Do hurricanes or freezing events regulate the sustainability of subtropical mangroves on the Gulf of Mexico coast?

Global warming has caused poleward mangrove expansion, but extreme climatic events have significantly impacted the mangroves along their boreal limits. This study aimed to determine which natural hazard is more important in limiting the sustainability and survival of subtropical black mangroves-hurricanes or freezing events? Satellite and drone images indicated Hurricanes Zeta and Ida (2020-2021) caused only minor impacts on mangrove area (similar to 5%, 6.32 ha) compared with the extensive mangrove degradation (defoliation and dry branches) caused by the winter freeze of Dec/2017-Jan/2018 (similar to 89%, 110 ha) at Port Fourchon, LA. However, mangroves impacted by that winter freeze had a faster recovery (similar to 1 year), while the losses of mangrove areas caused by those hurricanes were longer-lasting. This finding is novel and important because it implies that subtropical mangroves have low resistance but high resilience to winter freezes, while these forests present high resistance but low resilience to hurricanes. Overwash processes driven by hurricanes are the primary threat to mangroves at Port Fourchon due to the high rate of beach barrier retreat, which causes the burial of the back-barrier wetlands. Beach renourishment projects are essential to guarantee the stability of the beach barrier and slow down the increased losses of mangrove and salt marsh areas caused by hurricanes and relative sea level rise.