Historical changes in drought characteristics and its impact on vegetation cover over Madagascar

Abstract. Drought has become one of the most devastating natural hazards in recent decades causing severe vegetation degradation. This study aims to analyze the spatiotemporal characteristics of drought (duration, frequency, severity, intensity) over Madagascar during 1981–2022. In addition, it evaluates the relationship between the Standardized Precipitation Index (SPI) and the Normalized Difference Vegetation Index (NDVI) during 2000–2022, representing the impact of drought on vegetation over the studied area. Drought assessment was computed on SPI-3, SPI-6, and SPI-12 timescales, accompanied by seasonal and annual analyses. While the NDVI-SPI relationships were performed through the analysis of vegetation changes based on specific selected SPI time-periods and the correlation analysis. The findings reveal that drought events have become more consecutive during the most recent past (2017 to 2022) and intensified over the southern part of the country. Links between the drought occurrence and vegetation changes are confirmed: the occurrences of continuous negative values of seasonal and annual SPI increase vegetation losses, and the existence of smaller negative values of the wet season SPI relates to more vegetation degradation during the wet season. The correlation between NDVI and SPI emphasizes the NDVI-SPI relationship found with statistical significance, especially over southern Madagascar. These findings are crucial for complementing other climatic factors that influence Madagascar’s vegetation besides drought.