Saving the Rarest Plants on Earth

By Léo Azambuja

NTBG Research Biologist Ken Wood, left, and NTBG GIS and Drone Program Coordinator Ben Nyberg are seen here working with a drone in Kalalau in August 2019. Contributed photo

In 2020, while the world was focused on dealing with the COVID-19 pandemic, researchers and scientists at the National Tropical Botanical Garden were busy finding and cataloguing Kaua‘i’s endemic flora. Their effort means better tools to understand and preserve some of the Earth’s rarest plants.

“We were fortunate to have access to the extensive field observations and collections that NTBG have been maintaining from nearly 50 years of fieldwork on Kaua‘i,” said Nina Rønsted, NTBG Director of Science and Conservation.

The outcome of NTBG’s field work was used by the International Union for Conservation of Nature — the global authority on the status of the natural world and the measures needed to safeguard it — to update its Red List of Threatened Species last March. All of Kaua‘i’s endemic plants are now in the IUCN list.

“This pandemic meant we had more time to focus on analyzing these data and conducting the Red List assessments,” Rønsted said.

Since the 1840s, at least 134 native plant species in Hawai‘i have gone extinct, according to NTBG. That’s roughly 10 percent of Hawai‘i’s diverse flora of 1,367 endemic plants. Competition with invasive species, habitat disturbance and loss, new diseases and climate change have all contributed to these extinctions. For Kaua‘i, this is especially critical, since the Garden Isle has the highest rate of endemism and diversity than any other Hawaiian island. Endemism means a certain species is only found in a single geographic location, while a native species can also be found somewhere else.

“Kaua‘i stands out as the most species-rich Hawaiian island primarily due to its longer geological history,” Rønsted said. “Nearly 50 percent (673 species) of the native flora of Hawai‘i can be found on Kaua‘i and we have looked at the 256 of them which are only found on Kaua‘i.”

NTBG Conservation Biologist Seana Walsh is seen here in Honopū in April 2020. Photo by Ken Wood

NTBG Conservation Biologist Seana Walsh said 46 percent, or 554 taxa, of Hawai‘i’s endemic taxa occur on Kaua‘i. Out of that total, the Garden Isle is home to 251 single-island endemic taxa — these are species only found on Kaua‘i — and this number far surpasses the number of single-island endemic taxa on any of the other Hawaiian Islands.

“For our Red List assessment work, we also included taxa which are historically multi-island but now restricted to Kaua‘i because they’ve been extirpated from the other islands, such as Kadua cookiana. This resulted in conducting assessments for 256 taxa,” Walsh said.

Half of those assessments were conducted and published on the IUCN Red List of Threatened Species from 2015 to 2019. The other half were conducted and published in 2020 and 2021, according to Walsh. The IUCN Red List, she said, is the “global standard” for assessing the risk of extinction.

“It is important we conduct standardized assessments on the conservation status for all of our species, and the Red List is one of the most rigorous and widely recognized ways to do this,” Walsh said.

The data in the assessments are made available for scientists to answer questions that could help inform conservation practices. The published assessments highlight conservation challenges at the international level, and also open doors for conservation funding, Walsh said.

Rønsted said the IUCN Red List is considered the world’s most comprehensive online resource on the conservation status of the plants, animals and fungi. The list, she said, despite including about 15 percent of the world’s plant species and having gaps and areas not well-covered that can be easily overlooked, still provides a pretty good estimate of the state of conservation challenges and threats to global diversities.

NTBG botanist Dustin Wolkis collects Polyscias racemosa seeds during field work. Contributed photo

“The uniqueness of the Red List is that it is based on a set of internationally agreed and tried criteria, meaning all species are measured against the same criteria and it is therefore easy to compare the findings,” Rønsted said. “The Red List evaluation criteria include how large an area a species can be found in, how many individuals there are, how fragmented the population is and importantly if any declines or reductions in the species range or population size has been observed.”

Internationally, the Red List is increasingly being used by countries, governmental agencies and conservation organizations to develop conservation policies and priorities, said Rønsted, adding conservation funding agencies are using Red List status as criteria for funding. As a global reference, the Red List data is also being used to conduct wider analysis of the global conservation status and threats.

“It is therefore very important to highlight the conservation status and needs of the Hawaiian flora to an international audience using the globally used IUCN Red List criteria,” she said.

Federal government assessments under the United States Endangered Species Act are very important in Hawai‘i, and are supplemented with five-year reviews of all the listed species, according to Rønsted. But to highlight the weight of the IUCN Red List, the federal listing under the ESA shows only 45 percent of Kaua‘i’s single-island endemic vascular plants as threatened or endangered.

Rønsted said the results of these assessment suggest the conservation status of the Hawaiian flora is “underestimated” by the federal assessments, and a critical look should be taken at the potential need for conducting federal assessments of a higher proportion.

Additionally, Rønsted said the published Red List assessments can help to provide information that could be used to petition the U.S. Fish and Wildlife Service for protection under the ESA, which is already happening.

In order to reach remote areas, researchers used helicopter rides, hiked into rough terrain and even used ropes to climb or rappel down cliffs.

Cyanea kuhihewa. Photo by David Lorence

Drone work was also used in the research. Rønsted said NTBG GIS and Drone Program Coordinator Ben Nyberg is currently working with a group of Canadian researchers to repurpose a drone to be able to make precision collections of seeds or plant parts for further propagation.

The results often show positive outcomes. Rønsted said through this ongoing field work across Kaua‘i, they regularly find unknown populations of rare and endangered species.

“One example is Eurphorbia eleanoriae, which was previously considered a priority plant for the Plant Extinction Prevention Program due to having less than 50 individuals known in the wild. However, recent drone surveys helped find several unknown populations of this plant which allowed for it to be taken off the PEPP list again this year,” Rønsted said.

This wasn’t an effort by NTBG alone. Walsh said many people were involved in the assessment efforts, broadly from the IUCN Hawaiian Plant Specialist Group. Specific partners who played the largest roles include the state Department of Land and Natural Resources/Division of Forestry and Wildlife and the Plant Extinction Prevention Program.

“They provided necessary data and helped to conduct and review the assessments,” Walsh said.

NTBG Director of Science and Conservation Nina Rønsted, left, and biologist Michelle Clark are seen here in Hāʻupu in June 2020. Contributed photo

Rønsted said most of the assessments campaign done in 2020 were led by Walsh, Nyberg, NTBG Research Biologist Ken Wood and Rønsted herself in collaboration with State Botanist Matt Keir from DLNR/DOFAW and with some assessments also done by NTBG botanists David Lorence, Margaret Clark, Uma Nagendra, Tim Flynn, Dustin Wolkis and Merlin Edmonds, and by Adam Willams of DLNR/DOFAW and Scott Heinzmann from PEPP.

The Hawaiian Islands are often called the “extinction capital of the world.” The Islands, Rønsted said, stand out with having exceptionally more plant extinctions than other geographical regions, which is alarming as plant extinctions endanger other organisms, ecosystems and human well-being.

“However, Hawai‘i also stands out as having one of the highest levels of endemism of any floristic region of the world with nearly 90 percent of its circa 1,367 native plant taxa classified as endemic, found nowhere else on Earth,” Rønsted said.

She added isolated oceanic islands such as Kaua‘i are characterized by high endemicity, but the unique biodiversity of many islands is experiencing high extinction rates, primarily due to habitat disturbance and loss, competition with invasive species, spread of new diseases, and climate change.

“The assessment of Kaua‘i’s flora is the highest extinction risk reported for any flora to date and calls for urgent conservation measures of the unique floras of remote oceanic islands such as the Hawaiian Islands,” Rønsted said.

She encouraged residents to consider planting more native plants in gardens and yards. Also, many local nurseries have a selection of native plants which are well adapted for our environment. The Kauaʻi Invasive Species Committee maintains a list of invasive plants that we should avoid (www.kauaiisc.org/pono/do-not-plant-list/) and a list of pono nurseries that are committed to not sell these.

NTBG Research Biologist Ken Wood is seen here working with Melicope rostrata in Honopū in May 2020. Photo by Seana Walsh

Walsh said community members could help by learning more about our rich flora, getting out there to appreciate it — while following proper etiquette, such as cleaning your boots before and after hiking — and volunteering with an agency or organization that works to conserve rare plants on Kaua‘i.

IUCN was established on Oct. 5, 1948, under the initiative of the United Nations Educational, Scientific and Cultural Organization — known as UNESCO — and its first Director General, British biologist Julian Huxley. Today, IUCN is a membership union made of government and civil society organizations, with more than 1,400 member organizations and more than 18,000 experts worldwide.

The updated IUCN Red List includes more than 134,000 species assessed around the world, with 54,127 of them being plants. Each is given a rank in one of nine categories from species of least concern to extinct. Twenty-eight percent of all now assessed species are recognized as threatened, according to IUCN.

Visit www.ntbg.org or www.iucn.org for more information.