Silverswords: Hawaii’s iconic ‘ahinahina
The number of ‘ahinahina, or silverswords, at Haleakala Crater has declined by nearly 60 percent over the last two decades, experts said, and scientists are studying whether the decline could be linked to climate change.
Two mobile greenhouses have been stationed near visitors centers within Haleakala National Park since last year, which have allowed a small team of researchers to conduct drought-tolerance tests on ‘ahinahina seedlings at the lower and upper bounds of where the plants are found along Haleakala – the bottom of the crater (7,000-feet elevation) and near the summit (10,000 feet above sea level). The 12-month study is expected to finish next month.
“Everybody thinks of climate change as something that’s going to happen in the future, but what we’re seeing more and more is that we’re already seeing the effects of climate change,” said Paul Krushelnycky, a research scientist with University of Hawaii-Manoa’s College of Tropical Agriculture and Human Resources.
The decline in Haleakala’s iconic and federally protected silversword is an example of that, Krushelnycky said.
According to a 2013 census, there are about 45,000 ‘ahinahina left on Haleakala, but Krushelnycky said that based on data stemming back to the 1980s, that number has been on a downward trend since the 1990s.
At the same time, data gathered at the park over the last several decades also shows that average temperatures have been creeping upward, with less rainfall recorded.
“As scientists, we try to be careful, so I don’t want to say we’re 100 percent sure (plant) mortality is because of climate change, but it’s becoming harder and harder to provide an alternate explanation for what we’re seeing,” Krushelnycky said.
But the number of park visitors has also increased greatly in the last couple of decades; the park now attracts between 1 million and 2 million guests each year.
When asked whether that correlation could explain this drastic decline, Krushelnycky said it was unlikely.
“The only way that visitors could be impacting (‘ahinahina) is by stepping on the plants. That might be occurring inside or around the trail, but data we’ve collected to estimate the amount of decline are in areas that are all over the crater, most of them removed from places where people go,” Krushelnycky said, adding that many of dead plants he’s monitored did not show any signs of being trampled. “There was also no evidence of plant disease or pests, so we pretty much narrowed it down to water stress related to climate change.”
The ‘ahinahina decline has been stronger at lower elevations, Krushelnycky said, which could be explained by a number of theories. First, lower elevations are usually hotter and drier during drought conditions, thereby subjecting plants to greater water stress. But another theory is that there are inherent differences between ‘ahinahina at higher elevations and those at lower elevations, including possibly a stronger tolerance to drought conditions. If that is the case, researchers could, in the future, look at cross-breeding plants to build tolerance or outplanting certain plants to certain areas that correspond to their drought-tolerance levels.
Much of the ‘ahinahina study is as much about public outreach as it is about gathering data. Jesse Felts, a climate change intern who’s been working with Krushelnycky on the ‘ahinahina project for the past year, hosts workshops for students and teachers as part of his internship.
“A lot of people don’t understand exactly what climate change is,” Felts said. “A lot of people think it’s just temperatures getting warmer or it’s just sea level rise or more carbon in the atmosphere, but it has implications that affect every facet of our lives . . . from the reefs to the streams to the forests to iconic species like the silversword.”
The two mobile greenhouses have been stationed visibly in front of visitor centers so that guests could come up and see the experiments through clear plastic panels or read interpretive signs posted outside of the greenhouse. Oftentimes, guests will knock on the greenhouse to ask researchers about their work.
Haleakala National Park spokeswoman Polly Angelakis said that the project has helped hundreds if not thousands of people become aware of climate change and its widespread effects.
“The Haleakala ‘ahinahina is only found here, nowhere else on the planet,” Angelakis said of the threatened species. “They are the iconic species when people think about Haleakala, and if they become extinct here they’re gone from the planet.”
While the species of silversword found atop Haleakala is indeed endemic to the park, scientists said that other species of the plant can be found in the West Maui Mountains, and atop Mauna Kea and Mauna Loa on Hawaii Island.
But the Haleakala ‘ahinahina has the largest and most easily accessible population of all the species found in Hawaii, and it’s also one of the most recognizable, which drove now-retired research biologist Lloyd Loope to begin studying the plants when he joined the National Park Service in 1980.
Loope and other scientists established 11 ‘ahinahina plots on the sides of cinder cones in Haleakala Crater and counted them every fall. The plants were doing fine through the early 1990s but started declining sharply in the mid-1990s, Loope said.
“After 10 years, we realized that a dramatic change had apparently taken place and we began to suspect global climate change,” Loope said. When the Makawao resident retired from his job with the U.S. Geological Survey in 2012, he passed on his ‘ahinahina research to colleague Krushelnycky.
Last month, park officials reported an unusual abundance of ‘ahinahina in bloom, but that doesn’t necessarily mean the park will see more plants growing next year. Loope said most of the seedlings die shortly after being released and never grow into full plants. Additionally, ‘ahinahina flower only once before they die.
On average, ‘ahinahina can live between 45 and 50 years before they flower, though data suggest some may live up to 90 years, researchers said.
The ‘ahinahina project is a collaboration between UH-Manoa and the national park. It is funded by the National Park Service, the Pacific Islands Climate Science Center and the Hau’oli Mau Loa Foundation.
* Eileen Chao can be reached at firstname.lastname@example.org.