Ecological Risk Screening Summary - Reed Mannagrass (Glyceria maxima) - High Risk

Species that are considered high risk have a well-documented history of invasiveness in at least one location globally and are of establishment concern for the contiguous United States based on a climate matching analysis.

Glyceria maxima, Reed Mannagrass, is a plant that is native to the north temperate zone of Europe and Asia. It has become established in a number of countries around the world including the United States. Glyceria maxima has broad climate suitability and multiple modes of reproduction. The History of Invasiveness for Glyceria maxima is classified as High. The plant has been introduced as grazing forage for livestock but has also caused livestock deaths through cyanide poisoning in Australia and New Zealand. This species directly impacts a native species of concern in New Zealand by destroying the microhabitat needed for successful reproduction. Monocultures of G. maxima have negative impacts on insect and bird diversity and ecosystem services, including water flows. Glyceria maxima is regulated in the states of Connecticut, Massachusetts, Maine, New Hampshire, New York, Washington, and Wisconsin. The climate matching analysis for the contiguous United States indicates establishment concern for this species. The climate match for the majority of the contiguous United States is high with only parts of the central Gulf Coast, the Southwest, and small areas in the Western Mountains having low climate matches. The Certainty of Assessment for this ERSS is classified as High due to sufficient information available from reliable sources on the biology, distribution, invasion history, and impacts of introduction of this species. The Overall Risk Assessment Category for Glyceria maxima in the contiguous United States is High.