|
Organizers |
A tale of two lakes: droughts, El Niņos and major cultural change during the last 5000 years in the Cuzco region of Peru
by
Alex Chepstow-Lusty
Florida Institute of Technology
Coauthors: ECCUZ Members, Michael R. Frogley (University of Sussex), Brian S. Bauer (The University of Illinois at Chicago), Steve Boreham (University of Cambridge), Keith Bennett (Uppsala Universitet Geocentrum), Mark B. Bush (Florida Institute of Technology), Tino Aucca Chutas (ECOAN), Sharon R. Goldsworthy (University of Sussex), Alfredo Tupayachi Herrera (Universidad Nacional de San Antonio del Cusco), Melanie Leng (NERC Isotope Geoscience Laboratory), Denis-Didier Rousseau (University of Montpellier 2 and Lamont-Doherty Earth Observatory), Koen Sabbe (University of Gent), Geraldine Slean (University of Cambridge), Mieke Sterken (University of Gent)
The Cuzco region of Peru is part of a landscape that has witnessed significant anthropogenic modification since at least the beginning of the Holocene. This human manipulation of the environment appears to have been largely a response to changing climatic conditions, whereby c. 5000 years ago the 'early Holocene climatic optimum' (a time characterised by aridity in the Central Andes) gave way to a wetter period, that was punctuated by a series of droughts; some of these may be linked to extreme El Niņo episodes. This major climatic shift may not only have driven the establishment of agriculture in the region at that time, but also provided the impetus for many of the subsequent cultural changes.
Lake sediment cores provide an opportunity to understand how environmental and cultural events are linked by integrating continuous, well dated palaeoecological sequences with the archaeological record. The Cuzco region is extremely rich in archaeological remains and the two sites considered here, Marcacocha and the Lucre Basin, are both surrounded by significant Inca and pre-Inca remains.
Marcacocha (cored in 1993), located to the north-west of Cuzco, has provided a highly detailed record of human impact and climatic change spanning more than 4000 years. Using the abundance of sedge pollen as a sensitive proxy for lake-level, a series of marked drier episodes are clearly represented in the record at c. 900 BC, 500 BC, AD 100, AD 550, and over a broader period from AD 900-1800. These periods not only correspond closely with major droughts/extreme El Niņo episodes, but also with important cultural changes that occurred in the Cuzco region and elsewhere in the Central Andes.
By way of further supporting these interpretations, oxygen isotopes, invertebrates and other proxies have been analysed from sediments in the Lucre Basin south-east of Cuzco (cored in 1996). These provide strong evidence for climatic change being coincident with the collapse of the large Wari site of Pikillacta at the end of the first millennium AD. Pikillacta was an important imperial centre, strategically located on the margins of the Lucre Basin at the boundary with the neighbouring Tiwanaku polity. Interestingly, both the Wari and Tiwanaku states declined markedly at around this time, and it may be that the Medieval Warm Period, beginning c. 1 ka and evident from these records, was an important causative factor. Indeed, these unstable climatic conditions appeared to favour the later development of the Inca state, which expanded significantly after this period.
This integration of palaeoenvironmental information with archaeological, historical and contemporary sources provides an important potential resource for land management and conservation today in the Andes. This work forms part of a major new multidisciplinary initiative, ECCUZ (Environmental and Cultural changes in CUZco and adjacent regions), open to all interested collaborators.
Date received: April 30, 2002
Copyright © 2002 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caji-21.