Mangrove distribution and afforestation potential in the Red Sea

Mangrove ecosystems represent one of the most effective natural environments for fixing and storing carbon (C). Man-groves also offer significant co-benefits, serving as nurseries for marine species, providing nutrients and food to support marine ecosystems, and stabilizing coastlines from erosion and extreme events. Given these considerations, mangrove afforestation and associated C sequestration has gained considerable attention as a nature-based solution to climate adaptation (e.g., protect against more frequent storm surges) and mitigation (e.g. offsetting other C-producing activi-ties). To advance our understanding and description of these important ecosystems, we leverage Landsat-8 and Sentinel-2 satellite data to provide a current assessment of mangrove extent within the Red Sea region and also explore the effect of spatial resolution on mapping accuracy. We establish that Sentinel-2 provides a more precise spatial record of extent and subsequently use these data together with a maximum entropy (MaxEnt) modeling approach to: i) map the distribution of Red Sea mangrove systems, and ii) identify potential areas for future afforestation. From these cur-rent and potential mangrove distribution maps, we then estimate the carbon sequestration rate for the Red Sea (as well as for each bordering country) using a meta-analysis of sequestration values surveyed from the available literature. For the mangrove classification, we obtained mapping accuracies of 98 %, with a total Red Sea mangrove extent estimated at approximately 175 km(2). Based on the MaxEnt approach, which used soil physical and environmental variables to identify the key factors limiting mangrove growth and distribution, an area of nearly 410 km(2) was identified for potential mangrove afforestation expansion. The factors constraining the potential distribution of mangroves were re-lated to soil physical properties, likely reflecting the low sediment load and limited nutrient input of the Red Sea. The current rate of carbon sequestration was calculated as 1034.09 +/- 180.53 Mg C yr(-1), and the potential sequestration rate as 2424.49 +/- 423.26 Mg C yr(-1). While our results confirm the maintenance of a positive trend in mangrove growth over the last few decades, they also provide the upper bounds on above ground carbon sequestration potential for the Red Sea mangroves.

Automated summary

Mangrove ecosystems in the Red Sea have high efficiency in carbon fixation and storage, as well as providing other co-benefits. Assessment of mangrove extent in the Red Sea using satellite data and exploring the effect of spatial resolution on mapping accuracy were conducted. The distribution of Red Sea mangroves and potential areas for afforestation were mapped using a maximum entropy modeling approach. The carbon sequestration rates were estimated based on a meta-analysis of available literature. Results show a positive trend in mangrove growth and provide upper bounds on carbon sequestration potential for Red Sea mangroves.