Silverswords being coaxed back from near oblivion
By Christie Wilson
Advertiser Neighbor Island Editor
By Christie Wilson
Silverswords are making a comeback on the slopes of Mauna Loa and Mauna Kea after being reduced to near extinction by grazing animals.
Last winter marked a final full round of plantings of the Mauna Loa or Ka'u silversword, with 1,958 seedlings placed at three sites close to the Mauna Loa Trail by volunteers and Volcano Charter School students led by rare-plant specialist Ane Bakutis.
Since 2000, nearly 13,340 plants propagated at the University of Hawai'i's Volcano Rare Plant Facility have been put into the ground at Hawai'i Volcanoes National Park, according to Rhonda Loh, acting chief of the park's Natural Resources Division.
Visitors to the park already can see some of the plantings along hiking trails, and silverswords should become a more common sight in years to come.
Thousands of silverswords, or 'ahinahina, once ringed Mauna Loa's expansive slopes between the 5,000- and 8,000-foot elevations, but mouflon sheep and goats have gobbled up the giant rosette plants, leaving only three wild populations numbering several hundred individual plants.
"They're like ice cream to sheep," Bakutis said.
A different species of silversword that grows only on Mauna Kea was reduced to even fewer numbers and is the focus of a separate recovery program. Both plants are on the federal endangered species list.
"Silverswords are extremely unique to Hawai'i. You're not going to see these plants anywhere else on Earth. It's something that's our heritage that we need to preserve because it's part of what makes us special," Bakutis said.
Hawai'i silverswords, distinguished by dagger-shaped leaves covered in fine silver hairs, generally live from five to more than 50 years before blooming. They produce a 6-foot flowering stalk that puts out as many as 100,000 seeds. After flowering, the entire plant dies.
The wild population of Mauna Kea silversword at one point dwindled to as few as 32 individual plants growing outside of Waipahoehoe Gulch.
The Mauna Loa silversword declined to 300 individuals at its lowest count. Wild populations were identified on Kahuku Ranch land in Ka'u now owned by Hawai'i Volcanoes National Park, and on wet bog terrain in the state's Upper Waiakea Forest Reserve. A third population of silverswords was discovered in an extremely dry area of Ka'u only in 1996, but the plants were stunted to the size of teacups, Bakutis said.
"You'd have to stumble over them to see them," she said.
Conservation measures have included seed collection and propagation, construction of fenced enclosures, and controlled hunting of sheep and goats. Early propagation efforts suffered from a lack of genetic diversity, but that changed in recent years thanks to a managed propagation program developed by Rob Robichaux of the University of Arizona and the Hawaiian Silversword Foundation and other scientists.
Cuttings from wild populations were taken to the Volcano Rare Plant Facility, where botanists used makeup brushes to artificially pollinate the silverswords to ensure genetic diversity. Bakutis said the cuttings grew quickly under the controlled conditions, flowering within a year.
"We were able to get a lot of viable seeds over three years of flowering thousands of seeds, while in the wild that wouldn't have happened," she said. "They wouldn't have flowered at all and they probably would have died."
The effort produced 11,000 Mauna Kea seedlings and 25,000 Mauna Loa seedlings. Just as exciting to botanists is the nearly 90 percent success rate of the silversword plantings. Bakutis said normally only a third to half of the plants would be expected to survive once transferred to the wild. She's not sure why the silverswords are doing so well, except perhaps because they were planted at the end of a drought period on the Big Island.
IN THE WILD
Last year's acquisition by Hawai'i Volcanoes National Park of the 116,000-acre Kahuku Ranch on the southwest flank of Mauna Loa "opened a huge door for more restoration," Bakutis said.
Loh said the Kahuku silversword population represents the only naturally occurring population in the park.
Additional plantings on a smaller scale are planned for this year. Bakutis said the restoration program won't be judged a complete success until the silverswords reproduce on their own in the wild, which could take several years.
Other partners in the recovery efforts are the U.S. Fish and Wildlife Service and state Division of Forestry and Wildlife.
Reach Christie Wilson at firstname.lastname@example.org.