Easter Island Did Not Collapse From Overuse of Resources After All, Study Suggests

Researchers have long thought that hundreds of years ago, the population of the Pacific island Rapa Nui, or Easter Island, experienced a steep crash. Its residents were said to have used up all the land’s resources—cutting down its trees, depleting its soils and killing its seabirds. As a result, the number of islanders may have dwindled from as many as 25,000 people to only a few thousand.

But new research published last week in the journal Science Advances finds Rapa Nui, known for its large stone statues called moai, had less viable land for farming at the time than previously thought. As such, scientists suggest the island’s population didn’t experience a dramatic drop-off. It was just small to begin with.

The findings add to an existing body of research painting a picture of a society that doesn’t match the common narrative—one that was able to adapt to the limitations of the land, as opposed to one marked by human-caused ecological destruction, or ecocide.

“For at least a decade, the idea of ecocide through population growth and landscape mismanagement has been increasingly convincingly challenged for Rapa Nui,” Sue Hamilton, an expert on Rapa Nui at University College London who did not contribute to the findings, tells the Guardian’s Nicola Davis.

“Overall, this [study] highlights that although the Rapa Nui [people] are often portrayed as a collapsed culture bounded by socio-political competition, ecological overexploitation and megalithic overproduction, the discussion would be better served if it recognized the Rapa Nui as a Polynesian island culture of adaptation and survival that has thrived for almost a millennium,” Dale F. Simpson, an anthropological archaeologist at the University of Illinois who was not involved in the work, says to New Scientist’s James Woodford.

Polynesians settled Rapa Nui around 1,000 years ago, according to a statement from Columbia University. The remote island is located in the southeastern Pacific Ocean, around 2,200 miles west of Chile.

Rapa Nui, made of volcanic rock, is a difficult place to farm—it has limited soil productivity and few freshwater sources. To get around this issue, settlers turned to rock gardening—a technique that involves spreading pieces of broken-up rock over soil—to grow crops like sweet potatoes. The strategy disrupts air flow in a way that keeps the land cooler during the day and warmer at night, and it preserves soil moisture. Through weathering, the rocks also add mineral nutrients into the ground.

When Europeans arrived in the 18th century, only around 3,000 people lived on Rapa Nui. In previous studies, researchers found that roughly 2.5 percent to 19 percent of the land could have been covered with rock gardens at the time. Based on this amount of farming land—and the assumption that only a huge society could have created so many massive moai statues—previous estimates suggested the island once supported 17,500 or 25,000 people. This led to the idea that the population had been decimated before European arrival, perhaps by overfarming.

But the authors of the new study write that past work overestimated the extent of rock gardens by misidentifying roads, lava flows and vegetation for arable land. For the new paper, the authors used satellite imagery and machine learning to estimate how much land was used for rock gardening.

They found that less than one-third of a square mile was used for rock gardening on the roughly 63-square-mile island—only a fifth of the most conservative previous estimates, they write in the paper. Even if residents also ate fish and some other crops, the team argues Rapa Nui could not have hosted large populations.

“Our study confirms that the island couldn’t have supported more than a few thousand people,” Dylan Davis, a co-author of the study and archaeologist at Columbia University, tells the Guardian. “As such, contrary to the ecocide narrative, the population present at European arrival wasn’t the remnants of Rapa Nui society, but was likely the society at its peak, living at the levels that were sustainable on the island.”

Still, other researchers say the new study overlooks some rock garden sites. The paper significantly underestimates the coverage of rock gardens on Rapa Nui and how many people could have lived there, Christopher Stevenson, an archaeologist at Virginia Commonwealth University who was not involved in the new work but conducted previous studies on Rapa Nui rock gardens, tells Science News’ Bruce Bower.

Hamilton also tells the Guardian that it could be hard to accurately estimate population size based on the area of rock gardens. “The situation is quite simply more complex than this one line of study alone can resolve,” she says to the publication.

Will Sullivan | | READ MORE

Will Sullivan is a science writer based in Washington, D.C. His work has appeared in Inside Science and NOVA Next.