The remote, rugged cliff faces of Kalalau Valley on Kaua’i, Hawaii, are largely inaccessible to humans. For decades, researchers from the Kaua’i-based National Tropical Botanical Garden (NTBG) accessed these cliffs by hiking along treacherous ridgelines and rappelling down vertical cliff faces, scouring each nook and cranny for rare native plants. But now they have a new tool to help them: drones.
In late January, a drone flight made a startling discovery: Hibiscadelphus woodii, a relative of hibiscus last seen in 2009 and believed to be extinct, was still growing on the cliffside.
The species was first discovered in 1991, named in 1995, and deemed extinct in 2016. It has vibrant yellow flowers, which shift to a purplish hue over time. Researchers believe it is pollinated by native birds. While scientists had tried to use cross-pollination, grafting, and tip cuttings to propagate the plant, none of their attempts were successful.
The January drone flight captured one image believed to be H. woodii, tucked into a corner. In February, they set out on another mission to reconfirm what they saw, flying a drone to the original GPS coordinates and collecting more images, revealing three individual H. woodii plants on the cliffside.
“We were hoping to catch it in flower, but it wasn’t flowering at that time,” says Ben Nyberg, drone specialist for NTBG. (See how drones are used for conservation.)
Botany from the air
Nyberg was piloting the drone that made the discovery. He uses a grid system to scan the cliffs, also using his intuition to home in on patches to search. Nyberg gathers GPS points and marks attributes like elevation so plants can be found again.
But even if they know where the plants are, reaching them isn’t easy. The three H. woodii plants are in such a dangerous and difficult-to-reach location 500 to 600 feet below the ridgeline that no one has been able to travel to them yet.
“We’ve looked at possibly short hauling somebody to go in there, but the cliff section is so vertical and it’s so far down the cliff that we’re not sure that there would be enough space for a helicopter to fit there,” Nyberg says. “It would be very difficult and dangerous for someone to even get to the top of the cliff to rappel down to it.”
However, they’re hoping new technology can help with this dilemma. They are currently investigating a drone that can collect cuttings of plants, and they hope to use this new technology to have greater access to cliffside plants. NTBG has been using drones for around two and a half years in the area, which is known as a biodiversity hotspot. (See the surprising ways drones are saving lives.)
More hidden discoveries?
“Over the last few decades botanists at the NTBG have discovered 11 plant species new to science around the rugged Kalalau cliffs of Kaua’i,” says NTBG research biologist Kenneth R. Wood. “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.”
The recent drone rediscovery of H. woodii leaves scientists excited about the potential for this technology to find new species—and rediscover ones thought to be extinct—in even the most remote and treacherous areas.
“I think there’s really unlimited possibilities,” Nyberg says. “There’s so many different ways that this technology can be used in so many different fields.”