Half a century ago, the history of Easter Island became a cautionary tale about the collapse that would occur if humans overran their environment. More recently, that narrative has changed when it comes to Easter Island, the remote Chilean territory in the southeast Pacific that is famed for its monumental statues, called moai. The tale is still cautionary, but it has a different moral. The latest evidence comes from a study of satellite images of gardens where the island’s earliest inhabitants produced food.

Piecing them together, a group of researchers argues the island could have supported up to 3,000 or 4,000 people, not the 10,000 or more that some authors have claimed were there before Europeans arrived. According to those earlier authors, when Europeans arrived at Easter Island, or Rapa Nui, they found “the remnants of a society that used to be much bigger,” says archaeologist Dylan Davis, a postdoctoral researcher at Columbia University in New York who specializes in remote sensing and paleo climate. “The overall narrative is that people get there, they cut down all the trees trying to build these big statues, they use up all the resources doing that, and then they’re left in this state of chaos and [the society] collapses.”

But according to Davis and other coauthors of the new study, published in the June 21 issue of the journal Science Advances, the maximum size of the population was about the same as the Europeans reported.

Key evidence for that conclusion lies in island rock gardens where farmers used a technique known as lithic mulching. On the isolated volcanic island, mixing pulverized rock into the fairly infertile soil boosted nutrients, while arranging rocks on the surface helped maintain moisture. Adding up the scattered areas identified as former rock gardens and multiplying by the maximum amount of staple crops such as sweet potatoes and taro that could be produced in them gives an idea of the maximum possible human population, Davis says.

Lithic mulching is common on islands in Polynesia and elsewhere, and rock gardens have been measured before on Rapa Nui. But Davis says the satellite data used in past studies have overestimated the extent of these gardens.

Those studies, which employed visible and near-infrared (VNIR) satellite imagery, estimated that rock gardens covered between 4.9 square kilometers (1.89 square miles) and 21.1 square kilometers (8.15 square miles) of Easter Island’s total 163.6 square kilometers (63.17 square miles)—equivalent to an area slightly smaller than Washington, D.C. The data, Davis says, captured some areas that, while rocky, were not gardens.

Higher-resolution imagery

In the study, Davis and his team instead analyzed shortwave infrared (SWIR) satellite imagery, which compared to VNIR imagery has a higher resolution, penetrates cloud cover, and can detect soil type and moisture.

The analysis found a total of about 0.76 square kilometers (0.29 square miles) of rock gardens scattered around the island. That’s substantially less than previous estimates, but enough to support the lower estimated maximum population.

Although Davis says not everyone is convinced by his data, archaeologists have gradually adopted the view that the story of a catastrophic collapse on Rapa Nui is rooted in early European explorers’ bias and the lack of knowledge of germ theory at the time, says anthropologist Carl Lipo of Binghamton University in New York, a coauthor of the paper.

The first European to document a visit to Rapa Nui was Dutch explorer Jacob Roggeveen. After landing there on Easter Sunday in 1722, thus giving the island its non-Indigenous name, he reported a population of 2,000 to 3,000 people, described their impressive stone statues and noted that parts of the island were under cultivation. Spaniards who arrived in 1770 estimated about the same population. But British explorer James Cook, arriving four years later, found a society in disarray, fields abandoned, the population diminished and the statues neglected.

The European interpretation was that it would have taken many more people to erect the huge stone statues, so the original numbers must have been much larger, Lipo says. But it’s more likely that the Spaniards, during their brief stay, introduced diseases to which the islanders had no immunity, decimating the population.

Ecologists have also pointed to the eradication of palms, once common on the island but largely gone by the 18th century, as an indication of environmental disaster.

Role of a rat

But Lipo sees the palms’ demise as a natural consequence of the introduction of Polynesian rats (Rattus exulans) by the first Polynesians who settled the island. By devouring the island’s palm fruit, the rats may have caused the palm’s extinction; but he says the Rapa Nuians probably considered the rats, a food source, more valuable than the palms, which were useless for building houses or boats.

These conclusions could shift the story from one of collapse to one of resiliency and adaptation to changing conditions. “Everything that people say about the lack of vegetation and the wretchedness is really about transformation of the island into something that grows food for people,” Lipo says. “The fewer palm trees there were, the more land was available to grow food.”

Meanwhile, the huge statues could only have been constructed by communities that valued collaboration over individuality—a lesson for modern societies facing complex environmental problems, he adds.

The result is still a cautionary tale, but a more hopeful one, says Davis, who is using SWIR technology on Easter Island and in Madagascar, both places where people have dealt with changing climates for hundreds—or, in Madagascar’s case, thousands—of years. Using new technologies to study the archaeological record, Davis says, will help scientists “really pinpoint the strategies that have allowed people to succeed sustainably” in difficult places.