How Rapa Nui Lost a Tree, Only to Have It Sprout Up Elsewhere
The tree that goes by toromiro has been a fragile expat for more than a half-century. Little Sophora toromiro, is far from home, no longer present on Rapa Nui, the Pacific island where it evolved. Also known as Easter Island, or Isla de Pascua in Spanish, Rapa Nui is a speck of land in the Pacific, 2,200 miles from the west coast of Chile. The tiny island encompasses just 63 square miles, and it is quite flat, with a maximum elevation of less than 1,700 feet. The last date of the toromiro’s tenure on Rapa Nui is uncertain. Some accounts say it went extinct in the wild in 1960. Others say that it was gone by 1962, when Karl Schanz, a German meteorologist, clambered down to see the tree in the crater where it had last been spotted, and it was gone. Was it removed? Did it die, tip over and return to the earth? We will never know. Although the toromiro is gone from Rapa Nui, it survives elsewhere through luck—and pluck. Over the past century, the intermittent collecting of the toromiro’s seeds and their replanting in mainland locations have given the species purchase elsewhere. Each tree is a member of a small diaspora, with only a handful surviving in about a dozen different public and private botanical gardens around the world. This is a story of survival, persistence and, perhaps in some ways, dumb luck—a tree in decline that was rescued and whose seeds were sent to other places. Mention Easter Island to almost anyone, and if they’ve heard of it, they’ve likely heard of its statues. Imprinted in the popular imagination are its enigmatic, massive stone sculptures, or moai. Curious investigators have speculated for more than two centuries about how more than 900 of these mysterious statues—the largest being more than 30 feet tall and weighing over 80 tons—might have been moved to locations around the island, traveling miles from the site where they were quarried. The toromiro, though, is an invisible tree on the island, its story known to very few, and its existence marked more by its absence than its presence. The tree does have many close relatives. The Sophora genus is speciose, as biologists say—a crowded taxon consisting of some 60 different species, including a dozen closely related oceanic ones scattered across the Pacific. The toromiro is more of a shrub than a tree, and none of its close relatives is large—at least from descriptions recorded over the past century. The northernmost outpost for the Sophora genus is in Hawaiʻi, where Sophora chrysophylla is the primary food source for the palila, a critically endangered honeycreeper. Without S. chrysophylla, known as mamane in Hawaiian, the palila would not have survived the last century as its range dwindled. The subterranean pollen record reveals that the toromiro was abundant across much of Rapa Nui, where many other now-extinct plants also thrived. Paleobotanical evidence shows that the tree’s presence on the island dates back at least 35,000 years. Its seeds are both buoyant and salt-resistant, and they probably first arrived by water, floating onto the island, probably from another Pacific island, and then it did what species do: continued its evolutionary journey in a new place to become the tree we know today. But even before the toromiro disappeared from the island, it had been without a lot of endemic companions. Fewer than 30 indigenous seed-bearing plant species have survived on Rapa Nui to the present day, and weeds, along with naturalized, cultivated shrubs, are now the main plants growing there. The toromiro did not disappear precipitously but experienced a protracted decline. Humans arrived in Rapa Nui around the 12th century, probably not long after Polynesians reached the Hawaiian archipelago. Some hundreds of years after humans’ arrival, the island experienced a painful drop in biodiversity, and its carrying capacity plummeted as the native palm forests disappeared, replaced by grasslands. Food grew scarce, and occupants fled, thinning down to around 100 Rapa Nui at one point in the 19th century. In his deterministic 2005 book Collapse: How Societies Choose to Fail or Succeed, Jared Diamond claimed the occupants were lousy land managers. His analysis of why Rapa Nui became denuded of its plant life is now out of date, as later studies have revealed the island’s complexities. To sketch the story of the weakening grip of native plant life on Rapa Nui as a predictable story of human arrogance intersecting with a small, remote and evolutionarily vulnerable spit of land is tempting, but the tale is more nuanced than that. Natives there recorded centuries-old histories of careful but intermittent conservation strategies. Some scholars have asserted that the Little Ice Age stressed resources on the island between the 16th and 19th centuries, leading to the disappearance of palms and other important contributors to the islanders’ activities and well-being. Others have pointed to prolonged droughts, while still others have continued to argue that humans were highly complicit in the island’s declining biodiversity. Were groves of palm trees decimated to create systems for rolling the giant stone carvings from quarry to coastline, where most of them have sat for many hundreds of years? Perhaps. However the palms disappeared, their loss seems to have been a factor in the tumbling downturn of the island’s other trees, including the toromiro. The palms had made up the great majority of Rapa Nui’s tree cover, some 16 million trees that blanketed about 70 percent of the island. Some controversy remains about what particular species of palm flourished, but many believe it was Paschalococos disperta, the Rapa Nui palm. Jaime Espejo, a Chilean botanist who’s written extensively about the toromiro, noted that it probably lived in the undergrowth of the palm, lodged in an ancient ecosystem that no longer exists. Paleobotanists and archaeologists studying the island spotted the widespread loss of the palms in their investigations. At the same time, they found that the number of fish bones found in waste middens around the island dropped as fishing boats could no longer be constructed in large numbers from trees. The loss of access to fish must have been a devastating turn, because the human residents’ main proteins came from the sea. Soil erosion, likely exacerbated by deforestation and agriculture, led to further losses of the tree. Hooved animals, arriving with European explorers in the 18th century, were also certain culprits in the toromiro’s decline and disappearance. In Hawaiʻi, sheep consume that archipelago’s species of Sophora. Another creature implicated in the destruction of much of both Rapa Nui’s and Hawaiʻi’s plant life was the Polynesian rat (Rattus exulans), as well as the bigger ship rat (Rattus rattus) and Norwegian rat (Rattus norvegicus). These rats, landing on new island homes and able to reproduce quickly, found abundant food in the form of native seeds, plants and invertebrates—and no predators. They laid waste to plant life with shocking speed. An aerial view of a toromiro in Barcelona, Spain Daderot via Wikimedia CC0 Early European accounts and pollen records tell us that by about 1600, forests in the island’s craters had disappeared, and, with that, the toromiro declined into long-term scarcity and then extirpation. The New Zealand anthropologist Steven Fischer has noted that the last forest was probably cut for firewood around 1640, making wood the most valuable commodity on the island. Driftwood became precious. So scarce was wood, Fischer observes, that the pan-Polynesian word rakau, meaning “tree,” “timber” or “wood,” came to mean “riches” or “wealth” in the old Rapa Nui language—a meaning not present in any other use of the word elsewhere in Polynesia, including in Tahiti, Tonga, Hawaiʻi and New Zealand. It’s ironic that after the deforestation of the island’s trees, new linguistic meanings sprouted out of the island’s impending botanical doom. Amid these centuries-long difficulties, but long before the toromiro disappeared, a wood-based culture thrived. The Rapa Nui had a particular passion for carving; beyond their giant stone statues, they favored the toromiro for its durable and fine-grained wood and reddish hue. Although primarily used for ritual objects, the toromiro was also serviceable for building material in houses, household utensils, statuettes and paddles. These artifacts survive in museums around the world. Some of them are hundreds of years old, and they might provide unexpected addenda to our understandings of the tree’s deeper history, offered up through dendrochronological analysis. Studying the annual growth rings in the wood could provide details we lack: the pace of growth of the wood, environmental pressures acting on the tree, its ultimate size and many of the other clues revealed through laboratory work with wood specimens. Part of our lack of knowledge about the tree’s wood is because it has always been uncommon on the island, at least since Western contact. Rapa Nui came with inherent geographic disadvantages for plant survival, including few sheltered habitats with steep hillsides or deep ravines in which toromiro could remain hidden away from humans. The three volcanic craters on the island are the only such hiding places. In 1911, the Chilean botanist Francisco Fuentes noted that the toromiro was rare, only to be found in Rano Kau, the largest of the craters. The Swedish botanist Carl Skottsberg, who also worked on Hawaiian flora, visited Rano Kau in 1917 and found only a single specimen. A compelling global exploration of nature and survival as seen through a dozen species of trees. The final contact with the tree on its native soil occurred when the Norwegian explorer Thor Heyerdahl collected seeds from the last surviving example. This was likely the same tree that Skottsberg had found in the shelter of Rano Kau. The egg-shaped crater is about a mile across and has its own microclimate, largely out of the winds and weather, and protected from grazing ungulates by a rock formation. Foot traffic remained down in the last century, as little else lives in the crater that can be harvested or cut down. Innumerable swampy pockets of water make the area difficult to traverse. A beautiful, multicolored, shallow lake of open water and floating mats of peat cover much of the bottom of the crater. There, the tiny toromiro held on. Heyerdahl, who had already been traveling around the Pacific Ocean in the 1940s, became famous, or infamous, for floating a radical new theory: that the islands in the Pacific had been populated initially by American Indians from the mainland of South America, rather than by people from Asia or from other Polynesian islands. In 1947, he launched an expedition with a primitive raft named Kon-Tiki and made a 5,000-mile journey, heading west from Peru. What’s often lost in the voluminous writings about Heyerdahl and his oceanfaring obsessions was his interest in Rapa Nui. Björn Aldén, a Swedish botanist with the Gothenburg Botanical Garden, became friends with Heyerdahl and has worked to return the toromiro to its native land. In a letter to Björn, Heyerdahl decried the “tankelöse treskjaerere,” or “thoughtless woodcutters.” He noted how good it felt to have helped to save the species by collecting a handful of seeds that hung from the tree’s sole remaining branch. Heyerdahl couldn’t recount the exact date, or even the year, but thought it was sometime in late 1955 or early 1956. Heyerdahl handed the seeds off to paleobotanist Olaf Selling in Stockholm. They went to Gothenburg from there. Locals have a strain of national pride in Gothenburg for their role in the tree’s cultivation and survival. But recently, researchers in Chile discovered that another botanist preceded Heyerdahl in getting seeds off the island. Efraín Volosky Yadlin, an Argentinian-born immigrant, participated in the first agronomic studies on Rapa Nui. Sent there by the Chilean Ministry of Agriculture in the early 1950s, Volosky Yadlin collected seeds, apparently from the same tree that Heyerdahl would come upon a few years later, and proceeded to carry out his own propagation tests on the toromiro. Now the tree remains far afield, surviving in about a dozen locations around the world, mostly in botanical gardens including in Chile, in London and in southern France. Ultimately, researchers want to return the toromiro to Rapa Nui. But the tree still confronts challenges to surviving on its native ground, including a lack of genetic diversity and degraded soil on Rapa Nui. Past efforts to reestablish the tree have failed, but botanists are doing their best to overcome these hurdles. More studies will help researchers understand just what it will take to help the tree take root back on Rapa Nui and successfully end a long and difficult voyage. Excerpted from Twelve Trees: The Deep Roots of Our Future by Daniel Lewis. Published by Avid Reader Press / Simon & Schuster. Copyright © 2024. All rights reserved. Get the latest Science stories in your inbox. A Note to our Readers Smithsonian magazine participates in affiliate link advertising programs. If you purchase an item through these links, we receive a commission.
Before the toromiro disappeared from the island, at least two men grabbed seeds from the last remaining plant and brought them home
The tree that goes by toromiro has been a fragile expat for more than a half-century. Little Sophora toromiro, is far from home, no longer present on Rapa Nui, the Pacific island where it evolved. Also known as Easter Island, or Isla de Pascua in Spanish, Rapa Nui is a speck of land in the Pacific, 2,200 miles from the west coast of Chile. The tiny island encompasses just 63 square miles, and it is quite flat, with a maximum elevation of less than 1,700 feet.
The last date of the toromiro’s tenure on Rapa Nui is uncertain. Some accounts say it went extinct in the wild in 1960. Others say that it was gone by 1962, when Karl Schanz, a German meteorologist, clambered down to see the tree in the crater where it had last been spotted, and it was gone. Was it removed? Did it die, tip over and return to the earth? We will never know. Although the toromiro is gone from Rapa Nui, it survives elsewhere through luck—and pluck. Over the past century, the intermittent collecting of the toromiro’s seeds and their replanting in mainland locations have given the species purchase elsewhere. Each tree is a member of a small diaspora, with only a handful surviving in about a dozen different public and private botanical gardens around the world. This is a story of survival, persistence and, perhaps in some ways, dumb luck—a tree in decline that was rescued and whose seeds were sent to other places.
Mention Easter Island to almost anyone, and if they’ve heard of it, they’ve likely heard of its statues. Imprinted in the popular imagination are its enigmatic, massive stone sculptures, or moai. Curious investigators have speculated for more than two centuries about how more than 900 of these mysterious statues—the largest being more than 30 feet tall and weighing over 80 tons—might have been moved to locations around the island, traveling miles from the site where they were quarried. The toromiro, though, is an invisible tree on the island, its story known to very few, and its existence marked more by its absence than its presence.
The tree does have many close relatives. The Sophora genus is speciose, as biologists say—a crowded taxon consisting of some 60 different species, including a dozen closely related oceanic ones scattered across the Pacific. The toromiro is more of a shrub than a tree, and none of its close relatives is large—at least from descriptions recorded over the past century. The northernmost outpost for the Sophora genus is in Hawaiʻi, where Sophora chrysophylla is the primary food source for the palila, a critically endangered honeycreeper. Without S. chrysophylla, known as mamane in Hawaiian, the palila would not have survived the last century as its range dwindled.
The subterranean pollen record reveals that the toromiro was abundant across much of Rapa Nui, where many other now-extinct plants also thrived. Paleobotanical evidence shows that the tree’s presence on the island dates back at least 35,000 years. Its seeds are both buoyant and salt-resistant, and they probably first arrived by water, floating onto the island, probably from another Pacific island, and then it did what species do: continued its evolutionary journey in a new place to become the tree we know today. But even before the toromiro disappeared from the island, it had been without a lot of endemic companions. Fewer than 30 indigenous seed-bearing plant species have survived on Rapa Nui to the present day, and weeds, along with naturalized, cultivated shrubs, are now the main plants growing there.
The toromiro did not disappear precipitously but experienced a protracted decline. Humans arrived in Rapa Nui around the 12th century, probably not long after Polynesians reached the Hawaiian archipelago. Some hundreds of years after humans’ arrival, the island experienced a painful drop in biodiversity, and its carrying capacity plummeted as the native palm forests disappeared, replaced by grasslands. Food grew scarce, and occupants fled, thinning down to around 100 Rapa Nui at one point in the 19th century. In his deterministic 2005 book Collapse: How Societies Choose to Fail or Succeed, Jared Diamond claimed the occupants were lousy land managers. His analysis of why Rapa Nui became denuded of its plant life is now out of date, as later studies have revealed the island’s complexities. To sketch the story of the weakening grip of native plant life on Rapa Nui as a predictable story of human arrogance intersecting with a small, remote and evolutionarily vulnerable spit of land is tempting, but the tale is more nuanced than that. Natives there recorded centuries-old histories of careful but intermittent conservation strategies. Some scholars have asserted that the Little Ice Age stressed resources on the island between the 16th and 19th centuries, leading to the disappearance of palms and other important contributors to the islanders’ activities and well-being. Others have pointed to prolonged droughts, while still others have continued to argue that humans were highly complicit in the island’s declining biodiversity. Were groves of palm trees decimated to create systems for rolling the giant stone carvings from quarry to coastline, where most of them have sat for many hundreds of years? Perhaps.
However the palms disappeared, their loss seems to have been a factor in the tumbling downturn of the island’s other trees, including the toromiro. The palms had made up the great majority of Rapa Nui’s tree cover, some 16 million trees that blanketed about 70 percent of the island. Some controversy remains about what particular species of palm flourished, but many believe it was Paschalococos disperta, the Rapa Nui palm. Jaime Espejo, a Chilean botanist who’s written extensively about the toromiro, noted that it probably lived in the undergrowth of the palm, lodged in an ancient ecosystem that no longer exists. Paleobotanists and archaeologists studying the island spotted the widespread loss of the palms in their investigations. At the same time, they found that the number of fish bones found in waste middens around the island dropped as fishing boats could no longer be constructed in large numbers from trees. The loss of access to fish must have been a devastating turn, because the human residents’ main proteins came from the sea.
Soil erosion, likely exacerbated by deforestation and agriculture, led to further losses of the tree. Hooved animals, arriving with European explorers in the 18th century, were also certain culprits in the toromiro’s decline and disappearance. In Hawaiʻi, sheep consume that archipelago’s species of Sophora. Another creature implicated in the destruction of much of both Rapa Nui’s and Hawaiʻi’s plant life was the Polynesian rat (Rattus exulans), as well as the bigger ship rat (Rattus rattus) and Norwegian rat (Rattus norvegicus). These rats, landing on new island homes and able to reproduce quickly, found abundant food in the form of native seeds, plants and invertebrates—and no predators. They laid waste to plant life with shocking speed.
Early European accounts and pollen records tell us that by about 1600, forests in the island’s craters had disappeared, and, with that, the toromiro declined into long-term scarcity and then extirpation. The New Zealand anthropologist Steven Fischer has noted that the last forest was probably cut for firewood around 1640, making wood the most valuable commodity on the island. Driftwood became precious. So scarce was wood, Fischer observes, that the pan-Polynesian word rakau, meaning “tree,” “timber” or “wood,” came to mean “riches” or “wealth” in the old Rapa Nui language—a meaning not present in any other use of the word elsewhere in Polynesia, including in Tahiti, Tonga, Hawaiʻi and New Zealand. It’s ironic that after the deforestation of the island’s trees, new linguistic meanings sprouted out of the island’s impending botanical doom.
Amid these centuries-long difficulties, but long before the toromiro disappeared, a wood-based culture thrived. The Rapa Nui had a particular passion for carving; beyond their giant stone statues, they favored the toromiro for its durable and fine-grained wood and reddish hue. Although primarily used for ritual objects, the toromiro was also serviceable for building material in houses, household utensils, statuettes and paddles. These artifacts survive in museums around the world. Some of them are hundreds of years old, and they might provide unexpected addenda to our understandings of the tree’s deeper history, offered up through dendrochronological analysis. Studying the annual growth rings in the wood could provide details we lack: the pace of growth of the wood, environmental pressures acting on the tree, its ultimate size and many of the other clues revealed through laboratory work with wood specimens.
Part of our lack of knowledge about the tree’s wood is because it has always been uncommon on the island, at least since Western contact. Rapa Nui came with inherent geographic disadvantages for plant survival, including few sheltered habitats with steep hillsides or deep ravines in which toromiro could remain hidden away from humans. The three volcanic craters on the island are the only such hiding places. In 1911, the Chilean botanist Francisco Fuentes noted that the toromiro was rare, only to be found in Rano Kau, the largest of the craters. The Swedish botanist Carl Skottsberg, who also worked on Hawaiian flora, visited Rano Kau in 1917 and found only a single specimen.
The final contact with the tree on its native soil occurred when the Norwegian explorer Thor Heyerdahl collected seeds from the last surviving example. This was likely the same tree that Skottsberg had found in the shelter of Rano Kau. The egg-shaped crater is about a mile across and has its own microclimate, largely out of the winds and weather, and protected from grazing ungulates by a rock formation. Foot traffic remained down in the last century, as little else lives in the crater that can be harvested or cut down. Innumerable swampy pockets of water make the area difficult to traverse. A beautiful, multicolored, shallow lake of open water and floating mats of peat cover much of the bottom of the crater. There, the tiny toromiro held on.
Heyerdahl, who had already been traveling around the Pacific Ocean in the 1940s, became famous, or infamous, for floating a radical new theory: that the islands in the Pacific had been populated initially by American Indians from the mainland of South America, rather than by people from Asia or from other Polynesian islands. In 1947, he launched an expedition with a primitive raft named Kon-Tiki and made a 5,000-mile journey, heading west from Peru.
What’s often lost in the voluminous writings about Heyerdahl and his oceanfaring obsessions was his interest in Rapa Nui. Björn Aldén, a Swedish botanist with the Gothenburg Botanical Garden, became friends with Heyerdahl and has worked to return the toromiro to its native land. In a letter to Björn, Heyerdahl decried the “tankelöse treskjaerere,” or “thoughtless woodcutters.” He noted how good it felt to have helped to save the species by collecting a handful of seeds that hung from the tree’s sole remaining branch. Heyerdahl couldn’t recount the exact date, or even the year, but thought it was sometime in late 1955 or early 1956. Heyerdahl handed the seeds off to paleobotanist Olaf Selling in Stockholm. They went to Gothenburg from there.
Locals have a strain of national pride in Gothenburg for their role in the tree’s cultivation and survival. But recently, researchers in Chile discovered that another botanist preceded Heyerdahl in getting seeds off the island. Efraín Volosky Yadlin, an Argentinian-born immigrant, participated in the first agronomic studies on Rapa Nui. Sent there by the Chilean Ministry of Agriculture in the early 1950s, Volosky Yadlin collected seeds, apparently from the same tree that Heyerdahl would come upon a few years later, and proceeded to carry out his own propagation tests on the toromiro.
Now the tree remains far afield, surviving in about a dozen locations around the world, mostly in botanical gardens including in Chile, in London and in southern France. Ultimately, researchers want to return the toromiro to Rapa Nui. But the tree still confronts challenges to surviving on its native ground, including a lack of genetic diversity and degraded soil on Rapa Nui. Past efforts to reestablish the tree have failed, but botanists are doing their best to overcome these hurdles. More studies will help researchers understand just what it will take to help the tree take root back on Rapa Nui and successfully end a long and difficult voyage.
Excerpted from Twelve Trees: The Deep Roots of Our Future by Daniel Lewis. Published by Avid Reader Press / Simon & Schuster. Copyright © 2024. All rights reserved.
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