the contiguous United States indicates establishment concern for this species. Areas of high match were found in the Northeast, the Great Lakes region, and the Midwest, with isolated pockets in the Great Plains, Rocky Mountains, and Southwest region. The Certainty of Assessment was Medium due to the limited information about negative impacts of introduction of S. aloides and uncertainty in understanding the history of introductions around the species’ native range. The Overall Risk Assessment Category for this species is High.