Analysis of Spatial-Temporal Trends in Vegetation and Rainfall in the Sahel Region during 2000-2020

Abstract

Climate change has a profound impact on the natural resources in the Sahel region. To understand vegetation dynamics and precipitation changes, this study examines the spatial-temporal trends in the Sahel over the years 2000-2020. The MODIS Normalized Difference Vegetation Index (NDVI) and Merged Satellite-Gauge Precipitation Estimate (IMERG) datasets are utilized, employing linear regression and Pearson correlation analysis to assess the relationship between vegetation index and rainfall, and explore seasonal correlations to understand variations during the growing season (July-October). The results show an increase in average annual NDVI (0.0005 yr-1, p < 0.05) and precipitation (0.0003 mm/hr/yr, p < 0.05). NDVI (0.0009 yr-1, p < 0.05) and precipitation (0.0009 mm/hr/yr, p < 0.05) in the growing season also show a rise. The south-central Sahel experiences the largest NDVI increase (11.66%), while the northeast sees the highest precipitation rise (125.15%) from 2000 to 2020. Additionally, a correlation map between rainfall and NDVI highlights that during the growing season, 18.505% of pixels exhibit a positive correlation above 0.7 with the southwestern part showing the highest correlation. These seasonal correlations shed light on the intricate interactions between NDVI and rainfall in different periods, offering valuable insights for ecosystem management in the Sahel. This study provides valuable support for conservation efforts, highlighting the importance of understanding these trends urgently to safeguard the region’s natural resources and bolster the Africa-Water-Energy-Food-Health (AWEFH) Nexus.