SEASONAL CHANGES IN PLANT COVER IN THE AGNEBY WATERSHED (SOUTH-EASTERN COTE D IVOIRE)

With a surface area of 8450 km, the Agneby catchment is located in the south-east of Cote dIvoire, in West Africa. This watershed is located in a forest environment in Cote dIvoire, and has undergone rapid degradation as a result of successive agro systems. It encompasses a large part of the former cocoa loop. With the decline of the cocoa economy, new plantations such as oil palm, rubber and recently cashew (in the north) have emerged. Despite the existence of numerous studies based on high spatial resolution satellite images, detailed and continuous knowledge over time of the basins plant cover remains inadequate. However, remote sensing remains a unique tool that facilitates measurement through frequent observation of vast areas. The aim of this study is to analyse changes in vegetation cover in the Agneby catchment using MODIS Terra high spatial resolution satellite images. The series of images used to produce the Enhanced Vegetation Index (EVI) cover the period from 2000 to 2024, with a spatial resolution of 250 m, and are taken in January, March, June and November. The methodology adopted is based on statistical processing of the vegetation index series and on spatial dispersion statistics. The spatio-temporal analysis of the indices shows that the ombrophilous sector (south of the basin) is the most anthropised, which is reflected in a strong variation in seasonal activity. In the mesophilic sector (North and Centre), the variations are smaller and smaller in a South- North gradient. The peaks observed around 2005 and 2010 are linked to climatic factors, in particular particularly wet years, favouring a larger vegetative mass. In addition, the river mouth corresponds to the greater Abidjan area (Anyama and Songon).