Erosion of mangrove dominated muddy coasts in Vietnam and Indonesia: Processes and accelerating factors

Although there have been extensive studies of the erosion of mangrove-dominated muddy coasts, the information on the processes and drivers of erosion at fine scales of analysis is still lacking. Without this knowledge, the existing efforts to minimize erosion are just piecemeal solutions that only address the symptoms of the erosion process. The coastlines of the Mekong Delta in Vietnam (VMD) and Brebes Regency in Indonesia have been selected as case studies to address this issue. The aim of the paper is to document coastal erosion and the factors that accelerate the erosion process. This is achieved by using the participatory diagramming technique, which combines the analysis of photographs of erosion sites taken during field trips, detailed field observations, and responses from semi-structured interviews with erosion-affected communities in VMD and Brebes Regency, Indonesia. The results show that five dominant erosion processes identified in these two regions were burrow-induced erosion, clearcut-induced erosion, farming-induced erosion, pond-induced erosion, and boating-induced erosion. Of the five erosion processes, human activities have altered the characteristic of the mangrove forests, and are likely to have exposed areas to erosion, with wave action providing a tipping point by severely reducing the structural integrity of the coastal soil in sensitive areas and making them susceptible to collapse. However, many other areas in VMD and Brebes Regency, Indonesia have remained stable over time. The methodological approach proposed here appears to be applicable to other mangrove-dominated muddy coasts, which are characteristic of most anthropogenically affected tropical deltas. As human activities are closely linked to forestry policies in Vietnam and Indonesia, enforcement should be strengthened to significantly increase the impact of these policies in controlling coastal erosion and minimize the vulnerability of these areas to erosion.