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Science 9 May 2008:
Vol. 320. no. 5877, pp. 765 - 768
DOI: 10.1126/science.1154913
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Research Articles

Climate-Driven Ecosystem Succession in the Sahara: The Past 6000 Years

S. Kröpelin,1* D. Verschuren,2 A.-M. Lézine,3 H. Eggermont,2 C. Cocquyt,2,4 P. Francus,5,6 J.-P. Cazet,3 M. Fagot,2 B. Rumes,2 J. M. Russell,7 F. Darius,1 D. J. Conley,8 M. Schuster,9 H. von Suchodoletz,10,11 D. R. Engstrom12

Desiccation of the Sahara since the middle Holocene has eradicated all but a few natural archives recording its transition from a "green Sahara" to the present hyperarid desert. Our continuous 6000-year paleoenvironmental reconstruction from northern Chad shows progressive drying of the regional terrestrial ecosystem in response to weakening insolation forcing of the African monsoon and abrupt hydrological change in the local aquatic ecosystem controlled by site-specific thresholds. Strong reductions in tropical trees and then Sahelian grassland cover allowed large-scale dust mobilization from 4300 calendar years before the present (cal yr B.P.). Today's desert ecosystem and regional wind regime were established around 2700 cal yr B.P. This gradual rather than abrupt termination of the African Humid Period in the eastern Sahara suggests a relatively weak biogeophysical feedback on climate.

1 Africa Research Unit, Institute of Prehistoric Archaeology, University of Cologne, Jennerstraße 8, D-50823 Köln, Germany.
2 Limnology Unit, Department of Biology, Ghent University, K. L. Ledeganckstraat 35, B-9000 Gent, Belgium.
3 Laboratoire des Sciences du Climat et de l'Environnement, CNRS-CEA-UVSQ UMR 1572, L'Orme des Merisiers, F-91191 Gif-Sur-Yvette, France.
4 National Botanic Garden of Belgium, Domein van Bouchout, B-1860 Meise, Belgium.
5 Institut National de la Recherche Scientifique, Centre Eau, Terre et Environnement, 490 Rue de la Couronne, Québec, Québec G1K 9A9, Canada.
6 GEOTOP, Geochemistry and Geodynamics Research Centre, C.P. 8888, Université du Québec à Montréal, Succursale, Centre-Ville, Montréal, Québec H3C 3P8, Canada.
7 Geological Sciences, Brown University, Box 1846, Providence, RI 02912, USA.
8 GeoBiosphere Centre, Department of Geology, Lund University, Sölvegatan 12, SE-22362 Lund, Sweden.
9 Institut International de Paléoprimatologie, Paléontologie Humaine, Evolution et Paléoenvironnements, CNRS UMR 6046, Université de Poitiers, 40 Avenue du Recteur Pineau, F-86022 Poitiers, France.
10 Geoforschungszentrum Potsdam, Telegrafenberg, D-14473 Potsdam, Germany.
11 Lehrstuhl für Geomorphologie, Universität Bayreuth, Universitätsstraße 30, D-95440 Bayreuth, Germany.
12 St. Croix Watershed Research Station, Science Museum of Minnesota, Marine on St. Croix, MN 55047, USA.

* To whom correspondence should be addressed. E-mail: s.kroe{at}uni-koeln.de

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Comment on "Climate-Driven Ecosystem Succession in the Sahara: The Past 6000 Years".
V. Brovkin and M. Claussen (2008)
Science 322, 1326b
   Abstract »    Full Text »    PDF »
Response to Comment on "Climate-Driven Ecosystem Succession in the Sahara: The Past 6000 Years".
S. Kropelin, D. Verschuren, and A.-M. Lezine (2008)
Science 322, 1326c
   Abstract »    Full Text »    PDF »


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Science. ISSN 0036-8075 (print), 1095-9203 (online)