Exploring urban vegetation index trends, seasonal variations, and their correlation with temperature in Benin (West Africa)

Despite the vital role of seasonal urban vegetation dynamics in regulating temperatures and supporting sustainable climate management, this area remains largely unexplored in Benin. There is a growing need for precise insights into the cooling benefits of urban greenery to inform urban planning and climate adaptation strategies. This case study investigated the seasonal variations of the Normalized Difference Vegetation Index (NDVI) in Parakou using Landsat 7 and 8 data. Monthly NDVI series collected using Google Earth Engine (open source) were used, while the observed temperatures were obtained at the National Meteorological Agency of Benin for the city boundary. Mann-Kendall and Sen's slope tests were applied to assess the trends of NDVI and temperature in the study area. An analysis of variance, followed by the Student-Newman-Keuls (SNK) test, was used to examine the significance of seasonal variation in the NDVI and temperature. Afterward, a simple linear regression was performed to show the relationship between temperature and NDVI values. The results showed a nonsignificant trend (p-value > 0.05), with no increasing or decreasing tendency for NDVI (Sen's Slope = 0.000) and temperature (Sen's Slope = 0.002) from 2000 to 2023. However, NDVI and temperature variations across seasons showed significant differences (p < 0.000). The period from January to May recorded the lowest mean NDVI. A predominantly negative correlation between NDVI and temperature was observed from June to October, whereas a positive correlation emerged from November to May, likely due to rainfall deficit stress. The findings emphasize the importance of effective urban greenery management in supporting sustainable strategies for urban temperature reduction in similar environments. The study also highlights the need for future research to incorporate more robust vegetation indices, including the Enhanced Vegetation Index (EVI), Soil-Adjusted Vegetation Index (SAVI), and Green Normalized Difference Vegetation Index (GNDVI), investigate the physiological mechanisms through which urban greenery mitigates heat, and assess the role of periodic irrigation in enhancing vegetation resilience during dry seasons.