The Ganges delta has a great importance for its exceptional hydro-geological settings and deltaic floodplain wetland ecosystems. The floodplain is formed by the deposition of the Ganges, Brahmaputra and Meghna River. The physical characteristics of floodplains, geographic location, the multiplicity of rivers and the monsoon climate render wetland ecosystems highly vulnerable to natural disaster and anthropogenic activities. Flooding is a natural annual phenomenon of a river system which occupies a unique position in the culture, society and economy of Bangladesh. There are 257 rivers in Bangladesh, from which 59 rivers are transboundary rivers. All of these rivers play a prospective role in the economic development of the country. The deltaic floodplains of the Ganges–Brahmaputra–Meghna Rivers Delta are undergoing rapid hydro-morphological changes due to natural and anthropogenic causes. Historically, these three rivers have played a strong role in formation of deltaic floodplains and wetland ecosystems in the Ganges–Brahmaputra–Meghna (GBM) Rivers Delta. The GBM rivers system is continuously developing the active deltaic floodplains in the coastal region of Bangladesh. The deltaic wetlands are under threat due to extension of agricultural land use, shrimp cultivation, and saline water intrusion in the tidally active delta region. The main reasons of ecosystem degradation are the settlements development, urbanization processes and substantial uses of deltaic natural resources. The study investigated the role of river systems in the formation and development process of delta and salinity intrusion and its impact on wetland ecosystems in the tidally active deltaic floodplains in the coastal region. The objective of this study is to understand the role of river systems in the delta formation process and an analysis of deltaic floodplain and degraded wetland ecosystems of the Ganges–Brahmaputra–Meghna Rivers Delta in Bangladesh.

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Deltaic floodplains development and wetland ecosystems management in the Ganges–Brahmaputra–Meghna Rivers Delta in Bangladesh

:Coastal wetlands, such as saltmarshes and mangroves, that fringe transitional waters deliver important ecosystem services that support human development. Coastal wetlands are complex social-ecological systems that occur at all latitudes, from polar regions to the tropics. This overview covers wetlands in five continents. The wetlands are of varying size, catchment size, human population and human development. Economic sectors and activities in and around the coastal wetlands and their catchments exert multiple pressures that affect the state of the wetlands and the delivery of valuable ecosystem services. All the coastal wetlands were found to be affected in some ways, irrespective of the conservation status. The main economic sectors were identified as agriculture, animal rearing including aquaculture, fisheries, tourism, urbanisation, shipping, industrial development and mining. Specific human activities include land reclamation, damming, draining and water extraction, construction of ponds for aquaculture and salt extraction, construction of ports and marinas, dredging, discharge of effluents from urban and industrial areas and logging, in the case of mangroves. The main pressures were loss of wetland habitat, changes in connectivity affecting hydrology and sedimentology, as well as contamination and pollution. These pressures lead to changes in environmental state, such as erosion, subsidence and hypoxia that threaten the sustainabilty of the wetlands. There are also changes in the state of the ecology, such as loss of saltmarsh plants and seagrasses, and mangrove trees, in tropical wetlands. These changes in the structure and function of the wetland ecosystems affect the delivery of important ecosystem services that are often underestimated. The loss of ecosystem services impacts human welfare as well as the regulation of climate change by coastal wetlands. These impacts are likely to be further aggravated by climate change..

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Anthropogenic, Direct Pressures on Coastal Wetlands

The Sundarbans mangrove forest is an important resource for the people of the Ganges Delta. It plays an important role in the local as well as global ecosystem by absorbing carbon dioxide and other pollutants from air and water, offering protection to millions of people in the Ganges Delta against cyclone and water surges, stabilizing the shore line, trapping sediment and nutrients, purifying water, and providing services for human beings, such as fuel wood, medicine, food, and construction materials. However, this mangrove ecosystem is under threat, mainly due to climate change and anthropogenic factors. Anthropogenic and climate change-induced degradation, such as over-exploitation of timber and pollution, sea level rise, coastal erosion, increasing salinity, effects of increasing number of cyclones and higher levels of storm surges function as recurrent threats to mangroves in the Sundarbans. In this situation, regular and detailed information on mangrove species composition, their spatial distribution and the changes taking place over time is very important for a thorough understanding of mangrove biodiversity, and this information can also lead to the adoption of management practices designed for the maximum sustainable yield of the Sundarbans forest resources. We employed a maximum likelihood classifier technique to classify images recorded by the Landsat satellite series and used post classification comparison techniques to detect changes at the species level. The image classification resulted in overall accuracies of 72%, 83%, 79% and 89% for the images of 1977, 1989, 2000 and 2015, respectively. We identified five major mangrove species and detected changes over the 38-year (1977–2015) study period. During this period, both Heritiera fomes and Excoecaria agallocha decreased by 9.9%, while Ceriops decandra, Sonneratia apelatala, and Xylocarpus mekongensis increased by 12.9%, 380.4% and 57.3%, respectively.

https://www.mdpi.com/1999-4907/7/12/305/pdf

Mapping Long-Term Changes in Mangrove Species Composition and Distribution in the Sundarbans

Sundarbans are highly productive mangrove wetland ecosystems, contributing several social, financial and environmental benefits. The forests have a great role in the countries national economy, and provides livelihood for the local people through fishing, tourism, wood and non-wood products. But despite several laws, policies and management plans, the forest is now showing clear signs of degradation. The aim of this study is to explore the major causes of degradation of Sundarbans mangrove forest in Bangladesh and to propose a management approach for its sustenance. It was found that, biodiversity and ecosystem of the Sundarbans is threatened due to several natural and human induced pressures, including overexploitation of forest resources, changes in coastal land use, pollution from industrial and agricultural sources, oil spillage, upstream water flow reduction, increased salinity level, disease outbreaks, fire occurrence, climate change, rise in sea level, natural disasters, lack of knowledge about forest conservation, uncontrolled tourism, inadequate planning and management, and increase in man–animal conflicts. In this background, an integrated approach is proposed, by refining the existing management and combining updated information through supplementary scientific studies and expeditions on mangrove forests. Proper implementation of the proposed resilient strategies i.e., incorporate all stakeholders to protect the forest, awareness programs, reduced forest dependency of local people, strengthen monitoring, ecological restoration, implementation of legal bindings, disaster management and adequate research and planning can be helpful for sustainable management of Sundarbans and similar mangrove forests around the world.

Sundarbans mangrove forest of Bangladesh: causes of degradation and sustainable management options

Drought is a new challenge presenting natural calamities to modern civilized societies. Natural resources are the fundamental treasures of human life and are also the driving force for sustainable development and human civilization. Geographically, the surface land of the world is divided due to climatic and tectonic conditions. Human civilization, urban development, and agricultural cropping patterns are totally dependent on naval communication and water availability. The changing behavior or changing nature of climate and the scarcity of water and increase in temperature is creating annual droughts in different parts of the world. Soil formation and fertility development depend on the water supply and quality of surface and ground water storage. Due to climate change impacts such as droughts, cyclones, floods, and other natural calamities. It has been estimated that the similar characteristics appeared in the tropical and subtropical regions. It has also been indicated that by 2025, 1.8 billion people will be living in regions with absolute water scarcity and about two out of three people in the world could be living under considerations of water and natural resource stress. Therefore the sustainable use of natural resources including water, soil, forest, air, oil, gas, and petroleum in the mining sectors should be considered within terms of drought and other relevant environmental calamities. In such a crucial environmental situation, strategic drought mitigation policies and technological awareness is necessary to protect nature through mitigation and adaptation to drought and to reduce vulnerabilities to other natural calamities. The approaches are probable factors for drought mitigation and natural resources management in the vulnerable areas of the world could be considered as a priority basis environmental issue. Primary evaluation 3 3.

Handbook of Drought and Water Scarcity : Management of Drought and Water Scarcity

Through their complex network of river channels, the Ganges, Brahmaputra and Meghna Rivers cover an area of about 1.76 million km2, their boundaries extend across different countries such as Bangladesh, Bhutan, China, India, and Nepal. The Sundarbans are found at the coast of the Ganges River and are known as the world’s single largest mangrove forest with 3.5 percent of the world’s mangroves covering an area of 6017 km2. The Sundarbans wetlands act as a natural shield that protects the coastal area from storm surges and cyclones in pre and post monsoon periods. However, due to increased in irrigation of agriculture, industrial activity and the diversion of Ganges water at Farakka Barrage (India) in early 1975, both siltation and salinity have increased in the Sundarbans which is threatening the Sundarbans ecosystems. Consequently the dominant Sundari (Heritiera fomes) and Goran (Ceriops decendra) are affected by top-dying disease which is recognized as a key management concern. The Ganges water sharing is not just a geo-techno-political problem; it is also a humanitarian problem. So, interaction and educational awareness between concerned states are of great significant. The objective of this paper is to make a contribution towards the development and implementation of management plan for mangrove wetlands resources and to ensure that fresh water is supplied to the Sundarbans by the Ganges. Water salinity simulation and modeling would be a proper tool for decision making and allow planners to protect the Sundarbans ecosystems in future.

M. Shafi N. Islam

Papers

Threats to the Sundarbans Mangrove Wetland Ecosystems from Transboundary Water Allocation in the Ganges Basin: A Preliminary Problem Analysis