Why in News: A new scientific study published in April 2026 found that the Sundarbans mangrove ecosystem — the world’s largest — lost 10–15% of its ecological resilience between 2000 and 2024, amounting to 610–990 sq km of degraded forest. Climate change, rising sea levels, and increasing cyclone intensity are the primary drivers.
The Sundarbans — An Overview
The Sundarbans is the world’s largest mangrove forest, spanning the delta of the Ganga-Brahmaputra-Meghna river system across India and Bangladesh.
| Feature | Detail |
|---|---|
| Total area | ~10,000 sq km (India: ~4,200 sq km; Bangladesh: ~5,800 sq km) |
| Location | West Bengal (India) + Khulna/Satkhira/Bagerhat (Bangladesh) |
| River delta system | Ganga–Brahmaputra–Meghna |
| UNESCO Status | World Heritage Site (India: 1987; Bangladesh: 1997; both separate inscriptions) |
| Ramsar Site | Yes — both Indian and Bangladesh portions |
| Biosphere Reserve | Sundarbans Biosphere Reserve (India side) |
| Tiger reserve | Sundarban Tiger Reserve — India’s largest tiger reserve |
| Famous for | Only mangrove ecosystem with tigers (Royal Bengal Tiger — Panthera tigris tigris) |
The New Study: What Was Found
The study, using multi-temporal satellite imagery and ecological modelling, tracked ecological resilience — the capacity of the ecosystem to absorb disturbances and recover.
Key Findings
| Metric | Value |
|---|---|
| Resilience loss (2000–2024) | 10–15% of total ecosystem resilience |
| Area degraded | 610–990 sq km |
| Affected zones | Primarily coastal fringes and low-elevation interior islands |
| Most vulnerable areas | Southern Sundarbans (closer to Bay of Bengal coast) |
| Recovery rate | Declining — each disturbance takes longer to recover from |
Why is the Sundarbans Declining? Three Primary Drivers
1. Sea-Level Rise
- Global mean sea-level rise: ~3.7 mm/year (2024 data)
- Sundarbans sea-level rise: 8–10 mm/year — faster than global average due to land subsidence
- Land subsidence: natural compaction of delta sediments + reduced upstream sediment flow (dams on Ganga and Brahmaputra tributaries)
- Effect: Increased tidal inundation, longer submergence periods — mangrove roots need air exposure to survive
2. Cyclone Frequency and Intensity
| Major Cyclone | Year | Impact |
|---|---|---|
| Aila | 2009 | ~1,000 sq km of mangrove damage |
| Amphan | 2020 | Strongest ever recorded in Bay of Bengal; ₹1 lakh crore+ damage; severe mangrove loss |
| Yaas | 2021 | Compounded Amphan damage before recovery |
| Remal | 2024 | Category 4; Sundarbans coastal strip heavily affected |
As Indian Ocean warms, Bay of Bengal cyclone intensity (measured by wind speed and storm surge) is increasing. The Sundarbans acts as a natural storm buffer — but repeated intense storms are straining regenerative capacity.
3. Salinity Intrusion
- Freshwater flow into Sundarbans has declined sharply due to dams and barrages upstream on the Hooghly-Bhagirathi system
- The Farakka Barrage diverts water toward Kolkata port — reducing freshwater flushing of the Sundarbans
- Increased salinity stress forces many mangrove species to expend more energy on salt regulation, reducing growth and reproduction
- Species like Sundari (Heritiera fomes — the tree that gives Sundarbans its name) are particularly salt-stress sensitive
Biodiversity at Risk
The Sundarbans supports exceptional biodiversity:
| Species | Status |
|---|---|
| Royal Bengal Tiger | ~100–110 individuals (Indian side); classified Endangered (IUCN) |
| Irrawaddy Dolphin | Vulnerable (IUCN); significant Sundarbans population |
| Gangetic River Dolphin | Endangered; national aquatic animal of India |
| Saltwater Crocodile | Vulnerable |
| Olive Ridley Sea Turtle | Vulnerable; nesting sites in adjacent coast |
| Fishing Cat | Vulnerable |
| Masked Finfoot | Endangered; rare sighting |
Mangrove degradation directly threatens all of these by shrinking habitat, reducing prey base, and increasing saltwater exposure of freshwater-adapted species.
Ecosystem Services Under Threat
The Sundarbans provides critical services beyond biodiversity:
- Coastal protection: Mangroves absorb 75–90% of cyclone wave energy — protecting ~30 lakh people in coastal West Bengal and 10 crore+ in Bangladesh
- Carbon sink: Mangroves sequester ~5–10 times more carbon per hectare than tropical forests (blue carbon)
- Fisheries: Nursery ground for prawns, crabs, Hilsa — supporting ~4.5 million fishermen
- Livelihood: Honey collection (Maulipada/Moule communities), non-timber forest products
- Climate regulation: Buffers both temperature and moisture extremes in the Bay of Bengal system
Policy Response — India
Project Tiger / National Tiger Conservation Authority (NTCA)
- Sundarbans is a Tiger Reserve under Project Tiger (launched 1973)
- NTCA monitors tiger population via camera traps and genetic sampling
Integrated Management Plan
- India + Bangladesh: Joint management discussions under UNESCO’s World Heritage framework
- SAGAR (Security And Growth for All in the Region) — India’s maritime doctrine mentions Sundarbans ecology
Mangrove Alliance for Climate (MAC)
India is a founding member of the Mangrove Alliance for Climate (MAC), launched at COP27 (2022), which aims to double global mangrove coverage by 2030.
MISHTI Scheme (2023)
Mangrove Initiative for Shoreline Habitats and Tangible Incomes (MISHTI) — launched in Union Budget 2023-24:
- Target: Mangrove plantation along India’s coastline
- States: West Bengal (Sundarbans), Odisha, Andhra Pradesh, Tamil Nadu, Gujarat, Maharashtra
UPSC Relevance
| Paper | Angle |
|---|---|
| GS3 — Environment | Mangrove ecology; climate change impacts; biodiversity loss; ecosystem resilience |
| GS1 — Geography | Ganga-Brahmaputra delta; Bay of Bengal cyclones; sea-level rise; delta subsidence |
| GS3 — Economy | Blue carbon; fisheries; coastal protection services |
| GS2 — IR | India-Bangladesh transboundary ecosystem; UNESCO WHS obligations |
| Mains Keywords | Sundarbans, ecological resilience, sea-level rise, land subsidence, Cyclone Amphan, Cyclone Remal, Royal Bengal Tiger, MISHTI scheme, Mangrove Alliance for Climate, blue carbon, Farakka Barrage |
Facts Corner
| Item | Detail |
|---|---|
| Sundarbans total area | ~10,000 sq km (India ~4,200 + Bangladesh ~5,800) |
| Resilience loss (2000–2024) | 10–15% (610–990 sq km degraded) |
| UNESCO inscription (India) | 1987 |
| Tiger count (Indian side) | ~100–110 individuals |
| Sea-level rise (Sundarbans) | 8–10 mm/year (higher than global average due to subsidence) |
| Global sea-level rise average | ~3.7 mm/year |
| Royal Bengal Tiger status | Endangered (IUCN) |
| Sundari tree | Heritiera fomes — gives Sundarbans its name |
| Mangrove carbon storage | 5–10x more per hectare than tropical forests |
| MISHTI scheme | Mangrove Initiative for Shoreline Habitats and Tangible Incomes; Budget 2023-24 |
| Mangrove Alliance for Climate | Launched COP27 (2022); India founding member |
| Cyclone Amphan | 2020; strongest ever in Bay of Bengal |
| Farakka Barrage | Reduces freshwater flow → increases salinity in Sundarbans |
