The Sundarbans mangrove ecosystem is in news due to three important developments. First, scientists from IISER Kolkata detected airborne microplastics deep inside an uninhabited mangrove island of the Sundarbans Biosphere Reserve, showing that plastic pollution has now entered even protected natural ecosystems through the atmosphere. Second, the 2024–25 population assessment report recorded a rise in the estimated saltwater crocodile population in the Indian Sundarbans from 204–234 in 2023–24 to 220–242 in 2024–25. Third, the wider debate on India’s mangroves has again highlighted their role as nature-based solutions for sea-level rise, flood mitigation, storm protection, biodiversity and coastal livelihoods.
A new study by the Indian Institute of Science Education and Research (IISER), Kolkata, published in Science of the Total Environment, has found airborne microplastics over a completely uninhabited mangrove island deep inside the Sundarbans Biosphere Reserve. The study marks the first evidence of atmospheric microplastics inside a protected natural ecosystem in India.During an eight-day winter campaign in January 2025, scientists used high-volume air samplers at the Chula Kathi Protection Camp inside the Indian Sundarbans. They recorded an average of 10 ± 6 microplastic particles per 100 cubic metres of air, which was significantly higher than levels reported from several remote regions worldwide.
The study shows that the atmosphere is now acting as a pathway for plastic pollution. During land-breeze hours, microplastics from urban South Bengal, including Kolkata, were pushed into the forest interior. During sea-breeze hours, marine microplastics were carried inland from the ocean surface through bubble bursting and wave action.The role of fog was also significant. Researchers found that fog traps plastic particles in calm and humid air. These particles then remain near the mangrove canopy, increasing the possibility of deposition on leaves, sediments and soils.
The presence of airborne microplastics in the Sundarbans is serious because these particles can settle on mangrove leaves, disturb microbial cycles, contaminate soils and enter the estuarine food chain through fish and shellfish. The study also recorded average PM10 levels of 144 ± 14 µg/m³, which is above India’s permissible limit of 80 µg/m³, indicating chemical stress even inside a designated ecological sanctuary.Researchers urged policymakers to include airborne microplastics in India’s National Clean Air Programme (NCAP) and coastal pollution frameworks. This is important because plastic pollution is no longer limited to water and land; it has become a multi-domain environmental challenge.
The Indian Sundarbans has also recorded a rise in its saltwater crocodile population. The 2024–25 report on population assessment and habitat ecology of estuarine crocodiles estimated the population at 220–242, compared with 204–234 during the 2023–24 exercise. The report clarified that this is a population trend and not the exact number.The assessment was conducted between December 2024 and February 2025 with 23 teams. The exercise covered nearly 1,168 km of transect length, compared to 955 km in 2023–24. Direct and indirect sightings were recorded across the creek or transect length in the Sundarbans Biosphere Reserve.
Based on direct sightings of 213 crocodiles, including 108 in Sundarbans Tiger Reserve and 105 in South 24 Parganas division, the estimated number of saltwater crocodiles was placed between 220 and 242.The encounter rate improved from one crocodile per 7.6 km in the last exercise to one crocodile per 5.5 km of transect. The exercise covered nearly 70% of the total creek length of the Sundarbans.Crocodiles in the Sundarbans were found to prefer creek widths of 10–130 metres, with a median width of 90 metres. They preferred salinity between 10–23 PPT and ambient temperatures of 20°C–30°C for basking during winter months.
| Category | Basis / Finding |
|---|---|
| Adult crocodiles | More than 240 cm in length |
| Juvenile crocodiles | More than 90 cm but less than 180 cm |
| Adult sightings | 125 |
| Juvenile sightings | 88 |
| Total direct sightings | 213 |
| Estimated population | 220–242 |
The increase in hatchling sightings was described as encouraging because hatchling sightings are rare in a terrain like the Sundarbans.
The crocodile straying data shows that most rescues in the delta occur during May–June, which coincides with the nesting season. Most rescued crocodiles are female. This suggests that suitable nesting habitats in forested islands are becoming scarce, forcing nesting females towards fringe and human-dominated islands.
Mangroves are vital nature-based solutions for India’s coastal cities. They provide carbon sequestration, flood mitigation, protection against wind and waves, fisheries support and biodiversity habitat. India’s coastal cities have lost large areas of mangrove cover, making them more vulnerable to sea-level rise, storm surges, cyclones and floods.Mangroves are especially important because mature forests provide stronger coastal protection than newly planted mangrove saplings. Therefore, protecting existing mangrove stands is as important as restoration.
Mangroves support food and livelihoods, especially fisheries and aquaculture. They act as nurseries for several fish species. Without mangroves, nearly 80% of global fish catch would be directly or indirectly impacted.They also provide honey, fruits, salt, leaves, medicinal herbs and algae. Their complex root systems stabilise soil and reduce wave height by nearly 31%, helping protect coastal settlements and infrastructure from floods.The Pichavaram mangroves in Tamil Nadu protected nearly 1,700 people living between 100 and 1,000 metres inland during the 2004 Indian Ocean Tsunami. They also helped protect coastal hamlets during Cyclone Gaja in 2018.
Coastal cities such as Mumbai, Chennai and Kolkata are vulnerable to climate-related hazards. Mumbai faces risks from sea-level rise, coastal erosion, flooding and storm surges. Around 24% of Mumbai’s land is currently vulnerable.Urban expansion, land reclamation, waste dumping and infrastructure projects have affected mangroves. The Bombay High Court permitted CIDCO to cut 3,728 mangroves for the Ulwe coastal road connecting Mumbai’s Trans Harbour Link to Navi Mumbai.Although compensatory plantation is often proposed, young mangroves cannot provide the same ecosystem services as mature mangrove forests. Therefore, maintaining the functional integrity of mangrove ecosystems is essential.
Mangroves are shrubs or trees that grow in brackish water, where saline seawater meets freshwater. They are generally found in the intertidal zone and have complex root systems that help them breathe in waterlogged conditions and stabilise shifting soil.There are more than 70 known species of mangroves. Different species have different salinity tolerance, leading to zonation, where highly salt-tolerant species form the first line of defence against tides and less salt-tolerant species grow closer to freshwater inflows.
India is home to the Sundarbans, the world’s largest mangrove swamp forest, spread across India and Bangladesh. The Sundarbans covers nearly 43% of India’s mangrove cover, followed by the Kachchh coastline in Gujarat, which accounts for around 23%.
| Mangrove Type | Location / Feature |
|---|---|
| Deltaic mangroves | Mostly east coast |
| Non-deltaic mangroves | Mostly west coast |
| Island mangroves | Island ecosystems |
Mangrove cover is higher on India’s east coast because large river deltas are formed by the Ganga, Brahmaputra, Godavari, Mahanadi, Krishna and Kaveri rivers. West-flowing rivers have shorter courses and create smaller estuaries, so mangrove cover is generally lower on the west coast, except in regions such as Maharashtra and Gujarat.
The Sundarbans is an immense delta straddling West Bengal and Bangladesh, covering over 10,000 sq km. It is one of the world’s most important mangrove ecosystems and supports specialised biodiversity, including the estuarine crocodile.
| Institution / Report | Details |
|---|---|
| IISER Kolkata | Conducted study detecting airborne microplastics inside Sundarbans |
| Science of the Total Environment | Journal in which the microplastics study was published |
| National Clean Air Programme | Researchers urged inclusion of airborne microplastics under NCAP |
| Sundarbans Tiger Reserve / South 24 Parganas Division | Areas where crocodile sightings were recorded |
| 2024–25 Crocodile Population Assessment Report | Estimated saltwater crocodile population at 220–242 |
| IUCN | Mentioned in input in relation to aquaculture as fastest growing food-producing sector |
| Indian Council of Forestry Research and Education, Dehradun | Documented mangrove forest products such as honey, fruit, salt, leaves, medicinal herbs and algae |
| State of India’s Forests 2020 Report | Mentioned in relation to Mumbai’s mangrove cover |
| CIDCO | Given permission to cut 3,728 mangroves for Ulwe coastal road |
India needs to treat mangroves not merely as trees, but as complete living ecosystems. Conservation should focus on preventing encroachment, illegal logging, waste dumping and unplanned land diversion. Maintaining mature mangrove stands is essential because they offer stronger coastal protection than newly planted saplings.Research on ecosystem services of mangroves should be strengthened, and their economic value should be quantified. Citizen participation, restoration programmes and strict monitoring can help reduce the impact of coastal storms, sea-level rise and flooding on India’s coastal cities.Updated – 02 February 2024 | Mongabay, Updated – 18 August 2025 ; 08:57 PM | Times of India, Updated – 23 November 2025 ; 06:05 AM | Times of India