A new study led by researchers at the Lamont-Doherty Earth Observatory offers the clearest evidence yet that a centuries-long drought transformed life on Rapa Nui (Easter Island) beginning around the year 1550. The scientists collected sediment cores from two of the island’s few freshwater sources: Rano Aroi, a high-elevation wetland and Rano Kao, a crater lake. By analyzing the hydrogen isotope composition of plant leaf waxes within those cores, the team reconstructed a continuous, 800-year record of past rainfall trends, showing that annual precipitation declined and remained low for more than a century. The findings challenge long-held narratives of societal “collapse,” instead showing that Rapanui communities were resilient to profound climate stress. We spoke with lead author Redmond Stein about how the team uncovered this history and what it means for understanding the links between climate and culture.

How were you able to reconstruct Rapa Nui’s rainfall from so long ago, using leaf waxes from wetland sediments? What makes this approach more reliable than previous methods for studying Rapa Nui’s climate history?   

Sediments in lakes and wetlands accumulate slowly over time and preserve lots of information about the climatic and environmental conditions under which they were deposited. Many scientists have previously studied sediments from Rapa Nui and have inferred past environmental changes by looking at things like elemental abundances, pollen and plant macrofossils, and changes in how quickly the sediment accumulated. These proxies are incredibly valuable, but they can often respond in complex ways to multiple climate and environmental variables—for example, temperature, precipitation, and changes in human land use. Conversely, we think leaf waxes on Rapa Nui are only recording information about local rainfall and aridity. By measuring the composition of leaf waxes preserved in wetland sediments— the ratio of “heavy” to “light” hydrogen in these waxes varies in tandem with the ratio of hydrogen in the water that plants absorb from rain—we were therefore able to put a rough estimate on the magnitude of drought that occurred on Rapa Nui in the 16th century for the first time.

Your analysis reveals a prolonged drought on Rapa Nui beginning in the mid-16th century and lasting for centuries. How severe was this drought, and how did it coincide with social or cultural shifts on the island?

Based on our leaf wax analysis, we estimated a prolonged rainfall decrease of roughly 600-800mm (24-31 inches) per year relative to the previous three centuries on Rapa Nui. The timing of our inferred drought aligns with some major cultural shifts, including a decline in the construction of ceremonial “ahu” platforms; the emergence of Rano Kao lake as an important ritual site; and the beginnings of a new form of social hierarchy known as “Tangata Manu,” in which power could be achieved through athletic competition, rather than by ancestral lineage as traced through the moai statues. It’s difficult for archeologists to pin down the exact timing of these events, and there is still much debate about how society changed in the 16th to 18th century on Rapa Nui. But at the very least, we know the human geography of the island looked quite different than it had in the centuries prior. 

Your research adds to the work of others who have challenged the long-standing “ecocide” narrative about Rapa Nui’s history. How do your findings of a climate-driven shift further challenge this narrative? What do you hope the public takes away from this more nuanced view of the island’s history?

The ecocide narrative suggests that people on Rapa Nui destroyed their island by way of deforestation, eventually leading to a period of societal conflict and population collapse prior to European contact in the 18th century. This story has been popularized as a parable for global overconsumption, presenting the people of Rapa Nui as architects of their own destruction. Although it’s true Rapa Nui was gradually deforested and that this represented a major ecological transition on the island, many studies have cast doubt on the ecocide hypothesis. Perhaps most importantly, there is no strong evidence of a demographic collapse prior to European arrival. 

Our study and others now suggest that the people of Rapa Nui were dealing with drought beginning in the 16th century, which would have significantly impacted life on the already freshwater-poor island. Importantly, our hypothesis is not simply that regional climate changed, and that social and political hierarchies must have shifted in tandem, or that deforestation was unimportant, but rather that climate provides an important context for the human history of Rapa Nui. The exact mechanism by which a decrease in rainfall could have led to challenging circumstances is still unclear—for example, if this would have exacerbated soil erosion issues, led to a decline in drinking water, pushed people to find new freshwater resources, or impacted the ability of the vegetation to grow. Regardless, our study makes clear the history of Rapa Nui is much more nuanced than the ecocide narrative implies. 

Are there any lessons from Rapa Nui’s climate shift and the way residents adapted to it that might be relevant for us in the face of current climate change? 

The biggest lesson would be that people are resilient. But in the face of current climate change, I think it is most important to listen to the voices of people who are from Rapa Nui and other Pacific islands, who are already dealing with the effects. Their perspectives and insights will be much more relevant to addressing the problems of today, relative to any that we could glean from this study. Our research is not intended to produce a new parable for the modern times but rather push against the old one. 

What are the next steps for this research?

We have a much longer leaf wax isotope record from Rano Aroi that covers the last ~50,000 years of sediment deposition, and we are hoping to use this record to better understand how atmospheric circulation in the southeast Pacific responds to climate forcing on much longer timescales. Rapa Nui is located in the heart of the remote, southeast Pacific, over 3,000 kilometers off the coast of Chile and over 1,500 kilometers from the next inhabited island. It is the only source of terrestrial sediment in the area and therefore offers incredibly unique insight into how regional atmospheric dynamics have changed in the past. Controls on atmospheric circulation over the southeast Pacific are poorly understood and not very well represented in model simulations, so our record could ultimately prove very helpful in understanding regional climate.