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Global Risk Index for Mangroves
Context: The study, published in Communications Earth & Environment on April 5, 2025, brings together researchers from ETH Zurich and the University of Colorado Boulder. The risk index developed in the study shows how climate change—especially rising sea levels and stronger storms—will affect mangrove ecosystems globally by 2100.
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- The risk was modelled under three climate change scenarios, or Shared Socioeconomic Pathways (SSP), with varying levels of emissions:
- SSP2-4.5: Moderate emissions
- SSP3-7.0: Medium-high emissions
- SSP5-8.5: Very high emissions
Key Findings
- Risk to Mangroves by 2100: The risk index shows that over 56% of the world’s mangroves could face high to severe risk under the worst-case scenario (SSP5-8.5), which assumes very high emissions.
- About 34% of the most valuable mangroves, those crucial for coastal protection, carbon storage, and fisheries, could experience irreversible damage by 2100. This damage is termed a “regime shift”, indicating a permanent change in the ecosystem that may not recover.
- Climate Change Challenges: Mangroves can handle small changes in sea level and moderate storms, but the increasing frequency and intensity of tropical cyclones and rising sea levels due to climate change may push them past their adaptive limits.
- The combination of stronger storms and rising sea levels could create a vicious cycle where storms damage mangroves, causing peat collapse (land sinking) and preventing them from keeping pace with rising seas.
Major Mangrove Forests in India:
- Sundarbans (West Bengal): India’s largest mangrove forest and a UNESCO World Heritage Site, known for the Royal Bengal tiger and saltwater crocodiles.
- Bhitarkanika (Odisha): Second-largest mangrove ecosystem, rich in saltwater crocodiles and migratory bird species, located in the Mahanadi delta.
- Pichavaram (Tamil Nadu): Famous for its interconnected waterways and birdwatching, it offers a unique mangrove tourism experience.
- Krishna-Godavari (Andhra Pradesh): A vital breeding ground for fish and prawns, supporting both marine and freshwater biodiversity.
- Andaman & Nicobar, Gulf of Kutch, Thane Creek: These mangroves support endemic species, marine-terrestrial biodiversity, and play a key role in coastal protection.
Key Risks to Mangroves
- Storm Damage: Tropical storms can kill mangrove trees. After storms, the land beneath mangroves may sink (due to peat collapse), making it harder for them to adapt to rising sea levels.
- Ecosystem Services Under Threat:
- Coastal Protection: Mangroves block storm waves. However, storms can damage the forests, reducing their protective ability.
- Carbon Storage: Mangroves store large amounts of carbon. If destroyed, this carbon is released into the atmosphere, further exacerbating climate change.
- Support for Fisheries: Mangroves provide homes for fish and marine life. Their destruction can lead to a decline in fish populations, affecting food security and livelihoods.
Global Risk Hotspots
- The study identifies vulnerable regions where the risks to mangroves are expected to be most severe under the SSP3-7.0 scenario:
- Caribbean and Central America: Expected to face stronger storms.
- South and Southeast Asia: Home to large mangrove forests that store carbon and support local communities.
- Eastern Africa: Vulnerable to sea-level rise due to its low-lying geography.
- The Philippines: Has over 260,000 hectares of mangroves and faces severe storm threats by 2100, with a potential loss of mangrove functionality due to changing storm patterns.
Economic and Social Impacts
- 775 million people globally depend on coastal ecosystems, with mangroves alone providing $65 billion annually in flood protection.
- The economic losses from mangrove destruction are not currently included in global climate damage discussions, despite their significant role in protecting infrastructure, food sources, and climate regulation.
- Long-Term Concerns for Restoration: Mangrove restoration efforts may fail if they are planted in areas that become increasingly vulnerable to climate change.
- Mangroves take over 55 years to reach full functionality, meaning that replanted mangroves might not grow fast enough to keep up with the rapidly changing conditions.
Initiatives:
- Mangrove Alliance for Climate: Launched during the 27th Conference of Parties to the United Nations Framework Convention on Climate Change in 2022, aims to promote mangrove conservation globally.
- The International Union for Conservation of Nature (IUCN) plays a crucial role in highlighting the importance of mangrove ecosystems and advocating for their protection worldwide.
- Mangrove Initiative for Shoreline Habitats & Tangible Incomes (MISHTI): Launched in the 2023-24 Union Budget, MISHTI aims to restore/reforest mangroves covering approximately 540 km² across nine states and three union territories over five years. It includes financial assistance for local communities to undertake mangrove plantations, awareness campaigns, and participatory approaches involving NGOs and community institutions. It is expected to provide indirect economic benefits worth INR 51.78 billion annually and create an additional carbon sink of 4.5 million tonnes over ten years.
- Central Sector Scheme on ‘Conservation and Management of Mangroves and Coral Reefs’: Provides financial assistance to coastal states and union territories for implementing action plans specific to mangrove conservation, including surveys, alternative livelihoods, and awareness campaigns. It is part of the National Coastal Mission Programme under the Ministry of Environment, Forest & Climate Change.
Recommendations for Conservation
- The researchers urge that climate risks be incorporated into mangrove conservation and blue carbon planning:
- Restoring Mangroves in Safer Areas: Focus restoration efforts on locations less vulnerable to climate impacts.
- Engineering Solutions: Explore ways to help mangroves grow taller and withstand the effects of rising seas and stronger storms.
- Species Adaptation: Consider moving or mixing species to enhance resilience.
- Inclusion of Climate Hazards in Studies: Future research should incorporate additional climate threats such as marine heatwaves and droughts, and focus on how mangrove ecosystems can recover from disturbances.
