For field botanists with the Plant Extinction Prevention Program, a typical workday might mean trekking through remote forests, rappelling down steep cliffs, or flying by helicopter into hard-to-reach valleys. But the most exciting moments come when the crew finds one of Maui’s critically imperiled plants persisting in the wild.

The Plant Extinction Prevention Program  — or PEPP for short  — does exactly what its name suggests. PEPP protects Hawai‘i’s most critically endangered plants from extinction. The program, which employs five field crews across the state, cares for over 200 plant species, each with fewer than 50 individuals left in the wild. Some species are down to just a single known plant. Hawai‘i is often called the “Endangered Species Capital of the World.” Nearly half of the endangered or threatened plants in the United States are species endemic to Hawai‘i, meaning they are found nowhere else on Earth.

Endemic Hawaiian plants are especially vulnerable because they evolved in isolation, far from predators, grazing animals, or aggressive weeds. After European contact, humans began altering Hawai‘i’s landscape  — clearing forests and introducing new plants and animals at an unprecedented rate. Hawaiian plants could not adapt quickly enough to the changes. Today, more than 100 Hawaiian plant species have already been lost to extinction. Hundreds more are reduced to just a few wild individuals.

That’s where PEPP comes in. To prevent the last of Hawai‘i’s rare plant species from disappearing, the PEPP field crew collects seeds or takes cuttings from rare wild plants for research and propagation. The Maui PEPP crew checks in on each plant on their list about once a year, ideally when they’re fruiting. The majority of field days, however, are spent searching for rare plants — often seeking additional specimens known from only one or two individuals.

Maui PEPP’s crew of three spends long days surveying remote environments, hoping to locate even a single additional individual. “If there’s only one individual for the entire species, the best thing we can do is find more,” says Maui PEPP field coordinator Zach Pezzillo. “Even if we find just one more plant, and that brings the [population] to two, that would double our genetic diversity.” A diverse gene pool allows plant populations to remain resilient in the face of disease, environmental changes, and other threats  — and is key to preserving rare species over time.

The stakes are high when working with species on the brink of extinction. The wins feel huge and the losses insurmountable. Finding an additional plant can change the outlook for a species overnight. But those gains can disappear just as quickly.

In 2024, field botanist Remy Henderson spotted a rare Cyanea magnicalyx from a helicopter while flying to a field site in West Maui. Cyanea, called hāhā in Hawaiian, are among the island’s rarest, most magnificent endemic plants. Hawaiian Cyanea species typically grow on tall, unbranched stalks and sport long, tubular flowers that evolved alongside Hawai‘i’s native forest birds.

At the time Henderson spotted the Cyanea magnicalyx, there was just one other known individual in the species. When the crew finally reached the site Henderson had spotted from the air, they discovered the plant in bloom, covered in white-purple flowers. They collected fruit and admired its unusual beauty. The crew even found an additional individual nearby, bringing the total population to three. “It was spectacular,” says Pezzillo. “We were all stoked.”

But when the crew returned a little over a year later, they found both plants nearly dead, returning the known population to one. It was devastating. “You develop stories with these plants,” says Henderson, “and they become like a friend. When they die, it’s extremely sad.” Both Pezzillo and Henderson likened PEPP’s work to a plant hospice. “It’s like end-of-life care,” says Pezzillo. “We can try to keep the rats and slugs away and pull some weeds, but that’s all we can really do.”

Lately, keeping rare Hawaiian plants alive in the wild has gotten even harder. Pezzillo says that just in the last five years, he’s noticed a stark change in Maui’s native environments. “The forest around these plants is drying up and degrading. There are all these invasive species moving in at a scale that we can’t help or control.”

Habitat loss and invasive species are recurring themes in Hawai‘i  — both major drivers of extinction in the islands. On Maui, introduced and invasive plants now dominate 75 percent of the landscape. Many native species are confined to the island’s most remote reaches, where invasive pests, grazing animals, and human disturbance are limited.

Despite the heartbreak and uncertainty, PEPP’s work carries real reward. About 30 species have gone extinct in the wild since PEPP’s founding in 2003. Yet each has been saved in cultivation, with the goal of eventual reintroduction to the wild. Since 2020, 11 species previously believed extinct have been rediscovered. Some hadn’t been seen in over a century.

And then there’s the joy of finding a plant you’ve been searching for. Henderson recalls tracking a rare fern, Diplazium molokaiense, through a remote part of East Maui. “There was this historical [data] point, but [the fern] hadn’t been seen there since the early, maybe mid-1900s. I was really hoping to find it,” she says. “They grow in these specific waterfall habitats. You won’t just find them anywhere.”

When Henderson did find the fern, she didn’t recognize it until Pezzillo pointed it out. “He was like ‘Dude, that’s a Diplazium molokaiense right there!’” she laughs. Initially, she was disappointed she hadn’t recognized the plant she’d been searching for  — but Henderson says that moment made her a better botanist. “Since then, I found two new individuals of Diplazium molokaiense. It always feels like such a gift,” she says. “Every time you find something new, it’s a really special feeling.”

For the PEPP crew, this work is personal. But the loss of rare plants isn’t only felt by botanists. Everything is connected in a Hawaiian forest. When biodiversity is lost, it can trigger a chain reaction that disrupts the forest’s function  — and without healthy forests to capture rainwater and recharge aquifers, Hawai‘i loses its primary source of fresh water.

Most Maui residents and visitors will never encounter a wild plant on PEPP’s protection list, yet they can still support its survival. Cleaning boots and gear before and after hiking prevents the spread of invasive seeds and deadly plant pathogens. Choosing native Hawaiian plants for home landscapes over imported species helps push back against the island’s invasive footprint. For those who want to do more, donating to PEPP remains one of the most direct ways to support the work of preserving Hawai‘i’s rarest flora.

“These plants are relics from the past, a glimpse of what once was,” says Henderson. “It’s easy to let yourself be sad or feel hopeless about what’s happening. In this program, we might not be able to do everything. But there is hope of preserving things for longer.” For many of PEPP’s species, survival is a long, hard, uphill battle. “But ultimately,” Henderson says, “doing something is better than doing nothing.”

The Plant Extinction Prevention Program is a project of the Pacific Cooperative Studies Unit at the University of Hawai‘i at Mānoa, working in collaboration with state and federal agencies; pepphi.org