Search results for "pression anthropique"
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Erosion en milieu sableux cultivé au Niger : dynamique actuelle et passée en liaison avec la pression anthropique et les changements climatiques
2011
Sahelian ecosystems, especially those installed on sandy soils react very quickly and intensely to small climatic changes. In this semi-arid area, wind erosion which occurs mainly on cultivated millet fields and is threatening the sustainable use of land resources. Furthermore, the rapid population growth and the severe droughts of the twentieth century have had important impacts on ecosystems. To better manage this fragile environment, it is important first to understand how it works. This thesis was included in the framework of the AMMA project (African Monsoon Multidisciplinary Analyses) and was in the heart of a CORUS 2 (Coopération pour la Recherche Universitaire et Scientifique) progr…
Evolution des paysages Sahélines au cours des six dernières décennies dans la région de Niamey : de la disparition de la brousse tigrée à l'encroutem…
2010
In the Sahel, the rapid increase of the population during the last decades and the climate variation lead to an important environmental degradation. This work aims to measure the impacts of the human pressure on ecosystem during the six last decades. A diachronic cartography of a 100 km² area close to Niamey was done with aerial photographs (1950 and 1975) and GPS measurements (2009). Results showed that the tiger bush vegetation was completely cleared between 1950 and 2009 while the fallow decreases from 7 % to 1 %. In the sandy valley, the increase of cultivated fields from 20,7 % (1950) to 69,4 % (1975) favoured wind and water erosions which allowed surface soil crusting. Between 1975 an…