DOI: 10.5061/dryad.41ns1rnt2
title: Data from: Prolonged drought on Rapa Nui during the decline of megalithic monument construction

description: Drought may have contributed to changes in human geography on Rapa Nui in
 the late 16th and early 17th centuries, but there are currently no
 continuous paleoclimate records that provide direct, quantitative insight
 into local hydroclimate conditions during this time period. Here, we
 present new evidence for a multicentury rainfall deficit on Rapa Nui
 beginning at approximately 1550 CE, based on two independent
 reconstructions of hydrogen isotopes in rainfall inferred from hydrogen
 isotopes in leaf waxes preserved in wetland sediments. Chain-length
 distribution data suggests that known vegetation changes on Rapa Nui
 (e.g., palm deforestation) did not significantly influence the sources of
 leaf waxes for either wetland. Therefore, we assume that leaf wax hydrogen
 isotopes reflect isotopes in precipitation at a constant offset through
 time. We use instrumental data from the Global Network of Isotopes in
 Precipitation (GNIP) to show that there is a significant relationship
 between isotopes in precipitation over Rapa Nui and mean annual rainfall
 amount. We then apply the relationship between these two variables to
 estimate the magnitude of drought at 1550 CE, inferred from our leaf wax
 records. We estimate that the period 1550 CE to 1720 CE on Rapa Nui saw a
 600-800 millimeter decline in average annual rainfall relative to the
 previous three centuries. This drought is of greater magnitude than the
 drying observed in recent decades and likely posed significant challenges
 to the 16th-17th century inhabitants of Rapa Nui. 
description: # Data from: Prolonged drought on Rapa Nui during the decline of
 megalithic monument construction ## Description of the data and file
 structure Data.xlsx contains all leaf wax hydrogen isotope and
 chain-length distribution data files for sediment cores from Rano Aroi
 wetland and Rano Kao crater lake. All sheets are separately provided as
 CSVs under the same titles. The variable descriptions below are broken up
 by dataset. ### **Variable Descriptions**  **Data file:
 Rano_Kao_Hydrogen_Isotopes.csv** *Variable:* Depth (cm) *Description:*
 Depth of each sample in core KAO08-03. Depths are listed as the midpoint
 between the top and bottom of the sampling interval. *Variable:* Year (CE)
 *Description:* Modeled age of the sediment at each sample depth. See the
 Sharing/Access Information section for more information on the KAO08-03
 age-depth model. *Variable:* Max Age (CE) *Description:* Maximum age of
 the sediment at each depth, defined as the upper 95 % confidence interval
 of the age-depth model for KAO08-03. *Variable:* Min Age (CE)
 *Description:* Minimum age of the sediment at each depth, defined as the
 lower 95 % confidence interval of the age-depth model for KAO08-03.
 *Variable:* *n*-Alkanoic acid chainlength *Description:* Number of carbons
 in the n-alkanoic acids measured for hydrogen isotope composition
 *Variable*: dDwax (‰ VSMOW) *Description:* Hydrogen isotope composition of
 n-alkanoic acids in each sample, averaged across duplicate or triplicate
 measurements where appropriate. Values have been converted to the VSMOW
 scale and adjusted to account for the addition of a methyl group of known
 isotopic composition during the methylation procedure. *Variable*: 1s
 analytical uncertainty dDwax (‰) *Description:* Pooled standard deviation
 from all replicate measurements of a given chainlength, weighted by the
 number of replicates (n-1) for each sample. Samples run on the same
 reactor will have the same analytical uncertainty. *Variable*: number of
 replicates *Description:* Number of replicates per sample within the range
 of accepted peak sizes (&gt; 10Vs, &lt; 150Vs) **Data file:
 Rano_Aroi_Hydrogen_Isotopes.csv** *Variable:* Depth (cm) \ *Description:*
 Depth of each sample in core RAP-01-18 Drive 1. Depths are listed as the
 middle point between the top and bottom of the sampling interval.
 *Variable:* Year (CE) \ *Description:* Modeled age of the sediment at each
 sample depth. See the "Rano*_*Aroi_Age_Model.csv" section for
 more information on the RAP-01-18 Drive 1 age-depth model. *Variable:*
 *n*-Alkanoic acid chainlength \ *Description:* Number of carbons in the
 n-alkanoic acids measured for hydrogen isotope composition *Variable*:
 dDwax (‰ VSMOW) \ *Description:* Hydrogen isotope composition of
 n-alkanoic acids in each sample, averaged across duplicate or triplicate
 measurements where appropriate. Values have been converted to the VSMOW
 scale and adjusted to account for the addition of a methyl group of known
 isotopic composition during the methylation procedure. *Variable*: 1s
 analytical uncertainty dDwax (‰) \ *Description:* Pooled standard
 deviation from all replicate measurements of a given chainlength, weighted
 by the number of replicates (n-1) for each sample. Samples run on the same
 reactor will have the same analytical uncertainty. *Variable*: number of
 replicates \ *Description:* Number of replicates per sample within the
 range of accepted peak sizes (&gt; 10Vs, &lt; 150Vs) **Note:** Maximum and
 minimum age ranges for each depth in Rano Aroi are available in
 "Rano_Aroi_Age_Model.csv" or in the Data.xlsx spreadsheet.
 **Data file: Rano_Kao_Chain_Length_Data.csv** *Variable*: Depth (cm)
 *Description*: Depth of each sample in core KAO08-03. Depths are listed as
 the middle point between the top and bottom of the sampling interval.
 *Variable:* Year (CE)\ *Description:* Modeled age of the sediment at each
 sample depth. See the Sharing/Access Information section for more
 information on the KAO08-03 age-depth model. *Variable:* Max Age (CE)\
 *Description:* Maximum age of the sediment at each depth, defined as the
 upper 95 % confidence interval of the age-depth model for KAO08-03.
 *Variable:* Min Age (CE)\ *Description:* Minimum age of the sediment at
 each depth, defined as the lower 95 % confidence interval of the age-depth
 model for KAO08-03. *Variable:* Average Chain Length (ACL) 26-32
 *Description:* Average chain length for *n*-alkanoic acids with 26-32
 carbons *Variable:* CXX fractional abundance *Description:* Fractional
 abundance of n-alkanoic acids with XX number of carbons, relative to the
 total abundance of waxes C20-C32 **Data file:
 Rano_Aroi_Chain_Length_Data.csv** *Variable:* Depth (cm)\ *Description:*
 Depth of each sample in core RAP-01-18 Drive 1. Depths are listed as the
 middle point between the top and bottom of the sampling interval.
 *Variable:* Year (CE)\ *Description:* Modeled age of the sediment at each
 sample depth. See the "Rano*_*Aroi_Age_Model.csv" section for
 more information on the RAP-01-18 Drive 1 age-depth model. *Variable:*
 Average Chain Length (ACL) 26-32\ *Description:* Average chain length for
 *n*-alkanoic acids with 26-32 carbons *Variable:* CXX fractional
 abundance\ *Description:* Fractional abundance of n-alkanoic acids with XX
 number of carbons, relative to the total abundance of waxes C20-C32
 **Note:** Maximum and minimum age ranges for each depth in Rano Aroi are
 available in "Rano_Aroi_Age_Model.csv" or in the Data.xlsx
 spreadsheet. **Data file: Rano_Aroi_Input_File_for_BACON.csv** *Variable:*
 age *Description:* Radiocarbon (14C) age of dated materials (terrestrial
 macrofossils or pollen extracts) in years before present (yrs BP).
 "Present" is defined as 1950. *Variable:* error *Description:*
 Uncertainty in radiocarbon age (years). *Variable*: depth *Description:*
 Depth of each sample in core RAP-01-18 Drive 1. Depths are listed as the
 middle point between the top and bottom of the sampling interval.
 *Variable:* cc *Description:* Radiocarbon calibration curve applied to
 each sample in BACON. A cc of 3 indicates the use of the Southern
 Hemisphere calibration SHCal20. A cc of 0 indicates that the sample is
 from the postbomb period. **Note:** In Excel, this sheet contains the
 prior settings used when running the age-depth modeling software BACON for
 Rano Aroi core RAP-01-18. This information has been removed in the
 associated CSV file. **Dataset: Rano_Aroi_Age_Model.csv** **Note:** The
 age-depth model for Rano Kao core KAO08-03 was generated using CLAM.R 2.2
 with smooth spline interpolation and was previously published in Rull et
 al., 2018. Please see the Sharing/Access Information section for a full
 citation. The age model for Rano Aroi core RAP-01-18 Drive 1 was generated
 using the Bayesian depth modeling software BACON and is presented for the
 first time in this study. *Variable:* depth (cm) *Description:* Sediment
 depth in core RAP-01-18 Drive 1. *Variable:* min 95 % (yrs BP)
 *Description:* Minimum modeled age of each depth interval in yrs BP,
 defined as the lower 95 % confidence interval. *Variable:* max 95 % (yrs
 BP) *Description:* Maximum modeled age of each depth interval in yrs BP,
 defined as the upper 95 % confidence interval *Variable:* median (yrs BP)
 *Description:* Median modeled age of each depth interval in yrs BP
 *Variable:* mean (yrs BP) *Description:* Mean modeled age of each depth
 interval in yrs BP *Variable:* Age CE (yrs BP) *Description:* Modeled age
 of each depth interval in Common Era (CE) notation, calculated as
 1950-mean age. ## Sharing/Access information Monthly precipitation,
 temperature, vapor pressure, and hydrogen isotope data were downloaded
 from the Global Network of Isotopes in Precipitation (GNIP) Water Isotope
 System for Electronic Retrieval (WISER). Water isotope data from GNIP can
 be found at the following address:
 [https://www.iaea.org/services/networks/gnip](https://www.iaea.org/services/networks/gnip) Please note that Rapa Nui is labeled as "Isla de Pascua" in the GNIP database. The Rapa Nui dataset is currently undergoing recompilation (7/2025), but should be reposted to the GNIP site shortly. The age model for KAO08-03 was provided upon request by the authors of Rull et al., 2018. Rull, V. et al. CLAFS, a Holistic Climatic-Ecological-Anthropogenic Hypothesis on Easter Island’s Deforestation and Cultural Change: Proposals and Testing Prospects. Front. Ecol. Evol. 6, (2018).