Science et changements planétaires / Sécheresse


Description quantitative des régimes de feu en zone soudanienne d’Afrique de l’Ouest Volume 4, issue 1, Mars 1993

Centre commun de recherche des Communautés européennes, Institut des applications de la télédétection, Projet « Surveillance de la végétation tropicale » Terminal postal 440 21020 Ispra, Italie.
  • Page(s) : 37-45
  • Published in: 1993

Man-made fire is probably one of the most efficient agents of modeling, or changing environmental conditions in the sudanian zone of West Africa. It constitutes a tool of preference for most land use practices such as cropping, stock-farming and hunting. Individuals or institutions involved in management programmes are thus looking for ways to exploit man-made fire practices, such as a slash-and-burn, in their plans for rural development. Yet this exploitation requires reliable quantitative information regarding the phenomenon’s temporal and spatial dynamics. The imagery provided by the AVHRR sensor on board the NOAA satellites has been used here to try to monitor the activity of fire during the 1987/1988 dry season on the upper basin of the river Niger in Guinee, a region which presents a wide variety of ecological conditions. Starting from the temporal distribution of probable active fires, as derived from the satellite imagery, four behaviour rules, or «fire régimes», have been defined depending on the ecological domains. Several methods for quantifying these fire regimes are proposed and the results evaluated. The best result seems to be obtained by computing a cumulative sum of the mean numbers of fire events observed on a 10-day basis; each 10-day period being affected by a factor which increases from the begining to the end of the dry season. Quantified in this way, and despite the uncertainties remaining in the detection of active fires and in characterizing the vegetation cover affected, the fire regimes could constitute excellent environmental indicators in the broad sense of the term since they depend both on environmental conditions and land-use practices. In this perspective, monitoring fire regimes in tropical areas may allow deep ecological changes occuring in a given region to be detected.