Rainfall variability, vegetation dynamics, and the rainfall-NDVI relationship in the Sahel (1990–2022): a spatio-temporal analysis using CHIRPS and PKU GIMMS-MODIS data
Résumé
Abstract Since the 1980s, the Sahel has experienced a recovery in rainfall following the severe droughts of the 1970s and 1980s, accompanied by a ‘re‐greening’ signal revealed by satellite‐derived vegetation indices. However, the intensity and stability of the relationship between seasonal rainfall and vegetation dynamics remain insufficiently systematized across the full Sahelian transect for the recent period. In this study, the relationship between June–September (JJAS) rainfall totals and the normalized difference vegetation index (NDVI) is analysed over 1990–2022 for 84 stations distributed across Senegal, Mauritania, Mali, Burkina Faso, Niger, and Chad. JJAS rainfall is taken from the CHIRPS v2 dataset, and NDVI from the PKU GIMMS‐MODIS product, both aggregated to the JJAS seasonal scale. For each station, Pearson correlation coefficients between JJAS rainfall and NDVI are computed for the full period and for two sub‐periods (1990–2005 and 2006–2022), changes in correlation strength are assessed using Fisher’s Z test, and linear trends in rainfall and NDVI time series are estimated. Spatial fields of correlation and trend are obtained by inverse‐distance‐weighted interpolation and mapped at the regional scale. The results show an overall positive JJAS rainfall-NDVI correlation, but with marked spatial heterogeneity, including strong coupling in parts of Senegal and Niger, weaker or negative correlations in more anthropized or humid zones, and localized decoupling linked to land‐use change. Across the 84 stations, rainfall-NDVI coupling is remarkably stable: Fisher’s test detects only two stations in eastern Chad with a statistically significant strengthening of the correlation and a single station in northern Burkina Faso (Ouahigouya) with significant weakening, while more than 96% of stations show no significant change in correlation strength between 1990–2005 and 2006–2022. These findings confirm the key role of rainfall variability in driving Sahelian vegetation dynamics and provide useful insights for climate monitoring and the management of agro‐pastoral resources.
Citer ce document
Accès au document
Texte intégral en lecture en ligne, réservé aux abonnés SPHAERO et aux membres de l'institution. Se connecter
Voir l'article sur le site de la revueAuteur(s)
Statistiques
Consultations : 1
Téléchargements : 0