One of the most notorious mass extinction events in modern times occurred on a hilltop in coastal Ecuador in the 1980s. Ninety species of plants known from nowhere else on Earth—many of them new to science and not yet given a name—went extinct when the last cloud forests of the Centinela range were cleared for agriculture. The cautionary tale of Centinela has long been a driving force in the fight to save the world's rainforests. But did it really happen?
In a new study published in Nature Plants , an international team of botanists reveals that, indeed, it did not happen. The researchers – who spent years of scouring natural history museums, biodiversity databases, and the slopes of Centinela – found no proof of any extinctions, but abundant evidence that Centinela's flora lives on in the scattered remaining fragments of coastal Ecuador's forests.
"It's a miracle," said lead author Dawson White, postdoctoral researcher in the Department of Organismic and Evolutionary Biology at Harvard. "Many of Centinela's plants are still on the brink of extinction, but fortunately the reports of their demise were exaggerated. There's still time to save them and turn this story around."
The study revealed that one reason earlier researchers overstated the likelihood of extinction at Centinela was due to the fact that those researchers were collecting a bounty of new and undescribed species, with limited information on which plant species grow where in the world's most diverse forests. In the decades since, those early collections have provided more than 50 new species. As well, as botanists began to collect more widely and natural history museums digitized their specimens, plants previously thought to have gone extinct at Centinela have turned up at other sites in South America, while others were relocated in situ by the team. Of the 90 species originally presumed extinct, only one has not yet been rediscovered or confirmed to grow elsewhere.
"Understanding which plants are growing in a given Andean cloud forest is a monumental task because you will undoubtedly find new species", said White. "What our investigation highlights is that it takes decades of work from taxonomic experts to describe new species in such forests. And only once we have names for these species that are then noted in our scientific networks can we begin to understand where else these plants grow and their risk of extinction."
Ecuador, though small, is incredibly diverse, offering a good illustration of how challenging it is for scientists to monitor and protect tropical biodiversity. It contains more than 20,000 plant species, 4,000 of which occur nowhere else on Earth, hundreds of which lack names, and none of which have been fully mapped. Given these challenges, the study highlights the vital role of herbaria collections.
"Herbaria give us the fundamental 'what' and 'where' of plant biodiversity," said co-author Juan Guevara, Universidad de Las Américas in Quito. "They are what made it possible to solve this mystery. They're the basis of everything we know about which plants are threatened with extinction."
The authors also found that Centinela's forests are more resilient than originally thought. Recent field work has pinpointed a number of fragments of original forest that were previously overlooked due to their tiny sizes and remote locations. The team found these postage-sized remnants, often less than an acre in size, to harbor many species thought to have gone extinct—including Gasteranthus extinctus, a wildflower named after its own extinction that was rediscovered by the team in 2021.
"Over the last two years we've surveyed a dozen fragments in the region," said co-author Andrea Fernández, Northwestern University and the Chicago Botanic Garden. "They're tiny islands lost in a sea of plantations, but they're still full of astonishing plants."
Not only were the researchers surprised to find much of the old Centinela flora intact, they were doubly surprised to discover a bounty of new and previously undescribed plants as well. Over the past five years the researchers have described or discovered eight new species ranging in size from miniscule wildflowers to towering canopy trees.
"One of our most astonishing discoveries is a totally new species of canopy tree in the Cotton family," said Fernández. "It's one of the tallest trees we have encountered, but it's extremely rare; there could be only 15 individuals alive in Centinela. It's now being actively targeted by local loggers-, s-o we are rushing to describe this new tree species and get its seeds growing in botanic gardens."
Once given a wide berth because of its gloomy past, Centinela is now buzzing with scientists who see in its decimated forests abundant opportunities for research and conservation. In Ecuador, botanical gardens are establishing collections of the region's rarest, most threatened plants, while conservationists collect seeds for future reforestation efforts and look for long-term solutions to keep the remaining fragments standing. At the global scale, the resurrection at Centinela has inspired the launch of a new conservation initiative by Earth imaging company Planet Labs, which promises to boost conservation projects with high-quality satellite imagery.
While the new study corrects the record on one mass extinction event, it does not cast doubt on the biodiversity crisis underway around the world. According to the IUCN Red List, more than 45,000 species on Earth are currently threatened with extinction, including nearly half of all amphibians, a third of all corals, and a quarter of all mammals. Scientists at Kew Botanical Gardens curated a list of the more than 800 plant species presumed to have gone extinct to date.
"Plants in coastal Ecuador and a lot of other hard-hit places in the tropics are finding a way to hang on in the last nooks and crannies," said co-author Nigel Pitman, the Field Museum of Natural History. "They won't survive for long under those conditions, but we've still got time to act before they're gone forever."
