Seven centuries of precipitation variations in the Bolivian Altiplano inferred from the world’s highest-elevation tree-ring records: Environmental and sociocultural implications

MARIANO MORALES; AXEL E. NIELSEN; RICARDO VILLALBA; JEANETTE PACAJES; JAIME ARGOLLO; DUNCAN A. CHRISTIE

Corvallis, Oregon, USA.

Congreso; First Young Scientist Meeting and Third Open Science Meeting; 2009

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Due to the high sensitivity of dry farming and pastoralism to fluctuations in climate, droughts have a strong impact on the local population economies of the Bolivian Altiplano. Presently, this hypothesis is difficult to be tested due to the scarceness, shortness and inhomogeneity of the instrumental records in the tropics. The development of climate-sensitive and well-replicated tree-ring records from this tropical-montane region provide information not only to reconstruct past environmental conditions at various temporal scales, but also to understand particular events in the past human history in the Andes. The Altiplano offers a unique opportunity to achieve these goals. Polylepis tarapacana, a high-elevation species with remarkable dendrochronological potential, has been regularly used by pre-Columbian populations. In this study we utilize a tree-ring network of P. tarapacana chronologies, to reconstruct precipitation variability in the Bolivian Altiplano for the past 640 years. Periods of several decades with precipitation below the mean were observed in the reconstructions, as well as a negative trend in precipitation during the last 150 years. We identified a relationship between past climatic fluctuations and cultural changes. For instance, a major shift in settlement pattern during the 14th and 15th centuries has been identified by archeologist in the Altiplano-Puna and adjacent valleys. This process has traditionally been related to the onset of a state of endemic warfare. Archaeologists postulated that severe droughts triggered a period of regional hostility. Our precipitation reconstruction gives preliminary support to this idea, by showing two periods of severe droughts in AD 1380-1399 and 1432-1452.