Panicum niihauense is a rare species of grass

Grass

Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...

 known by the common names lau 'ehu and Niihau panicgrass. It is endemic to Hawaii

Hawaii

Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...

, where it has been found on the islands of Niihau

Niihau

Niihau or Niihau is the seventh largest of the inhabited Hawaiian Islands in the U.S. state of Hawaii, having an area of . Niihau lies southwest of Kauai across the Kaulakahi Channel. Several intermittent playa lakes provide wetland habitats for the Hawaiian Coot, the Black-winged Stilt, and the...

 and Kauai

Kauai

Kauai or Kauai, known as Tauai in the ancient Kaua'i dialect, is geologically the oldest of the main Hawaiian Islands. With an area of , it is the fourth largest of the main islands in the Hawaiian archipelago, and the 21st largest island in the United States. Known also as the "Garden Isle",...

. It has not been observed on Niihau since 1949, and there are fewer than 40 individuals remaining on Kauai, not counting a few individuals that have been deliberately planted in appropriate habitat. The grass is a federally listed endangered species

Endangered species

An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...

 of the United States.

The only naturally occurring specimens of the grass grow in Polihale State Park

Polihale State Park

Polihale State Park is a remote wild beach on the western side of the Hawaiian island of Kauai. It is the western most publicly accessible area in Hawaii, although the privately owned island of Niihau is further west. The beach is miles away from the town of Kekaha, and it can only be reached via...

. There they grow on sand dunes

Dune

In physical geography, a dune is a hill of sand built by wind. Dunes occur in different forms and sizes, formed by interaction with the wind. Most kinds of dunes are longer on the windward side where the sand is pushed up the dune and have a shorter "slip face" in the lee of the wind...

 and they are threatened by the use of off-road vehicle

Off-road vehicle

An off-road vehicle is considered to be any type of vehicle which is capable of driving on and off paved or gravel surface. It is generally characterized by having large tires with deep, open treads, a flexible suspension, or even caterpillar tracks...

s. The habitat is also impacted by the invasion

Invasive species

"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....

 of non-native plants

Introduced species

An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...

 such as Chloris barbata (swollen fingergrass), Leucaena leucocephala (haole koa), Prosopis pallida

Prosopis pallida

Prosopis pallida is a species of mesquite tree. It has the common names kiawe, huarango, and American carob, as well as "bayahonda" and "algarrobo blanco" . It is a thorny legume, native to Colombia, Ecuador and Peru, particularly drier areas near the coast...

(kiawe), Atriplex semicoccata (Australian saltbush), and Verbesina encelioides

Verbesina encelioides

Verbesina encelioides is a flowering plant in the family Asteraceae. The species is native to the United States and Mexico. It is naturalized in the Middle East, Spain, Argentina, Australia and the Pacific islands....

(golden crown-beard).