Mangrove forests are deteriorating due to over-exploitation, deforestation, land reclamation and pollution. Large areas of mangroves have been cleared for fish and shrimp farming. Agricultural practices and industrial development, urbanization, over-logging in coastal areas as well as the unregulated discharge of liquid and solid wastes are the most serious threats. 

Overall, the causes of deterioration of the Sundarban mangrove forest ecosystem could be classified into:

• Anthropogenic
• Natural
• Other (or miscellaneous)

Importance of Mangroves in maintaining coastal ecology:

• Basis of a complex marine food chain.
• Creation of breeding habitat for birds and water animals.
• Filtering and assimilating pollutants from upland run-off.
• Stabilization of bottom sediments.
• Water quality improvements.
• Protection of shorelines from erosion.
• Mangroves are the first line of defence for coastal communities. They stabilize shorelines by slowing erosion and provide natural barriers protecting coastal communities from increased storm surge, flooding, and hurricanes.

Anthropogenic Causes: 

• Over-exploitation and Illegal Forest Cutting: Over-exploitation of forests to meet the growing requirement of the people is one of the main problems facing the Sundarban.
• Shrimp Farming: The rapidly expanding shrimp farming industry possesses the crucial cause for deteriorating the mangrove forests in Bangladesh. 
• Pollution: Industrial development, agriculture and aquaculture near the river basins has led to the production of huge amounts of garbage, wastewater,  pollutants and other effluents being discharged to the mangrove wetland.
• Management Failure: The mangrove forest is disappearing because of the three main management failure reasons: lack of skilled and well-trained officials and failure of institutions and conflicting activities, poor planning and knowledge of coastal land use and implementation of the development plan that does not include environmental protection principles.
• Other Uses: Population is increasing day by day putting under pressure food production; mangroves are often converted to salt pans, agricultural fields and aquaculture farms.
• Diseases: “Top dying” is the disease of the dominant Sundari trees (Heritiera fomes) one of the biggest causes for deteriorating the forest.
• Fire. Fire may have caused some of the most serious damage of the mangrove ecosystem in recent years. Trees in an area around one km2 at Napitkhali under Chandpai range of the world’s largest mangrove forests are burning rapidly.

Natural Causes

• Natural Disasters, Climate Change and Sea Level Rise: Various natural calamities like cyclone, floods, storms, coastal erosion, naturally shifting hydrology, climate change and sea-level rise may destroy trees and animals even faster. 
• Global warming is expected to cause changes such as higher temperatures, sea-level rise and changing rainfall patterns, as well as more abrupt effects, such as an increase in the intensity and frequency of extreme events such as floods, storm surges and cyclones and sea-level rise.
• Nutrient depletion: Especially phosphorus and nitrogen was found to be directly connected with the decline in forest cover. 

Other Causes

• Other causes behind mangrove forest deterioration are loss of soil fertility, geomorphological changes, high salinity ecological succession, inadequate regeneration and low yield 

The deterioration of mangroves can lead to serious consequences, including a reduction in biodiversity, species decline, genetic erosion, extinction, increased flooding, and decline in water quality. The government has attempted to introduce some initiatives to protect these important ecosystems but the sustainability of these resources could not be achieved due to the lack of sound management strategies. A sustainable management plan should be developed by involving all beneficiaries and stakeholders and should be effectively implemented to conserve the world’s largest mangrove ecosystem for present and future generations.