There was no ecocide or overpopulation on Rapa Nui

June 24 () –

A new study challenges the ecocide narrative to explain the collapse of the Polynesian culture of Easter Island (Chile), ensuring that the population never increased to unsustainable levels.

Instead, the research maintains that the Polynesians who arrived on Rapa Nui, as they called it, found ways to cope with the island’s severe limitations and They maintained a small, stable population for centuries.

The evidence for this conclusion is a recently documented inventory of ingenious “rock gardens” where the islanders grew highly nutritious sweet potatoes, a staple of their diet. The gardens covered only enough area to support a few thousand people, researchers say. The study was published in the journal Science Advances.

“This shows that the population could never have been as large as some of the previous estimates,” he said. it’s a statement lead author Dylan Davis, a postdoctoral researcher in archeology at the Columbia Climate School. “The lesson is the opposite of collapse theory. People were able to be very resilient in the face of limited resources by modifying the environment in a way that helped them.”

Easter Island is possibly the most remote inhabited place on Earth and one of the last to be colonized by humans, if not the last. The closest continental mass is central Chile, almost 3,500 kilometers to the east. About 5,100 kilometers to the west are the tropical Cook Islands, where settlers are believed to have arrived around 1200 AD.

The 100-square-kilometer island is made entirely of volcanic rock, but unlike lush tropical islands like Hawaii and Tahiti, eruptions stopped hundreds of thousands of years ago and the mineral nutrients brought by the lava They eroded from the soils a long time ago.

Located in the subtropics, the island is also drier than its tropical sisters. To complicate matters, the surrounding ocean waters drop steeply, meaning the islanders had to work harder to capture sea creatures than those who lived on Polynesian islands surrounded by accessible and productive lagoons and reefs.

To deal with this, settlers used a technique called rock gardening or lithic mulch. This involves scattering rocks over low surfaces that are at least partially protected from salt spray and wind. In the interstices between the rocks, They planted sweet potatoes.

Research has shown that rocks, from golf ball size to larger, disrupt winds that dry the atmosphere and create turbulent airflow, reducing higher daytime surface temperatures and increasing temperatures. lower during the night. The smaller pieces, broken by hand, reveal fresh surfaces loaded with mineral nutrients that are released into the soil as they wear away.

Some islanders still use the gardens, but even with all this work, their productivity is marginal. The technique has also been used by indigenous peoples in New Zealand, the Canary Islands, and the southwestern United States, among other places.

Some scientists have argued that the island’s population must have been much larger than the 3,000 residents observed by early Europeans, partly due to the huge moai; it would have taken hordes of people to build them, the reasoning went.

Therefore, in recent years, researchers have tried to estimate these populations in part by investigating the extent and production capacity of rock gardens. Early Europeans estimated that they covered 10% of the island.

A 2013 study based on visual and near-infrared satellite images returned a margin of error of between 2.5% and 12.5%, a wide margin of error because these spectra distinguish only areas of rocks versus vegetation, not all of which are gardens. Another 2017 study identified around 3,100 hectares, or 19% of the island, as suitable for growing sweet potatoes.

Using various assumptions about crop yields and other factors, studies have estimated that past populations could have increased to 17,500, or even 25,000, although they could also have been much smaller.

In the new study, members of the research team conducted field studies of rock gardens and their characteristics over a five-year period. Using this data, they then trained a series of machine learning models to detect gardens through satellite images adjusted to the newly available shortwave infrared spectra, which highlight not only rocks but also places with higher soil moisture and nitrogen. , which are key features of the gardens.

The researchers conclude that rock gardens occupy only about 188 hectares, less than 0.5% of the island. They say they may have missed a few small ones, but not enough to make a big difference. Starting from a series of assumptions, they claim that if the entire diet was based on sweet potatoes, These gardens could have supported around 2,000 people.

However, based on isotopes found in bones and teeth and other evidence, it is likely that people in the past got between 35% and 45% of their diet from marine sources, and a small amount from other, less common crops. nutritious, such as banana, taro and sugar cane. If these sources were taken into account, the supporting capacity of the population would have increased to about 3,000 people, the figure observed at the time of European contact.

“There are natural rock outcrops everywhere that have been misidentified as rock gardens in the past. Shortwave imagery gives a different picture,” Davis said.

Carl Lipo, an archaeologist at Binghamton University and co-author of the study, said the idea of ​​a population boom and bust is “still pervading the public mind” and in fields like ecology, but archaeologists are quietly moving away. her.

The accumulation of evidence based on radiocarbon dating of artifacts and human remains does not support the idea of ​​huge populations, he said. “The people’s lifestyle must have been incredibly laborious,” she said. “Think about sitting around breaking rocks all day.”

The island’s population is now almost 8,000 people (plus about 100,000 tourists a year). Most food is now imported, but some residents still grow sweet potatoes in former gardens, a practice that grew during the 2020-2021 COVID pandemic shutdowns, when imports were restricted. Some also turned to continental agricultural techniques, plowing the soil and applying artificial fertilizers. But this is unlikely to be sustainable, Lipo said, as it will further deplete the thin soil cover.