Text by Sarah Ruppenthal | Images by IJfke Ridgley
It’s likely the tiny fern sitting in the greenhouse wouldn’t catch your eye. Standing less than a foot high, with fronds barely reaching six inches in length, it seems unremarkable. But looks can be deceiving, because this little fern is a pretty big deal.
The fern, Athyrium haleakalae, is a newly discovered species that grows in one place on Earth: Haleakalā, its namesake. There is a sole Athyrium haleakalae under study at the Olinda Rare Plant Facility in Upcountry Maui. Its relatives—of which there are estimated to be only 300—remain on the windward side of Haleakalā, within the headwater drainage systems of the Hāna Forest Reserve, Ko‘olau Forest Reserve, and the Kīpahulu District of Haleakalā National Park.
The road to discovering Athyrium haleakalae, Maui’s sixth known single-island endemic fern, was paved in the 1980s, when crews erected a boundary fence to give Haleakalā National Park a reprieve from the feral pigs, goats, cattle, and axis deer that were decimating its native vegetation. This plan paid off, so decades later, the state Department of Land and Natural Resources Division of Forestry and Wildlife, with the help of the East Maui Watershed Partnership and several local, state, and federal partners, set out to build a conservation fence to protect thousands of acres of watershed lands outside of the park, on the windward slopes of Haleakalā—a region so remote that it’s only accessible by helicopter. This project presented a golden opportunity for field biologists and botanists to tag along and conduct surveys in the biologically rich area.
That is what a group of conservationists did four years ago, when they hitched a ride on a helicopter bound for a “fence camp” deep in the recesses of the Hāna Forest Reserve, an uninhabited region replete with thick brush, rugged gulches, large waterfalls, and freshwater streams. The team included Ken Wood of the Kaua‘i-based National Tropical Botanical Garden, Hank Oppenheimer of the Maui Nui Plant Extinction Prevention Program, Keahi Bustamente of the Leeward Haleakalā Watershed Restoration Partnership, and Givonn Osterneck, then a crew leader with the East Maui Watershed Partnership.
That day, as the four men trudged along collecting specimens, tagging plants, and keeping an eye out for invasive species, Wood spotted something peculiar. It was a tiny fern that he initially presumed to be a juvenile plant, given its diminutive size. But upon closer inspection, he noticed that the undersides of its fronds had mature sporangia (the dot-like structures that make and store spores), indicating that the fern had reached adulthood. His curiosity piqued, Wood wandered over to Oppenheimer, who had paused next to a waterfall. “Ken said, ‘Have you been seeing this little fern?’” Oppenheimer recalls. “I pointed at one above me and said, ‘You mean this one?’” Like Wood, Oppenheimer had instinctively lifted a frond to inspect its sporangia. “It was very unusual that it was so small and so fertile,” Oppenheimer says.
Thoroughly puzzled, Wood and Oppenheimer showed the plant to Bustamente and Osterneck, who were equally intrigued. The men began to have an inkling that the fern was one of a kind, but just to be sure, they sent a few samples to Wood’s herbarium on Kaua‘i to be analyzed.
As it turns out, they were right.
A year later, as Wood continued to study the fern samples, Oppenheimer and Bustamente returned to the Hāna Forest Reserve. This time, they were joined by Steve Perlman, then a botanist with the National Tropical Botanical Garden, and now, the statewide specialist for Hawai‘i’s Plant Extinction Prevention Program, to survey a new site not far from the first one. There, they hit the jackpot: Several hundred Athyrium haleakalae clung to the craggy edges of plunge pools and the steep walls of streams. After taking a few samples, the trio carefully extracted one fern to be placed at the Olinda Rare Plant Facility, where it is now closely monitored by a horticulturist.
Then, a few months later, another discovery: A botanist stumbled upon Athyrium haleakalae more than a mile away in a gulch in Haleakalā National Park, which extended the fern’s range.
It became clear that Athyrium haleakalae had a preferred habitat: the vertical walls of streams, particularly near waterfalls. “It loves running water,” Oppenheimer says. Eventually, it was determined that the fern is uniquely adapted to survive in these areas. It is also able to withstand flooding torrents. However, despite its hardy nature, Athyrium haleakalae is considered critically endangered. The fern’s fate hangs in the balance, due to threats to its limited habitat from invasive species—a bleak reminder of the importance of conservation efforts. “The stewardship of our natural resources is an awesome responsibility,” Oppenheimer says. “It’s not lost on us.”
As Athyrium haleakalae was making itself known on Maui, Wood was busy making a case for it to be accepted as a valid species. His hard work paid off: He and Warren Wagner, a research botanist with the Smithsonian Institution, co-authored a paper about Athyrium haleakalae, which was published on PhytoKeys (a peer-reviewed, open-access online journal) in January.
Athyrium haleakalae may have made its public debut as a known species, but Oppenheimer says the research has only just begun. He and his colleagues believe that further studies, especially in similar habitats along adjacent drainage basins, could lead to the discovery of more fern colonies. “We want to know why this plant grows in some places and not others,” Oppenheimer says. “There are many unanswered questions.”
For more information, visit dlnr.hawaii.gov/ecosystems/rare-plants/facilities/olinda.