Easter Island, also known by its Polynesian name Rapa Nui, is a tiny island in the middle of the vast Pacific Ocean and is widely known for its great coastal beauty and for the moai, a collection of nearly 1,000 ancient carved sculptures of people, many of which once rested atop stone platforms called ahu. These statues, which face inland, away from the sea, are considered to be products of extraordinary ingenuity and craftwork, and they are also signposts of a once well-established island civilization.
“The moai represented important ancestors in every lineage, incarnating the spirits and the power of the founding ancestors,” observed archeologist Andrea Seelenfreund in her 2015 book entitled “Rapa Nui.”
“The moai represented important ancestors in every lineage, incarnating the spirits and the power of the founding ancestors” The statues are illustrative of the island’s mysterious past. Around 1400 A.D. as many as 10,000 people lived on the island, but by the early 1800s there were just 100 people surviving. The virtual disappearance of a population and the remarkable artifacts the Polynesian Rapanui people left behind, intrigue and attract thousands to the ecologically fragile place, feeding an industry which, while economically essential to the island’s 6,000 residents, is exacerbating a growing crisis: a water shortage. From a look at Easter Island on a map or satellite image it might seem unlikely that this tiny volcanic island in the middle of the eastern Pacific Ocean would struggle for fresh water.
“You would think it’s just wet and raining there all the time, but that’s not the case,” said Lamont Associate Research Professor William D’Andrea. “There is a dry zone in the southeastern Pacific because of the Andes, and it influences the amount of rain that falls. There is evidence that Easter Island has gone through extreme wet and dry periods in the past.”
An opportunity to investigate this drought pattern for a major research project – funded by the Center for Climate and Life at Lamont, the Vetlesen Foundation, the Explorers Club of New York, and the College of William and Mary Reves Center for International Studies – and the mystery surrounding the enigmatic people of Rapa Nui, drew D’Andrea and a team to the island in March 2018. The collaborative field team, which also included Lamont’s Lorelei Curtin; archaeologist Andrea Seelenfreund from Chile’s Universidad Academia de Humanismo Cristiano; Nicholas Balascio and James Van Hook from the College of William and Mary in Virginia; and Raymond Bradley from University of Massachusetts, Amherst, successfully collected sediment cores from the wetlands of Rano Kau, Rano Raraku, and Rano Aroi, recovering geologic records that likely span the past 30,000 years on Rapa Nui and which they are now using to examine many aspects of climatic, environmental, and human land-use history.
During the expedition, the team observed that the lake at Rano Raraku, the famous quarry from which the ancient Rapanui people carved the moai, is completely dried up and the lakebed is exposed. This marked change occurred only in the past year or two previously the lake was a site of an annual local competition that involved swimming and boating. This competition had to be relocated to the ocean this year because of the desiccation of the lake.
“No one we met remembered a year when they couldn’t do the competition in this lake,” said D’Andrea. “The most relevant and interesting question is, are we seeing something to indicate this is where water resources are headed into the future? Is this island facing a future with less freshwater, or is this just an aberration?”
To answer these questions, the researchers use the sediments gathered, which accumulate year after year like pages of a book, to see if there is a common thread, tracing both the population changes through time and the impact of natural and anthropogenic climate change. D’Andrea, a paleoclimatologist, studies how environments have evolved by reconstructing climate history from the molecules preserved in lake sediment cores. Lipid molecules from plants and algae are preserved in the sediments that accumulate each year on the bottom of lakes and the ocean. D’Andrea analyzes these compounds to learn how temperature, precipitation, and evaporation have changed throughout the island’s history.
“You would think it’s just wet and raining there all the time, but that’s not the case”
This is the first time that scientists are analyzing Easter Island lakebed cores with this method. “I became interested in the research after talking to colleagues who had been working there before and had been wrestling with a couple of different problems. They were trying to understand the climate history, but the tools they were using were limited. They hadn’t tried to use the type of measurements that we make in our lab,” said D’Andrea. Colleagues wanted D’Andrea’s help to ascertain when people first arrived on Rapa Nui and what the climate was like then.
“We know that it must have been drier in the past, because this lake had dried out for thousands of years. During that time, it wasn’t accumulating any new sediment. Polynesians settled Rapa Nui sometime between 600 and 1200 A.D., which is late compared with other Pacific islands. Was the timing of their arrival somehow related to water availability? And did they have to deal with extended periods of drought during their 1,000 years on the island?”
The long-held prevailing theory about the demise of the Rapanui culture is that they mismanaged the resources of the island. As the story goes, they destroyed the island’s ecology and therefore it could no longer support them, and because of that their entire culture collapsed; this concept has been termed “ecocide.”
But, there’s controversy about whether the Easter Islanders really represent an example of people whose resource use and potential resource mismanagement led to the downfall of their culture.
The ecocide theory is often used to suggest an allegorical comparison between the demise of the Rapanui society and what could happen to all of humanity as the impact of global warming and exploitation of resources continue to cause environmental degradation.
“But the evidence for that narrative on Rapa Nui is weak and incomplete,” said D’Andrea. “The idea has been challenged. So we would like to weigh in and help understand what kinds of natural climate changes the Rapanui people had to deal with, and also help provide new evidence about when they first arrived. We seek to uncover new objective, observational evidence to address some of these questions.”
By evaluating the molecular remains in the sediment cores, D’Andrea and team hope to illuminate Easter Island’s mysterious past and at the same time inform a deeper understanding of human resilience and vulnerability to climate change.
“The idea has been challenged. So we would like to weigh in and help understand what kinds of natural climate changes the Rapanui people had to deal with, and also help provide new evidence about when they first arrived. We seek to uncover new objective, observational evidence to address some of these questions.”