JLE

Science et changements planétaires / Sécheresse

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Afrique, paléoclimats et déforestation Volume 4, issue 4, Décembre 1993

Author
CNRS Luminy, Laboratoire de Géologie du Quaternaire, Case 907, 13288 Marseille Cedex 9, France
  • Page(s) : 221-31
  • Published in: 1993

The present paper puts the problem of planetary deforestation into the broader context of paleoclimatic geological history. Without being exhaustive, it provides a picture of current knowledge concerning the existence, through geological time, of various periods known for their arid climatic conditions. After a short introduction explaining the method used to reconstitute the history of past plant life, the mutual interactions between the extensive massifs of dense forest and their role in the global climate’s water and carbon cycles will be briefly discussed. The geographical breakdown of today’s major plant systems, with the expansion of the savannahs, dates back 12 million years. The earlier dry phases followed the rhythm of the major glacial/interglacial cycles, and lasted some ten times longer than the interglacial periods so favourable to the development of forests across the globe. This, however, remains to be proved for Africa over a period of at least 100,000 years. In order to understand what effects man has had, it is first necessary to understand climates of the past. To be able to determine paleoclimatic variability, climatic parameters have been quantified. The example of Burundi illustrates interactions between climatic conditions and forest development long before man was responsible for any substantial deforestation.