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Resilience of the Sundarbans Mangroves
Context:
A study titled “Resilience of Sundarban mangroves in South Asia to Weather Extremes and Anthropogenic Water Pollution” was conducted by researchers from IIT Bombay, IISER Kolkata, and ISRO’s National Remote Sensing Centre, Hyderabad.
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Researchers studied vegetation productivity (how efficiently mangroves convert solar energy into biomass) and flux data (gaseous exchanges of CO2 and water vapour between plants and the atmosphere).
The Sundarbans, located in India and Bangladesh, are the world’s largest stretch of mangrove forests. They serve as a critical ecosystem, providing defence against cyclones, supporting diverse wildlife, and helping combat global warming. A significant portion of the Sundarbans is recognised as a Ramsar Site (wetlands of international importance), and the Indian side of the region has been designated as a UNESCO World Heritage Site since 1987.
Key Findings:
- Resilience to Stress: Mangroves in the Sundarbans recover from physiological stress (like cyclones) quickly—within 1 to 2 weeks—and maintain stable productivity despite a decline in nutrient composition due to pollution.
- Nutrient Composition Changes: The study found that the ratio of nitrogen to phosphorus (N/Ph) in the mangroves shifted significantly, with nitrates increasing (due to acid rain) and phosphates decreasing from 2013 to 2015.
- Stable Productivity: Despite declining nutrient levels due to human pollution, mangroves maintained stable productivity by adjusting their interactions with hydro-meteorological factors.
- Link Strength and Memory: Mangroves adapt to stress by altering their interaction with the environment.
- “Link strength” refers to how interconnected various components of the mangrove ecosystem are, while “memory” refers to the mangroves’ ability to remember and store responses to past stress events (like cyclones).
What Are Mangroves and Their Importance?
- Mangroves are unique trees capable of thriving in salty coastal waters.
- The Sundarbans exist in the delta formed by the Ganga, Brahmaputra, and Meghna rivers, receiving both freshwater and tidal saline water.
- According to the Global Mangrove Alliance, the Sundarbans provide habitat for endangered species such as the Bengal tiger, Irrawaddy river dolphin, finless porpoise, and estuarine crocodile.
- Mangroves act as a nursery for 90% of aquatic species along India’s east coast and serve as a bio-shield against coastal storms.
- They play a significant role in carbon sequestration, extracting up to five times more carbon than terrestrial forests.
- The Indian Sundarbans were classified as endangered under the IUCN Red List of Ecosystems in 2020.
Significance of the Study
- The study highlights that while the Sundarbans have shown resilience, their ability to self-repair has limits.
- Understanding the resistance of mangroves to stressors is crucial in identifying their breaking point and formulating conservation strategies.
- The study urges a deeper understanding of the limits of resistance and critical transitions in mangrove ecosystems due to anthropogenic stressors.
- The findings highlight the need for scientifically driven solutions to protect and restore mangroves in South Asia.
Threats to the Sundarbans
- The Sundarbans mangroves, especially in non-protected regions, face numerous threats such as:
- Exposure to cyclones and storms.
- Rising sea levels.
- Unsustainable practices in agriculture and aquaculture.
- Reduced freshwater supply.
- Air pollution and land erosion.
- Depletion of marine resources, including declining fish populations.
Restoration Efforts
- Nature Conservancy India is working to restore 100 hectares of degraded mangrove habitats and monitor 60 hectares of previously initiated restoration projects in the Indian Sundarbans.
- This aligns with the MISHTI (Mangrove Initiative for Shoreline Habitats & Tangible Incomes) initiative by the Government of India.
- NITI Aayog has released a comprehensive report titled “Greening and Restoration of Wastelands with Agroforestry (G.R.O.W)”, focusing on the recovery and restoration of wetlands across India.
- The report introduces the Agroforestry Suitability Index (ASI), a tool developed using remote sensing and GIS technologies to assess the suitability of different regions for agroforestry.
- Sundari Mangroves Project: Launched to restore 4,500 hectares of degraded mangroves in West Bengal, this project is supported by private sector partners like EcoAct and Meensou India.
