Late Pleistocene climate change,nutrient cycling,and the megafaunal extinctions in North America |
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| Authors: | J Tyler Faith |
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| Institution: | 1. Environmental Stewardship Group, Los Alamos National Laboratory, MS J978, Los Alamos, NM 87545, USA;2. Department of Anthropology, University of Colorado Boulder, Campus Box 233 UCB, Boulder, CO 80309-0233, USA;3. Geophysics Competency, Council for Geoscience, PO Box 572, Bellville, 7535, South Africa;4. Centre for Coastal Palaeoscience, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth, 6031, South Africa;5. Institute of Human Origins, School of Human Evolution and Social Change, Arizona State University, Tempe, AZ 85287-2402, USA;6. Evolutionary Studies Institute, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa;7. Research Laboratory for Archaeology, University of Oxford, Oxford, OX1 3QY, UK;8. Department of Geological Sciences, University of Cape Town, South Africa;9. Department of Anthropology, University of Colorado Denver, P.O. Box 173364, Denver, CO 80217-3364, USA;1. Institute of Zoology, Zoological Society of London, Regent''s Park, London NW1 4RY, UK;2. Key Laboratory of Vertebrate Evolution and Human Origin of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China;3. School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK;4. Department of Earth Sciences, Natural History Museum, London SW7 5BD, UK;1. Laboratório de Macroecologia, Universidade Federal de Goiás, Campus Jataí, Cx. Postal 03, 75804-020, Jataí, GO, Brazil;2. Programa de Pós-graduação em Ecologia e Evolução, Universidade Federal de Goiás, Cx. Postal 131, 74001-970, Goiânia, GO, Brazil;3. Departamento de Ecologia, ICB, Universidade Federal de Goiás, Cx. Postal 131, 74001-970, Goiânia, GO, Brazil;1. Bay Path University, Longmeadow, MA, USA;2. Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain;3. Institut Català de Paleoecologia Humana i Evolució Social (IPHES), Tarragona, Spain;4. Area de Prehistoria, Universitat Rovira i Virgili (URV), Tarragona, Spain;5. Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Berlin, Germany;6. Museum of Paleontology and Department of Anthropology, University of Michigan, MI, USA;7. Natural History Museum, London, UK;8. Natural History Museum of Vienna, Vienna, Austria;1. Instituto de Ciencias de la Tierra, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile;2. Departamento de Paleontología, Facultad de Ciencias Geológicas, Universidad Complutense de Madrid, 28040 Madrid, Spain;3. Departamento de Geología Sedimentaria y Cambio Medioambiental, Instituto de Geociencias (CSIC, UCM), 28040, Madrid, Spain;4. Earth and Planetary Sciences Department, University of California Santa Cruz, Santa Cruz, CA 95064, USA;5. Institut Català de Paleoecologia Humana i Evolucio Social (IPHES), C. Marcel-lí Domingo s/n, Campus Sescelades URV (Edifici W3), 43007 Tarragona, Spain;6. ICREA. IPHES, Institut català de Paleoecologia Humana i Evolució Social, Universitat Rovira i Virgili, c/ Marcel·lí Domingo s/n (Edifici W3), Campus Sescelades, E-43007 Tarragona, Spain;7. Departamento de Ecología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Chile |
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| Abstract: | This study proposes an ecological mechanism for the terminal Pleistocene population collapse and subsequent extinction of North American megafauna. Observations of modern ecosystems indicate that feedback mechanisms between plant nutrient content, nitrogen cycling, and herbivore–plant interactions can vary between a nutrient accelerating mode favoring increased herbivore biomass and a nutrient decelerating mode characterized by reduced herbivore biomass. These alternate modes are determined largely by plant nitrogen content. Plant nitrogen content is known to be influenced by atmospheric CO2 concentrations, temperature, and precipitation. It is argued that Lateglacial climate change, particularly increases in atmospheric CO2, shifted herbivore–ecosystem dynamics from a nutrient accelerating mode to a nutrient decelerating mode at the end of the Pleistocene, leading to reduced megafaunal population densities. An examination of Sporormiella records – a proxy for megaherbivore biomass – indicates that megafaunal populations collapsed first in the east and later in the west, possibly reflecting regional differences in precipitation or vegetation structure. The fortuitous intersection of the climatically driven nitrogen sink, followed by any one or combination of subsequent anthropogenic, environmental, or extra-terrestrial mechanisms could explain why extinctions took place at the end of the Pleistocene rather than during previous glacial–interglacial cycles. |
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