Sundarbans, a UNESCO World Heritage Site, is witnessing a significant decline in ecological resilience, as highlighted by a study published in Communications Earth & Environment. The study points to a phenomenon called “critical slowing down”, indicating that the ecosystem is becoming slower in recovering from disturbances and increasingly unstable.
Key Findings
- 10–15% of Sundarbans forest area (≈610–990 sq km) has lost resilience over 2000–2024
- Total area of Sundarbans: >10,000 sq km
- Signs of decline include:
- Slower recovery from disturbances
- Increased fluctuations in productivity
- Rising ecological instability
Critical Slowing Down Phenomenon
- Indicates reduced ecosystem resilience
- Ecosystem takes longer to recover after disturbances
- Leads to higher variability and instability
- Considered an early warning signal of ecological collapse
Impact of Cyclones & Climate Change
Major Cyclones Triggering Decline
- Cyclones: Sidr, Rashmi, Aila (2007–2009)
- Result: Large forest areas shifted to lower resilience categories
Examples of Decline
- 820.97 sq km, 732.54 sq km, 1,138.74 sq km shifted from resilient to moderately resilient
- Further degradation: moderately resilient to weakly resilient
Most Vulnerable Regions
Central & South-Eastern Sundarbans (Seaward zones)
- From Satkhira to Sharankhola ranges
- Includes Chandpai & Sharankhola ranges
Shala River Corridor
- Despite freshwater inflow, remains highly vulnerable
- Located along cyclone pathways
Indian Sundarbans (Western part)
- Lower resilience compared to Bangladesh
- Severe decline near northern boundaries
New hotspot: North-eastern region
Human-Induced Pressures
Key Anthropogenic Factors
- Encroachment & Shrimp Farming
- Illegal logging of dominant trees
- Upstream dams leads to reduced freshwater flow which increased salinity
- Excess phosphorus in sediments leads to nutrient imbalance & oxygen deficiency
Ecological Changes & Species Impact
Species Composition
- Fast-growing species:
- Avicennia officinalis, Excoecaria agallocha
- Slow-growing species:
- Heritiera fomes (Sundari)
- Bruguiera sexangular
- Xylocarpus mekongensis
Observations
- Taller canopy species now under stress
- Northern regions: taller growth
- Seaward saline zones: stunted growth
Climate Factors Affecting Resilience
- Rising temperatures leads to reduced species diversity & canopy height
- Rainfall:
- Positive role: reduces salinity
- Negative trend: erratic patterns reduce benefits
Disease Impact
“Top Dying Disease”
- Affects Sundari tree (Heritiera fomes) since 1960s
- Consequences:
- Decline in timber value
- Forest shifting from carbon sink to carbon source
- Estimated loss: $16.72 million annually (timber value)
Broader Global Context
- Similar resilience decline observed in Amazon Rainforest
- Indicates global trend of weakening tropical forest ecosystems
Structural & Functional Decline
- Reduction in:
- Canopy height
- Leaf traits
- Species diversity
- Result:
- Forest becoming more uniform
- Reduced ecological stability
Conservation & Protection Measures: Recommended Steps
- Protection of mature trees from poaching
- Strengthening patrolling & enforcement
- Community participation & awareness
- Integration of climate considerations into policy
What are Mangroves?
- Salt-tolerant trees growing in intertidal zones
- Also called tidal forests / oceanic forests
Distribution
- Found between 25°N and 25°S latitudes
- Thrive in low-energy coastal environments
Special Features
- Pneumatophores: Roots for breathing in oxygen-poor soil
- Stilt roots: Provide support in muddy terrain
- Vivipary: Seeds germinate on parent tree
- Salt regulation: Excretion or filtration mechanisms
- Succulent leaves: Store water
Sundarbans Significance
- Located in Ganga–Brahmaputra–Meghna delta
- Only mangrove forest with tiger population
- High biodiversity and ecological importance