[NEW DELHI] Evidence that mangrove forests in the Maldives are “drowning” due to rising sea levels should act as a wake-up call for conservation efforts, researchers warn.

Mangrove forests protect tropical and subtropical coastlines, acting as a barrier against coastal erosion, flooding, and cyclones or typhoons.

For coastal communities, they play an important part in improving resilience against the effects of climate change.

But in 2020, a mangrove “dieback” occurred – a condition defined by gradual worsening of tree health – affecting nearly a quarter of mangrove-rich islands in the Maldives, according to a study in the journal Scientific Reports.

“[Mangrove forest] loss could have major negative consequences for local populations, both because these ecosystems provide vital services such as food resources, water purification, and materials like wood, firewood, and because of the cultural importance of the mangroves.”

Federico Cerri, scientist, Marine Research and Higher Education Center

Satellite images showed that some islands lost more than half of their mangrove forests due to the rising sea level.

Federico Cerri, a scientist affiliated with Marine Research and Higher Education (MaRHE) Center in the Maldives, who was not involved in the research, told SciDev.Net: “The study highlights a critical and impactful issue for mangrove conservation, signalling a wake-up call for global efforts in the context of the intensifying climate crisis.”

To evaluate mangrove dieback, the researchers used remote sensing, dendrology (the scientific study of trees) and sediment-related studies.

They found a substantial decrease in mangrove health after 2020, compared with mangrove health before 2020.

In dead trees, as compared with living trees, there were greater signs of salinity stress or the struggle of tree roots to survive in raised salt levels, an important factor responsible for tree death.

The researchers observed that in the Maldives, sea levels increased at a rapid annual rate of more than 30 millimetres from 2017 to 2020. A climate phenomenon called Indian Ocean Dipole took place during the end of this period, leading to warmer sea surface temperatures and a rise in the Western Indian Ocean sea-level.

While mangroves will naturally accumulate their own sediment, allowing them to adjust to gradually increasing seas, this rapid rate of sea-level increase outpaced the sediment deposition in mangrove trees, leading to their death by drowning.

“Our findings reveal that while mangroves can adapt to gradual sea-level rise, they are vulnerable to extreme events that could become more frequent with climate change,” said Vasile Ersek, an author of the study and associate professor at the geography and environment department of Northumbria University, in the UK.

“This vulnerability is particularly concerning for Small Island Developing States, where mangroves provide essential ecosystem services including coastal protection, support for fisheries, and carbon storage.”

Small Island Developing States are low-lying coastal countries facing specific challenges, such as susceptibility to natural disasters. Their populations are among the most vulnerable to the impacts of the climate crisis.

“[Mangrove forest] loss could have major negative consequences for local populations, both because these ecosystems provide vital services such as food resources, water purification, and materials like wood, firewood, and because of the cultural importance of the mangroves,” said Cerri.

Mangroves are also vital for biodiversity, offering habitats and food sources for many marine and land-dwelling species, he added.

The dieback of mangroves in the Maldives serves as an “early warning system” for how these crucial ecosystems might respond to future climate conditions globally, particularly in low-lying islands, according to Ersek.

“[We] urgently need adaptive conservation strategies that consider both the immediate threats from extreme events and long-term climate change impacts,” he told SciDev.Net.

“Such measures could include implementing restoration projects that enhance mangrove resilience, such as selecting more salt-tolerant species and ensuring adequate sediment supply to help mangroves keep pace with sea-level rise.”

This piece was produced by SciDev.Net’s Asia & Pacific desk.