Study on carbon dioxide atmospheric distribution over the Southwest Indian Ocean islands using satellite data: Part 1 – Climatology and seasonal results

International audienceThe forests of the Southwest Indian Ocean (SWIO) islands States are large carbon sinks. Rapid population growth in these islands is responsible for deforestation, which in turn is the main source of carbon dioxide (CO 2) emissions. This study is divided into two parts: The present study (Part 1) describes the seasonal vertical and surface spatial distribution of CO 2 over the SWIO islands and the temporal variation of surface CO 2 concentrations using data measured by the Tropospheric Emission Spectrometer (TES) on board the Aura Satellite. The CO 2 hotspots over these islands were identified and assessed to determine if they were associated with deforestation and forest degradation anthropogenic activities. Areas of minimum or low CO 2 atmospheric loading were also identified, and investigated to determine if they coincided with strong sink areas. Atmospheric CO 2 concentration was building-up from summer to spring. The spatial extent of CO 2 hotspots was found to increase from summer to spring. Over the study region, semi-permanent stable layers at 700 hPa and 500 hPa were shown to separate the troposphere into three layers of CO 2. Furthermore, surface CO 2 levels over all the study areas were found to be increasing during the period of the investigation. Part 2 of this study demonstrates the influence of meteorology and associated air transport on atmospheric CO 2 distribution over the study region

Modélisation de la fragmentation de la forêt dense sèche du parc national Mikea (sud-ouest de Madagascar) : cas de la commune d'Analamisampy

Valorisation Durable des Formations Sèches Côtières, Toliara, MDG, 17-/09/2018 - 19/09/201

: Observation using multidimensional Landsat TM satellite images of the impacts of the transfer of forest management to local communities: case of Didy commune, Alaotra-Mangoro region, Madagascar

article publié en français, avec un résumé étendu en anglais, et 5 planches couleur hors-texte (p. 22-26)International audienceStudying the case of the local administrative unit ("commune" ) of Didy (Center-North of Madagascar) the authors used Landsat TM imagery (1994, 2001 and 2009) to produce multitemporal land cover maps. The aim is to evaluate the effectiveness of the program transferring the management of forested areas to local communities. Multispectral images have been atmospherically corrected, then used as inputs into a SVM (Support Vector Machine) algorithm to derive the land cover classification. Results indicate generally positive impacts of the management transfer program, i. e. a decrease of forest clearings and the conservation of forest cover.A partir du cas de la commune de Didy (Centre-Nord de Madagascar), les auteurs. ont établi, à l'aide d'images Landsat TM (1994, 2001 et 2009), des cartes d'occupation du sol à différentes dates afin d'évaluer l'efficacité du programme de transfert de la gestion forestière aux communautés de base locales. Les images multispectrales acquises à différentes dates ont été soumises à des corrections atmosphériques puis classifiées pour chaque date à l'aide de la méthode de classification non paramétrique SVM (Séparateur à Vaste Marge). Les résultats montrent en général des impacts positifs de l'installation des Transferts de Gestion (TG) sur le ralentissement des défrichements et le maintien de la couverture forestière

Water and land security in drylands : response to climate change

In southwestern Madagascar, the Mikea forest is a highly diverse ecosystem of great biodiversity, whiëh mixes dry deciduous forest in the eastern part and xerophytic thicket in the western coastal area. However, dry forests and shrubs are rapidly destroyed due to slash-and-burn cultivation (hatsaky) and exploitation offorest resources by riparian communities and extemal operators. The aim of this paper is to evaluate forest fragmentation in the Mikea national park, by comparing past and recent forest maps. The analysis of forest fragmentation is based on landscape indices. The changes in forest cover have been detected from time-series SPOT satellite images registered over 15 years (1999, 2005, and 2014). Between 1999 and 2014, forest area is reduced by 39.8% which is equivalent to an annual forest Joss rate of 4.6%. The forest fragmentation is associated with a significant decrease in forest patch size. The mean patch size decreases from 37,228 to 18,731 ha from 1999 to 2014. The primary direct causes are economic driven due to intense anthropogenic activities such as wood charcoal production, Jogging, accompanied by frequent wild land tires. The indirect cause is the absence of a sustainable environmental management and conservation strategy

Transitions agraires au sud de Madagascar : résilience et viabilité, deux facettes de la conservation : actes du séminaire de synthèse du projet FPPSM

La conservation des forêts ne doit pas occulter la vie des familles qui vivent des ressources forestières. Au fur et à mesure que les massifs forestiers se fragmentent, et les forêts sèches plus rapidement que les forêts humides, les activités agricoles occupent un espace plus important. Mais l'une et l'autre de ces dynamiques sont interdépendantes. C'est donc en modélisant leurs interactions que l'on peut faire apparaître des trajectoires viables. Ces résultats sur la résilience et la viabilité apportent à la conservation un nouvel éclairage en montrant comment la réconciliation des peuples avec leurs forêts, puis l'accord de toutes les parties prenantes sur un objectif de conservation, permettraient de s'engager vers une gestion durable

Remote sensing training in scientific master in France and Africa: Educational choices according to students' academic initial training and first distance learning feedback in Cameroon

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The age and petrogenesis of alkaline magmatism in the Ampasindava Peninsula and Nosy Be archipelago, northern Madagascar

The Ampasindava alkaline province consists of a series of circular and elliptical intrusions, lava flows, dyke swarms and plugs of Cenozoic age emplaced into the Mesozoic-Cenozoic sedimentary rocks of the Antsiranana basin (NW Madagascar) and above the crystalline basement. The magmatism in the Ampasindava region is linked to a NW-SE trending extensional tectonic setting. New 40Ar/39Ar age determinations on feldspar separate of alkali granites and basaltic dykes yielded ages of 18.01 ± 0.36 Ma and 26 ± 7 Ma, respectively. Alkali basalts and basanites, nepheline syenites and phonolites, and silica saturated-to-oversaturated syenites, trachytes, granites and rhyolites are the main outcropping lithologies. These rocks have sodic affinity. The felsic rocks are dominant, and range from peraluminous to peralkaline. The mantle-normalized incompatible element patterns of the mafic lavas match those of Na-alkaline lavas in within-plate rift settings. The patterns are identical in shape and absolute concentrations to those of the Bobaomby (Cap d’Ambre) and Massif d’Ambre primitive volcanic rocks. These geochemical features are broadly compatible with variable degrees of partial melting of incompatible element-enriched mantle sources. The mineralogical and geochemical variations are consistent with fractional crystallization processes involving removal of olivine, feldspar, clinopyroxene, amphibole, Fe-Ti oxides and apatite. Removal of small amount of titanite explains the concave upward lanthanide pattern in the evolved nepheline syenites and phonolites, which are additionally rich in exotic silicates typical of agpaitic magmas (eudialyte, F-disilicates)