flickr/David Eickhoff

KAUAI, Hawaii—When botanist Steven Perlman first started working with the Brighamia insignis, a critically endangered Hawaiian flower species, there were still several hundred of them left in the wild.

“Right now we think there’s one plant left,” said Perlman, who now works in the Plant Extinction Prevention Program, or PEPP, at Kauai’s National Tropical Botanical Garden (NTBG).

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Perlman can often be found rappelling down cliffs, hiking deep in forests, or roping across waterfalls searching for the most endangered native plants in Hawaii.

Some species, like Brighamia insignis, are only found on steep cliffs because those are the places that invasive predators can’t reach.

“We’ve helicoptered around Kauai, looked with binoculars, went up and down the cliffs in ropes looking, but there’s just one plant left,” Perlman said.

“They’re really spectacular,” Perlman said of the long, tubular flowers.

Their main pollinator, the green sphinx moth, is so rarely seen now that PEPP had to hike deep into the forest and climb cliffs to hand pollinate the flowers.

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“I’d go and pollinate them on cliffs in areas where it was 1,000 feet down to the sea,” Perlman said.

By cross-pollinating the plants, PEPP was able to retrieve seeds and grow more of the plants. But just when progress was being made, two strong hurricanes in 1982 and 1992 blew most of the remaining Brighamia insignis flowers off the cliff.

Invasive weeds grew back in their place, while goats and insects ate many of the remaining plants and their seeds. The species is now nearly extinct in the wild.

Luckily for the Brighamia insignis, it’s unique flowers caught the attention of gardeners and botanical gardens all over the world, so there are tens of thousands being grown in captivity, Perlman said.

Sadly, the same is not true for most of Hawaii’s endangered native plants.

Brighamia insignis at the United States Botanic Gardens.
Sarah Stierch (CC BY 4.0)

“Hawaii is known as the extinction capital of the U.S. because we have always had a lot of endangered species because of evolution—over 90% of plants in Hawaii are endemic to Hawaii,” Perlman said. Endemic, or native, means they don’t grow in the wild anywhere else.

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“They are unique, and were created over millions of years on islands in the middle of the Pacific Ocean,” Perlman said.

But Hawaii’s biodiversity is under threat.

About 130 of the state's 1,360 native plant species have already gone extinct, Perlman said. One-third of all the plants listed as endangered by the U.S. government are native to Hawaii.

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Part of the threat comes from introduced predators like feral pigs, goats, and deer which eat the plants, and also from invasive plant species that crowd out the native ones.

Additionally, climate change can exacerbate those threats by extending the range of certain invasive species, such as the strawberry guava in Hawaii, said Christian Giardino, a scientist with the Institute of Pacific Islands Forestry of the USDA Forest Service.

“The strawberry guava, a low-elevation tropical equatorial species from Brazil, grows better at low than high elevation,” Giardino said. “Two things happen when we have warming, you expand the potential range for the strawberry guava, they can go higher, and to they increase their water use and for Hawaii especially in the (drier) areas that can be a big deal."

Once established, strawberry guava quickly invades—and eventually dominates—native Hawaiian forests. Shown here, is an aerial view of a strawberry guava invasion in Wao Kele o Puna, on the island of Hawaii.
Photo courtesy of Carnegie Airborne Observatory

Amid threats from climate change and invasive species, PEPP works on all of the Hawaiian islands to preserve native plant species. To qualify for the program, a plant species must have fewer than 50 individuals left in the wild.

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“They are really right at the edge of extinction,” Perlman said. Perlman goes out in the field every week to collect seeds from every known individual of an endangered species. Afterward, they can be grown in nurseries and living collections or stored in a seed bank.

“We get new collections every week,” Dustin Wolkis, seed bank manager at NTBG, said.

At the seed bank, seeds collected by PEPP and other NTBG botanists are analyzed by a team that determines whether and how long they can be stored.

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“Some people think seeds can be stored forever—that’s a fallacy," Wolkis said. "Every seed has an expiration date and we don’t know what that is for a large amount of species."

The seed bank can dry out and freeze some seeds, called orthodox seeds, in large refrigerators, but others can’t be stored at all, Wolkis said. For those species, known as “recalcitrants,” the seeds are germinated and grown in nurseries or living collections.

One of those living collections is NTBG’s Limahuli Garden and Preserve on the north shore of Kauai.

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The garden is working with a plant Perlman had rediscovered after it hadn’t been seen in 60 years—the Cyanea rivularis, a rare flowering plant in the bellflower family.

“There were only eight plants in Kauai where I rediscovered it,” Perlman said. “We had to go on a steep hike and rope over a waterfall to get there—it was a 10-hour hike to get there.”

The team retrieved five seeds, and the plant is now being cultivated as a special project at Limahuli Garden and Preserve.

Lumahuli Garden in Kauai.
Renee Lewis

“This is the end of the pipeline, when we put the plants back into the wild to create a functioning ecosystem,” Kawika Winter, director of Limahuli Garden and Preserve, said.

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Most of the plants Winter works with do well, and there are more success stories than losses, he said. That’s because Winter and others with NTBG have painstakingly removed invasive trees, weeds, and other plants that have crowded out native species.

After invasive plants are removed from an area, native plants can be planted to replace them—everything from the tallest trees to the ferns on the ground, Winter said. Restoration requires a careful balance of canopy in order to let just enough light to the ground to encourage native ground cover and mid-level plants, but not allow invasive weeds to take over.

“Once we’ve restored the native forest structure, we can have those rare plants succeed,” Winter said.

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Preserving native biodiversity is personal for Winter because of his native Hawaiian ancestry.

“In the 21st century we are trying to remain a viable indigenous culture,” Winter said. “For Hawaiian culture, plants are a vehicle for transmitting stories and traditions to the next generation, if the plants go that’s a whole lot of stories lost.”

The fight to save plants is a “fight to save our culture and society,” Winter said.

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Most of the time, endangered plants are not as beautiful as the Brighamia insignis, or as charismatic as some of the endangered animal species that have grabbed media attention. But they do have value, Winter said. Others agreed.

“Plants need a PR firm," said Kieron Suckling, executive director of the Center for Biological Diversity. "I think we could rename them and instead of using the word ‘plants’ we refer to them as what they are—the basis of all life on earth."

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The only thing that doesn’t directly or indirectly eat plants is plants, Suckling said, because they eat the sun.

In a world where one in five plants are at risk of extinction, it’s more important than ever to communicate the threat to plants, what’s at stake, and to direct funding towards preserving them, Suckling said.

While climate change is “increasingly worrisome,” Suckling said that invasive species and loss of habitat were the current drivers of extinction.

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“If we keep going like we’re going, many plants will go extinct long before the impacts of climate change take hold,” Suckling said.

Hawaii is a biodiversity hotspot for the United States, thanks to its isolation. The same is true for Florida and California. Florida because it was never covered by glaciers and California because of its Mediterranean climate and diversity of soil types, Suckling said.

Preserving those areas with multiple conservation strategies is key, according to Suckling.

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One method is managing the land to remove or prevent invasive species from colonizing areas so that native plants can be replanted. However, Suckling argued that was labor-intensive and expensive—and should only be used for those plants that really can’t survive if they’re not in a truly native habitat.

Other times, endangered species can be planted in mixed native and invasive habitats and still do well, Suckling said.

“The third level is when you’ve got to get these species into a captive breeding program,” Suckling said. “There’s quite a few species now with huge numbers actually growing in botanical gardens, even people’s backyards.”

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While those plants are gardened and are not a part of an ecosystem, it is still an important strategy to ensure endangered species are not lost forever, Suckling said.

“There’s been a number of plants reduced to living in a pot and from that, slowly and steadily, they’ve been able to go back out into the wild— you’ve got to do all three of those with plants,” Suckling said.

Botanists in Hawaii believe that a species can be revived even if only one or a small number of seeds exist because of how plants colonized the islands in the first place. Many of the species evolved on the islands from just one founder seed.

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Preserving biodiversity requires people to have a relationship with their their own native plant species, Giardino said.

“There is untapped power in your average biodiversity enthusiast in taking a strong interest in their local flora and fauna,” Giardino said. “It doesn’t take a large number of people to make a difference with native species.”