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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 (~ 5%, 6.32 ha) compared with the extensive mangrove degradation (defoliation and dry branches) caused by the winter freeze of Dec/2017–Jan/2018 (~ 89%, 110 ha) at Port Fourchon, LA. However, mangroves impacted by that winter freeze had a faster recovery (~ 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. [ABSTRACT FROM AUTHOR]

The high sea‐level stand during the mid‐Holocene is a benchmark in mangrove dynamics along the north‐east/south‐east coast of Brazil and provides a reference point for landward and seaward mangrove migrations corresponding to changes in relative sea level (RSL). However, evidence of the impacts associated with RSL fall on the northern Brazilian coast is scarce. Multi‐proxy data from the highest tidal flats of the Bragança Peninsula in northern Brazil revealed modern herbaceous areas were occupied by mangroves Rhizophora and Avicennia from ~6250 to ~5850 cal a bp, and only Avicennia between ~5850 and ~5000 cal a bp. The same tidal flats were vegetation‐free between ~5000 and ~4300 cal a bp. A combination of a high sea‐level stand (0.6 ± 0.1 m) at ~5000 cal a bp and a dry early–middle Holocene in the Amazon probably caused an increase in porewater salinity of tidal flats, which resulted in a mangrove succession from Rhizophora to Avicennia dominance. RSL fall accentuated this process, contributing to mangrove degradation between ~5000 and ~4300 cal a bp. RSL fall, and a wetter period over the past ~4300 cal a bp caused a mangrove migration from highest to lowest flats, followed by expansion of herbaceous vegetation on the highest flats. [ABSTRACT FROM AUTHOR]