Easter Island residents have found ingenious ways to adapt to the harsh environment. Recent research challenges the long-held view of ecological collapse on Easter Island and instead shows that the population has remained stable thanks to effective resource management.

About 1,000 years ago, a small group of Polynesians traveled thousands of miles across the Pacific Ocean to settle in one of the most isolated places on Earth, a small, uninhabited island they called Rapa Nui. There they built hundreds of “moai” or giant stone statues, which today are the emblem of a vanished civilization. Later their numbers reached unacceptable levels; They cut down all the trees, destroyed the seabirds, depleted the soil and ultimately destroyed the environment. When Europeans discovered the island in 1722 and named it Easter Island, their population and civilization had collapsed and only a few thousand people remained. At least that’s the old story told in academic studies and popular books like Jared Diamond’s 2005 Collapse.

Reconsidering ecological theory with new research

A new study challenges this narrative of ecocide, arguing that Rapa Nui’s population never grew to unsustainable levels. Instead, settlers found ways to cope with the island’s strict limitations and maintained a small, stable population for centuries. Proof: a recently developed list of elaborate “rock gardens” where islanders grow the highly nutritious sweet potatoes that form the basis of their diet. According to researchers, the gardens only took up enough space to support a few thousand people. The research was recently published in the journal Science Developments .

“This suggests that the population may never have been as large as some of the previous estimates,” said lead author Dylan Davis, a postdoctoral researcher in archeology at the Columbia Climate School. “The lesson is the opposite of the collapse theory. Humans have managed to be very resilient in the face of limited resources by changing the environment in helpful ways.”

Geographic and agricultural problems on Easter Island

Easter Island is perhaps the most remote inhabited place on Earth and one of the last, if not the last, places inhabited by humans. The nearest land mass is central Chile, located approximately 2,200 miles to the east. About 3,200 miles to the west are the tropical Cook Islands, where settlers are believed to have sailed from around 1200 AD.

The 63-square-mile island is composed entirely of volcanic rock, but unlike tropical islands like Hawaii and Tahiti, eruptions stopped hundreds of thousands of years ago and the mineral nutrients carried by the lava have long since separated from the soil. Located in the subtropics, the island is also drier than its tropical counterparts. To make matters worse, the surrounding ocean waters are decreasing significantly; This means the islanders have to work harder to collect marine life than Polynesian islanders, who are surrounded by accessible and fertile lagoons and reefs.

To deal with this problem, settlers used a technique called rock gardening or rock mulching. This consists of scattering stones on low surfaces that are at least partially protected from salt spray and wind. Sweet potatoes were planted in the spaces between the stones. Studies have shown that rocks, from golf ball-sized to boulder-sized, block dry winds and create turbulent airflow, lowering daytime highest surface temperatures and raising nighttime lowest temperatures. Smaller pieces broken by hand reveal fresh surfaces full of mineral nutrients that entered the soil during weathering. Some of the islanders still use the gardens, but despite all this work, their efficiency is negligible. This technique was also used by indigenous people in New Zealand, the Canary Islands, and the American Southwest, among other places.

Reevaluating historical population estimates

Some scholars suggest that the island’s population must have been much larger than the roughly 3,000 once observed by Europeans, in part due to the massive moai; Logic dictates that it would take a lot of people to build them. Therefore, in recent years researchers have attempted to evaluate these populations in part by examining rock garden sizes and production capacity. Early Europeans believed they occupied 10% of the island. A 2013 study based on visual and near-infrared satellite images found a rate between 2.5% and 12.5%; This is a large margin of error because these spectra only distinguish between rock fragments and vegetation, which are not all gardens. In another study conducted in 2017, it was determined that approximately 7,700 decares of land, or 19% of the island, was suitable for sweet potatoes. Studies that made various assumptions about yields and other factors have shown that past populations may have reached 17,500 or even 25,000, but may have been much lower.

In the new study, members of the research team conducted on-site surveys of rock gardens and their features over a five-year period. Using this data, they then trained a series of machine learning models using satellite imagery tuned to newly available shortwave infrared spectra to detect the gardens; These spectra highlight not only rocks but also areas with high soil moisture and nitrogen, key features of gardens. .

The researchers concluded that the rock gardens covered only 188 acres (less than half a percent of the island). They say they may have missed some minor points, but not enough to make a difference. Making a series of assumptions, they say that if the diet were based entirely on sweet potatoes, these gardens could support about 2,000 people. However, based on isotopes found in bones, teeth, and other evidence, humans in the past probably obtained 35% to 45% of their diet from marine sources and small amounts from other less nutritious crops such as bananas, taro, and sugar cane. . Taking these resources into account, the population would increase to approximately 3,000, the number observed at the time of European contact.

Modern perspectives and ongoing research

“Natural rocks, which were once thought of as rock gardens, are everywhere. Shortwave imaging reveals a different picture,” Davis said.

The idea of ​​population booms and busts “still permeates the public consciousness” in fields such as ecology, but archaeologists have quietly abandoned the idea, said Carl Lipo, an archaeologist at Binghamton University and a co-author of the study. He said the collection of evidence based on radiocarbon dating of artifacts and human remains did not support the idea of ​​a large population. “The way people live must be incredibly labour-intensive,” he said. “Imagine sitting around breaking rocks all day.”

Current situation and agricultural practices on Easter Island

Now the island has a population of almost 8,000 (plus about 100,000 tourists per year). Most produce is now imported, but some residents still grow sweet potatoes in ancient gardens; This practice is a practice that has become widespread during the 2020-2021 quarantine period due to the Covid epidemic, when imports were restricted. Some also turned to mainland techniques of farming, plowing and using artificial fertilizers. But Lipo said this is unlikely to be sustainable as it would further deplete the thin soil cover.

Seth Quintus, an anthropologist at the University of Hawaii who was not involved in the research, said he saw the island as “a good example of human behavioral adaptation in a dynamic environment.” The new study and others like it “offer an opportunity to better document the nature and scope of adaptation strategies,” he said. “Surviving the drier subtropics on Rapa Nui, which is more isolated and geologically older, was a real challenge.”