In 2020, more than a quarter of the Maldivian islands containing mangrove forests saw their trees experiencing a gradual deterioration before dying, a condition known as dieback.
Mangroves play an essential role in protecting coastal regions by acting as natural barriers against storms, erosion and flooding. As biodiversity hotspots, they are vital nurseries for marine species such as crabs, prawns and fish making them crucial for food security and livelihoods in many coastal communities. They also provide valuable resources such as construction materials for housing.
Researchers found that sea levels around the Maldives rose at an accelerated rate of over 30mm per year between 2017 to 2020. Towards the end of this period, an unusually intense climate phenomenon known as the Indian Ocean Dipole occurred. This caused warmer sea surface temperatures and an increase in sea level in the Western Indian Ocean.
Although mangroves naturally build up their own sediment, allowing them to adapt to gradually rising seas, this rate of sea level rise was too fast for the mangroves to keep pace.
As tidal movements are more limited in the basin areas where many mangrove forests grow, the rising sea level meant that seawater effectively flooded the forests. This lack of tidal movement and flooding prevented the mangroves from building the sediment they needed to stay above water. They eventually lost their resilience and died off by drowning.