A Fighting Chance
By Scott Kirkwood 
When European voyagers landed on the shores of the Big Island about 230 years ago, the higher terrain of Mauna Loa volcano was covered by the native Mauna Loa silversword, which numbered in the tens of thousands, if not hundreds of thousands. At that time, the island harbored no terrestrial mammals, save a single native bat species. But Europeans brought with them domesticated animals including pigs, goats, sheep, and cattle—all of which would eventually become wild; years later, mouflon sheep were also introduced as game animals. Soon enough the animals’ browsing, trampling, and uprooting of native plants took its toll on the island’s unique vegetation. Many animals found the nutritious and delicious silversword to be irresistible. Because silverswords had evolved in the absence of ungulates, their unbranched structure and single rosette of leaves made them painfully vulnerable. As a plant that flowers only once in a lifetime, the silversword’s ability to procreate is greatly limited. And it’s not the only plant struggling to survive.
“Even though Hawaii accounts for only about two-tenths of 1 percent of all the land area in the United States, it accounts for more than 35 percent of all federally listed threatened and endangered plants,” says Rob Robichaux, professor of ecology and evolutionary biology at the University of Arizona and president of the Silversword Foundation. “The level of endangerment is so vastly out of proportion to the land area that it dwarfs what’s going on in the rest of the United States. The chief culprits impacting Hawaii’s native plants are nonnative animals, especially ungulates.”
Silverswords are Hawaii’s highest-profile plants because of their striking beauty, which has made them icons much like the saguaro cacti of the Southwest. So the Park Service is working with the Silversword Foundation, the University of Hawaii’s Volcano Rare Plant Facility, and other government agencies to restore the plants to the landscape. By the late 1990s, when the Mauna Loa silversword was in its most precarious state, fewer than 1,000 plants were scattered in three different sites totaling only about three acres. Returning the plants to their former prevalence meant tackling a number of challenges.
“Mauna Loa silverswords live for ten to 50 years, flower once, and then die,” says Tim Tunison, chief of resources management with Hawaii Volcanoes National Park. “As ‘obligate cross-pollinators,’ they require another plant nearby to set their seed—unlike many other plants that can reproduce on their own—which means that if you’re going to recover the species you need large numbers of plants within a short distance of one another.”
To that end, beginning in 1999, botanists gathered seeds from the remaining populations and germinated them in a greenhouse at the Rare Plant Facility. After about six to nine months, the seedlings grew to about four to five inches tall, at which point they were planted on state land and federal land in the national park, a process that continues today.
In the six years since the program began, more than 20,000 seedlings have been planted on Mauna Loa. A startling 70 percent of those plants have survived, yielding nearly 14,000 silverswords, including more than 8,000 within the park itself. In recent years, thousands of seedlings have been flown by helicopter to planting sites within the park, where Park Service worker, students, and other volunteers await with trowels in hand.
Visitors to the park will soon be able to see Mauna Loa silverswords from hiking trails for the first time in decades. As the plants begin to flower in a few years, botanists will collect and spread their seeds in additional sites across the volcano’s slopes, further expanding the scope of the recovery.
“The question often arises, why keep going if we’ve already introduced 20,000 plants, given the large number of other plant species in Hawaii that are also endangered?” says Robichaux. “But our goal is to achieve true recovery for the Mauna Loa silversword—if we can do that, it may improve the prospects for successfully returning many other endangered plants to Hawaii’s landscapes, and that’s what really motivates us.”
Scott Kirkwood is senior editor for National Parks magazine. |
