Sundarban Mangrove Ecosystem – Biodiversity, Significance & Conservation Challenges

Sundarban Mangrove Ecosystem: Biodiversity, Ecological Significance & Conservation Challenges

The Sundarban mangrove forest is not just a collection of trees growing in saline water – it is a living, breathing ecosystem that supports an extraordinary array of life and provides invaluable services to millions of people. The Sundarban Tiger Reserve Annual Report 2022-23 offers a comprehensive look at this unique ecosystem, its current status, and the challenges it faces in an era of climate change and human pressure.

What Makes Sundarban Mangroves Special?

The Sundarban Tiger Reserve is situated at the southernmost extremity of the lower Gangetic delta, bordering the Bay of Bengal. This landscape can be described as a maze of estuaries, river channels, and creeks encompassing numerous islands of various shapes and sizes.

Key Facts About Sundarban Mangroves:

The Mangrove Vegetation

The Sundarban mangrove forest contains an incredible diversity of plant species adapted to survive in challenging conditions – high salinity, tidal inundation, and low oxygen levels in waterlogged soils.

Major Mangrove Species Documented

The annual report highlights several key mangrove species found in the reserve:

1.     Sonneratia griffithii – A critically endangered mangrove species

2.    Rhizophora mucronata – The loop-root mangrove

3.    Rhizophora apiculata – The tall-stilt mangrove

4.    Avicennia alba – White mangrove

5.    Avicennia marina – Grey mangrove

6.    Sonneratia apetala – Keora, a pioneer species

7.     Kandelia candel – A true mangrove species

Ecological Zones in Sundarban

The report identifies two distinct ecological units based on salinity patterns:

1. Western Portion (West of River Thakuran):

·         Receives sweet water flow from the Hooghly River

·         Lower salinity levels

·         Mostly in South 24-Parganas Forest Division

·         Supports different mangrove associations

2. Central Mangrove Patch (Between Harinbhanga and Thakuran Rivers):

·         Where Sundarban Tiger Reserve falls

·         Practically cut off from upstream freshwater flow

·         Fed by backwaters of Bay of Bengal

·         Very high salinity regime

·         Eastern side bordering Bangladesh receives some sweet water from Kalindi River

Biodiversity Treasures of Sundarban

The Sundarban mangrove ecosystem harbors an extraordinary array of wildlife, many of which are globally threatened.

Mammals

Aquatic Mammals

·         Gangetic Dolphin (Platanista gangetica) – Endangered

·         Irrawaddy Dolphin (Orcaella brevirostris) – Endangered

Reptiles

The mangrove ecosystem provides critical habitat for numerous reptile species:

Horseshoe Crabs – Living Fossils

One of the most fascinating inhabitants of Sundarban waters is the horseshoe crab, considered a living fossil as they are thought to be more than 400 million years old. Of the four species found worldwide, two are found in Sundarban:

1.     Tachypleus gigas – The coastal horseshoe crab

2.    Carcinoscorpius rotundicauda – The mangrove horseshoe crab

These ancient creatures play vital roles in the ecosystem and are indicators of environmental health.

Avian Diversity – Kingfisher's Paradise

Sundarban is renowned as a kingfisher's paradise. Of the 12 species of kingfishers found in India:

·         10 species are found in Sundarban (according to the report, though another section mentions 8 – likely a minor discrepancy)

Important bird species include:

·         Goliath Heron (Ardea goliath) – The world's largest heron

·         White-bellied Sea Eagle – Iconic raptor of mangrove waterways

·         Brahminy Kite – Common raptor

·         Spoonbills, Egrets, and Storks – Wading birds

·         Trans-Himalayan migratory birds – Winter visitors

Heronries and Breeding Colonies

During the monsoon, numerous heronries form in Sundarban, harboring large bird populations that come to breed. These colonies are critical for the survival of many waterbird species.

Ecological Services of Mangroves

The Sundarban mangrove ecosystem provides invaluable services that extend far beyond its boundaries:

1. Nursery Grounds for Fisheries

Mangroves serve as nurseries for shellfish and finfish, sustaining the coastal fisheries of the entire eastern coast of India. The complex root systems provide shelter for juvenile fish, crabs, and shrimp.

2. Natural Shelter Belt

The mangrove forests act as a natural shelter belt, protecting the hinterland from:

·         Storms and cyclones

·         Tidal surges

·         Sea-water seepage and intrusion

·         Coastal erosion

3. Sediment Trapping

Mangroves trap debris and silt, stabilizing the near-shore environment. This process:

·         Prevents coastal erosion

·         Builds land over time

·         Maintains water quality

4. Bio-filtration

Certain mangrove species act as bio-filters, as they have been found to bio-accumulate heavy metals. They filter:

·         Groundwater

·         Storm-water runoff containing harmful pesticides

·         Industrial pollutants

5. Groundwater Recharge

Mangroves collect rainwater and slowly release it to the underground reservoir, recharging groundwater aquifers that sustain surrounding communities.

6. Carbon Sequestration

Mangroves are among the most carbon-rich forests in the tropics, storing carbon in both vegetation and waterlogged soils.

Threats and Conservation Challenges

The 2022-23 report implicitly highlights several challenges facing the Sundarban mangrove ecosystem:

1. Salinity Stress

The central mangrove patch, where the Tiger Reserve falls, has very high salinity due to reduced freshwater flow from upstream. This affects:

·         Mangrove species composition

·         Prey base for tigers

·         Overall ecosystem health

2. Climate Change Impacts

Rising sea levels, increased cyclone intensity, and changing rainfall patterns threaten the delicate balance of the ecosystem. The report mentions a published research article on "Environmental Challenges in Sundarban Tiger Reserve: A UNESCO World Heritage Site."

3. Human Pressure

Approximately 4.5 million people live in the biosphere reserve (2011 Census), depending on forest and forest-based resources. This creates:

·         Pressure on natural resources

·         Human-wildlife conflict

·         Habitat degradation

4. Limited Freshwater Flow

The central mangrove patch is practically cut off from upstream sweet water flow, leading to very high salinity that affects biodiversity.

5. Cyclones and Storm Surges

As a natural shelter belt, mangroves face the brunt of cyclones originating in the Bay of Bengal, which can cause extensive damage to vegetation.

Conservation Efforts in 2022-23

Despite challenges, the Sundarban Tiger Reserve implemented several conservation measures:

Plantation Activities

While no new mangrove or non-mangrove plantations were created in 2022-23, maintenance work continued:

·         1st Year Maintenance: 60 hectares of Greening Sundarban Plantation (₹2.40 lakh)

·         2nd Year Maintenance: 500 hectares of Greening Sundarban Plantation (₹20.00 lakh)

·         1st Year Maintenance of Mangrove Plantation: 1.5469 hectares under State Development Scheme

Protection Measures

·         E-Patrolling: Introduction of smart patrolling using mobile applications to record patrolling activities, wildlife sightings, and offences in real-time

·         Anti-poaching Camps: 20 land-based camps and 11 floating camps/check-posts

·         Nylon Net Fencing: 108 km along forest-village interface to prevent tiger straying

Community Engagement

·         JFMCs: 26 Joint Forest Management Committees covering 38 revenue villages

·         Alternative Livelihoods: Fish fingerling distribution, ice block machines, and pond re-digging

·         Awareness Programs: Anti-plastic drives, school adoption programs, and medical/veterinary camps

The Way Forward

The Sundarban mangrove ecosystem requires sustained conservation efforts:

1.     Maintaining freshwater flow to reduce salinity stress

2.    Climate change adaptation strategies for both wildlife and communities

3.    Sustainable livelihood options to reduce forest dependence

4.    Scientific monitoring of ecosystem health indicators

5.    Trans-boundary cooperation with Bangladesh for landscape-level conservation

6.    Community involvement in protection and management

Conclusion

The Sundarban mangrove ecosystem is an irreplaceable natural treasure – a UNESCO World Heritage Site, a Biosphere Reserve, and the only mangrove habitat in the world supporting a significant tiger population. The 2022-23 Annual Report of Sundarban Tiger Reserve documents both the extraordinary biodiversity of this ecosystem and the dedicated efforts to conserve it for future generations. As climate change and human pressures intensify, the protection of this unique mangrove forest becomes not just a local or national priority, but a global imperative.