The wetland ecosystems of Bangladesh

The wetland ecosystems of Bangladesh

By dr.fourkan Ali

Introduction: Wetlands are the predominant and the most productive and feature of Bangladesh. They play a very vital role in the life ar1d environment of this country from an environmental point of view; the most influential feature of Bangladesh is the vast amount of water flowing through a flood plain. This paper will provide an overview of the wetlands of Bangladesh, its importance as a very productive ecosystem, other benefits and attributes and the need of a sustainable management strategy.

Wetland Ecosystems: Ecologically the wetlands (such as rivers, beels, lakes, canals and other seasonal and perennial wetlands) in Bangladesh are potential habitats for a large variety of plants and animals. The production potential of open-water fisheries in Bangladesh has been reduced and continued to be reduced every year as more and more of the fish population areas are removed or altered for human encroached construction, flood control, or food grain production Besides fish species, aquatic plant species diversity is also reduced which hampered like of different wetland dependent birds (indigenous, endemic and migrat0l’Y), amphibians, reptiles, and mammals.

After the ’70s, when scope for further encroachment to the forested areas reduced significantly in the country, people started encroaching wet-lands to meet their demands for shelter and staple food in an unsustainable way this resulted in tremendous disruptions in the wetlands ecosystems of Bangladesh.

Although the country is relatively small, only about 144,000 square kilometers, Bangladesh serves as the drainage path for a catchments area that is nearly 10 times larger. The catchments basin of the combined Ganges, Brahmaputra and Meghna rivers covers more than 1.5 million square kilometers. Bangladesh receives nearly 1.2 trillion cubic meters of water pier year: Ninety percent of this originates from outside Bangladesh in Indian, Nepal, Burma and Bhutan.

Due to the deltaic character of the country Bangladesh is composed of numerous wetlands. The total wet season wetland area in Bangladesh has been estimated at about 7.5 million hectares, according to Akonda. The following table lists the type of wetlands and the amount of area they comprise during the wet season.

Table: Types of Wetlands and their estimated area during the Wet Season

WETTAND TYPES                                                             AREA (000 ha)

Permanent rivers and streams                                            480

Estuaries and mangrove swamps                      610

Shallow lakes and marshes                                                 120-290

Large water storage reservoirs                                          90

Small tanks and fish ponds                                                150-180

Shrimp ponds                                                                       90-115

Seasonally-flooded flood plains                        5,770

Source: A Directory of Asian Wetlands, 1989

Types of Wetlands in Bangladesh

There are many types of wetlands in Bangladesh which can be categorized broadly into five different groups according to their basic biological and physical characteristics. In this section a system which has been adapted for the Bangladesh context from the classification used by Dugan will be described. The five major groups are categorized as: marine, estuarine, riverine, lacustrine, and palustrine. The main factor which is characteristic of the marine and estuarine groups is the presence of ocean saltwater the remaining three groups are considered as freshwater wetlands.

Saltwater

Marine: Primarily this refers to permanent shallow saltwater wetlands such as shallow bays, It also inc udes coral formation like those located at St.Martins island off Teknai in Corrs Bazaar district.

Estuarine: These systems occur where the saltwater of the ocean mixes with the freshwater flowing in riverine systems. Estuarine wetlands are generally influenced by the movement of tides. Examples would include tidal marshes; inter tidal mud, salt or sand flats; and, inter tidal forested wetlands. One well-known exam le of estuarine wetland in Bangladesh is the Sundarbans which has been declared as a Ramsar site. This estuarine wetland is the world's largest mangrove swamp and covers some 1,000,000 hectares of land and water in Bangladesh and India. The freshwater moving south through the Sundarbans influences the saltwater from intruding north.

Freshwater

Rivrine: These systems are the predominant features that are found in Bangladesh. in fact, the vast majority of Bangladesh landform has been determined by the erosion and sedimentation forces of the large rivers meeting within its boundaries. It has been estimated that rivers, streams, and canals total at least 24,000 kilometers in length, according to Rashid, except for those of the Chittagong Region, all belong to one of the three major river systems: the Ganges-Padma, Brahmaputra-Jamuna and the Surma-Meghna.

Lacustrine: These are Lake systems and include haors, baors, beels and man-made features such as Kaptai Lake in the Chittagong Hill Tracts. 'They can also include the ponds, and dighees, that are formed in villages as a result of earth-raising activities. Bangladesh has only three naturally occurring true lakes. These are located in the Chittagong Hill Tracts and the Barind Tract. True lakes have steep sides and are very deep in comparison to their surface area. Their water level also stays relatively constant. Vegetation is usually limited in the lacustrine systems to either phytoplankton, floating plants rooted to the lake bottom.

Palustrine: These are ecosystems relating to marshes and swamps. They are shallow in water depth and have large areas of emergent wet-land vegetation. BCAS characterizes palustrine system as: permanent freshwater marshes and swamps with emergent vegetation; permanent peat-forming freshwater swamps dominated by Typha; and freshwater swamp forest, such as the lowland hijal (genus Barringtonia) forests of the haor region.

Usually palustrine ecosystems are the site of former lacustrine ecosystems. Gradually overtime, pre-existing lake systems become shallower Erosion-borne sediments are transported into the systems and are deposited on the bottom. In addition, as plants and other organisms die, their remains sink to the bottom and are decomposed. Consequently, the bottom rises, the lake becomes shallow, and a change in vegetation occurs. The ecosystem becomes less suitable for submerged plans and more suitable for emergent vegetation. The lacustrine system gradually changes to or is succeeded by the palustrine ecosystem. This demonstrates that ecosystems are not constant, rather dynamic, and change over time.

A list of different types of wetland ecosystems in Bangladesh has been assembled in the following table. Common English names, types (such as M for marine, E for Estuarine and so on), Bangla names and brief descriptions of their characteristic have also been included in the table.

Table: Lists of the major wetland ecosystems in Bangladesh:

Common name	Bangla name	Characteristics
Pond [L]	Deghee, Pukun, Pushkuni	Perennial. In rural areas ponds are generally constructed when new homesteads are raised. A very big pond is called as deghee. Generally these ponds are used for bathing, ozu (ablution, cleaning before prayer), washing, and fish culture.
Creeks [E]	Nala	Common in coastal areas where water remains during high tide but moves away during low tide.
Canal [R]	Khal	Often these are human-made connections between rivers and other water bodies such as beels and bide. Distributaries of rivers to floodplains.
River [R]	Nodi, Nod, Gaang	Channeled flow in nature. Main rivets of Bangladesh come from India’s hilly areas. Bangladesh’s economy and peoples lives are highly dependent on these rivers.
Single Natural Depression [L]	Beel	Natural depressions where water retention is generally common throughout the year.

Multiple Natural Depression [L]	Haor	Single water body in the wet season which splits into a number of pockets during the dry season.
Ox-bow lake [L]	Baor	Depressed part of a dead river; generally connected with the nearest river by a canal.
Lake [L]	Lake, Roth	Commonly constructed in urban areas. Other types are situated in hilly areas. The Kaptai lake is one exception in that it was human-made for a hydro-electric project.
Floodplain [R]	Bonna Plabito Alaka	Belt of low and flat ground, present on one or both sides of a river-channel, subject to inundation by a flood at least annually and characterized by alluvium soil.
Mangrove [E]	Sundarbans	Genus of tropical shrubs or tree which grows in salt-water swamps in the estuaries of rivets in Asia and America. Sundarbans of Bangladesh is the largest mangrove forest in the world.
Coral reef [M]	Probal	Found at St. Martins Island, Teknaf.
Spring [R]	Jharna, Chara	Wetland in hilly areas. People use the water for various purposes, such as agriculture and household needs.

M: Marine                                    E: estuarine                                  R: riverine     

L: lacustrine                                 P: palustrine

                       

                

Functions and Benefits of wetlands

In Bangladesh, wetlands serve a wide variety of functions, such as control, water purification, protection from natural disasters, some: livelihood, and habitat for wildlife and fish. Some of these benefits available only in a certain type of wetlands; whereas, the majority these benefits are common for all types. Included in the following discussion are many of the types of benefits (values, attributes, functions, uses) provided by wetlands with some examples.

A. Water Supply:

(a) Water supply to people: In Bangladesh, the rural population is 84.8% of the total national population. A good proportion of this population uses the surface water from wetlands for its everyday neat Examples of wetland used by local inhabitants are: washing of household goods, bathing, cooking, and drinking,

(b)Water supply to other wetlands: Wetlands can function as a war source for other wetlands. For instance, a river or beel is often the source of water for canals which lead to other beels, flood plains, and distributions.

(c)Water supply to groundwater: Groundwater is constantly being naturally discharged (used) through evaporation and transpiration; and artificially through extraction by shallow and deep tube wells Wetlands recharge the groundwater supply through infiltration and deep percolation. Wetlands serve a vital role in maintaining a balanced hydrological cycle which is important for our survival.

(d)Water supply to agriculture: Wetlands serve as a source of irrigation water: About 50 percent of the demand for irrigation to our agricultural fields is supplied by surface water Out of this, 50 percent is by gravity flow 48 percent by low lift pumps, and 22 percent by traditional me .

(e)Water supply to industry: Wetlands are water sources for mechanical processes and equipment operation in many industries. The washing and cooling of machines is an example. Wetlands are also water sources when used as one of the raw materials of the final product.

B. Flow Regulation and Flood Control:

(a) Reservoir/water storage: The water-bearing capacity of wetlands helps to balance water flow following rain events. Wetlands capture rain water and release the water slowly and evenly during the rain and flood season, this reservoir function helps to reduce the intensity of floods and helps to prevent flash flooding. The reserve provided by the wetland reservoir helps to meet water needs during the dry season.

(b) Drainage network: Wetlands provide the routes for water passage through Bangladesh. They serve as collection points for various surface water sources, The Bangladesh river-system is an integrated drainage system and each wetland acts as a drainage component of this system.

C. Protection from Natural Calamities:

(a) Cyclone and storm surge: Wetlands in the coastal areas, such as mangrove forests, provide a buffer to dissipate the energy form strong winds or waves. For instance, the Sundarbans protects the people who live on its northern borders from the storms that come from the Bay of Bengal located on its southern shores.

(b) Erosion: Wetlands help protect lands from the loss of valuable top-soil by wind or water movement. Wetlands have greater moisture availability in their soil and, therefore, suffer less erosion due to wind action. The presence of wetlands ensures that adjoining areas are moist enough to protect against wind erosion. In Bangladesh, wetland vegetation plays a vital role in protecting and from erosion by wave action and overland surface run-off of storm water the vegetation helps to slow the water velocity and allows suspended and dissolved sediments to settle.

(c) Prevention of salinity intrusion:

Surface water: In the coastal areas, saline water can intrude through surface or groundwater in most cases salinity intrusion is not desirable because the water is IDU salty and is not suitable for agriculture or other uses. One exception is Mari culture or cultivation of shrimp which requires mixed fresh and saline water (brackish conditions). Freshwater flow is necessary to prevent the movement of saline Waller north from the Bay of Bengal into me delta of Bangladesh. Since fresh-water wetlands serve as the source and network for freshwater flow in the rivers, their areal extent and water volumes determine the minimum freshwater water flow available to counteract the intrusion of the saline waters. If this flow is high then the occurrence of salinity intrusion through surface water is les. Nowadays, the water discharge towards the Bay of Bengal has decreased significantly due to water control activities upstream. As a result, saline water intrusion has increased, and affecting areas in the Sundarbans.

Groundwater Wetlands influence groundwater flows in much the same way as surface water when the coastal ground layers are permeable, saline water can intrude into the groundwater Fresh groundwater moving towards the sea meets the saltwater and prevents saline water intrusion. The recharge of groundwater by freshwater wetlands through infiltration and deep percolation ensures a sufficient counter force against the intruding saline water. Destruction of freshwater wetlands and removal of groundwater by extensive well water extraction greatly reduces groundwater flows. This encourages intrusion of saline water into the groundwater systems.

It is very important to retain the freshwater layer in low-lying coastal areas because it ensures supply of drinking and washing water for the local communities and irrigation water for agriculture. This fresh water quality has a great influence in the vegetation cover and bio-diversity as a whole, Also, salinity of the soil is prevented by the freshwater layer.

D. Sediment Deposition:

(a)Soil fertility recharge: Plants consume soil minerals and nutrients. Over time, this can deplete the soil fertility Wetlands help to recharge the soil fertility by trapping mineral particles and organic matter carried in flood water When a flood recedes, mineral panicles and organic miter settle on the soil making it more fertile. Thus the soil fertility is recharged for agriculture occurring on these wetlands.

(b) Land accretion (formation of new land): About 2.4 billion tons of sediment comes to Bangladesh each year through its river system. The strong river currents carry the majority to the Bay of Bengal past the edge of the continental shelf and into the submerged canyon, Swatch of No Ground. Nonetheless, many new char lands (braided islands) in the major rivers and estuaries are being formed. The new chars provide land for agriculture and settlement. Unfortunately the unconsolidated nature of the new chars makes them very susceptible to erosion and flooding each year.

E. Habitat and Biodiversity:

(a) Habitats for wildlife: Wetlands provide shelter; feeding, breeding and nursery support to wildlife. They support a rich diversity of biological species. Banglad5h’s wetlands support more than 550 species of plants, about 300 species of birds (resident and migratory), 120 species of commercially important fish, S0 species of reptiles, some 42 species of mammals and eight species of amphibians. The Sundarbans, the world’s largest mangrove forest, is an important habitat for many types of mammals, reptiles amphibians, and birds. The Sundarbans are also known for being the home to the Royal Bengal Tiger (Panthera tigris).

(b) Gene bank: Every organism is composed of either single or multiple cells. The characteristic of each organism (size of animal, shape of leaf, color of person's complexion, number of fingers) are determined by information stored chemically within the genes of each cell nucleus. The word gene is derived from the Greek word genos which means birth, this gene information tells the cell how to reproduce and function within an organism, and this is how the characteristics of the parent organisms are passed to their offspring. As generations of organisms slowly adapt to changes in environmental conditions, the new information is stored in the genes and passed to successive generations.

A bank is a place to store important items. Genetic information is an important material for conservation and research. Scientists have developed gene banks which are sophisticated systems for collecting and storing genetic information in the form of seeds. For example, the search for improved varieties of high yielding rice has benefited from the gene information found in certain wild rice varieties found in wet-lands. The gene material from the wild rice can be joined to the domestic rice. This additional information can improve disease resistance qualities or improve survival following periods of seasonal flooding.

The enormous diversity of species found in wetlands creates a similar database or pool or genetic information composed of various resident organisms. There are many local varieties of rice and also other plants in wetlands that may be of commercial importance. They can provide a valuable collection of gene information for ensuring the continued development of improved varieties for the future. Thus wetlands function as natural banks for storing and preserving genetic information. This gene bank function serves both research and conservation purposes. If the wetlands are destroyed, the genetic information in them is permanently lost for human kind’s future use.

F. Water Purification:

(a) Biological purification: Nutrients come from a variety of sources such as run-off of fertilizer form agricultural fields, human and animal wastes, and industrial discharge. Mostly these nutrients are inorganic phosphors and nitrogen; Wetland plants can neutralize, absorb or transform the nutrients into organic plant tissue. For example, the wet-land plant duckweed, can take up such inorganic agents, this helps to clean the water and provides improved water quality benefits for communities downstream.

In some instances, toxic substances are discharged into waterways. These pollution sources include pesticides from agriculture fields and Discharge or run-off of oils and toxic agents from industrial sites or mining activities. Such toxic materials do not decompose easily; however, they can bind to the surface of fine sediments. The sediments can eventually settles out of the water in the wetlands. Some wetland plant species, such as water hyacinth, can absorb metals into the plant tissue and help to remove the substances from the flowing water

(b) Flushing action: Floods clean the countryside by washing flooded areas. This function of the wetlands is known as flushing nail during floods; the organic and inorganic wastes are diluted, neutralized or absorbed by the large ecosystem. The wastes are still present in the system but now they are distributed among a much larger area

G. Natural Cycles:

(a) Hydrological Cycle: This cycle describes the movement of water between the earth's surface and the atmosphere, Wetlands serve as a major source of the water vapor that enters the atmosphere and eventually returns as precipitation. In addition, the wetlands serve as the drainage ways which channel the precipitation into the rivers and oceans. Wetlands are a principal component of the hydrological cycle.

(b) Bio-geo-chemical cycle: The bio-geo-chemical cycles describe the cyclical movement of minerals and elements between the biotic and abiotic components of the ecosystem. The amount of available elements in nature affects the life-cycle of organisms. Part of each cycle occurs within living biotic organisms; other parts occur as chemical actions in the abiotic environment. The flow of elements is cyclical ml matter is reused.

(c) Production cycle: Wetlands are one of the most productive ecosystems of the earth's surface. They are a highly productive site for photosynthesis which converts sunlight energy into bio-mass.

H. Socio-economic and cultural significance:

(a) Livelihood and profession: In Bangladesh, wetlands are an integral pan of the life of rural people. Many people’s live are depended on the fishery sector. People who do not fish professionally often fish to meet their protein needs. In addition to fishing, wetlands are a site for gathering important plants, animals and raw materials, such as wood, clay and sand. In addition to fishermen, boatmen, sand-divers and farmers are also very much dependent on wetlands. Some of these wet-land-dependent socioeconomic activities are the only means of livelihood for a large group of people.

(b) Recreation and aesthetic value: People tike to go to wetland sites for recreation purposes and for spending their leisure time. Wetland landscapes provide a natural scenic beauty a wetlands aesthetic beauty attracts people and gives them pleasure.

(c) Religious and spiritual significance: Wetlands are important sites for religious gatherings, ritual bathing and melas (exhibitions). On the banks of the river Turag in Tongi, the world‘s second largest Muslim gathering takes place each year. Langalbandh is famous for Hindu ritual bathing ceremonies. Wetland sites are often selected for meals based on Bangladesh’s history.

(d) Scope for eco-tourism and earning foreign currency: This sector is in its infancy However there is a substantial foundation for the view that the country’s natural resources, especially the Sundarbans, could support the development of this sector Bangladesh’s economy is currently supported by commercially exporting wetland dependent species, like as shrimp. Other commercially important species are frogs, turtles, snake skins and lizard skins.

I. Production of food and other materials:

(a) Food: Wetlands provide rice, fish, meat and vegetable. The majority of the food for Bangladeshi people comes form wetlands. The inland capture fishery is Bangladesh’s most important fishery sub-sector in terms of total catch, source of employment, and supply of animal protein. It is based on the country's vast freshwater resources and some 270 species of fin and shellfish which inhabit them. Essential habitats for the inland fishery comprise open and closed Walter habitats, including rivers, canals, flood plains, large seasonal water bodies (haors), smaller wetlands (beels), and ox-bow lakes (baors). Although discrete in the dry season, these water bodies become interconnected during the monsoon and provide critical habitats for the completion of the life cycles of a large number of fish species.

(b) Fodder and fertilizer: Wetlands provide food for animals (fodder). Examples of this food include straw, water, hyacinth and snails. Decomposed wetland organic matter is used as fertilizer frequently wetland soil is also used as fertilizer for homestead gardening.

(c) Medicine: Wetland plants are used as medicine for treating various diseases. Some wetland organisms are also used as raw material for processed medicines.

(d) Building materials: Wetlands provide most of Bangladesh‘s building materials, such as sand, timber leaves, straw goal pata, reed, cane water hyacinth and hogla. Sand is essential for making buildings and other concrete structures. Timber, water hyacinth, reed and cane are used for making furniture. Some wetland plants are also used for making mats and baskets and for packing fish, as well as for many other purposes.

J. Navigation:

Wetlands serve as waterways for the movement of people and their goods by water transportation, especially in the wet seasons. In 1990-91, about 43,562,000 metric tons (MT) of goods were transported by the Bangladesh Water Transport Authority. This is about 34 percent of the total amount of goods transported by road, rail, water and air every year a large number of passengers use the waterways to reach their destinations. During the wet season waterways are the principal means of transport in vast areas of Bangladesh.

K. Energy sources:

(a) Fuel: Wetland materials such as straw dry leaves and dry plants are used as fuels in the rural areas.

(b) Hydroelectric power: Wetlands with strong currents are often used for producing hydroelectric power in Bangladesh; the only hydroelectric power plant is located at Kaptai, Rangamati.

(c) Tidal energy: Although tidal energy has not yet been used for electric power production purposes in Bangladesh, this energy is being used in navigation and shrimp cultivation. People use tidal energy to get brackish water into their shrimp fields; they trap the water in their fields during high tide. People can start with a heavy boat load from their local ghat (dock) by using tidal energy

Conclusion: The above-mentioned discussion listed many of the functions and benefits of wetlands found in Bangladesh. In terms of future development, wetlands are a primary resource for Bangladesh. The sustainability of development in Bangladesh will depend upon the proper management of wetlands so that they can continue to provide the maximum development benefits to the country these benefits will no longer be available to Bangladesh if wetlands continue to be destroyed.

Dr.Fourkan Ali

Mob: 01711579267, Tel: 041 2832052

Email- dr.fourkanali@gmail.com