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Researchers from Switzerland and United States have developed a risk index for mangroves as well as associated biodiversity and ecosystem services in various scenarios.
It is the first study to map how two major climate threats — rising sea levels and more frequent tropical cyclones — will affect mangrove ecosystems around the world. This index will guide how we protect mangroves in the future.
The study, published in the journal Communications Earth & Environment on April 5, 2025, brings together scientists from the Institute for Environmental Decisions ETH Zurich and Department of Ecology and Evolutionary Biology, University of Colorado Boulder.
The global risk index shows how dangerous it could become for mangroves by 2100 under three possible shared socioeconomic pathways (SSP) future scenarios: SSP2-4.5 (moderate emissions), SSP3-7.0 (medium-high emissions) and SSP5-8.5 (very high emissions).
Over 56 per cent of the world’s mangroves could be at high or severe risk, under the worst-case scenario (SSP5-8.5).
Even more worrying, about 34 per cent of the most valuable mangroves, those that provide strong coastal protection, carbon storage and support fisheries could face serious and possibly irreversible damage. This is called a “regime shift”, meaning the ecosystem may change completely and may not recover.
Mangroves can adapt well to storms and small sea-level changes. But climate change is testing their limits and creating unfavourable conditions in which they may perish.
Worryingly, the most useful mangrove areas that provide critical benefits or ecosystem services like coastal protection, carbon storage and fishery support are also the most at risk, the scientists warned in the study.
Using the risk index, scientists projected how future changes in storm strength and sea levels could harm mangroves. Under the SSP3-7.0 scenario, for instance, 52 per cent of mangroves could fall under high to severe risk. The danger increases when strong storms and rising seas happen in the same place.
Storms can kill mangrove trees. After storms, the land under mangroves may sink in a process called peat collapse, making it harder for them to keep up with rising sea levels. This creates a dangerous loop.
Mangroves provide three key services that are now at risk. They protect coasts by blocking storm waves but damage from storms can remove this shield. They store a lot of carbon in their trees and soil. This carbon is released into the air, adding to climate change, when mangroves are destroyed.
Mangroves also support fisheries by giving homes to fish and sea life. If they disappear, fish numbers can fall, affecting food and jobs for many people. There is a risk of losing these benefits exactly where people need them most, the authors of the report pointed out.
The study showed global risk hotspots, especially under the SSP3-7.0 scenario:
The Caribbean and Central America, where storms are expected to get stronger
South and Southeast Asia, where large mangrove forests store carbon and support many people
Eastern Africa, where the land is low and sea-level rise is a big threat
The Philippines is one of the most at-risk countries. It has over 260,000 hectares of mangroves and already gets hit by many storms. By 2100, it may face storm patterns never seen before.
This could damage the structure of mangrove forests and reduce the services they provide. Replanted mangroves may not grow fast enough to cope since they take more than 55 years to match the function of natural forests.
The researchers also highlighted the impact on people and economies. Around 775 million people depend on coastal ecosystems, they noted. Moreover, mangroves alone provide $65 billion worth of flood protection each year. However, the losses linked with the collapse of magrove ecosystems are not currently included in global climate damage discussions.
Infrastructure is at risk in Central America. In Southeast Africa, all mangrove services like food, climate regulation and protection are threatened.
In Australia and the Pacific Islands, blue carbon projects may be in danger. Even if moderate sea-level rise brings some carbon benefits, stronger storms could still damage the mangroves.
Climate risks must be included in how we plan mangrove conservation, the scientists urged. If mangroves are restored in risky places, those efforts may fail in a few decades, they said, recommending steps such as:
Restoring mangroves in safer areas
Using engineering to help mangroves grow taller and survive
Moving or mixing species to improve resilience
Climate risks must be part of planning and funding for blue carbon and mangrove projects, the authors urged. Further, climate hazards such as like marine heatwaves and droughts should be included in future studies, which should focus on how ecosystems recover, they added.