Chile - November 02, 2023 A new study challenges the ecocide narrative to explain the collapse of Polynesian culture on Easter Island, Chile, claiming that the population never increased to unsustainable levels. Instead, the research argues that the Polynesians who arrived on Rapa Nui, as they called it, found ways to cope with the island's severe constraints and maintained a small and 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 just enough area to sustain a few thousand people, the 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," lead author Dylan Davis, a postdoctoral researcher in archaeology at Columbia's School of Climate, said in a statement. "The lesson is the opposite of the 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 colonised by humans, if not the last. The nearest landmass is central Chile, almost 3,500 kilometres to the east. Some 5,100 kilometres to the west are the tropical Cook Islands, from which settlers are believed to have arrived around 1200 AD.The 100-square-kilometre island is made up entirely of volcanic rock, but unlike lush tropical islands such as Hawaii and Tahiti, eruptions ceased hundreds of thousands of years ago and the mineral nutrients brought in by the lava have long since eroded from the soil. Located in the subtropics, the island is also drier than its tropical sisters. To complicate matters, the surrounding ocean waters drop sharply, meaning that the islanders had to work harder to capture marine creatures than those living on Polynesian islands surrounded by accessible and productive lagoons and reefs. To cope with this, the settlers used a technique called rock gardening or lithic mulching. This consists of spreading rocks on 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 the rocks, from golf-ball sized to the largest, disrupt the winds that dry the atmosphere and create turbulent airflow, which reduces higher surface temperatures during the day and increases lower surface temperatures at night. Smaller pieces, broken up by hand, expose fresh surfaces laden with mineral nutrients that are released into the soil as they are worn 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 had to have been much larger than the 3,000 residents observed by early Europeans, in part because of the huge moai; it would have taken hordes of people to build them, the reasoning goes.In recent years, therefore, researchers have tried to estimate these populations in part by investigating the extent and production capacity of the rock gardens. Early Europeans estimated that they covered 10% of the island. A 2013 study based on visual and near-infrared satellite imagery yielded 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 about 3,100 hectares, or 19% of the island, as suitable for sweet potato cultivation. Based on 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 surveys of rock gardens and their features over a five-year period. Using this data, they then trained a series of machine learning models to detect gardens through satellite imagery fitted to newly available shortwave infrared spectra, which highlight not only rocks, but also locations with higher soil moisture and nitrogen, which are key features of the gardens. The researchers conclude that the rock gardens occupy only about 188 hectares, less than 0.5% of the island. They say they may have missed some small ones, but not enough to make a big difference. Based on a number of assumptions, they say that if the entire diet was based on sweet potatoes, these gardens could have supported about 2,000 people. However, based on isotopes found in bones and teeth and other evidence, it is likely that people of the past got 35-45% of their diet from marine sources, with a small amount from other less