Long-term vegetation trends and driving factors of NDVI change on the slopes of Mount Kilimanjaro

This study examines Mount Kilimanjaro, a Tanzanian volcano that is the highest mountain in Africa. KIlimanjaro has undergone significant land cover changes on its lower slopes, but that has received less attention relative to its highly-studied glaciated summit. This study analysed long-term MODIS NDVI-monthly mean value data for Kilimanjaro, from 2000 to 2022. Random Forest machine learning was used to determine the driving factors of NDVI change, examining long-term vegetation trends.

The normalised difference vegetation index (NDVI) was used as a proxy for vegetation density and productivity to track changes in vegetation dynamics. The time series of NDVI provided valuable information about vegetation patterns and changes over time. NDVI is affected by two major factors of global change: regional weather patterns or climate dynamics and direct changes in land cover.

The study found that NDVI values in the Kilimanjaro region significantly experienced a dynamic change process, involving an initial decrease and subsequent increase over the period of 2000-2022. The decreases in NDVI values are slightly related to the ENSO warm phase, while the increasing NDVI values are related to the ENSO Neutral phase.

Moreover, these NDVI changes are sensitive to elevation, with areas at elevations between 1400m to 2600m indicating an improvement in vegetation density or health, while declines are observed below 1400m and above 2600m. Overall, this study provides valuable insights into the long-term vegetation trends and driving factors of NDVI change on the slopes of Mount Kilimanjaro.