How daredevil drones find nearly extinct plants hidden in cliffs

How daredevil drones find nearly extinct plants hidden in cliffs

Dec 10 (Reuters) – Ben Nyberg stood on a sharp ridge along Hawaii’s Na Pali coast, his eyes scanning the leafy nooks of nearby red rock ridges. It was quiet, save for the faint hum of a drone flying among flocks of curious white-tailed tropicbirds.

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

Its bushy bright green leaves stood out from the other plants clinging to the cliff, looking like something out of a Dr. Seuss book. (Graphic — 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 reduced to near extinction.

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

For decades, the search for these hard-to-reach plants and the collection of samples has been carried out by intrepid botanists who abseiled with a rope from the dangerous cliffs to hunt what had been lost.

But this daredevil approach meant it was easy to miss plants. The ropes could only stretch so far, there were few clips on the steep cliffs, and the sightlines were often obstructed by bushes.

Thanks to new technologies, scientists can now reach places too risky for humans and search for the last survivors before it is too late.

In 2016, Nyberg, who is the 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 inaccessible to goats. But the foliage now spread before Nyberg amounted to more than 100 plants. He flew the drone within 5 meters (16 feet) of the greenery, taking high-resolution photos to confirm his findings at the lab.

Nyberg and the National Tropical Botanical Garden (NTBG) team, working with the State of Hawaii’s Division of Forestry and Wildlife, rediscovered three species thought to be extinct or locally extinct from Kauai and discovered larger populations of many other critically endangered species with smaller populations over 100 individuals.

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

In the case of such findings, “it was just excitement,” Nyberg said. “Even one or two plants would be a big hit. Now we may have a little more time before extinction.


Today, two out of five plant species in the world 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 found only on the island.

Invasive species like feral pigs, habitat loss, and landslides from heavy rains threaten many Hawaiian plants.

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

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

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

“It’s kind of like a card trick,” Ronsted said. “If you remove too much, it will fall.”


Locating rare plants in the wild is only half the battle. To protect species for the long term, botanists must 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 pieces of plants growing in perilous places.

Known as the Mamba (Multi-Use Aerial Manipulator Bidirectionally Actuated), the robotic arm hangs on a cable below a drone and is equipped with eight propellers and a trimming mechanism that can be controlled by pilots a mile away. distance.

By separating the Mamba from the drone, it can move quickly and precisely in windy environments and avoids the risk of the drone colliding with cliff faces.

At full extension, the Mamba can reach the target plant at a maximum distance of 4 meters (13 feet).

The Mamba is remotely controlled by scientists who can maneuver the robotic arm’s nimble metal wrist and dynamic clippers. The Mamba is programmed to carefully pick plant samples, even the smallest and most delicate. Collections take less than 10 minutes.


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

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

The robot “can make the difference between extinction and survival,” Nyberg said.

But species still need to be released back into the wild to make a full comeback. Scientists hope to bring them back to their cliffside terrain within a year or two.

They might even use drones to bombard collected seeds, packing them into sticky balls of fertilizer that can cling to steep cliffs.

But they may not even need to be dropped on such dangerous ground. It’s possible “that these plants occurred on flat land before we had goats here,” Nyberg said.

Read more:

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

Our standards: The Thomson Reuters Trust Principles.

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