Checking the regreening of the Sahel by means of multitemporal analysis of NDVI in Niger

Resumen

Most of research points that African countries in general, and the countries of the Sahel in particular, are undoubtedly among the most vulnerable of world regions to climate change. The Sahel is a semiarid interface running east–west from the Atlantic Ocean to the Red Sea, and between the arid Sahara desert in the north and the savannas and forests to the south. Recently various scientists have detected an increase in vegetation cover through satellite imagery in some sahelian countries. Rainfall and/or the implementation of local agroforestry management practices known as Farmer Managed Natural Regeneration (FMNR) are discussed as possible factors explaining this regreening. The aim of our study is to check and estimate the increase of tree cover in a region of the Southwest of Niger (Dosso) by means of Landsat NDVI differences along thirty years. We used two Landsat scenes (path/row: 192/051) from 1985-1988 and 2014.-2016 These images were preprocessed using Google Earth Engine. NDVI differences were mapped. An increase of NDVI values was observed, especially in the south of the study area. In addition a validation of the NDVI increase map is being performed using Collect Earth (Open Foris) software. Collect Earth is a free Java-based tool supported by FAO that facilitates land use assessment through a sampling approach and a set of free imagery (i.e. Google Earth, Bing Mpas and Digital Globe).Validation approach is currently being carried out to confirm the tree cover increase in Dosso region.