Three Decades of Mangrove Ecosystem Recovery Following Avicennia marina Afforestation in an Arid Coastal Environment: Remote Sensing Evidence from the Red Sea

Mangrove restoration is increasingly recognized as an effective nature-based solution for biodiversity conservation, climate-change mitigation, and coastal resilience. However, long-term evaluations of restoration outcomes remain scarce, particularly in arid coastal environments. This study assesses three decades of ecosystem recovery following the afforestation of Avicennia marina at Sajid Bay, Farasan Archipelago, Saudi Arabia. A total of 1050 seedlings were transplanted in 1994 into an unvegetated intertidal area and monitored using multi-temporal satellite imagery and Normalized Difference Vegetation Index (NDVI) analysis from 1994 to 2024. Results revealed a progressive expansion of mangrove cover to 15.48 ha over the 30-year period, corresponding to an average annual increase of approximately 0.516 ha yr−1. Spatial patterns of expansion were strongly influenced by local geomorphological and hydrodynamic conditions. Central areas characterized by low wave energy and stable sediments exhibited the highest rates of colonization and vegetation development, whereas peripheral areas exposed to greater hydrodynamic stress expanded more slowly. The establishment of reproductive stands enabled natural regeneration, transforming the original plantation into a self-sustaining mangrove ecosystem. The findings demonstrate that relatively small-scale afforestation efforts can trigger long-term ecosystem recovery when implemented under suitable environmental conditions. The transition from planted seedlings to a naturally regenerating mangrove forest highlights the importance of site selection, hydrodynamic suitability, and ecological processes in determining restoration success. This study provides rare empirical evidence of long-term mangrove recovery in an arid coastal system and offers a practical conservation framework for restoring degraded coastal habitats throughout the Red Sea region and other environmentally comparable coastlines.