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Caractérisation et suivi de la déforestation en milieu tropical par télédétection : application aux défrichements agricoles en Guyane française et au Brésil

Abstract : For several decades, tropical deforestation has been considered as a major ecological threat. Wrongly or rightly, shifting slash and burn cultivation is usually blamed. In this thesis, we present a multi-sensor investigation of deforestation due to agricultural clearings and their spatial evolution in Amazonian forest. Two versions of clearings are considered : the French Guiana variant, known locally as abattis, and the Brazilian variant, currently described as pioneers fronts. These modes of agricultural colonization are associated with specific land use techniques, and induce deforestation at various scales. Pioneers fronts derive primarily from a political initiative to organize the agricultural use of the forest, but clearings extend rapidly out of control and the monitoring becomes difficult. On the other hand, clearings known as abattis, despite their limited extent, multiply very often in an unplanned way. These clearings are generally spontaneous and itinerant, and occur in a context where land statute is precarious and the demand for land increases. Therefore, the need for monitoring becomes critical. The methodology we used to assess and follow-up damages affecting the forest comprises two main stages. The first consists in characterizing clearings patterns on optical images (NOAA AVHRR, Spot 4 VEGETATION, Landsat TM, Spot XS, aerial photographs) and radar data (JERS, ERS). The second step deals with data processing in order to highlight the spatial evolution of clearings and explain land use dynamics. Image analyses are associated with the analysis of socio-economic data resulting from field surveys. These two steps lead to the development of a remote sensing-based strategy for the monitoring and the management of Amazonian forest. This strategy is divided into monitoring levels corresponding to sensors characteristics and clearings extension. For an efficient operational monitoring, we pointed out image processing methods adapted to geographical and climatic context of the wet tropical areas. We also suggested socio-economic and environmental indicators which can supplement observation with images provided by satellites.
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Moise Tsayem Demaze. Caractérisation et suivi de la déforestation en milieu tropical par télédétection : application aux défrichements agricoles en Guyane française et au Brésil. Sciences de l'Homme et Société. Université d'Orléans, 2002. Français. ⟨tel-00592532⟩

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