How daredevil drones find nearly extinct plants hidden in cliffs

By RockedBuzz 8 Min Read

By Daisy Chung, Gloria Dickie and Simon Scarr

(RockedBuzz via Reuters) – Ben Nyberg stood on a sharp ridge along Hawaii’s Na Pali coast, his eyes scouring the leafy recesses of nearby red rock ridges. There was silence except for the faint hum of a drone flying among flocks of curious white-tailed tropical birds.

Nyberg guided the drone closer to the opposite ridge, scanning the iPad in his hands, which served as a scope. Then he saw it: Wilkesia hobdyi.

Its tufted bright green leaves stood out from the other plants clinging to the cliff, appearing like something out of a Dr. Seuss book.

Graphics: The Vanguard:

A member of the sunflower family known by its common name dwarf iliau, W. hobdyi was once abundant on the Hawaiian island of Kaua’i. But after Europeans introduced goats to the island in the late 1700s, the plant was nearly extinct.

Isolated from landmasses, W. hobdyi had never evolved defenses against starving livestock, such as bitter leaves or sharp thorns.

For decades, the search for such hard-to-reach plants and the collection of specimens was done by intrepid botanists who abseiled down treacherous cliffs to search for what was lost.

But this reckless approach meant it was easy to lose plants. The ropes could only stretch so far, there were few clip-ins on steep cliffs, and the view was often obstructed by bushes.

New technologies have allowed scientists to reach places too risky for humans and look for the last surviving individuals before it’s too late.

In 2016, Nyberg, who serves as GIS and drone program coordinator at the National Tropical Botanical Garden, helped launch an aerial program to search for rare species with drones.

In the case of W. hobdyi, there were thought to be fewer than 600 individuals growing along the Na Pali coast. Many of Kauai’s endangered plants grow only on the steepest cliffs, where goats can’t reach. But the foliage now shed before Nyberg amounted to more than 100 plants. He flew the drone within 5 meters (16 feet) of the green, taking high-resolution photos to confirm his lab findings.

Nyberg and the National Tropical Botanical Garden (NTBG) team, in collaboration with the Hawaii State Division of Forestry and Wildlife, rediscovered three species thought to be extinct or locally extinct from Kauai and discovered larger populations of several other endangered species of extinction with populations smaller than 100 individuals.

The drone would eventually discover 5,500 new individuals in just a few months after years of searching, an increase of more than 900% of the plant’s known population.

In the case of such discoveries, “it was just excitement,” Nyberg said. “Even one or two implants would be a big hit. Now, we may still have some time before extinction.”


Today, two out of five plant species globally are threatened with extinction. The situation is often even worse on islands that have a high rate of endemism – species that grow nowhere else in the world – and are cut off from potential refuges.

Kauai has 250 plant species that can only be found on the island.

Invasive species such as feral pigs, habitat loss, and landslides from heavy rains threaten many of Hawaii’s plants.

About 10 percent of Kauai’s plants are already extinct or extinct in the wild, and an additional 87 percent are endangered, according to a 2020 assessment for the International Union for the Conservation of Nature’s Red List of Threatened Species.

“Things are really special here because we’re so far away from everything,” said Nina Ronsted, director of science and conservation at NTBG who led the assessment. “Each plant plays a very specific role” in the environment.

Species such as na’ena’e (Dubautia waialealae) that grow in the island’s swamp forests are critically endangered. The loss of a single species can throw an entire ecosystem out of balance.

“It’s kind of like a tower of cards,” said Ronsted. “If you take off too much, it will fall off.”


Finding rare plants in nature is only half the battle. To protect species in the long term, botanists need to collect samples – seeds and genetic material – which they can grow in greenhouse nurseries. This helps provide an insurance policy against extinction.

In 2020, Nyberg and Canadian researchers from Outreach Robotics began developing a special robotic arm that they could attach to a drone to carefully cut off pieces of plants growing in dangerous places.

Known as a Mamba (Multi-Use Aerial Manipulator Bidirectional Actuated), the robotic arm dangles on a cable underneath a drone and features eight propellers and a cutting mechanism that can be controlled by pilots from a mile away.

By separating the Mamba from the drone, it can move quickly and accurately in windy environments and avoids the risk of the drone crashing into rock faces.

At maximum extension, the Mamba can reach the target plant up to 4 meters away.

The Mamba is operated remotely by scientists who can operate the robotic arm’s nimble metal wrist and dynamic scissors. The Mamba is programmed to carefully collect samples from even the smallest and most delicate plants. Collections take less than 10 minutes.


Mamba has so far collected 29 cuttings or seeds of 12 endangered species. These include samples of wahine noho kula, a rare violet believed to be extinct on Kaua’i and only recently rediscovered by survey drone.

The seeds and cuttings are now growing in the NTBG nursery, while some seeds are being stored in the seed bank for future conservation efforts.

The robot “may mean the difference between extinction and survival,” Nyberg said.

But the species still needs to be returned to the wild to make a full comeback. Scientists hope to return them to their rocky terrain within the next year or two.

They could even use drones to bomb harvested seeds, packing them into balls of sticky fertilizer that can cling to steep cliffs.

But it might not even be necessary to let them fall into such treacherous ground. It’s possible that “these plants developed on flat land before we had goats here,” Nyberg said.

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(Reporting by Gloria Dickie in London and Daisy Chung in Sunnyvale, California; Art by Daisy Chung, Simon Scarr and Sudev Kiyada; Editing by Katy Daigle and Lisa Shumaker)

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