International Journal of Research and Innovation in Social Science (IJRISS) |Volume VI, Issue IX, September 2022|ISSN 2454-6186
Dome TINE1*, Mbagnick FAYE2, Guilgane FAYE3
1Cheikh Anta DIOP University of Dakar, Department of Geography, Applied Remote Sensing Laboratory (ARL), BP 5005, Dakar, Senegal.
2Cheikh Anta DIOP University of Dakar, Department of Geography, Laboratory of Climatology and Environmental Studies (LCE), BP 5005 Dakar, Senegal.
3Cheikh Anta DIOP University of Dakar, Department of Geography, Physical Geography Laboratory, BP 5005 Dakar, Senegal.
*Corresponding Author
Abstract: The aim of this contribution is to analyse the impact of rainfall variability on vegetation cover dynamics in the northern part of the Southern Rivers. The methodology adopted is based on the processing of rainfall data (1961-2018), Landsat satellite images and time series of Normalized Difference Vegetation Index (NDVI). The results show a highly contrasted rainfall variability, highlighted by the Standard Precipitation Index (SPI). The latter shows that annual variations in rainfall are slightly in favour of drought. The temporal profile of the NDVI revealed two periods with different rates of change. A first period from 1984 to 2000, characterised by good phenological activity, with good vegetation cover, and a second period from 2001 to 2018, marked by a significant decrease in vegetation cover. Spatial analysis of the evolution of vegetation formations reveals a north-south density gradient accompanied by an increase in dense forest and the regression of open savannah.
Keywords: Rainfall variability, dynamics, vegetation cover, Southern Rivers.
I. INTRODUCTION
The Rivières du Sud are characterised by highly contrasting rainfall variability along a south-north gradient. The importance of the climatic gradient explains to a large extent the differences in landscape and flora in the northern regions of the Rivières du Sud [1]. Rainfall decreases from the Guinean regions to the Sahel and Sahara. They are marked by frequent droughts, the most significant of which date from the 1970s, 1980s and 1990s. These droughts are remarkably severe, persistent, and widespread, and have caused major changes in natural and human systems [2]. Their impacts have been dramatic at all scales. The decrease in rainfall has been, overall, greater than in countries further away from the ocean [3]. Moreover, this drought was not only felt in the Sahelian regions of northern Senegal, but in the whole country [4]. It had a severe impact on Basse-Casamance, a region that is already in the sub-humid tropical domain. This strong decrease in rainfall has had repercussions on river flow, on the supply of groundwater and on the