- A drone surveying a cliff face in a remote part of Kalalau Valley in Hawaii’s Kaua‘i Island has confirmed the presence of Hibiscadelphus woodii, a relative of hibiscus that was last seen alive in 2009, and thought to be extinct.
- Biologists first spotted four H. woodii plants in March 1991, but three of the plants were crushed and killed by falling boulders between 1995 and 1998. The remaining known individual was last observed alive in 2009, and then seen dead in 2011.
- However, by flying into difficult-to-reach areas, drones are uncovering secrets of previously unexplored cliff habitats.
In January this year, a drone surveying a cliff face in a remote part of Kalalau Valley on the Hawaiin island of Kaua‘i chanced upon something unexpected: In one of the images captured by the drone, botanists spotted what they thought was a Hibiscadelphus woodii, a relative of hibiscus last seen alive in 2009.
To confirm their sighting, researchers from the National Tropical Botanical Garden (NTBG), a Kaua‘i-based nonprofit that studies tropical plants, flew a drone in the same place using GPS coordinates from the original photograph. This particular drone was equipped to take very close-up pictures of individual plants, and the images it captured reaffirmed the team’s suspicions: they could see at least three individual H. woodii plants on the cliff face. None were flowering though, Ben Nyberg, a geographic information system (GIS) specialist and drone operator for the NTBG, told National Geographic.
H. woodii produces striking yellow flowers that turn purplish-maroon as they age. Researchers say the flower is likely pollinated by native honeycreeper birds, including the Hawaiʻi ʻamakihi (Chlorodrepanis virens).
“NTBG revolutionized cliff survey in Hawaii in the 1970s utilizing ropes, and now we are applying drone technology to go even further,” Nyberg told Forbes.
It was Kenneth R. Wood, a botanist with the NTBG, and his colleagues who first discovered four H. woodii plants in March 1991. The small trees were growing on a steep slope below the rim of Kalalau Valley in northwestern Kaua‘i, accessible only by climbing ropes, and seemed unlike any other plants they had seen before. Researchers formally described the new-to-science species of plant in a paper published in 1995, naming the species after Wood.
The researchers also wrote about the impending threats to the tiny population of the extremely rare species: accessible areas above the cliffs where the plants were found had been severely degraded by feral goats and pigs, they said, adding that the H. woodii plants were “susceptible to damage by falling rocks dislodged by these animals, which aggravate erosion.”
The joy of finding the new species was indeed short lived. Three of the plants were crushed and killed by falling boulders between 1995 and 1998. The remaining known individual was last observed alive in 2009, and then seen dead in 2011. All attempts to propagate H. woodii by methods including cutting, grafting and tissue culture failed, as did efforts at cross-pollination with closely related species, earning it a listing of extinct on the IUCN Red List.
However, by flying into difficult-to-reach areas, drones are uncovering secrets of previously unexplored cliff habitat. “And while this may be the first discovery of its kind, I am sure it won’t be the last,” Nyberg said in a statement.
The cliff area where the H. woodii individuals were spotted, for example, is so far down and vertical that it would be risky to get someone to rappel down it. But drones make access to such rough terrain much easier, Nyberg told National Geographic.
In fact, drone technology has enabled researchers at NTBG, who have spent decades rappelling down cliff faces, to find new populations of extremely rare plant species, including the Laukahi (Plantago princeps var. anomola), Euphorbia eleanoriae and Wilkesia hobdyi.
The latest discovery of new individuals of H. woodii suggests there’s much more to be learned about Kaua‘i’s extremely rich and unique plant diversity.
“Over the last few decades botanists at the NTBG have discovered eleven plant species new to science around the rugged Kalalau cliffs of Kaua‘i,” Ken Wood, a research biologist at the NTBG, said in a statement. “When examining floristic diversity throughout the Hawaiian Islands, no other valley compares to Kalalau in the number of its unique species. Kalalau Valley also contains the highest number of threatened plant species, with 51 that are currently federally listed as endangered.”
Banner image of Hibiscadelphus woodii by Ken Wood/National Tropical Botanical Garden.