In the Mataveri Otai nursery on the island of Rapa Nui, Estefany Paté cradles a bag of soil with a 10cm sprout like it is a baby. She caresses its leaves. “It’s been so emotional to have it here,” says Paté, who works for Chile’s National Forest Corporation (CONAF).
“It was here before us; it was here before the moai,” she says, referring to the megalithic statues that dot the island. “It has a sentimental value.”
She is hugging a sprout of Sophora toromiro, a tree that was declared extinct in the wild in the 1960s and which scientists have been trying to bring back ever since.
The species grew only on the remote island of Rapa Nui – also known as Easter Island – in the middle of the Pacific. Oral history suggests toromiro wood was used for sacred artefacts and the moai kavakava, small wooden figurines that mimic the large stone faces that overlook the island’s slopes.
Over time, archaeological records show, it became popular for construction, firewood and feeding cattle.
Sonia Haoa Cardinali, a local archaeologist, says: “The toromiro must have been one of the last plants left in the community as they faced botanical impoverishment – they used it for many things.”
By the 1960s it faced extinction in the wild due to overuse and changes in the island’s environmental conditions. Invasive species now make up more than 90% of the island’s vegetation.
Seeds from the last specimen left on the Chilean island were brought to safety in the national botanical garden in Viña del Mar in the 1950s, where they have since germinated into 98 trees for research and reproduction. But all attempts to bring toromiro back to Rapa Nui have failed so far.
“My father took care of the trees, but they all died,” says Maria Tuki, whose father, Manuel Tuki, was involved in attempts to reintroduce the tree to the island in the 1980s.
But now scientists think they have found a solution.
Toromiro belongs to a family of pea plants that establishes symbiotic relationships with soil bacteria, known as rhizobia, which allow them to “fix nitrogen” from the atmosphere – converting the gas into a form plants can use. Each species has a matching microbial partner that lives in its root nodules.
Macarena Gerding, a legume agronomist at Concepción University, says the toromiro’s bacteria are also likely to be extinct on Rapa Nui, which may be why reintroduction efforts have failed.
Her team came up empty-handed when they scoured local soils for toromiro-specific rhizobia. So they looked for them in related species, and found a match in three strands from Chile and New Zealand. They tested them in the lab, inoculating seedlings with the bacteria. “The difference is very clear,” says Gerding.
Their work reinforces a growing body of research that shows trees have intimate, interconnected relationships with microbial life – and that reintroductions of tree species can often fail without the right microbiome to support them.
In 2018, the scientists brought 40 tiny seedlings back to Rapa Nui’s nursery, and about 30 more plants each in 2019 and 2021. Over the past six years, the team has also discovered other fungi and bacteria that help toromiro synthesise nutrients despite soil degradation, as well as promoting root growth and helping the plant tolerate water shortages.
A batch of potted plants with these new microbial additions arrived at the nursery late last year.
“I’m confident that these organisms can make a difference,” says Gerding. “But I think we still have to look after those plants for a while.”
Nurturing the plants until they are ready to return to the wild is Paté’s job at Mataveri Otai, where 33 toromiro trees are at different stages of growth.
“It’s been a super-ambitious task to resurrect this species,” says Paté. “It’s been very complicated – the climate didn’t used to be like this.”
For the species to be no longer classed as extinct on the island, a tree must produce its own seeds. One plant from the 2021 batch flowered for the first time last year, but did not make any seeds.
“I can’t wait for it to give us flowers again, and hopefully seeds,” says Paté. Then plants will be taken from the nursery to the rest of the island.
Locations for the reforestation project need to be carefully evaluated, though, says the project’s forest engineer, Jaime Espejo. “Out in the open field, I think it’s impossible,” he says.
Since toromiro needs shade and moisture, he plans to put the saplings in plots of land with palm trees or close to the island’s volcanic craters.
Not everybody in the local community has faith in the project, as many have been stung by its failures in the past, says Espejo. Some islanders believe the island has changed too radically for the plant to thrive, while others wonder whether the real essence of the ancient toromiro has been lost for ever.
But his team aims to rely on local families who believe in the project to take care of toromiro in their back yards.
Sara Paté Roe’s family is waiting to take care of the experimental saplings and dreams of planting them in her fields. “I hope to see the toromiro come back to the island,” she says. “It’s one of the most precious woods we’ve had.”
“It is important to return to planting things that are ours.”
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