page_title: Amaranthus brownii
section_title: Distribution and habitat
hierarchical_section_title: Amaranthus brownii / Distribution and habitat
caption_attribution_description: Deutsch: Luftaufnahme der Insel Nihoa, Nordwestliche Hawaii-Inseln English: Aerial view of Nihoa Island, Northwestern Hawaiian Islands Français&#160;: Photo vue aérienne d'île de Nihoa, îles Hawaïennes sous le vent
context_page_description: Amaranthus brownii was an annual herb in the family Amaranthaceae. The plant was found only on the small island of Nihoa in the Northwestern Hawaiian Islands, growing on rocky outcrops at altitudes of 120–215 m. It was one of nine species of Amaranthus in the Hawaiian Islands, but was the only endemic Hawaiian species of the genus. It was first discovered during the Tanager Expedition in 1923 by botanist Edward Leonard Caum. A. brownii differed from other Hawaiian species of Amaranthus with its spineless leaf axils, linear leaves, and indehiscent fruits.
  It was one of 26 vascular plants on Nihoa, 17 of which are indigenous, six alien, and three endemic only to Nihoa, including A. brownii, the Nihoa fan palm or loulu, and the Nihoa carnation. A. brownii was considered the rarest plant on Nihoa and had not been directly observed on the island since 1983, and is now considered to be extinct. Past expeditions collected plant samples and seeds, but no specimens managed to survive ex-situ conservation efforts outside of its native habitat. There are no known plants or seeds from A. brownii in any botanical garden.
context_section_description: Amaranthus brownii had a very limited range; it was found only on the 0.65 km² (0.25 sq mi) island of Nihoa, located 275 km (171 mi) northwest of Kauai. It is thought that this endemic plant had probably always been rare and restricted to Nihoa. Its former habitat is managed by the United States Fish and Wildlife Service and protected as part of the Hawaiian Islands National Wildlife Refuge in the Papahānaumokuākea Marine National Monument. A. brownii was one of three endemic and endangered species only found on Nihoa, along with the Nihoa fan palm (Pritchardia remota) and the Nihoa carnation (Schiedea verticillata). At least nine other native plant species can be found in its habitat, including Hawaiian goosefoot (Chenopodium oahuense), lovegrass (Eragrostis variablis), koali ʻawa (Ipomoea indica), goat's foot (Ipomoea pes-caprae subsp. brasiliensis), Panicum torridum, naupakas (Scaevola sericea), Sicyos pachycarpus, ʻilima (Sida fallax), and Nelson's horsenettle (Solanum nelsonii).
  The plant grew during the moist, winter season from December through July in Nihoa's coastal dry shrubland habitat in shallow soil on rocky outcrops in exposed areas between 120–215 m (394–705 ft). At the time of its discovery in 1923, botanists first observed the plant growing in great quantity on the ridges towards Miller Peak and on eastern ridges of the island. Expeditions in the early and mid-1960s failed to identify any specimens, but in 1969, ethnobotanist Douglas E. Yen of the Bishop Museum collected specimens near Miller Peak. Derral R. Herbst and Wayne Takeuchi of the FWS collected the last known specimen on July 27, 1980. Carl C. Christensen also visited Nihoa in 1980 to reevaluate endemic species last observed on the Tanager Expedition. Sheila Conant and Mark S. Collins visited Nihoa in 1980 as well; Conant returned twice in 1981, first with Mark J. Rauzon and later with Audrey L. Newman. In 1983, Conant visited the island with Wayne C. Gagné. Conant found A. brownii growing on the island in 1981 and 1983, by which time only two populations of 35 plants were thought to exist: 23 plants were found near Miller Peak and 12 plants in Middle Valley. The two plant populations were separated by a distance of approximately 0.4 km (0.25 mi).
  Prehistoric Polynesian habitation on Nihoa may have initially led to a decrease in the plant population of A. brownii. Major threats to the plant included invasive species, fire, and hybridization with other Amaranthus species. Inbreeding was a serious threat, as the small plant population must reproduce within its own circle resulting in genetic defects. A. brownii was also forced to compete with the non-native weed (Portulaca oleracea), the plant's main alien species threat. In 2002 and 2004, the invasive gray bird grasshopper (Schistocerca nitens) presented an even larger threat to A. brownii. First recorded on the island in 1977, the increasing population density of gray bird grasshoppers led to massive defoliation on the island, leaving A. brownii at greater risk of predation. In 2004 alone, an estimated 400,000 gray bird grasshoppers destroyed almost 90% of the vegetation on Nihoa. All these threats may have contributed to its ultimate extinction.
caption: Aerial view of Nihoa. In 1983, W. Gagné recorded 12 plants living on the island.[10]
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