Phenological zoning and characterization of natural Senegalese rangelands using remote sensing data

peer reviewedLes métriques phénologiques qui expriment certains événements du cycle de vie des plantes, tels que l'émergence, la croissance et la sénescence, principalement liées aux conditions météorologiques et au climat, ont été utilisées afin : (i) de déterminer, à travers les parcours naturels du Sénégal, des entités "phénoclimatiques" homogènes ou phénorégions par classification non-supervisée des images de la série temporelle (1999-2013); (ii) d’analyser l’homogénéité des phénorégions en comparant l’évolution interannuelle de l’indice et des quantités de précipitation et (iii) de donner leurs principales caractéristiques biophysiques. Les résultats obtenus montrent que le domaine pastoral sénégalais peut être subdivisé en trois phénorégions à partir de la grande intégrale du NDVIS10 qui donne les entités spatiales les plus homogènes dans lesquelles les paramètres biophysiques comportent une variation latitudinale caractéristique du Sahe

Optimisation des propriétés thermiques et mécaniques du béton à base de pierre ponce

Ce travail s'inscrit dans le cadre de la valorisation des matériaux locaux de construction. En effet, l'utilisation des matériaux locaux dans la construction permet l'accès au logement à moindre coût. Cet avantage ne doit pas primer sur les critères fondamentaux de choix des matériaux de construction que sont la sécurité du bâtiment et le confort thermique. Un compromis thermomécanique est nécessaire puisque les résistances thermiques et mécaniques varient en sens inverse. Pour prendre en compte cet aspect nous avons, à partir de plusieurs formulations du béton à base de pierre ponce, effectué des essais de caractérisations mécaniques et thermiques. Les résultats obtenus nous ont permis de déterminer la formulation qui concilie le mieux les caractéristiques thermiques et mécaniques. Afin que la méthode utilisée puisse être appliquée à d'autres matériaux de construction, l'optimisation a été faite en utilisant des variables adimensionnelles Journal des Sciences Pour l'Ingénieur Vol. 6, 2006: 25-3

Impact of future climate change on malaria in West Africa

Understanding the regional impact of future climate change is one of the major global challenges of this century. This study investigated possible effects of climate change on malaria in West Africa in the near future (2006–2035) and the far future (2036–2065) under two representative concentration pathway (RCP) scenarios (RCP4.5 and RCP8.5), compared to an observed evaluation period (1981–2010). Projected rainfall and temperature were obtained from the coordinated regional downscaling experiment (CORDEX) simulations of the Rossby Centre Regional Atmospheric regional climate model (RCA4). The malaria model used is the Liverpool malaria model (LMM), a dynamical malaria model driven by daily time series of rainfall and temperature obtained from the CORDEX data. Our results highlight the unimodal shape of the malaria prevalence distribution, and the seasonal malaria transmission contrast is closely linked to the latitudinal variation of the rainfall. Projections showed that the mean annual malaria prevalence would decrease in both climatological periods under both RCPs but with a larger magnitude of decreasing under the RCP8.5. We found that the mean malaria prevalence for the reference period is greater than the projected prevalence for 6 of the 8 downscaled GCMs. The study enhances understanding of how malaria is impacted under RCP4.5 and RCP8.5 emission scenarios. These results indicate that the southern area of West Africa is at most risk of epidemics, and the malaria control programs need extra effort and help to make the best use of available resources by stakeholders.The CORDEX project.http://link.springer.com/journal/704am2023Geography, Geoinformatics and MeteorologySchool of Health Systems and Public Health (SHSPH)UP Centre for Sustainable Malaria Control (UP CSMC

Impact of future climate change on malaria in West Africa

Understanding the regional impact of future climate change is one of the major global challenges of this century. This study investigated possible effects of climate change on malaria in West Africa in the near future (2006–2035) and the far future (2036–2065) under two representative concentration pathway (RCP) scenarios (RCP4.5 and RCP8.5), compared to an observed evaluation period (1981–2010). Projected rainfall and temperature were obtained from the coordinated regional downscaling experiment (CORDEX) simulations of the Rossby Centre Regional Atmospheric regional climate model (RCA4). The malaria model used is the Liverpool malaria model (LMM), a dynamical malaria model driven by daily time series of rainfall and temperature obtained from the CORDEX data. Our results highlight the unimodal shape of the malaria prevalence distribution, and the seasonal malaria transmission contrast is closely linked to the latitudinal variation of the rainfall. Projections showed that the mean annual malaria prevalence would decrease in both climatological periods under both RCPs but with a larger magnitude of decreasing under the RCP8.5. We found that the mean malaria prevalence for the reference period is greater than the projected prevalence for 6 of the 8 downscaled GCMs. The study enhances understanding of how malaria is impacted under RCP4.5 and RCP8.5 emission scenarios. These results indicate that the southern area of West Africa is at most risk of epidemics, and the malaria control programs need extra effort and help to make the best use of available resources by stakeholders.The CORDEX project.http://link.springer.com/journal/704am2023Geography, Geoinformatics and MeteorologySchool of Health Systems and Public Health (SHSPH)UP Centre for Sustainable Malaria Control (UP CSMC

Eco-geographical diversity of cowpea bradyrhizobia in Senegal is marked by dominance of two genetic types

The genetic diversity of native cowpea rhizobia originating from 60 sites across four eco-geographic zones in Senegal Was studied. More than 300 cowpea nodules were analyzed by PCR-RFLP of the 16S-23S rDNA InterGenic Spacer region (IGS). Alignments of IGS sequences indicated that all genotypes were grouping within the Bradyrhizobium genus. The geographical distribution showed that apart from five IGS types, the others were specifically found in only one region. The diversity was significantly higher in the Senegal River valley zone, which presents lower mean annual rainfalls and slightly alkaline soils. Interestingly, two IGS types dominated the Senegalese rhizobial collection, one IGS type (VI) was found on more than half of the nodules collected in the northern Senegal River valley while another IGS type (I) was recovered from the great majority of nodules in the three other regions sampled. Two representative strains from each of these two dominant types were isolated and further analyzed. Multi Locus Sequence Analyses using 6 housekeeping genes indicate that they belong to a new Bradyrhizobium species closely related to B. yuanmingense. Phylogenetic analyses of 2 symbiotic genes nodC and nifH show that they are clustered with B. arachidis. Physiological tests on these strains have shown that under laboratory conditions, the growth of the IGS type VI strains was slightly less affected by a higher osmotic strength in the medium and to alkaline pH, which corroborates the soil physico-chemical parameters

Soil moisture estimation in Ferlo region (Senegal) using radar (ENVISAT/ASAR) and optical (SPOT/VEGETATION) data

The sensitivity of the radar signal to the seasonal dynamics in the Sahel region is a considerable asset for monitoring surface parameters including soil moisture. Given the sensitivity of the radar signal to vegetation mass production, roughness and soil moisture, the main problem has been to estimate the contribution of these three parameters to the signal. This study aims to circumvent this problem by combining radar with optical data. The DMP (Dry Mater Product) extracted from SPOT data allowed to estimate vegetation mass production. Surface roughness was estimated from radar data during the dry season. Because during the dry season, radar signal is only conditioned by soil roughness in this region a Radiative Transfer Model (RTM) was used: it consists in a microwave scattering model of layered vegetation based on the first-order solution of the radiative transfer equation and it accounts for multiple scattering within the canopy, surface roughness of the soil, and the interaction between canopy surface and soil. This model was designed to account for the branch size distribution, leaf orientation distribution, and branch orientation distribution for each size. In this study, the RTM has been calibrated with ESCAT (European Radar Satellite Scatterometer) data, and has been used in order to estimate soil moisture. The results obtained have allowed to track the spatial and temporal dynamics of soil moisture on the one hand, and on the other hand the influence of geology and morphopedology on the spatial dynamics of the soil moisture variability. These results are promising despite the fact that the inversed RTM often faces difficulties to interpret the signal for saturated soils, giving an aberrant value of soil moisture more often than not

Spatial epidemiology of urban health risks in select West African cities

West African cities face critical societal challenges that are linked to environmental and health changes. These challenges are further exacerbated by urbanization dynamics, climate change, socio-economic mutation and lack of capacity for sustainable urban development, governance and basic services delivery. The deficiency of environmental sanitation and ecosystem services have led to high complexity of urban health risks inequalities, resulting in the need for more research on efficient urban health policies. The purpose of this contribution is to present the main findings on the spatial epidemiology of diarrhaea and malaria, and their associated risks factors in the following select West African cities. Spatial variability of exposure to diarrhaea and malaria transmission is linked to several health risks such as lack of access to water and sanitation, solid wastes management, urban flooding