Multi-temporal satellite image analysis for detecting the changes in mangrove vegetation between Allith and Alqahma on the Red Sea coast.

The mangroves on the Red Sea coast, home to the most economically valuable plants, are currently experiencing significant spatio-temporal changes. A few previous studies used satellite data to monitor the mangroves in Saudi Arabia. As an extension of these studies, we aim to detect the differences in the density and coverage of the mangroves that grow between Allith and Alqahma on the Red Sea coast, produce a digital map for the region, and determine the natural and anthropogenic factors that affect mangrove growth. We used multi-spectral satellite images from moderate resolution imaging spectroradiometer (MODIS) Aqua, Landsat-5 Thematic Mapper (TM), Landsat-8 operational land imager (OLI), and modern-era retrospective analysis for research and applications, version 2 (MERRA-2) captured during 1990-2022. The data were processed and analysed using the optimised soil-adjusted vegetation index, classification method, overlay, and change detection to develop a digital map of the spatio-temporal changes in the mangroves from 1990 to 2022. The results indicated a decrease in mangrove density in the study area. Furthermore, the mangroves did not experience any significant increase in coverage from 1990 to 2022, with the highest rate of increase being 0.27 %. The highest coverage rate (0.29 %) was recorded in 1990, and the lowest (0.24 %) was recorded in 2013. This study concludes that optimal temperature, rain, wind, waves, salinity, nutrient concentration, and bay characteristics are the important favourable factors for mangrove growth. In contrast, anthropogenic activities (particularly those that lead to pollutant release), overgrazing, and diseases are harmful factors that lead to mangrove deterioration. Our study highlights the need to support and develop mangrove rehabilitation projects while minimising the influence of anthropogenic activities on the ecosystem.