By Léo Azambuja
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 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