Désertification au Sahel: Historique et perspectives

in Bulletin de la Société Géographique de Liège (2010), 54

Over the last decades, the Sahel of West Africa has suffered two dramatic contiguous droughts. Currently, and since the late 1980s, rainfall amounts tend to catch up with the pre-1970 levels. However ... [more ▼]

Over the last decades, the Sahel of West Africa has suffered two dramatic contiguous droughts. Currently, and since the late 1980s, rainfall amounts tend to catch up with the pre-1970 levels. However, this improvement seems to occur through increased rainfall intensities but the duration of the rainy season did not significantly change since the 1970s and the 1980s. On the other hand, the Sahelian population has tripled since 1950 and it is foreseen to be multiplied by 10 by the second half of the 21st century. Increasing urban population levels are still much more impressive and cause profound environmental degradation. Such an increasing human pressure leads to uncontrolled deforestation in order to satisfy the needs in fuel and construction wood and to make place for shifting cultivation. In addition, larger and larger herds occupying contracting pasture areas leads to overgrazing and trampling. All these processes provoke the degradation of the vegetation cover, a constant diminution of crop yields, and a strong reduction of the biodiversity. This article provides a state of the art of recent findings and controversy that surround the desertification processes. We conclude that, if the droughts of the 1970s and 1980s have had dramatic consequences for the population of the Sahel, the future very high human pressure on the environment will most likely enhance the desertification of the southern fringe of the Sahara, especially in the case of the alarming climate change scenarios forecasting rainfall decrease all over the Sahel. [less ▲]

Sélection d'espèces ligneuses adaptées à la fixation biologique de dunes au Niger

in Geo-Eco-Trop (2009), 33

Seven woody species, of which five natives (Acacia senegal, A. raddiana, A. nilotica, Bauhinia rufescens, Balanites aegyptiaca) and two imported (Prosopis juliflora and P. chilensis) have been tested in ... [more ▼]

Seven woody species, of which five natives (Acacia senegal, A. raddiana, A. nilotica, Bauhinia rufescens, Balanites aegyptiaca) and two imported (Prosopis juliflora and P. chilensis) have been tested in terms of biological sand dunes fixation in the Southern east of Niger Republic. In nursery, species underwent a water stress by interrupting the watering during six days. Foliar hydration has been determined in order to evaluate their capacity to limit water loss. In a field experiment, species have been planted on a mechanically prefixed sand dune cord in order to test their ability for stabilization of sand dunes. Survival rates during the first three years have been calculated and height growth was measured. In nursery, results showed that, after six days of water stress, Acacia senegal, A. raddiana, P. chilensis and A. nilotica are the four species limiting the best the water losses. Results on site showed that the best combination in sand dunes fixation, in this zone, would be the association of one or the other of Prosopis (high survival rate and fast growth) with A. raddiana and/or A. nilotica (survival and growth relatively substantial and more important economic interest). [less ▲]