Search results for "sahel"
showing 10 items of 31 documents
Agronomy and climatology of a 100 000 km² watershed in West Africa.
2011
7 pages; International audience; Sahelian regions are considered as particularly vulnerable to climatic variability and change for two reasons: the dominant role of rainfed agriculture in their economies and their weakness of water resources management. The physiological response of an individual plant to the climatic variations of parameters is well documented, but extrapolation to regional food production still remains very dubious. On the Bani, a tributary of the Niger River in Mali, climatic variables representative of the agroclimatic constraints of the cultures (dynamics of the rainy season and occurrence of extreme events) were evaluated from observed past data and simulated future d…
Relationships between societies and their environment in the Sahel in southwestern Niger over the past four thousand years : a geoarchaeological appr…
2013
The Sahel, a zone between the Sahara Desert and the Sudan forests, is currently experiencing major environmental changes. Since the droughts in 1970s and 1980s, and with the high population growth rate, vegetation cover has deteriorated considerably, contributing to increased runoff and soil erosion. Starting from this observation, we undertook the study of past societies in the Niamey region, to assess their impact on the environment. The lack of archaeological data meant that it was necessary to identify key indicators of occupation during the Neolithic and the Iron Age. In addition to providing new evidence to date the Neolithic site of Kirkissoy, a sedimentary study was conducted on a p…
Climate and agriculture: empirical evidence for countries and agroecological zones of the Sahel
2022
International audience; ow heterogenous is the impact of climate change across space and the type of agricultural production? In this paper, we investigate the relationship between climate change and variability, measured by temperature and rainfall, and agricultural production at the country and agroecological zone levels of the Sahel. We consider a crop production index and five cereals (maize, millet, sorghum, wheat and rice). Based on an original climate database and an agricultural production function estimated for the period 1961–2016, we show that average rainfall and temperature during the growing season indeed have highly heterogeneous effects on agricultural production, depending …
Different trends of neighboring populations of Lesser Kestrel: Effects of climate and other environmental conditions
2019
The sensitivity of population trends to the climate and environment is generally considered a species-specific trait. However, evidence that populations may show different responses to the climate and environmental conditions is growing. Whether this differential sensitivity may arise even among neighboring populations remains elusive. We compared the trends of two neighboring populations of the Lesser Kestrel Falco naumanni, using data from a 12-year survey of 158 colonies in Sicily, Italy; the two populations inhabiting a lowland and an highland area, respectively. Population trends were modeled through the TRIM algorithms implemented in R (package rtrim). A reversed U-shaped population t…
Mesures continues du flux d'érosion éolienne sur les champs de Mil traditionnels au Sud-Ouest du Niger : Impacts des résidus de culture.
2010
International audience; Au Sahel, l'effet des résidus de culture sur l'érosion éolienne, a été essentiellement étudié avec des taux de recouvrement supérieurs à la réalité. La présente étude vise à déterminer l'impact sur l'érosion des couverts réellement rencontrés en milieu paysan. Pour cela, des suivis continus de flux d'érosion éolienne ont été effectués pendant trois campagnes agricoles sur deux parcelles de même taille (1,5 ha) présentant des états de surface contrastés: PA avec une surface nue et PB cultivée traditionnellement en mil. Sur le champ traditionnel, les résidus de cultures empêchent toute érosion au coeur de la saison sèche et diminuent de plus de trois fois le flux horiz…
Six années de suivi du flux d'érosion éolienne sur un sol sableux cultivé au Sahel : Impacts des résidus de culture et de l'encroûtement
2013
In the Sahel, wind erosion occurs particularly in cultivated fields. This work was leaded at Banizoumbou in Niger where wind erosion fluxes have been measured for six years. The aims of this study was i) to monitor crop residues cover on traditional field and to quantify its influence on wind erosion ii) to characterize the impacts of soils crusting on erosion flux, iii) to characterize the impact of herbaceous strips on wind flux. Results showed that crop residues efficiently prevent cultivated fields from wind erosion during the dry season (January to April) and considerably reduce erosion fluxes at the beginning of the rainy season (May to July). Under a minimal crop residues cover rate …
Les changements futurs de la mousson africaine.
2013
7 pages; International audience; Nous analysons l’effet du changement climatique sur la mousson d’Afrique de l’ouest par l’utilisation de huitmodèles CMIP5 sous scénario RCP4.5, la réalisation d’un multi-modèle et l’approche « one model, one vote ». Les résultatsmontrent l’apparition d’un contraste pluviométrique zonal entre le centre et l’ouest du Sahel. Une mousson plus intensepermettrait une hausse de la convergence d’humidité et des précipitations au centre du Sahel. Un renforcement du jet d’estafricain et de la subsidence sur l’ouest du Sahel y permettrait en revanche une baisse de la pluviométrie.
Les vagues de chaleur au Sahel : caractérisation, mécanismes, prévisibilité.
2016
The mechanisms controlling Sahelian heat wave (HW) variability are examined on the period 1979-2014 using the GSOD observational database and ERA-Interim reanalyses. HW events are analyzed through all terms of the atmospheric energy balance, showing a predominant role of incoming shortwave radiation on daily maximum temperature (Tx) and atmospheric water vapor on minimum temperature (Tn). The low-frequency warming trend, not explained by the previous terms, is thought to relate to the increase of greenhouse gases concentrations, due to anthropogenic emissions. The predictability of Sahelian HW events is assessed for lead times reaching up to 15 days. The model's skill, biases and uncertaint…
Impact du climat sur la santé : modélisation régionale des poussières pour les épidémies de méningites au Sahel.
2014
6 pages; International audience; Les épidémies des méningites bactériennes constituent encore à l’heure actuelle un problème de santé publiquemajeur en Afrique de l’Ouest. Chaque année, au coeur de la saison sèche (de janvier à mars), 25 000 à 250 000 cas sontenregistrés par l’Organisation Mondiale de la Santé (OMS) dans la zone latitudinale 10-15°N, plus communément appelée« ceinture de la méningite ». L’importance des facteurs sociétaux dans l’expansion des épidémies est indéniable. Cependant,une série d’études récentes a permis de mettre en lumière le rôle important du climat. Ainsi, l’intensité des épidémies sembleliée à des conditions de circulation atmosphérique spécifiques quelques m…
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…