It lives on Hawaiian cliff sides and is inaccessible to humans.

By Dan Nosowitz
April 24, 2019

Small drones equipped with cameras aren’t only good for taking selfies in front of waterfalls. It turns out they can also be used to find plants thought to be extinct in the wild. Say hello to Hibiscadelphus woodii, also known as "Wood’s hau kuahiwi."

This tropical plant was first spotted in 1991 in Hawaii, then classified as its own new species in 1995. Only four of the plants were found at the time and died shortly after discovery—the last one was found dead in 2011. Scientists thought that was it for this plant and declared it extinct in the wild.

Image courtesy of Ken Wood, National Tropical Botanical Garden.
Image courtesy of Ken Wood, National Tropical Botanical Garden.

But this year, researchers at the National Tropical Botanical Garden flew drones out to a remote cliff in Kauai’s Kalalu Valley, which is an area of sheer, narrow cliffs, basically inaccessible to humans; this is not a place with hiking trails and fountains to refill your water bottle. Coming in by air is just about the only way to get in. There, growing off of a vertical cliff face, three Wood’s hau kuahiwi plants were found via drone. The video is amazing; set the quality to as high as it goes, and enjoy some Planet Earth-style footage.

The plant itself is a member of the Hibiscadelphus genus. These plants are smaller trees and are somewhat similar to hibiscus. Unlike hibiscus, however, the flowers—which are bright yellow, turning purple later—never fully open. The theory is that these plants evolved this way to make them attractive to Hawaiian birds called honeycreepers, which have long, curved beaks.

A total of eight of these Hibiscadelphus species are known to science, all in Hawaii, and they’re all incredibly rare. Several of them are only known from one or two individuals, and once those die, the species is assumed extinct. They’re at risk of big changes like the introduction of rats, the loss of honeycreeper birds, and destruction of their habitat.

But their numbers are so low that random chance also affects them. Living on the sides of cliffs, falling boulders are a fact of life. But when there are only one or two known members of a species, a single falling rock can mean extinction.

The rediscovery is great news, though. Researchers now know more about these rare plants and where they might live—and it unlocks hope that more species thought to be extinct might yet survive.


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