Monitoring mangroves could prove invaluable for developing new coastal erosion models. We present a multiscale modeling approach for mangrove shoreline fluctuations observed over 10 years using satellite imagery acquired along the open, dynamic muddy coast of French Guiana. We aimed to gain a better understanding of the complex interactions between ocean waves and mud banks by simulating the processes that lead to both mangrove erosion and expansion. We found that fluctuations in seafront mangroves could be simulated with acceptable accuracy along 200 km of coastline. In the absence of mud banks, seasonal wave forcing resulted in erosion rates reaching 1100 m/y. Our findings indicate that wave energy can be reduced by 90% at all locations when the extent of mud banks exceeds 2000 m in front of the mangroves. Finally, we discuss the potential of this innovative modeling approach for anticipating coastal changes.