An Analysis of Mangrove Resistance and Resilience in the Philippines Following Super Typhoon Odette

Mangrove forests provide many ecosystem services along tropical coastlines that help sustain natural and human systems. In particular, these habitats are home for commercially viable seafood and serve as a buffer reducing storm energy from damaging coastal communities. The rise in the frequency and intensity of tropical cyclones makes monitoring mangrove damage extent important for understanding present coastal hazards and their attributions, making predictions of coastal buffering capacity changes, and providing timely alerts about high impact regions. Super Typhoon Odette was a Category 5 cyclone that made landfall on Siargao Island, Philippines on December 16, 2021. An unprecedented southern track across more than nine major islands resulted in severe damage to many isolated coastal communities that had not experienced a cyclone in generations. In this study, we created an early-alert tool for the Philippines to quantify mangroves experiencing recovery or degradation after the cyclone. Using open-source Landsat 8 - Sentinel-2 multispectral imagery and Google Earth Engine, we developed pre-storm and post-storm image composites to quantify dynamic changes in the coastal environment through standard measures of forest greenness. Our results include spatially-explicit information of mangrove areas exhibiting die-off indicators. An early-alert model provides mangrove resilience forecasting within a few months post-storm which can direct restoration efforts before die-off occurs. Outcomes from the early-alert model are made available nearly instantaneously through a web app with open accessibility and visualization across the Philippines, enabling timely decision making. Moreover, the web app was tailored alongside Filipino stakeholders to address key resilience and sustainability concerns. This early alert tool, including the model and web app, are scalable to other regions experiencing immediate cyclone impacts and can track recovery on different time scales. Our assessment of the impacts of Typhoon Odette provides critical information on mangrove resiliency thresholds and indicators of mangrove die-off that serve to improve sustainability efforts and future cyclone damage projection.