Abstract
Extreme weather events are a cause of mangrove forest loss and degradation globally. Almost half of the world’s mangroves are found in the tropical cyclone belt, and forests often experience disturbance in structure, functioning and ecosystem service provision. Understanding the factors that increase the vulnerability of mangroves to such disturbances is a challenge. Using a novel remote sensing analysis combining water class change with vegetation classification, we showed that mangrove loss across multiple cyclone events is influenced by previous erosion history, suggesting that the prior state of the coastline affects susceptibility to future disturbance events. During Cyclone Amphan in May 2020, more than 1,200 km2 of mangroves were damaged and 40.6 km2 of shoreline was lost. Cyclone Amphan caused the most damage out of three recent cyclones, with the most mangrove loss (18.8%) experienced along shorelines that were eroding over the past 35 years. This can be explained by the long-term effect of erosion on the overall intertidal morphology of the shoreline. Landscape-scale mangrove management, particularly of sediment budgets is essential to switch previously eroding mangroves to a state where they can withstand cumulative storm impacts.
Highlights
Extreme weather events account for 11% of contemporary global mangrove forest loss, with their proportion in the 21st century increasing relative to human drivers of deforestation (Goldberg et al, 2020)
The net erosion of shoreline was highest during Cyclone Bulbul and lowest during Cyclone Fani, erosion as a proportion to shoreline damage was highest (14.47%) during Cyclone Bulbul and least for Cyclone Amphan (9.96%)
A substantial proportion of the world’s mangrove forests are impacted by cyclonic activity, and while we have an improved understanding of mangrove dynamics and response to storms at the stand level (Krauss and Osland, 2020), this study contributes insights to how mangrove forests respond to cyclones at the landscape level
Summary
Extreme weather events account for 11% of contemporary global mangrove forest loss, with their proportion in the 21st century increasing relative to human drivers of deforestation (Goldberg et al, 2020). Cyclones cause a range of disturbances on mangrove forest structure, functioning, and geomorphology, including immediate defoliation and short-term biomass loss, changes in carbon and nutrient cycling, peat collapse, and eventual marine transgression (Castañeda-Moya et al, 2010; Jones et al, 2019; Krauss and Osland, 2020). This leads to observable impacts on the ecosystem services that mangrove forests provide, such as their ability to store and sequester carbon to regulate the global climate (Friess et al, 2020; Peneva-Reed et al, 2021). Such information will allow us to evaluate the suitability of mangrove forests as a tool for ecological disaster risk reduction in cyclone-prone areas
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