Endangered Species in the Pacific Islands

Recovery Plan for the Mauna Kea Silversword

The Mauna Kea silversword (Argyroxiphium sandwicense ssp. sandwicense), also known as ahinahina in Hawaiian, is a giant rosette plant found only in the alpine areas of Mauna Kea volcano on the island of Hawai‘i. It is very rare event when the plant flowers because individual plants may live from three to over 50 years before flowering! After flowering, the entire plant dies. There are five populations of this rare plant and only one of them is a naturally occurring. There is an estimated total of 8,000 Mauna Kea silverswords, of which only approximately 20 are wild individuals

Mauna Kea Silversword - Photo credit Marie Bruegmann/USFWS

Habitat & Distribution:
The Mauna Kea silversword may have been abundant on all slopes of Mauna Kea between 8,528 and 12,464 feet (2,600 to 3,800) elevations in prehistoric times. The decline of the silversword has been attributed to browsing by feral ungulates, particularly sheep and goats.

Currently, the species has been reduced to a single naturally occurring population in Waipahoehoe Gulch. Between 1973 and 1982, the State of Hawai‘i outplanted silverswords in three exclosures within in the Mauna Kea Forest Reserve near Pu'u Nanaha at 9,086 feet (2,770 meters) elevation, near skyline jeep trail at 9,184 feet (2,970 meters), and at Waipahoehoe Gulch at 9,184 feet (2,800 meters). Additional reintroduction efforts have increased the numbers to approximately 8,000 individuals.

There are several distinct vegetational and climatic zones of Mauna Kea. The upper region from 11,152 to 12,464 feet (3,400 to 3,800 meters) elevation is barren alpine cinder desert. The region between
10,496 to 11,152 feet (3,200 to 3,400 meters) elevation is scrub desert. The region between 9,512 and 10,496 feet (2,900 and 3,200 meters) elevation may have been the area of the original treeline of Mauna Kea but is now alpine scrub. Open mamane (Sophora chrysophylla) forest begins between 8,528 and 9,512 feet (2,600 and 2,900 meters) elevation. This is the region in which both the Pu‘u Nanaha and Waipahoehoe exclosure occur, and is believed to have once supported large populations of Mauna Kea silverswords.

The annual rainfall is between 19.5 and 31.2 inches (500 and 800 millimeters) a year, and annual mean temperature is about 11 degrees celcius.

Recovery:
The Mauna Kea silversword was federally listed as an endangered species on March 21, 1986. In 1909, the upper sloped of Mauna Kea above 7,872 feet (2,400 meters) elevation were declared a Forest Reserve.

The Hawai‘i Department of Land and Natural Resources Division of Forestry and Wildlife has been actively involved in the preservation and restoration of the Mauna Kea silversword by building fences and exclosure, and outplanting. The vegetation of Mauna Kea was not protected until 1935, when a fence was constructed along the lower boundary of the Forest Reserve. Beginning 1974, the silversword seed was germinated and plants were greenhouse-grown at Hawai‘i Volcanoes National Park. Additional reintroduction efforts have increased the number of founders from 2 to 6, and the numbers from 800 to 8,000. The silversword has been extensively studied by scientists at the University of Hawai‘i (Manoa), the University of California (Davis), and the University of British Columbia, Vancouver.

Actions identified in this recovery plan are protecting all remaining plants from feral ungulates, fire and human-related disturbances; monitor and research existing populations; develop and implement a program to enhance regeneration within existing populations; and reestablish the silversword within areas of historic abundance, and verify recovery objectives.