Long-term loss of coral reef in the Gulf of Aqaba estimated from historical aerial images

Located at the northern tip of the Red Sea, the Gulf of Aqaba coral reef, is highly susceptible to anthropogenic pressure associated with the massive development of the two neighbor cities of Eilat and Aqaba. Over the years the has been extensively studied in a umber of research and monitoring programs, which provide detailed information on a variety ecological,physiological, biogeochemical and physical variables. Due to the local nature of these surveys, while the state of the reef at specific times and locations is very well characterized, long term changes in the reef as a whole are hardly documented. Here, through analysis of historical aerial images, we address one of the most important aspects of this knowledge gap, and quantify how much coral reef were lost due to human activity with respect to a baseline level prior to the establishment of the City of Eilat in 1949. Our results show that through construction of infrastructures, human activity has led to the loss of more than 4,810 m 2 of coral reef, either directly by the construction (most importantly the Eilat Port) or indirectly by changing environmental conditions, which in turn damage the reef - for example by intensifying accumulation of sand on top of it. Our results show that historical aerial images can provide a unique source of information on the spatial characteristics of marine, coastal and terrestrial systems prior to the era of Earth observation satellites.