What transformed Easter Island? The answer isn’t what we thought

For years, the popular story about Easter Island has sounded like a warning. People cut down every tree to haul giant stone heads across the landscape, wrecked the environment, and then their society collapsed.

The treeless island we see today looks like the final scene of the story. But that narrative turns out to be wrong in some very important ways.

Research on Rapa Nui – as the island is called in its Indigenous language – reveals a different past.

The famous moai statues, which represented ancestors, helped bring communities together. They were not dragged on wooden rollers, but moved upright with ropes.

The human population did not crash until Europeans arrived in the 18th century. The loss of the island’s forest involved people, but it also involved millions of hungry rats.

The palm trees of Easter Island

Archaeologist Carl Lipo at Binghamton University and anthropologist Terry L. Hunt at the University of Arizona have spent years studying Rapa Nui. Their recent study digs into what really happened to the island’s palm forest.

“The human impact on these environments is very complex,” said Lipo. “Sometimes there are unintended consequences, like the rats. In this case, the modification of the environment wasn’t a human disaster.”

Long before people arrived, Rapa Nui was covered in large palm trees, a now-extinct species related to the Chilean wine palm, Jubaea chilensis.

These palms could live up to 500 years, and they took around 70 years just to reach maturity and bear fruit. By the time Europeans reached the island in 1722, only a few palms remained.

“The Europeans basically describe a treeless island, but they also describe palms and palm leaves. It’s hard to know whether they’re using the term to describe some other tree,” noted Lipo.

Coconut palms, the kind many people picture on tropical beaches, did not arrive until the 1950s.

Arrival of the Polynesian rat

When Polynesian voyagers set out across the Pacific, they carried a full “survival kit” with them, including crops such as taro, sweet potatoes, bananas, and yams. They also brought dogs, chickens, and pigs.

A smaller passenger came with this package too – the Polynesian rat. This animal is small and arboreal, spending much of its time in trees.

“Because of their genetics and the ‘founder’s effect,’ they have unique haplotypes. We can trace the colonization of people and, to some degree, the number of colonizations by how variable the rats are as they move across the Pacific,” explained Lipo.

A place where rats could thrive

Exactly how these rats got into outrigger canoes is still debated. They could have snuck on board, or people may have brought them on purpose as a backup food source.

A European naturalist working after contact once saw a local man walking with rats in his hands. The man said they were for lunch.

Rat bones appear in ancient trash heaps, or middens, across many Pacific islands.

When Polynesians reached Rapa Nui around 1200 CE, the rats found a place with no predators and an endless supply of palm nuts.

The rats can have multiple litters in a single year, so their numbers shot up into the millions in only a short time. “Palm nuts are rat candy,” Lipo said. “The rats went bananas.”

Palms could no longer return

Along with plants and animals, Polynesian settlers brought farming methods that had worked on other islands.

One of these was slash-and-burn agriculture. Farmers cleared and burned patches of forest, and ash temporarily boosted the nutrients in the soil.

On older volcanic islands like Rapa Nui, rain can wash nutrients out of the ground, so that kind of boost helped crops grow.

“We see this in New Guinea and other places across the Pacific. But on Rapa Nui, the trees grow so slowly, and they don’t grow back due to rat predation on the palm nuts,” Lipo said.

With rats eating most of the seeds, the usual cycle where fields are abandoned and forests slowly return could not happen.

A shift in food production

As the palms failed to come back, people changed their approach. They created fields covered with stones, a technique called stone mulching.

The rocks helped trap moisture, shield soil from wind, and add bits of mineral material as they broke down – all of which supported crops such as sweet potatoes.

While the palm forest disappeared, food production shifted to cleared land and carefully managed gardens.

The palms themselves were not hardwood trees; they were more like giant grasses and could not supply strong timber for canoes, houses, or firewood.

“It’s a sad loss of a palm forest, but it wasn’t a disaster for the people,” Lipo said. “It wasn’t a necessary part of their survival.”

Waves of change on Easter Island

Some palms likely survived into the early years of European occupation. A new wave of change came in the 19th century with sheep ranching.

Grazing animals would have eaten any young palm seedlings trying to grow back, silencing the last chance for the trees to recover.

The original Polynesian rats, once so numerous, ended up in trouble too. On many islands they were pushed out by the larger Norway rat, which arrived with European ships, or were eaten by newly introduced predators such as hawks.

Islanders in the region still talk about years when rodent numbers explode and then suddenly crash, a boom-and-bust pattern that has played out again and again.

Behind the famous statues and the bare hills, the story of Rapa Nui is about unintended consequences and constant adjustment on one of the world’s most remote inhabited islands, where the closest neighbors are 1,200 miles away.

“We have to be more nuanced in our understanding of environmental change,” Lipo said. “We are part of the natural world; we reshape it often for our benefit, but that doesn’t necessarily mean that we create an unsustainable world for ourselves.”

The full study was published in the Journal of Archaeological Science.

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