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Nonlinear climate change and Andean feedbacks: an imminent turning point?

Authors

  • M. B. BUSH,

    1. Department of Biological Sciences, Florida Institute of Technology, 150 W. University Blvd., Melbourne, FL 32901, USA
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  • J. A. HANSELMAN,

    1. Department of Biological Sciences, Florida Institute of Technology, 150 W. University Blvd., Melbourne, FL 32901, USA
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    • 1Present address: J. A. Hanselman, Department of Biology, Westfield State College, Westfield, MA, USA.

  • W. D. GOSLING

    1. Department of Biological Sciences, Florida Institute of Technology, 150 W. University Blvd., Melbourne, FL 32901, USA
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    • 2Present address: W. D. Gosling, Department of Earth and Environmental Sciences, CEPSAR, The Open University, Milton Keynes, UK.


M. B. Bush, tel. +1 321 674 7166, e-mail: mbush@fit.edu

Abstract

A 370 000-year paleoecological record from Lake Titicaca provides a detailed record of past climate change in which interglacial periods are seen to have some elements of commonality, but also some key differences. We advance a conceptual feedback model to account for the observed changes that includes previously ignored lake effects. Today Lake Titicaca serves to warm the local environment by about 4–5 °C and also to increase rainfall. We observe that as water levels in the lake are drawn down due to warm, dry, interglacial conditions, there is a possible regional cooling as the lake effect on local microclimates diminishes. Positive feedback mechanisms promote drying until much of the lake basin is reduced to salt marsh. Consequently, the usual concept of upslope migration of species with warming would not be applicable in the Altiplano. If, as projected, the next century brings warmer and drier conditions than those of today, a tipping point appears to exist within ca. 1–2 °C of current temperatures, where the relatively benign agricultural conditions of the northern Altiplano would be replaced by inhospitable arid climates. Such a change would have profound implications for the citizens of the Bolivian capital, La Paz.

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