On Easter Island, also known as Rapa Nui, a tree once popular for construction, firewood, feeding cattle and making sacred artefacts became extinct. Easter Island is a special territory of Chile in the southeastern Pacific Ocean.
The overused tree also was challenged by changes in environmental conditions. By the 1960s, Easter Island’s vegetation was 90 percent invasive species, according to a Feb. 28, 2025 article written by Sofia Quaglia in The Guardian Weekly, a United Kingdom publication. The struggling flowering tree, called Sophora toromiro, was declared extinct in the wild.
In the 1950s, dedicated people brought seeds from one of the last toromiro trees on Easter Island to a national botanical garden in Viña del Mar, Chile’s fourth largest city. It is located on the Pacific coast. They managed to germinate the seeds into 98 trees, which were used for research and reproduction.
Though their success was heartening, when they brought toromiro trees back to Easter Island, the trees didn’t survive. Why did they grow in Viña del Mar but not on Easter Island?
Enterprising scientists came up with a solution. It involves the soil bacteria rhizobia. Toromiro trees are part of the pea family, and they have established a symbiotic relationship with rhizobia. The bacteria takes nitrogen from the atmosphere and converts it into a kind of gas that toromiro trees can use.
A symbiotic relationship is a close, long-term connection between different biological species that benefits two or more of them. Trees and certain soil bacteria need each other to survive. It’s like that with all kinds of species, including those on our planet. We need each other to survive and thrive.
It is likely that rhizobia was becoming extinct on Easter Island. Without that soil bacteria, the newly sprouted toromiro trees could not survive. A team led by Macarena Gerding, a legume agronomist at Concepción University, a private university in Chile, searched related species and found some. They came from three strands in Chile and New Zealand. The enterprising agronomists inoculated some of the seedlings with the bacteria. The experiment worked!
When 40 tiny toromiro seedlings with the bacteria in them were planted at Mataveri Otai Nursery on Easter Island in 2018, they did well. Thirty more seedlings were brought from Viña del Mar in 2019 and 2021, and they did well too. Gerding’s team has discovered that other fungi and bacteria are also helping the trees. They provide nutrition, promote root growth, and help the trees grow in spite of water shortages.
Even so, the trees were still considered extinct because they were not producing their own seeds. In 2021, one of the trees at Mataveri Otai Nursery flowered, but the flowers had no seeds. Team members hope that the trees will eventually produce their own seeds. Then they can be moved from the nursery to the rest of the island and flourish once again.
