Dynamic Change in Normalised Vegetation Index (NDVI) from 2015 to 2021 in Dhofar, Southern Oman in Response to the Climate Change

Abstract

Climate change poses a major threat to vegetation and land cover worldwide. The loss of vegetation as a result of climate change can alter the functions and structure of the environment and its ecological systems. In the first part of this study, Sentinel-2 data, normalised different vegetation index (NDVI), and multiple regression methods were used to examine the impacts of the climatic factors of humidity, rainfall, and air temperature on vegetation dynamics from 2015 to 2021 in Dhofar, Southern Oman. In the second part of this study, random forest regression was employed to model the relationships between the NDVI and temperature, humidity, rainfall, soil map, geology map, topographic wetness index, curvature, elevation, slope, aspect, distance to buildings, and distance to roads. The multiple regression values revealed significant associations between the spatial distributions of the NDVI and the abovementioned climatic factors. The findings also indicated an increase of 1 °C in air temperature fluctuations between 2018 and 2021 over all five sites, with a strong tendency over Qairoon Hairiti Mountain. The rainfall records clearly indicated an increasing tendency from 2018 to 2020 due to the impact of frequent cyclones. Therefore, the results revealed a significant increase of 0.01 in the vegetation cover trend in 2018, 2019, and 2020 along the Sadah Mountain range and the eastern part of the Jabal Qara Mountains under the areas directly impacted by the cyclone, whereas there was a decrease along the western mountain range consisting of Jabal Qara and Jabal Qamar Mountains due to the impact of warm, dry air. The results revealed that NDVI values were sensitive to heavy rainfall over Jabal Samhan Mountain. The 12 variables that influenced NDVI levels had different levels of importance. Soil types, elevation, slope, rainfall, curvature, humidity, and temperature had the highest importance, while topographic wetness index, distance to urban area, aspect, distance to roads, and geology map had the lowest. The findings provide a significant foundation for Oman’s planning and management of regional vegetation, water conservation, and animal husbandry.