Storm surge and ponding explain mangrove dieback in southwest Florida following Hurricane Irma

Mangroves buffer inland ecosystems from hurricane winds and storm surge. However, their ability to withstand harsh cyclone conditions depends on plant resilience traits and geomorphology. Using airborne lidar and satellite imagery collected before and after Hurricane Irma, we estimated that 62% of mangroves in southwest Florida suffered canopy damage, with largest impacts in tall forests (>10m). Mangroves on well-drained sites (83%) resprouted new leaves within one year after the storm. By contrast, in poorly-drained inland sites, we detected one of the largest mangrove diebacks on record (10,760ha), triggered by Irma. We found evidence that the combination of low elevation (median=9.4cmasl), storm surge water levels (>1.4m above the ground surface), and hydrologic isolation drove coastal forest vulnerability and were independent of tree height or wind exposure. Our results indicated that storm surge and ponding caused dieback, not wind. Tidal restoration and hydrologic management in these vulnerable, low-lying coastal areas can reduce mangrove mortality and improve resilience to future cyclones. Mangroves are adapted to cope with tropical storms, but might be threatened by rising frequency and intensity of these events. Here the authors document one of the largest mangrove diebacks on record following Hurricane Irma in Florida, and show a greater role of storm surge and ponding rather than wind as a mechanism for mangrove dieback.

Automated summary

Mangroves provide buffer for inland ecosystems against hurricane winds and storm surge, but their ability to withstand harsh cyclone conditions depends on plant resilience traits and geomorphology. Research shows that Hurricane Irma caused canopy damage to 62% of mangroves in southwest Florida, with tall forests being most impacted. While well-drained sites were able to resprout new leaves within a year, poorly-drained inland sites experienced one of the largest mangrove diebacks on record triggered by Irma. The study indicates that storm surge and ponding were the primary causes of mangrove dieback, rather than wind exposure.