Mangrove Disturbance and Response Following the 2017 Hurricane Season in Puerto Rico

Mangrove ecosystem responses to tropical cyclones have been well-documented over the last half century. Variability in tree mortality, aboveground biomass accumulation, canopy closure, and subsequent recovery has been explained by species, size, and geomorphology. This study gauges the initial response and short-term recovery of Puerto Rico's mangroves following the 2017 hurricane season. Survival probability of tagged trees decreased with time, and the mean mortality across all sites was 22% after eleven months. Mean canopy closure loss was 51% one month after the hurricanes, and closure recovery rates decreased with time following the storms. Aboveground biomass accumulation decreased by 3.5 kg yr(-1) per tree, corresponding to a reduction of 8.6 Mg ha(-1) yr(-1) at the stand level. Eleven months later, the mangroves recovered to 72% canopy closure and to nearly 60% of their pre-storm growth rates. Species, size, and geomorphology were found to play a role, while an influence of surrounding land cover and urbanization could not be detected. Larger trees suffered 25% more mortality than smaller size classes, and Laguncularia racemosa suffered 11% less mortality than other species. Forests in tidally restricted canals experienced more canopy loss but faster recovery than open embayment systems. Canopy closure for some forests is not forecasted to return to pre-storm levels in the next 20 years, which when combined with changes in hurricane frequencies may or may not be sooner than the next extreme hurricane disturbance. These findings suggest that size, species, and geomorphology are important in mangrove resilience to tropical storms and that urbanization does not play a role. Managing mangrove ecosystems for optimal shoreline protection will depend upon knowing which forests are at greatest risk in a future of changing tropical cyclone strength and frequency.