Easter Island has long been put forward as a prime example of humans undermining their own survival by destroying the environment they rely on. But now fresh data is turning the narrative on its head.
Also known as Rapa Nui, the remote island in Polynesia is well known for its huge stone statues called “moai” and for the idea that its growing population collapsed because of “ecocide”.
The theory – promoted by experts including the Pulitzer prize-winning author Jared Diamond – suggests islanders chopped down palm trees at an unsustainable rate to create gardens, harvest fuel and move statues, which brought on disaster. As a result, the population encountered by Europeans in the 18th century was a shadow of what it had once been.
However, a new study has added to a growing body of evidence offering a very different view.
“Our study confirms that the island couldn’t have supported more than a few thousand people,” said Dr Dylan Davis, a co-author of the work from Columbia University. “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.”
Writing in the journal Science Advances, Davis and colleagues reported how they harnessed high-resolution shortwave infrared and near-infrared satellite imagery and machine learning to identify archaeological sites of rock gardening – a practice employed by the inhabitants of Easter Island to grow crops, including sweet potatoes.
The results suggest only 0.76 km2 of land was used in this way – far below previous estimates which, the team said, misidentified features such natural lava flows.
As a result, Davis and colleagues have suggested that rock gardening alone could only have supported about 3,900 people at most, a long way off previous estimates of up to 17,000. Indeed, the average figure is just 2,000 people, although this could be increased to up to 4,000 people if other foods, for example from fishing or foraging, are considered.
“One of the major arguments for an ‘ecocide’ was that the populations must have been very large in order to build all of the moai statues,” said Davis.
“However, archaeological evidence does not support a large population and studies of the moai themselves suggest that a small population could have built and moved them. It just required cooperation.”
Davis added that while the first people to arrive on Rapa Nui in about AD1200-1250 found an island covered in forest but with limited soil nutrients, it was the arrival of the seed-eating Polynesian rat that caused the tree population to wane.
“When Europeans arrived in the 18th century, they found a society living within their means, growing much of their food in rock gardens in an otherwise unfarmable landscape,” he said.
Prof Sue Hamilton, an expert on Rapa Nui from University College London who was not involved in the work, said the study was not the first to call earlier ideas into question.
She said: “For at least a decade, the idea of ecocide through population growth and landscape mismanagement has been increasingly convincingly challenged for Rapa Nui.”.
But while Hamilton called the new work “ingenious”, she said it had limitations – some of which the authors acknowledged – including that it was not possible to prove that the size of the population could be extrapolated from the extent of the rock gardening, and that the rock gardens may date from different times. She also argued that some rock gardening sites had been overlooked.
“The situation is quite simply more complex than this one line of study alone can resolve,” Hamilton said.