Ecological Risk Screening Summary - West Indian Marsh Grass (Hymenachne amplexicaulis) - 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.

Hymenachne amplexicaulis, Western Indian Marsh Grass, is a plant that is native from Central Mexico through much of South America. This species is a perennial grass that has been introduced and established populations in the United States, Australia, and southeast Asia. It can outcompete native vegetation due its ability to reproduce quickly and survive in a wide array of conditions. The species also has impacts on native fauna, water flows, and crop economics. The History of Invasiveness for Hymenachne amplexicaulis is classified as High due to the
documentation of negative impacts. The climate matching analysis for the contiguous United States indicates establishment concern for this species. The southeastern United States already has established populations and the climate match for this area was the highest; the climate match was the lowest in the Rocky Mountain Region. The Certainty of Assessment is classified as High due to the quantity and quality of information available regarding the assessment elements. The Overall Risk Assessment Category for Hymenachne amplexicaulis in the contiguous United States is High.