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.
The Crested Mosquitofern, Azolla cristata, is a small floating aquatic fern native to North, Central, and South America. This species is native in the United States, however the exact extent of the native range of this species is unclear due the taxonomic confusion associated with the genus Azolla. This fern is a nitrogen fixer and as such has been used in agriculture, particularly in rice production. A. cristata is rarely found in the aquarium and water garden trades. This species has been reported as introduced and established in Canada, India, Japan, South Africa, Mozambique, Portugal, and Italy. Multiple peer-reviewed reports document negative impacts of introduction including forming thick mats, competing with other plants, blocking navigation, and increasing difficulty and costs to commercial fishing. The history of invasiveness is High. The overall climate match to the contiguous United States is High. A majority of high match was found where A. cristata is likely native, in the East and the Southwest. Despite the uncertainty in the taxonomy of the Azolla genus, the certainty of this assessment is High because of clear documentation of negative impacts and because the high climate match likely underestimates true climate match. The overall risk assessment category for Azolla cristata is High.
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High Risk
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