Largest Wetland

The Sundarbans constitute the largest wetland in India and one of the most extensive contiguous mangrove ecosystems in the world. Situated in the delta formed by the Ganga, Brahmaputra, and Meghna rivers, the Sundarbans stretch across the southern part of West Bengal and extend into neighbouring Bangladesh. This vast intertidal region represents a unique mosaic of tidal waterways, mudflats, and mangrove forests, covering an area of approximately 10,000 square kilometres, of which around 4,200 square kilometres lie within India. The Sundarbans are globally recognised for their rich biodiversity, ecological significance, and role in protecting coastal communities from natural disasters.

Geographical and Ecological Setting

The Indian Sundarbans lie within the South 24 Parganas and North 24 Parganas districts of West Bengal, bounded by the Hooghly River to the west and the Ichamati–Kalindi–Raimangal rivers to the east. The landscape consists of an intricate network of tidal rivers, creeks, and estuaries interspersed with islands that are constantly reshaped by tides and sediment deposition.
The region’s climate is tropical maritime, with hot, humid summers, a heavy monsoon season, and mild winters. Annual rainfall ranges between 1,500 and 2,000 millimetres, largely concentrated between June and September. The tidal amplitude varies between 3 and 5 metres, and saline water intrudes into many creeks, influencing vegetation distribution and species composition.
The Sundarbans represent a transitional zone between freshwater and marine ecosystems. Their brackish water environment supports a wide array of flora and fauna adapted to fluctuating salinity, tidal submergence, and sedimentation patterns. The region acts as a natural buffer zone, mitigating the effects of coastal erosion, cyclones, and storm surges that frequently impact the Bay of Bengal.

Vegetation and Mangrove Ecosystem

The hallmark of the Sundarbans is its dense mangrove vegetation, one of the most diverse on Earth. More than 90 mangrove species have been recorded, including both true mangroves and associated species. Prominent among these are:

• Heritiera fomes (locally called Sundari), after which the region derives its name.
• Avicennia alba and Avicennia marina, known for their salt tolerance.
• Rhizophora mucronata and Ceriops decandra, characterised by distinctive stilt roots.
• Excoecaria agallocha, a common species in intermediate salinity zones.

Mangrove plants exhibit remarkable adaptations such as pneumatophores (breathing roots), viviparous germination (seeds germinate while attached to the parent tree), and salt-filtering mechanisms. These adaptations enable survival in waterlogged, saline, and oxygen-deficient soils.
The mangrove forests provide vital ecological services, including carbon sequestration, nutrient cycling, and habitat protection for marine and terrestrial organisms. They also stabilise the coastline, trapping sediments and reducing the impact of tidal and storm waves.

Fauna and Biodiversity

The Sundarbans host an exceptionally rich biodiversity, recognised under the UNESCO World Heritage List and designated as a Ramsar Wetland of International Importance in 2019. The ecosystem supports more than 260 species of birds, 120 species of fish, 42 species of mammals, and 35 species of reptiles.
The most iconic inhabitant is the Royal Bengal Tiger (Panthera tigris tigris), adapted to a semi-aquatic environment and known for its ability to swim across wide estuarine channels. The Sundarbans Tiger Reserve, established in 1973, covers approximately 2,585 square kilometres, making it one of India’s largest and most significant conservation areas.
Other notable species include:

• Estuarine crocodile (Crocodylus porosus)
• Gangetic dolphin (Platanista gangetica)
• Fishing cat (Prionailurus viverrinus)
• Lesser adjutant stork (Leptoptilos javanicus)
• Olive ridley and green sea turtles

The mangrove creeks serve as important nursery grounds for fish, prawns, and crabs, supporting local livelihoods through sustainable fisheries. The area’s wetlands also act as crucial stopovers for migratory birds along the East Asian–Australasian Flyway.

Human Settlement and Livelihoods

The Indian Sundarbans are home to nearly 4.5 million people who depend on the wetlands for agriculture, fishing, honey collection, and forest produce. The population lives under challenging conditions due to frequent cyclones, flooding, and salinity intrusion.
Agriculture is largely restricted to highlands, with rice as the principal crop, though productivity is low due to soil salinity. Fishing and aquaculture constitute the primary sources of income, alongside honey and wax collection managed by local forest cooperatives. The collection of non-timber forest products is regulated to minimise ecological disturbance, and the Forest Department enforces strict conservation measures within the core areas of the biosphere reserve.
Traditional knowledge systems and community participation play vital roles in resource management. Programmes promoting eco-tourism, mangrove restoration, and alternative livelihoods have been initiated to reduce pressure on forest resources and enhance socio-economic resilience.

Environmental Importance and Functions

The Sundarbans serve multiple ecological functions vital to regional and global environmental stability:

• Flood Regulation: The wetlands absorb excess monsoon runoff, reducing flood intensity in upstream regions.
• Storm Protection: Dense mangrove belts act as natural barriers against cyclones and tidal surges.
• Carbon Storage: Mangroves are efficient carbon sinks, sequestering large quantities of carbon dioxide and mitigating climate change.
• Water Filtration: Wetlands trap sediments and pollutants, improving water quality.
• Biodiversity Support: The ecosystem sustains a wide range of species across terrestrial, aquatic, and marine environments.

Because of these functions, the Sundarbans play a vital role in maintaining ecological balance and protecting coastal communities from natural disasters.

Threats and Conservation Challenges

Despite its ecological richness, the Sundarbans face multiple environmental and anthropogenic threats. Major issues include:

• Rising sea levels and coastal erosion caused by climate change, resulting in submergence of low-lying islands such as Lohachara and Suparibhanga.
• Salinity intrusion affecting freshwater habitats and agricultural productivity.
• Illegal logging and poaching, posing threats to forest integrity and wildlife populations.
• Overfishing and unsustainable aquaculture, leading to habitat degradation.
• Pollution from upstream industrial and agricultural sources.

Cyclones such as Aila (2009), Amphan (2020), and Yaas (2021) have caused severe ecological and infrastructural damage, highlighting the region’s vulnerability to extreme weather events.
Conservation measures are coordinated through the Sundarbans Biosphere Reserve, established under UNESCO’s Man and the Biosphere Programme in 1989. The Indian government and international agencies have implemented projects focusing on mangrove afforestation, community-based resource management, and climate adaptation strategies. The integration of traditional knowledge with scientific management has become central to sustaining this fragile ecosystem.

Significance in National and Global Context

The Sundarbans hold immense significance for India’s ecological security, climate resilience, and biodiversity conservation. They are a natural shield protecting the densely populated Gangetic delta from storm surges and cyclones, while also serving as one of the most productive ecosystems on the planet.
Globally, the Sundarbans represent a critical site for understanding the impacts of climate change on coastal wetlands, sea-level rise, and mangrove ecosystem dynamics. Their conservation is not merely a regional concern but a matter of international environmental priority, reflecting the intricate relationship between human societies and natural ecosystems in the face of a changing climate.