Mapping the potential loss and migration of mangroves in Northwest Madagascar due to sea level rise

Madagascar’s mangroves comprise 2% of the world’s total, but are at risk of loss due to increasing sea level rise (SLR). Vertical elevation gain (VEC) via sediment accumulation has historically allowed mangroves to adjust to SLR, but currently in many parts of the world, SLR is outpacing VEC. This study focuses on the Ambanja-Ambaro Bays (AAB) region in Northwestern Madagascar, with a 7km buffer inland to capture the terrestrial mangrove data and satellite altimeter data for sea level in the Indian Ocean from 2000 to 2016. Rates of change were determined for both SLR based on altimeter data from the Topex/Poseidon and Jason-1, 2, and 3 satellites and VEC data collected from 2016 to 2017 by the NGO Blue Ventures. DEM (from ASTER satellite tiles) and slope were combined with existing land cover classification data from Jones et al. (2016) to determine the potential of mangroves to migrate inland in response to SLR.

马达加斯加的红树林占全球总量约2%，但因海平面上升（sea level rise，SLR）加剧而面临消失风险。历史上，通过沉积物积累实现的垂直高程增益（vertical elevation gain，VEC）曾帮助红树林适应SLR，但当前全球多地SLR增速已超过VEC。本研究聚焦马达加斯加西北部的安班贾-安巴罗湾（Ambanja-Ambaro Bays，AAB）区域，设置7公里内陆缓冲区以获取陆地红树林数据，并采用2000至2016年印度洋海平面的卫星高度计数据。基于托佩克斯/波塞冬（Topex/Poseidon）卫星及Jason-1、Jason-2和Jason-3卫星的高度计数据，以及非政府组织蓝色冒险（Blue Ventures）2016至2017年收集的VEC数据，本研究测定了SLR与VEC的变化速率。研究将数字高程模型（digital elevation model，DEM，源自ASTER卫星影像瓦片）和坡度数据，与琼斯等人（Jones et al.，2016）已有的土地覆盖分类数据相结合，以评估红树林响应SLR向内陆迁移的潜力。