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.
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.
Read More: Columbia Climate School
