Invasive Species Hot Spots in the National Wildlife Refuge System

The Invaders  Melaleuca and Old World climbing fern infest more than 80 percent of the habitat area within Loxahatchee Refuge. At 100,000 acres, it is the worst infestation of these invasive plants in southern Florida.  

The Invaders  The refuge is threatened by an invasive cordgrass, Spartina alterniflora, which rapidly infests intertidal mudflats and salt marshes. Mudflats are crucial habitat for shorebirds, waterfowl, clams, crabs, and oysters. 

The Invaders  Phragmites, or common reed, has infested and degraded more than half of the refuge's valuable marshes. Thriving in habitat disturbed by human activities, Phragmites outcompetes native plants and replaces them with dense, stands unusable as nesting and feeding sites for many bird species.

The Invaders The highly invasive Chinese tallow tree shades out native grasses and transforms grasslands, prairies and brushlands into tallow woodlands. The tallow trees grow virtually anywhere there is moisture in the ground, including dikes, the edges of impoundments, and fields. 

The Invaders  Invasive yellow starthistle rapidly forms dense impenetrable stands, particularly in disturbed areas. Yellow starthistle is best adapted to open grasslands, and able to complete its life cycle earlier than native perennials, allowing it to use up available water and outcompete native plants.

The Invaders  Pepperweed forms a blanket over the ground that shuts out sunlight, and reduces native species' ability to survive. It spreads mainly by underground roots. Infestations degrade and eliminate the plant diversity that many birds and wildlife depend upon for food, cover, and nesting.

The Invaders  Canada thistle, a noxious weed and serious threat to American agriculture, has been spreading rapidly in recent years. Canada thistle thrives in non-forested plant communities such as prairies, barrens, glades, sand dunes, fields and meadows that have been impacted by disturbance.

The Invaders  Saltcedar, an invasive tree species, has taken over approximately 6,000 acres of the 15,000-acre riparian floodplain in Bosque del Apache, and is threatening large tracts of riparian floodplain throughout the Southwest.

The Invaders Nutria, beaver-like rodents native to South America, devastate marshes by digging underneath and overturning marsh plants to feed on their roots. The combined impact of nutria damage with a rising sea level wipes out habitat needed by more than 250 bird species. 

The Invaders Mississippi Sandhill Crane National Wildlife Refuge is threatened by nonnative fire ants, as well as a rapidly spreading nonnative weed called cogon grass. Cogon grass is degrading and destroying the last remaining savannah habitat, the last bastion of the Mississippi Sandhill Crane.