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Dynamique récente d'évolution des mangroves de la région de Toliara (Madagascar)

Authors: Andriatsiaronandroy onjanamboa, Ricardo;

Dynamique récente d'évolution des mangroves de la région de Toliara (Madagascar)

Abstract

Mangroves have many ecological, socio-economic and climate change mitigation values and functions vital for the littoral populations around the world and in Madagascar.This richness induce them intense exploitation, subjecting to strong natural and anthropogenic pressures. However in Madagascar "the mangroves are very poorly understood and we do not have the elements necessary for a good diagnosis", while they are presented as of perpetual regression in the Madagascar Southwest region. This study aims at identifying, mapping and quantifying the evolution (since 1949) of 5 mangrove’s sites in the Southwest : Manombo-Fitsitike, Ambondrolava, Ankiembe, Sarodrano and Andriambe. It also aims the diagnosis of the different factors of evolution putting in perspective the anthropogenic and natural pressures. To achieve these objectives, two approaches were adopted : geomatics based on the diachronic analysis of Spot images from1987, 1998, 2012 and 2014 associated with aerial photographs (1949) and field work with floristic inventories, physico-chemical measurements, particle size analyzes of substrates and surveys. The results show complex and contrasting trend evolution’s dynamics between growth, stability and regression. In the end, based on the knowledge gained on the mangroves dynamic over more than 60 years, it is possible to make available to all a tool to help decision-making and sustainable and adequate management to protect and conserve these ecosystems, particularly in the context of climate change that will impact natural changes and anthropogenic forcing.; Les mangroves présentent des fonctions et valeurs écologiques, socio-économiques et d’atténuation du changement climatique majeures et vitales pour la population littorale dans le monde et à Madagascar. Leur richesse en fait des milieux intensément exploités, les soumettant à de fortes pressions naturelles et anthropiques. Pourtant à Madagascar « les mangroves sont très mal comprises et nous n'avons pas en main les éléments nécessaires à un bon diagnostic » alors qu’on associe celles de la région Sud-ouest à un état de perpétuelle régression. Cette thèse a pour objectifs l’identification, la cartographie et la quantification de la dynamique d’évolution (depuis 1949) des mangroves de 5 sites du Sud-Ouest : Manombo-Fitsitike, Ambondrolava, Ankiembe, Sarodrano et Andriambe. Elle vise aussi à diagnostiquer les différents facteurs d’évolution en faisant la part des pressions anthropiques et naturelles. Pour atteindre ces objectifs, deux approches ont été adoptées : la géomatique se basant sur l’analyse diachronique d’images Spot de 1987, 1998, 2012 et 2014 associées à des photos aériennes de 1949 et des recherches sur terrain avec des inventaires floristiques, des mesures physico-chimiques, des analyses granulométriques des substrats et des enquêtes. Les résultats montrent des dynamiques d’évolution complexes et contrastées entre progression, stabilité et régression. Au final, en s’appuyant sur les connaissances acquises sur les dynamiques d’évolution des mangroves sur plus de 60 ans, il est possible de mettre à la disposition de tous un outil d’aide à la décision et à la gestion durable et adéquate pour protéger et conserver ces écosystèmes, particulièrement dans le contexte du changement climatique qui va impacter les dynamiques d’évolution naturelles et les forçages anthropiques.

Country
France
Related Organizations
Keywords

Evolution, Geographic information Systems, Télédétection, [SHS.GEO]Humanities and Social Sciences/Geography, Recent dynamics, Remote sensing, Systèmes d’information Géographique, Toliara (Madagascar), Anthropogenic factors, Facteurs anthropiques, Facteurs naturels, Dynamique récente, Natural factors, Mangrove

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  • citations
    This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
    0
    popularity
    This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
    Average
    influence
    This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
    Average
    impulse
    This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
    Average
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citations
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
0
Average
Average
Average
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