From The University of Arizona
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Media Contact
Kyle Mittan
News Writer
mittank@arizona.edu
520-626-4407
Research Contact
Terry Hunt
School of Anthropology
tlhunt@arizona.edu
520-621-3015
Rapa Nui’s iconic moai represent the islanders’ deified ancestors, who colonized the island around 1200. Terry Hunt/School of Anthropology/UArizona
Some 800 years ago, a small band of Polynesians sailed thousands of miles across the Pacific to settle one of the world’s most isolated places – a small, previously uninhabited island they named Rapa Nui. There, they erected hundreds of “moai,” or gigantic stone statues that now famously stand as emblems of a vanished civilization.
Eventually, their numbers ballooned to unsustainable levels; they chopped down all the trees, killed off the seabirds, exhausted the soils and in the end, ruined their environment. Their population and civilization collapsed, with just a few thousand people remaining when Europeans found the island in 1722 and called it Easter Island. At least that is the longtime story, told in academic studies and popular books like Jared Diamond’s 2005 Collapse.
A new study challenges this narrative of “ecocide”, saying that Rapa Nui’s population never spiraled to unsustainable levels. Instead, the settlers found ways to cope with the island’s severe limits, and maintained a small, stable population for centuries.
The evidence: a newly sophisticated inventory of ingenious “rock gardens” where the islanders raised highly nutritious sweet potatoes, a staple of their diet. The gardens covered only enough area to support a few thousand people, say the researchers. The study was published Friday in the journal Science Advances.
Map of Rapa Nui and its location in the southeastern Pacific.
Satellite data provided by Maxar. Service layer credits: NASA Shuttle Radar Topography Mission
Easter Island in the Pacific Ocean. Britannica
Easter Island and the islands between it and South America.
Date 1986
Source http://www.lib.utexas.edu/maps/islands_oceans_poles/easterisland.jpg
“Used by permission of The General Libraries, The University of Texas at Austin.”
Terry Hunt, a professor in the University of Arizona School of Anthropology in the College of Social and Behavioral Sciences who has studied Rapa Nui for more than two decades, is a co-author on the new paper.
“Our more than 20 years of archaeological field research on Rapa Nui continues to challenge long-held assumptions about the island’s past,” said Hunt, who is also dean emeritus of the W.A. Franke Honors College. “We see clear evidence that while ancient islanders faced difficulties, they also found ingenious solutions, adapting to life on the island in a sustainable way.”
Dylan Davis, a postdoctoral researcher in archaeology at the Columbia Climate School, is lead author on the study.
“This shows that the population could never have been as big as some of the previous estimates,” Davis said. “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.”
The secret to a stable society? Rock gardens
Easter Island is arguably the most remote inhabited spot on Earth, and one of the last to be settled by humans. The nearest continental landmass is central Chile, nearly 2,200 miles to the east. Some 3,200 miles to the west lie the tropical islands of French Polynesia, where settlers are thought to have sailed from around the year 1200.
The 63-square-mile island is made entirely of volcanic rock, but unlike lush tropical islands such as Hawaii and Tahiti, eruptions ceased hundreds of thousands of years ago, and mineral nutrients brought up by lava have long since eroded from soils. Located in the subtropics, the island is also more dry than its tropical brethren. To make things more challenging, surrounding ocean waters drop off steeply, meaning islanders had to work harder to harvest marine creatures than those living on Polynesian islands ringed with accessible and productive lagoons and reefs.
To cope, the settlers used a technique called rock gardening, or lithic mulching. This consists of scattering rocks over low-lying surfaces that are at least partly protected from salt spray and wind. In the spaces between rocks, they planted sweet potatoes and taro. Research has shown that rocks from golf ball-size to boulders disrupt drying winds and create turbulent airflow, reducing the highest daytime surface temperatures and increasing the lowest nighttime ones. Smaller bits, broken up by hand, expose fresh surfaces laden with mineral nutrients that get released into the soil as they weather.
“The rock mulch solved the island’s problems of nutrient-poor soils, seasonal and daily temperature fluctuations, and the ever-present damaging effects of strong winds and salt spray,” Hunt said. “The use of rock mulch created sustainable agriculture for a relatively small population.”
Some islanders still use the gardens, but even with all this labor, their productivity is marginal. The technique has also been used by Indigenous people in New Zealand, the Canary Islands and the U.S. Southwest, among other places.
Rapa Nui settlers used a technique called rock gardening, or lithic mulching, which involved planting sweet potatoes and taro among scattered rocks to protect the crops from salt spray and wind. Terry Hunt/School of Anthropology
Some scientists have argued that the island’s population had to have once been much larger than the 3,000 or so residents first observed by Europeans in part because of the massive moai; the reasoning is that it would have taken hordes of people to construct them. In recent years, researchers have tried estimating these populations in part by investigating the rock gardens’ extent and production capacity. Early Europeans estimated they covered 10% of the island.
A 2013 study [Journal of Archaeological Science] based on visual and near-infrared satellite imagery came up with 2.5% to 12.5% – a wide margin of error because these spectra distinguish only areas of rock versus vegetation, not all of which are gardens. Another study in 2017 [Frontiers in Ecology and Evolution] identified about some 7,700 acres, or 19% of the island, as suitable for sweet potatoes. Making various assumptions about crop yields and other factors, studies have estimated past populations might have risen as high as 17,500, or even 25,000, though they also could have been much lower.
In the new study, members of the research team did on-the-ground surveys of rock gardens and their characteristics over a five-year period. Using this data, they trained a series of machine-learning models to detect gardens through satellite imagery tuned to newly available shortwave infrared spectra, which highlights not just rocks, but places of higher soil moisture and nitrogen, which are key features of gardens.
The researchers concluded that rock gardens occupy only about 188 acres – less than one-half a percent of the island. They say they might have missed some small ones, but not enough to make a big difference. Making a series of assumptions, they say that if the entire diet were based on sweet potatoes, these gardens may have supported about 2,000 people. However, based on isotopes found in bones and teeth and other evidence, people in the past probably managed to get 35% to 45% of their diet from marine sources, and a small amount from other less nutritious crops including bananas, taro and sugar cane. Factoring in these sources would have raised the population carrying capacity to about 3,000 – the number observed upon European contact.
“There are natural rock outcrops all over the place that had been misidentified as rock gardens in the past. The short-wave imagery gives a different picture,” said Davis.
Carl Lipo, an archaeologist at Binghamton University and a co-author of the study, said that the population boom-and-bust idea is “still percolating in the public mind” and in fields including ecology, but archaeologists are quietly retreating from it. Accumulating evidence based on radiocarbon dating of artifacts and human remains does not support the idea of huge populations, he said.
“People’s lifestyle must have been incredibly laborious,” he said. “Think about sitting around breaking up rocks all day.”
The island’s population is now nearly 8,000, plus about 100,000 tourists a year. Most food is now imported, but some residents still grow sweet potatoes in the ancient gardens – a practice that grew during the 2020-2021 lockdowns of the pandemic, when imports were restricted. Some also turned to mainland farming techniques, plowing soils and applying artificial fertilizer. But this is not likely to be sustainable, said Lipo, as it will further deplete the thin soil cover.
The latest milestone
The new study marks the latest milestone finding on Rapa Nui involving UArizona professor Hunt, an expert on the Pacific Islands who has studied Rapa Nui for more than two decades. The islanders’ oral traditions tell of how the statues were “walked,” using a series of ropes, into their final places to be displayed for ceremonial purposes. Hunt and Lipo helped demonstrate the practice with a full-size moai replica in a 2012 National Geographic documentary.
Terry Hunt and Carl Lipo: The Statues That Walked | Nat Geo Live
In a 2019 study [PLoS One], the two found that Rapa Nui islanders built the statues near freshwater sources. The research helped answer the long-asked question of why the statues ended up in their respective locations, considering how much time and energy went into building them.
In a 2020 study [Journal of Archaeological Science], Hunt helped disprove a widespread theory that the Rapa Nui people decimated their crops to make room for the moai, leading the first Europeans who arrived to the island on Easter Sunday 1722 to find a society that had collapsed. In fact, Hunt and his colleagues found through radiocarbon dating that Rapa Nui islanders continued to build, maintain and use the monuments for at least 150 years beyond 1600.
Last year, Hunt was among the first to see a newly discovered moai statue – the first one found at the bottom of a lakebed – opening a new trove of questions about how the statues were used by the islanders.
An aerial image of the newly found moai on Rapa Nui, pictured with Joaquín Soler Hotu, a member of Comunidad Indígena Ma`u Henua, the organization that manages the island’s national park and whose members made the recent discovery. Terry Hunt/School of Anthropology
He has returned to Rapa Nui this summer with his colleagues to continue field research on the island.
Additional co-authors on the new paper are Robert DiNapoli of Binghamton University and Gina Pakarati, an independent researcher on Rapa Nui.
See the full article here .
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State of the Planet is the news site of the Columbia Climate School, which includes the Earth Institute, Lamont-Doherty Earth Observatory, and all of their affiliated research centers and educational programs.
The Earth Institute is a research institute at Columbia University that was established in 1995. Its stated mission is to address complex issues facing the planet and its inhabitants, with a focus on sustainable development. With an interdisciplinary approach, this includes research in climate change, geology, global health, economics, management, agriculture, ecosystems, urbanization, energy, hazards, and water. The Earth Institute’s activities are guided by the idea that science and technological tools that already exist could be applied to greatly improve conditions for the world’s poor, while preserving the natural systems that support life on Earth.
The Earth Institute supports pioneering projects in the biological, engineering, social, and health sciences, while actively encouraging interdisciplinary projects—often combining natural and social sciences—in pursuit of solutions to real world problems and a sustainable planet. In its work, the Earth Institute remains mindful of the staggering disparities between rich and poor nations, and the tremendous impact that global-scale problems—such as the HIV/AIDS pandemic, climate change and extreme poverty—have on all nations.
Columbia University was founded in 1754 as King’s College by royal charter of King George II of England. It is the oldest institution of higher learning in the state of New York and the fifth oldest in the United States.
University Mission Statement
Columbia University is one of the world’s most important centers of research and at the same time a distinctive and distinguished learning environment for undergraduates and graduate students in many scholarly and professional fields. The University recognizes the importance of its location in New York City and seeks to link its research and teaching to the vast resources of a great metropolis. It seeks to attract a diverse and international faculty and student body, to support research and teaching on global issues, and to create academic relationships with many countries and regions. It expects all areas of the University to advance knowledge and learning at the highest level and to convey the products of its efforts to the world.
Columbia University is a private Ivy League research university in New York City. Established in 1754 on the grounds of Trinity Church in Manhattan Columbia is the oldest institution of higher education in New York and the fifth-oldest institution of higher learning in the United States. It is one of nine colonial colleges founded prior to the Declaration of Independence, seven of which belong to the Ivy League. Columbia is ranked among the top universities in the world by major education publications.
Columbia was established as King’s College by royal charter from King George II of Great Britain in reaction to the founding of Princeton College. It was renamed Columbia College in 1784 following the American Revolution, and in 1787 was placed under a private board of trustees headed by former students Alexander Hamilton and John Jay. In 1896, the campus was moved to its current location in Morningside Heights and renamed Columbia University.
Columbia scientists and scholars have played an important role in scientific breakthroughs including brain-computer interface; the laser and maser; nuclear magnetic resonance; the first nuclear pile; the first nuclear fission reaction in the Americas; the first evidence for plate tectonics and continental drift; and much of the initial research and planning for the Manhattan Project during World War II. Columbia is organized into twenty schools, including four undergraduate schools and 15 graduate schools. The university’s research efforts include the Lamont–Doherty Earth Observatory, the Goddard Institute for Space Studies, and accelerator laboratories with major technology firms such as IBM. Columbia is a founding member of the Association of American Universities and was the first school in the United States to grant the M.D. degree. With over 14 million volumes, Columbia University Library is the third largest private research library in the United States.
The university’s endowment stands among the largest of any academic institution. Columbia’s alumni, faculty, and staff have included: Founding Fathers of the United States—among them a co-author of the United States Constitution and a co-author of the Declaration of Independence; U.S. presidents; foreign heads of state; justices of the United States Supreme Court, one of whom currently serves; Nobel laureates; Fields Medalists; many members of National Academy of Sciences; living billionaires; Olympic medalists; Academy Award winners; and Pulitzer Prize recipients.
The University of Arizona enrolls over 49,000 students in 19 separate colleges/schools, including The University of Arizona College of Medicine in Tucson and Phoenix and the James E. Rogers College of Law, and is affiliated with two academic medical centers (Banner – University Medical Center Tucson and Banner – University Medical Center Phoenix). The University of Arizona is one of three universities governed by the Arizona Board of Regents. The university is part of the Association of American Universities and is the only member from Arizona, and also part of the Universities Research Association.
Known as the Arizona Wildcats (often shortened to “Cats”), The University of Arizona’s intercollegiate athletic teams are members of the Pac-12 Conference of the NCAA. The University of Arizona athletes have won national titles in several sports, most notably men’s basketball, baseball, and softball. The official colors of the university and its athletic teams are cardinal red and navy blue.
After the passage of the Morrill Land-Grant Act of 1862, the push for a university in Arizona grew. The Arizona Territory’s “Thieving Thirteenth” Legislature approved The University of Arizona in 1885 and selected the city of Tucson to receive the appropriation to build the university. Tucson hoped to receive the appropriation for the territory’s mental hospital, which carried a $100,000 allocation instead of the $25,000 allotted to the territory’s only university Arizona State University was also chartered in 1885, but it was created as Arizona’s normal school, and not a university). Flooding on the Salt River delayed Tucson’s legislators, and by the time they reached Prescott, back-room deals allocating the most desirable territorial institutions had been made. Tucson was largely disappointed with receiving what was viewed as an inferior prize.
With no parties willing to provide land for the new institution, the citizens of Tucson prepared to return the money to the Territorial Legislature until two gamblers and a saloon keeper decided to donate the land to build the school. Construction of Old Main, the first building on campus, began on October 27, 1887, and classes met for the first time in 1891 with 32 students in Old Main, which is still in use today. Because there were no high schools in Arizona Territory, the university maintained separate preparatory classes for the first 23 years of operation.
Research
The University of Arizona is classified among “R1: Doctoral Universities – Very high research activity”. UArizona is the fourth most awarded public university by National Aeronautics and Space Administration for research. The University of Arizona was awarded over $300 million for its Lunar and Planetary Laboratory (LPL) to lead NASA’s 2007–08 mission to Mars to explore the Martian Arctic, and $800 million for its OSIRIS-REx mission, the first in U.S. history to sample an asteroid.
The LPL’s work in the Cassini spacecraft orbit around Saturn is larger than any other university globally.
The University of Arizona laboratory designed and operated the atmospheric radiation investigations and imaging on the probe. The University of Arizona operates the HiRISE camera, a part of the Mars Reconnaissance Orbiter.
While using the HiRISE camera in 2011, University of Arizona alumnus Lujendra Ojha and his team discovered proof of liquid water on the surface of Mars—a discovery confirmed by NASA in 2015.
The University of Arizona receives more NASA grants annually than the next nine top NASA/JPL-Caltech-funded universities combined. The University of Arizona’s Lunar and Planetary Laboratory is actively involved in ten spacecraft missions: Cassini VIMS; Grail; the HiRISE camera orbiting Mars; the Juno mission orbiting Jupiter; Lunar Reconnaissance Orbiter (LRO); Maven, which will explore Mars’ upper atmosphere and interactions with the sun; Solar Probe Plus, a historic mission into the Sun’s atmosphere for the first time; Rosetta’s VIRTIS; WISE; and OSIRIS-REx, the first U.S. sample-return mission to a near-earth asteroid, which launched on September 8, 2016.
The University of Arizona students have been selected as Truman, Rhodes, Goldwater, and Fulbright Scholars. According to The Chronicle of Higher Education, UArizona is among the top producers of Fulbright awards.
The University of Arizona is a member of the Association of Universities for Research in Astronomy , a consortium of institutions pursuing research in astronomy. The association operates observatories and telescopes, notably Kitt Peak National Observatory just outside Tucson.
Led by Roger Angel, researchers in the Steward Observatory Mirror Lab at The University of Arizona are working in concert to build the world’s most advanced telescope. Known as the Giant Magellan Telescope (CL), it will produce images 10 times sharper than those from the Earth-orbiting Hubble Telescope.
GMT will ultimately cost $1 billion. Researchers from at least nine institutions are working to secure the funding for the project. The telescope will include seven 18-ton mirrors capable of providing clear images of volcanoes and riverbeds on Mars and mountains on the moon at a rate 40 times faster than the world’s current large telescopes. The mirrors of the Giant Magellan Telescope will be built at The University of Arizona and transported to a permanent mountaintop site in the Chilean Andes where the telescope will be constructed.
Reaching Mars in March 2006, the Mars Reconnaissance Orbiter contained the HiRISE camera, with Principal Investigator Alfred McEwen as the lead on the project. This National Aeronautics and Space Agency mission to Mars carrying the UArizona-designed camera is capturing the highest-resolution images of the planet ever seen. The journey of the orbiter was 300 million miles. In August 2007, The University of Arizona, under the charge of Scientist Peter Smith, led the Phoenix Mars Mission, the first mission completely controlled by a university. Reaching the planet’s surface in May 2008, the mission’s purpose was to improve knowledge of the Martian Arctic. The Arizona Radio Observatory , a part of The University of Arizona Department of Astronomy Steward Observatory , operates the Submillimeter Telescope on Mount Graham.
The National Science Foundation funds the iPlant Collaborative in with a $50 million grant. In 2013, iPlant Collaborative received a $50 million renewal grant. Rebranded in late 2015 as “CyVerse”, the collaborative cloud-based data management platform is moving beyond life sciences to provide cloud-computing access across all scientific disciplines.
In June 2011, the university announced it would assume full ownership of the Biosphere 2 scientific research facility in Oracle, Arizona, north of Tucson, effective July 1. Biosphere 2 was constructed by private developers (funded mainly by Texas businessman and philanthropist Ed Bass) with its first closed system experiment commencing in 1991. The university had been the official management partner of the facility for research purposes since 2007.
