Remote Sensing and GIS Approach (Benin) to Mapping of the Geospatial Dynamics of Plant Formations in the Upper Ouémé Sub-Catchment, West Africa

Abstract

This work aims to map the geospatial dynamics of plant formations in the upper Ouémé sub-watershed from 1995 to 2020, i.e. 25 years. To achieve this objective, the combination of different methodological approaches were used. These are the remote sensing and GIS approach, Benaz plant formation inventory techniques, direct field observations and the calculation of the normalized vegetation index. Processing of satellite images from Landsat TM 5 (1995), Landsat 7 ETM+ sensors from 04-23-2002 and 05-14-2005, Landsat 8 OLI/TIRS from 03-04-2015 and 03-06-2015 and finally that of Sentinel-2B of 04-23-2020 enabled the results to be achieved. Thus, different classes of forest entities were discriminated (dense forests, gallery forests, open forests and wooded savannas, wooded and shrubby savannas and grassy savannas). Between 1995 and 2020, the rate of plant formations increased from 95.98 to 66.32%, i.e. a plant cover of 611,971 ha in 1995, 591,672 ha in 2005, 561,595 ha in 2015 and 422,528 ha in 2020 with a NDVI which oscillates between -0.076 and 0.315 during this last year. Benaz's method has made it possible to carry out ecological and phytosociological surveys and to measure the diameters and heights of trees in the identified formations. Despite the efforts to conserve and protect the natural resources available to the study area, wood resources are in decline, as they are subject to anthropogenic pressure amplified by population growth and uncontrolled activities.