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Environment


Environment the aggregate of conditions affecting the existence or development of life and nature. The overall global environment is declining fast and for Bangladesh it has been doing so more rapidly during the last few decades because of many obvious reasons. Bangladesh passed an act on environmental conservation in 1995. However, the environmental problems of the country are becoming acute because of population explosion, lack of adequate forest areas and nearly complete absence of any controlling measure on the part of industry or the transport system. A few articles on the environment of Bangladesh are given below:

• State of environment

• Environmental pollution

• Environmental degradation

• Inundation and flood

• Areas of environmental concern

• River Erosion and siltation

• Environmental protection agency

• Environmental planning and management

• Greenhouse effect and global

• Environment Education

• NEMAP

• Environment policy

State of environment Globally Bangladesh has great importance for its exceptional hydro-geographical setting. Three mighty rivers, the padma, the brahmaputra and the meghna drain a total catchment area of about 1.5 million sq km, of which only 8 percent of the drainage area lies within Bangladesh. Most of the drainage basin is located in the neighbouring countries. Bangladesh has been formed over tens of thousands of years, composing a very thick layer of sedimentary deposition as the heavily laden rivers slow down in the Bangladesh delta. The following aspects made Bangladesh significant from the environmental point of view: Bangladesh is one of the largest deltas in the world and is criss-crossed by numerous rivers, their tributaries and distributories; the country is characterized by very low general relief composed of very thick sedimentary deposition (the thickest in the world); Bangladesh has the world's largest mangrove forest and the longest sandy beach in the world; the highest population density in the world and a very high demand on natural resources; vast variations in amount of surface water availability between wet and dry seasons (extreme flood and drought); the rate of water flow through Bangladesh is tremendous. The outflow is second only to that of the Amazon river system in South America. In both breadth and total annual volume the Padma-Lower Meghna river is the third largest in the world.

The above-mentioned characteristics of Bangladesh make the country vulnerable to natural disasters as well as environmental hazards.

The land is largely low-lying floodplain. The physical characteristics of the land, geographic location, the multiplicity of rivers and the monsoon climate render Bangladesh highly vulnerable to natural disasters such as floods and cyclones. Seasonal extremes of water availability, ie flood and drought, are characteristics of Bangladesh. These natural phenomena act as significant constraints in achieving sustainable socio-economic development.

Physical environment Climate- Bangladesh's climate is a tropical monsoon climate characterized by marked seasonal variations. Abundant rainfall during the monsoon (July-October) is followed by a cool winter period (November-February), then a hot, dry summer (March-June). In the hot season, the average maximum temperature is 34°C and the average minimum is 21°C. Average maximum temperature in winter is 29°C and the minimum is 11°C.

The rainfall in the region shows great temporal and spatial variations. Seventy to eighty percent of the annual rainfall occurs in the monsoon season. After summer the warm, moist air of the monsoon sweeps up the bay of bengal from the Indian Ocean producing some of the highest recorded rainfalls in the world. The heaviest rainfall is largely over the upper catchment area, particularly in the Indian states of Meghalaya and Assam and over Northeast Bangladesh.

The average annual recorded rainfall within Bangladesh varies from about 1100 mm in the extreme west to about 5700 mm in the northeastern corner of the country. Rainfall in the Himalayas ranges from 2,000 to 15,000 mm annually.

Hydrology- Bangladesh is characterised by an exceptional hydro-geographical setting. Three major rivers, the Padma, the Brahmaputra and the Meghna, drain a catchment extending over Bhutan, Nepal, India, Bangladesh and China (Tibet). The total area of the Ganges-Brahmaputra-Meghna drainage basin is about 1.5 million sq km of which approximately 62 percent is in India, 18 percent in China, 8 percent in Nepal, 4 percent in Bhutan and 8 percent in Bangladesh.

In the last hundred kilometres run to the sea the combined Padma, Brahmaputra and Meghna rivers forms a single flow that is two and half times the rate of the Mississippi. Although the total area of the South Asian watershed is slightly less than half the area of the central basin of the United States, it receives four times the area's total annual rainfall.

There are over 250 large rivers in Bangladesh. The major rivers can be classified as either 'unstable' such as the Meghna or 'very unstable' such as the Padma and jamuna. This implies that water and flooding are major factors of consideration in the development of Bangladesh.

Bangladesh is prone to three main types of flooding: (i) flash floods result from heavy rainfall from upstream and create a flood wave along a river. Riverbank erosion, loss of land and severe crop damage are common problems during these events; (ii) monsoon floods are due to heavy continuous rainfall on impounded or poorly draining areas where precipitation exceeds infiltration. These are annual, expected events upon which the agriculture of the country has traditionally depended for the replenishment of the soil and for the water required for wet rice and jute cultivation; (iii) cyclonic floods are the most serious of the flooding events. They can cause serious disasters and occur mainly in the coastal regions.

Physiography- Bangladesh can be divided into three main physiographic divisions: Tertiary hills, Pleistocene terraces, and recent plains. The tertiary hills are situated in Rangamati, Bandarban, Khagrachari, Cox's Bazar, Chittagong, Sylhet, Maulvi Bazar and Habiganj districts. These hills are formed mainly of sandstone, shale and clay. The average altitude of these hills is 450 m.

The Pleistocene terraces comprise mainly the Madhupur and the Barind Tracts, Bhawal's Garh and the Lalmai hill area. These terraces were formed about 25,000 years ago. The approximate area of the barind tract is 9320 sq km. The average height of the tract from the adjacent flood plains is 6 to 12 metres. Madhupur and Bhawal stretch over 4103 sq km where the average height from the adjacent floodplain is 30 m. The Lalmai Hill area of Comilla district comprises 34 sq km and is on average 15 m higher than the adjacent flood plain.

The recent plains comprise 124,266 sq km of the country (86 percent). Recent plains can be further classified into five types: piedmont plain, flood plain, deltaic plains, tidal plains and coastal plains. The five types of plains are generally expressed by the common term 'flood plain'.

The flood plains have an altitude of 0 to 10 m and are low in relief. The average gradient from the northeast to the coast is less than 20 cm per km. South of Dhaka the slope averages 1.6 cm/km. About 50 percent of the land area is below 12 m altitude (height from the sea level) and 75 percent of the area lies below 29 m.

The flood plains of Bangladesh are mainly composed of deltaic silt plains, built up from both alluvial and marine deposits. Because of the low altitude and relief of the land, water travels very slowly on the plain and the rivers have a tendency to meander. The recent plains have been developed, and are being re-worked continuously through the processes of erosion and deposition, and by recurring flooding or inundation.

Soil types and their characteristics- The country is generally composed of a thick layer of sediment, deposited over tens of thousands of years by the flowing rivers. It is estimated that 2.4 billion tons of sediment are transported annually through Bangladesh. The different physiographic divisions are characterized by different types of soil. The tertiary hill areas are characterized by 'hill soils' that are mainly composed of tertiary rocks and unconsolidated Tertiary and Pleistocene sediments. The soil is usually acidic with pH varying from 4.0 to 4.5. The soil texture allows comparatively lower infiltration. High porosity allows high moisture content.

The Pleistocene terraces are composed of 'old alluvial soils' which were formed from the alluvium of the Pleistocene period. They stand on high land above the flood level. They are clayey in texture and reddish to yellowish in colour due to the presence of iron and aluminium. They are highly aggregated and have a high phosphate fixing capacity. The soil is acidic with pH ranging from 6 to 6.5.

The recent plains are composed of 'recent alluvial soils'. Since soil composition in the upstream area is an important factor in determining the properties of the down-stream soils, variations are common in the properties of soils in different river basins. Gangetic alluvium is rich in calcium, magnesium and potassium. It also contains free calcium carbonate. The soil is characterized by nitrogen and phosphate deficiency as well as by alkalinity. The pH range is 7.0 to 8.5.

Tista silt tract soils are sandy to sandy loam in texture, without any developed profile. They are flooded every year and, as a result, are replenished by fresh deposits annually. The pH varies from 6 to 6.5. The coastal saline tract is part of the active flood plain, but is subject to flooding by saline water at high tide. A large part of the tract is occupied by mangrove forest, where some soils contain large amounts of sulphide in their profile. The soil is generally neutral but tends to be on the alkaline side. The pH varies from 6.9 to 7.5.

Soil workability and its influence on cropping patterns- The agricultural potential of flood plain soils is determined as much by hydrology as it is by soil properties. Depth and duration of seasonal flooding and the relative risk of crop damage by floods are the main determinants of cropping patterns. Soil permeability and moisture holding capacity are as important as soil fertility (micronutrient availability). Most floodplain areas have low elevation which ranges around 1m, with the permeable loamy soils on the higher land and impermeable clays in the depressions. These elevation differences determine local differences in the depth and duration of seasonal flooding. Differences in elevation of as little as 30 cm can be highly significant for crops, cropping varieties and seasonal rotations in relation to flooding characteristics.

The agricultural potential of tertiary soils is moderate in poorly drained soils and in deep upland soils. It is much lower in shallow upland soils. The agricultural potential of the sandy hilly soil is severely limited by their erodibility, aggravated by heavy rainfall and depleted soil fertility resulting from repeated jhum cultivation (slash and burn and shifting agriculture in the hilly areas). This soil is best suited for tree crops or forest production.

Biological environment Forest resources- In the past three decades, the stock of forest trees has declined at a tremendous rate. Huge areas of forestland have been illegally converted into croplands. Though an up to date forest inventory is unavailable, it is estimated that the forest cover has been reduced more than 50 percent since the 1970s. In 1970 there were over 20,000 acres of sal forest in the Madhupur Tract; twenty years later, approximately 1,000 acres remained. Estimates in 1990 revealed that Bangladesh had less than 0.02 ha of forestland per person, one of the lowest forest to population ratios in the world.

On the basis of location characteristics, forests can be classified under three types: (i) Hill forests, covering an area of 1.15 million acres including 296,300 acres of plantations, mainly in the Rangamati and Sylhet areas; (ii) Mangrove forests, consisting of 1.45 million acres of natural mangroves (sundarbans) and 2,50,000 acres of artificially raised mangrove plantations in the coastal belts and offshore islands for flood protection; and (iii) Plain land sal forests, covering about 3,00,000 acres in Gazipur, Sherpur, Mymensingh, Rajshahi, Rangpur and Dinajpur district. The Forest Department controls about 3.617 million acres of lands in these areas.

Wetlands- Bangladesh has an enormous area of seasonal wetland. In fact, half of the country could be delineated as such. The area under perennial wetlands is much smaller and is principally permanent rivers and streams, shallow freshwater lakes and marshes (haors, baods, and beels), fish ponds and estuarine systems in the extensive mangrove swamps.

Environmental pollution agents

Wetland resources are crucial to the environment of Bangladesh. Both perennial and seasonal wetlands provide habitats to a large variety of flora and fauna. Wetlands also provide subsistence for a significant proportion of the population through their fishery resources. The fishermen of Bangladesh are traditionally among the poorest of the rural dwellers. Numerous wetland plants are harvested for use as medicines, food, fodder and building materials. Unfortunately the wetland habitats are under constant threat from human encroachment and flood control and irrigation schemes.

Biodiversity- Bangladesh possesses rich biodiversity, especially in the forested and wetland areas. Approximately 5,000 species of flowering plants are found in Bangladesh (Bangladesh Country Report for UNCED 1992). The country has 266 inland and 442 marine fishes, 22 amphibians, 109 inland and 17 marine reptiles, 388 resident and 240 migratory birds, 110 inland and 3 marine mammals (Red List of Threatened Animals of Bangladesh, IUCN-Bangladesh 2000). Some species have been identified as threatened. Of the known vertebrates, 13 have already become extinct from Bangladesh territory. Of the inland fish species 54 are threatened. The number of threatened amphibians, inland reptiles, resident birds, and inland mammals are 8, 58, 41, and 40 respectively.

The loss of plant diversity has not yet been studied and documented in detail. Some individual studies have been carried out to identify threatened plant species and it was found that about 100 vascular plants are threatened.

The main reasons for the loss of biodiversity are: (i) disruption of wetland habitats through encroachment on and destruction of fauna migration paths; (ii) human encroachment on forest lands for agricultural, settlement and commercial purposes; (iii) indiscriminate felling of trees for fuel and construction resulting in a reduction of tree cover areas and habitats; (iv) over-exploitation of particular resources such as medicinal plants, bamboo and cane leading to loss of protective habitat; (v) over-exploitation of wildlife; (vi) monoculture of (HYVs) or less diversified cropping leading to agrochemical build-up; (vii) destruction of mangrove forests; and (viii) shifting (slash and burn) agriculture.

Socio-economic environment Population- Bangladesh is the most densely populated country in the world. At present, the population is increasing at around 2 percent per year. The 2001 census put the population at 12,92,47,233 (about 130 million).

Land use Due to the high population density and influence of agriculture based livelihood, pressure on the country's limited land is tremendous. People are even living and using the land in the very low-lying coastal areas that are much exposed to cyclones and storm surges. A little over 63 percent of the total land area of Bangladesh is under agriculture, the vast majority being used for wet rice cultivation. Forests (including community and village groves) account for almost 20 percent of the land area and human settlements cover 16 percent.

Forests and wetlands have faced the double-barrelled threat of a growing population in terms of increased exploitation of forest products and outright conversion of forest lands for both settlement and cultivation purposes. During the 1970s population growth outstripped agricultural production. As a result agricultural lands underwent expansion, severely encroaching on forestlands.

Throughout the 1980s the introduction of advanced technologies, such as high yield varieties of rice, altered the traditional cropping patterns. This made it possible to expand the crop without utilising more land. This vertical expansion (more crop yield on the same area of land) has almost reached its limit. Horizontal expansion (aerial expansion of cropped area) into forests and increasingly into wetlands is on the increase. More wetland areas are lost to agriculture daily. When water is drained from the wetlands the delicate ecology that maintains the fertility of the land is upset. This increases the need for new agricultural lands or increased fertiliser use to make up for lost production.

Agricultural lands in the polder areas of the south are being encroached upon by shrimp cultivators. Here the land is embanked to contain salt-water ponds for a shrimp cash-crop. Though use as a shrimp pond renders the soil too saline for cropping, it is predicted that more agricultural lands will be converted into big shrimp ponds (gher) in southern Bangladesh. [Mamunul Haque Khan]

See also biodiversity; climate; wetland.

Environmental pollution Pollution broadly means disruption of man's own environment and refers primarily to the fouling of air, water, and soil by wastes or harmful materials. The population explosion in the last few decades has aggravated the pollution problem. More people mean more consumption, and therefore more pollution.

There can be air pollution, water pollution, and soil pollution. The pollution from solid wastes is a major problem in Bangladesh. The cities generate a considerable amount of solid wastes. At present, Dhaka city alone generates about 5000 million tons of solid wastes per day. The amount increases with the increase of population every year.

The domestic, commercial, street sweeping, combustible and non-combustible wastes include discarded food, grass, plants, paper, cardboard, textiles, plastics, polythene materials, glass, metals, and construction debris.

Environment.jpg

There are about 1000 small and large industries in Dhaka city producing a large amount of toxic and hazardous wastes contributing significantly to environmental degradation. In the Hazaribag area of Dhaka there are 149 tannery units daily producing about 20,000 litres of liquid wastes and 120 m tons of solid wastes; nearly all of these are dumped in the buriganga river, and a part is thrown into nearby drains and sewers. These wastes contain sulphuric acid, chromium, ammonium chloride, ammonium sulphate, calcium oxides etc. These may seep into the ground causing ground water pollution. Also, the intense, unpleasant odour affects the health of the people of the surrounding area. tannery wastes have a very serious and negative effect on the ecosystem.

The unplanned shrimp cultivation in the coastal belt of Bangladesh has increased the salinity in the soil, which has lost its natural productivity. Nothing grows in a large area surrounding these places.

The Department of Environment (DOE), Government of Bangladesh conducted a survey in Dhaka city for noise pollution from March 9 to April 7, 1997 for twenty schools and hospitals where the acceptable limit is 45 dB. The highest value of 84 dB was recorded in front of viquarunnesa noon school followed by 82 dB near bangabandhu sheikh mujib medical university, and 80 dB near dhaka medical college and Hospital. An 82 dB noise level was recorded near Residential Model School and College, Mohammadpur. Another survey was conducted in May 1999 by the DOE in the industrial, commercial and residential areas. Tejgaon and Hazaribag areas showed an average of 75dB, whereas at Farmgate, Shapla Chattar, Mohakhali, and Banglamotor areas, the recorded noise level varied from 90dB to 85dB. The residential areas of Dhanmondi, Cantonment, Banani, and Gulshan recorded an average of about 65dB. The areas of Mirpur and Mohammadpur showed little over 60dB noise level as against a record high of 90dB at Tikatooly and Shakharipatty. [M Shamsul Islam and Quamrun Nessa Begum

Industrial pollution' Environmental degradation resulting from the emissions or offensive products of the mills, factories, and other industrial establishments. The industrial sector in Bangladesh accounts for about 20% of the GDP, of which the manufacturing sector shares 11%. This trend has been observed mainly in ready-made garments, textiles, leather and other export-oriented manufacturing sectors. While strong industrial sector growth is beneficial in terms of employment and income, it also adds to environmental degradation.

A study identified the spatial distribution of the most polluted 'hot spots' in Bangladesh. The six environmental hot-spot districts are: Dhaka, Gazipur, Narayanganj, Chittagong, Khulna, and Bogra. These districts contribute more than 50% of the national pollution load in 4 of the 6 pollutant groupings, and in the case of total particulates and biological oxygen demand (BOD), they contribute about 35% each. The six groupings of pollutants are: toxic chemicals discharged into the land (about 300 chemicals, treated here in aggregate); toxic chemicals emitted into the air; total particulate in air; sulphur dioxide emissions; toxic bio-accumulative metals discharged in water (including arsenic, chromium, lead, mercury, and zinc); and 5-day biological oxygen demand.

The national pollution profile shows that industrial subsectors contribute to a large percentage of pollution loads in the country. The following table shows the most polluting industrial subsectors in Bangladesh, defined as those which contributed at least 5 percent to the national total of one or more of the pollutant clusters. In total, the 12 highest polluting industrial subsectors contribute more than 85% for three of the pollutants considered (toxic chemicals to land, toxic metals to water, and SO2); more than 70% for two more pollutants (toxic chemicals to air and BOD); and more than 50% of the sixth pollutant (total particulates). [M Aminul Islam]

Air pollution In Bangladesh, apart from fossil fuel combustion, the other sources of air pollution are the brick kilns, fertiliser factories, sugar, paper, jute and textile mills, spinning mills, tanneries, garment, bread and biscuit factories, chemical and pharmaceutical industries, cement production and processing factories, metal workshops making grills, doors and windows for building, sawdust from saw mills and dust from ploughed land, and salt particles from ocean waves near the off-shore islands and coastal lands. These sources produce an enormous amount of smoke, fumes, gases and dust, which create the condition for the formation of fog and smog.

Certain industries in Bangladesh emit hydrogen sulfide (H2S), ammonia, chlorine, and some other odorous chemicals that may be poisonous and cause irritation. Some time people of Dhaka and other cities are so used to these that they seldom care these as air pollution problem. Hazaribag tanneries which are located near the city is an example of this. In the processing of leather the toxic and pollutant gases like chlorine, SO2, H2S and amonia are emitted. Some buildings are poorly designed and because of lack of adequate ventilation, the trapped pollutants like tobacco smoke, gases from stoves and furnaces and household chemical substances cannot escape into the atmosphere.

In this way indoor air pollution can be five to ten times that of the dirtiest air outside. This may cause headache and other health problems. Sometimes the houses are built on rocks and soils which give out radioactive radon gas from their basement. If this gas is inhaled for a long time it may cause lung cancer.

Dhaka, the capital of Bangladesh is the most densely populated city in the world, with a population very of about 16 million recorded in 2011. The means of transport are motor vehicles, babytaxies and tempos, and a large number of them are operating with two-stroke engines. These engines are less fuel-efficient and release more than forty times the amount of hydrocarbons and carbon monoxide in the air than the four-stroke diesel engines.

DOE has set the following air quality standards for Bangladesh. Concentration of air pollutants should not exceed these values for different locations mentioned in the table (in micro gram/metre3).

Table 1 Tolerable concentrations of air pollutants (B5g/m3) [SPM- suspended particulate; SOx- sulfur oxides].

Location SPM SOx CO NO
Industrial and mixed use 500 120 5000 100
Commercial 400 100 5000 100
Residential and rural 200 80 2000 80
Sensitive areas (Hospitals and Educational Institutions) 100 30 1000 30

[M Shamsul Islam and Quamrun Nessa Begum]

Noise pollution The incidence of noise pollution in Bangladesh is becoming a problem of far-reaching consequences. In the absence of a traffic rule curbing the use of horns, the noise problem has become acute in many parts of the cities and towns. Motor cars, trucks, buses, mini buses, aeroplanes, motor cycles, trains, construction works and noises from industrial plants are sources of noise pollution. The term pollution is being used because the noise level is so high that it causes various kinds of diseases of the ear in human beings.

Noises are measured in units called decibels. Decibels may have a range from 1 to 160; 1-60 decibels being the acceptable level; 60-100 level is regarded as annoying, and 100-160 level may cause damage to hearing. It has been estimated that the average noise level in North America, for example, is doubling every 10 years or so. The noise level in Bangladesh is also increasing. [M Aminul Islam]

Radiation pollution A kind of invisible pollutant, radiation can cause serious harm to people. The source of radiation is the sun and outer space, from where it reaches the earth. Most of the effects of radiation are due to radioactive materials-especially from the fallout of nuclear weapons (radioactive dust), nuclear power plants and various electronic devices. Among these laser ray, x-ray machine, coloured television set, microwave oven are worth mentioning.

It is not yet known what effects small amounts of radiation have upon human bodies. The rate of radiation is measured in terms of rems: 1 rem =1 in 10,000 probable deaths by cancer; 0-200 rems = increasing cancer risks; 300-500 rems = death by radiation diseases.

The damaging effects of radiation is best seen in regard to cell development. If the cell dies or gets well by itself then there are no ill effects later on, but a damaged cell at a later stage can become cancerous (a process of getting septic). If the reproductive cells of humans are affected, the inevitable effect is that they become sterile. Further, if along with the cell bodies, spermatozoa or egg-cells (ovary) are attacked, then new-born babies are likely to be crippled or suffer from mental derangement.

The problem of the disposal of radioactive wastes has caused serious concern throughout the world. There are instances of radioactive wastes being thrown into the deep sea, much to the dismay of people living around the oceans. The incidence of throwing radioactive waste materials into the Bay of Bengal in particular has increased the concern of the people in the subcontinent and in Southeast Asia. Today the situation is such that pollution caused by harnessing nuclear energy has aroused anxiety all over the world and there is a need for mobilizing public opinion against the use of nuclear power in order to ensure the safety of human beings and animals at large. [M Aminul Islam]

Soil pollution Soil exists in a thin layer of the earth's crust. On the basis of the characteristics of soils, an agricultural system is developed. Natural processes take many years for a soil to be formed for agricultural use. In Bangladesh soils are developed in layers, mostly azonal in characteristics. While owing to flooding every year new layers of soils are deposited, the textural characteristics of old soil layers are also seen to be modified or altered. Of late soil pollution has become a serious threat, as there is a lack of proper soil management practices.

Apart from the loss in terms of soil productivity, soil erosion has been one of the major factors generating pollution. Soil erosion is the wearing away of soil. Thus a qualitative change in the soil is brought about by erosion, which affects the binding of the soil, making it loose and fragile. Moreover, if trees, vegetative covers including grass or plants as soil cover or those that hold soil in place are removed or destroyed, the process of soil erosion is hastened by winds blowing bare soils away and rains washing away more. Floods also remove soils from one place to another, thus bringing in qualitative change in soil structure.

The point to reflect here is that both the processes of erosion and removal of soil gradually make soils infertile, disrupting the natural ecosystem of the area as well. Unplanned, uncoordinated land use and agricultural methods are the causes of environmental degradation. By the same token, clearing of land for the construction of roads and settlements, together with the felling of trees and deforestation also causes erosion.

For a higher yield of improved varieties of crops there is a need for use of fertilisers and pesticides. Fertilisers provide extra doses of nutrition to the soil and help raise productivity. But use of a large amount of fertiliser decreases the ability of bacteria to break down humus into various nutrients in the normal process.

Use of pesticides these days, to have a higher yield of crops, especially food crops, is on the increase. It often becomes necessary to use pesticides to destroy weeds and insects that harm crops, but if pesticides are used in excess or in large amounts, they harm bacteria and other helpful organisms in the soil, thereby reducing the yield of crops. [M Aminul Islam]

Water pollution  Any undesirable and harmful change in the quality of water. Water pollutants come from the wastes of homes, industries, agricultural farms, and wastes from human beings and livestock. Industrial acids, pesticides, oil, and different types of toxic materials may destroy aquatic plants and animals. Phosphates, chemical fertilisers, detergents, and animal manure pollute the water system by supplying excess nutrients for aquatic life resulting in the pollution known as ‘eutrophication’. Following the excessive growth and subsequent death of algae, the bacteria uses up high amounts of oxygen from the water for the consumption of those dead algae, and this results in oxygen deficiency in water.  

Air and water pollution agents

Industrial and municipal wastes pollute Bangladesh rivers and water sources. DOE observe that sulfuric acid and phosphoric acid from TSP factory in Chittagong, Karnafuli Paper Mills of Chandraghona, Paper Mill of Sylhet, Carew and Company of Darshana, Khulna shipyard and Fish processing factory, Olympic and Kaderia textile mills of Dhaka dispose of their millions of gallons of liquid wastes to the nearby rivers and waterways and thus pollute the water.

There are more than 140 industries in Kalurghat, Nasirabad, Patenga, Kaptai, Bhatiary, Barab Kunda, Fauzdarhat and Sholoshahar in Chittagong. All their wastes fall in the waters of the karnafuli and the Bay of Bengal. Chittagong has 19 tanneries, 26 textile mills, 1 refinery, 1 TSP fertiliser, 2 chemical, 5 fish processing, 2 cement factories, 1 paper rayon mill, 1 steel, 2 soap factories, 2 insecticide factories, 4 dyeing factories, and about 75 other small industries.

The water of the Buriganga river of Dhaka is being polluted by 53 industries of Postogola and Fatullah, and 151 tanneries of Hazaribag. Tanning wastes contain sulfuric acid, chromium, ammonium sulfate, chloride, and calcium oxides. These may seep into groundwater polluting both the surface and groundwater resources. The odour of tanneries affects the health of the people in surrounding areas. From the Tongi area, at least 29 industries pollute the turag river, and 42 big industries are responsible for throwing their wastes in the shitalakshya river.

Several industries and match factories of Rupsa industrial area, Khulna are polluting the Rupsa river with their wastes. The Khulna Newsprint Mill, Hardboard Mills, Goalpara Thermal Power Station, Jute and Iron Industries of Khalishpur are depositing all their wastes into the bhairab river. The Khulna Newsprint Mill discharges about 4500 cubic metre of wastewater per hour in the river Bhairab, in which suspended undissolved solid materials are present.

Apart from the wastes of industries in towns, the river Padma is also polluted by upstream wastewater from the Ganges. The Ganges in India carries nearly 8,62,000 sq km of Ganges plain wastes. Seven hundred cities along the banks of the Ganges dump about 1200 million litres of wastes per day and the downstream community of Bangladesh is forced to deal with this already polluted water.

In Chittagong, the number of fish in the Karnafuli has decreased because of water pollution, and many fishermen of Rangunia, Raujan, Boalkhali, and Anwara upazila have become unemployed. An industry in Chittagong known as 'ship breaking' thrives along the 20 km long coast from Fauzdarhat up to Kumira. During the scrapping operation, a large amount of remnant engine oil and oil deposited on the bottom of the ship exudes out to the Bay of Bengal polluting the sea thoroughly to a great distance. Large amounts of metal of different kind are also mixed with seawater to pollute the water further. The incoming and out-going ships for Chittagong and Mangla ports are causing serious pollution with their solid and liquid wastes thrown indiscriminately to the seawater. The ships bound for Mangla Port covers a distance of about 100 km along. The pasur river runs through forests of the Sundarbans and the liquid and solid wastes of the ships passing through this river are thrown into the water are polluting the forest areas; deforestation may result in future.

Bangladesh and West Bengal, India are facing a serious problem of water pollution from the metal Arsenic. After its first detection in 1983, the School of Environmental Studies (SOES), Jadavpur University, India organised an international conference in Calcutta in 1995 on Arsenic, and highlighted the urgent need for serious studies across the border in Bangladesh. Arsenic contamination has been identified in some more districts of West Bengal since then. The Dhaka Community Hospital (DCH) and SOES, Jadavpur, West Bengal carried out a field survey to detect groundwater arsenic contamination in Bangladesh from August 1995 to February 2000. Actual field survey was done for 239 days. WHO recommended the safe level of Arsenic as <0.01mg/l and the maximum permissible limit as <0.05mg/l. During the last 5 years, 64 districts were surveyed, and it was found that in 54 districts, arsenic in groundwater was above 0.01 mg/l, including 47 districts where it was above 0.05 mg/l. The remaining 10 apparently safe districts may not remain safe in future.

A report published in January 1999 by the British Geological Survey jointly with the Department of Public Health Engineering (DPHE), Bangladesh gives the number of people exposed to groundwater arsenic poisoning as 18.5 to 22.7 million, assuming an uncertainty of about 10%.

The arsenic contamination problem has become so urgent in Bangladesh that most of the universities of Bangladesh are conducting research in this line. The object is to develop remedial strategies that minimise arsenic poisoning. Arsenic contamination of land (as in Victoria and other places of Australia) has been reported from spent mining material and mining sands.

DCH and SOES have analytical information on 15,969 hand tube wells (with depth from 6.4 m to 40 m) from 47 districts of Bangladesh where groundwater showed arsenic levels above 0.05 mg/l. DCH is responsible for testing tube wells and health-screening components of the programme, including incidence of arsenic poisoning. [M Shamsul Islam and Quamrun Nessa Begum]

Environmental degradation While environmental problems merge imperceptibly into development problems, the socio-economic development of Bangladesh has been constrained further owing to the inadvertent manipulation of the environment, bringing in disequilibrium between resource development and utilization. Much land is being abused, and overuse has resulted in land degradation. The problem, however, lies with the implementation of the principle of optimum land use. The major consequences of changes in land use and land cover are resource depletion, loss of rural land, land degradation, deforestation, desertification, soil loss, salinization, loss of wetlands, loss of biodiversity, and loss of cultural diversity. The key issue is the magnitude of the changes induced by the changes in land use over an extensive area. There is much concern today in Bangladesh about environmental stresses leading to environmental degradation, namely the increasing aridity being experienced in the western and northwestern zone, particularly in the districts of Rajshahi, Dinajpur, Bogra, and some areas of Kushtia and Jessore.

The degradation of the biological environment including the human use system of the region has exacerbated the risk of erosion, salinization and above all desertification. Of late, concern has been expressed about the fact that the progressive desiccation and consequent expansion of sandy area have been due to recent changes in the weather system. It is possible that the climate is becoming drier, exacerbating the process of desertification. But there appears to be evidence of increasing aridity in recent years owing largely to changes in landforms, formation of char lands and drying up of rivers as a result of the withdrawal of Ganges water upstream, and degradation of the vegetative cover (diminution of forest resources), soil erosion, waterlogging and salinization (increase of salinity further inland). It seems that rapid deterioration in the quality of the environment has already ensued, with a gradual decrease in land productivity.

The conversion of wetlands to agricultural and urban uses is another factor in land degradation. Several hundred wetlands have already disappeared and some of the larger ones are in the process of being degraded. The total area of wetlands now in Bangladesh has been variously estimated at between 7 and 8 million ha. These include rivers, estuaries, tanks, fish ponds, and some other lands which are seasonally inundated to a depth of 30 cm or more. Historically and culturally wetlands have been integral parts of human habitation in Bangladesh. Wetland resources in a country like Bangladesh are of enormous economic importance, especially for retaining fish, wildlife and various other vegetative covers. But owing to high population density the wetland resources of Bangladesh have been markedly impacted in both quantity and quality by habitat loss, changes due to water development and management projects and unplanned and uncoordinated agricultural extension.

Urbanization as a process has impacted adversely on the environment at large. Although Bangladesh experiences a low level of urbanization, the rate of growth of the urban population has been rapid during the last few decades. The unabated growth of population in general has already overburdened the inadequate public service infrastructures of urban centres. Moreover, over 30% of the population in most of the urban centres lives in squatters and slums. The strain on human services and the physical structure are severe, and air and water pollution, waste disposal problems health problems are endemic. Moreover, industrialization accompanied by urbanization with a view to generating economic growth and providing much needed employment is also a contributor to air and water pollution and the ill health of millions. However, these problems of poor infrastructure and environmental degradation are being compounded by an increase in the migration of rural people towards urban centres for seeking employment.

Environmental degradation is also caused by such factors as flooding (in both on-shore and off-shore areas) and cyclonic storms in the coastal areas. Apart from gigantic social problems, the floods invariably lead to the deterioration of the general standard of living of the people and the quality of the environment.

A pervasive recurring phenomenon, the frequency of occurrence and magnitude of the drought hazard have a profound bearing on such aspects as environmental deterioration and quality of life. Some of the severe droughts occurring in Bangladesh affected as high as 47 percent of land area and 53 percent of the population.

Loss of productive cropland through erosion, natural hazards like floods, cyclones, drought and salinity and human intervention involving natural processes have been as critical as development of infrastructures for transportation, energy production and irrigation structures leading to environmental degradation. All these processes involved in land use transformation bring about changes in biogeochemical cycles, in biodiversity, and in the climate system. [M Aminul Islam]

Inundation and flood Some of the devastating natural hazards in Bangladesh are caused by floods induced by the excessive run-off and rise in river water levels in floodplain areas. The duration, magnitude, area and extent of flooding have increased alarmingly in recent years. According to various estimates, roughly one-third of the total area of the country, inhabited by well over 35 million, is normally prone to flooding.

Flooding has two connotations. It is referred to as Barsa and bonnya. Barsa (June-October) is a period of normal inundation and is taken as a benevolent agent facilitating agricultural activities. As long as the floodwater does not overtop homestead land, and more particularly when crops in the field are not submerged, it is regarded as a normal flood. Bonnya is taken as a disastrous or damaging phenomenon when the timing, duration and magnitude of the inundation are abnormal, homesteads and land adjacent to homesteads becoming submerged and cropland going under floodwater by a few centimetres.

No systematic records of annual floods of olden times are available; the earliest one of which there are records occurred in 1769. In recent times, major floods occurred in Bangladesh in 1954, 1955, 1956, 1962, 1963, 1968, 1970, 1971, 1974, 1976, 1987, 1988 and 1997, and 2000. It is to be mentioned here that the definitions of 'abnormal' as opposed to 'normal' flood vary among different agencies responsible for collecting data on flooding. [M Aminul Islam]

See also flood.

Areas of environmental concern Some of the important areas of environmental concern are:

Coastal environment The coastal zone of Bangladesh has been vulnerable to both physical and cultural intervention, surviving as an area of much environmental concern. Along more than 700 km of shoreline, the diverse coastal features, dynamic as well as complex in nature, have been subject to a combination of the natural and cultural processes leading to the modification of natural coastal environment. Relatively rapid changes in landforms due to erosion and sedimentation have occurred in the coastal areas. Physical evidence of changing conditions is apparent in eroding riverbanks; areas of new deposition and consequent changes in landforms are also present. Coupled with these, the high upland discharge with a heavy sediment load, severe tidal activity at the head of the Bay of Bengal, piling up of water at the coast during monsoon are some of the extreme conditions including rapid morphological instability of the area.

Within the time span of more than 200 years the estuary has gone through changes in shape, channel migration and southward growth of islands. The phenomena of storm surges and tidal bores have also been associated with the rapid changes of environmental conditions. Tidal bores have been found to occur immediately after low water at rising tide, but not under all tidal conditions thereby, a new damage potential is also being created at an accelerating rate by occupancy of coastal areas subject to high winds, wave action and salt water flooding associated with storms.

Besides, the coastal zone is the home of the world's largest ecosystem, the Sundarbans mangrove forest. The human intervention for development of the area has been such that the morphological features have been subjected to a very sensitive and fragile ecosystem of the coastal zone.

Southwestern region salinity problem The combined flow of the Padma, Brahmaputra and Meghna rivers transports fresh water to the coastal area through several estuaries. Of the rivers carrying sediments to southwestern regions, the river gorai and its distributaries play a major role. The Gorai river, the major distributary of the Ganges is the major source of water supply to the major part of the southwestern zone. The upland fresh water flows through the Gorai-Madhumati govern the state of salinity of the region. The withdrawal of water upstream at Farakka (India) has reduced the flow as well as the level of sweet water downstream. The river Gorai, being choked up at the mouth, is unable to carry water downstream during the dry season because of the drastic fall of the Padma water level. As a result of the reduced flow of water to the southwestern region the intrusion of saline water progressively upstream has made the region vulnerable to increasing salinity.

The situation is further aggravated by the fact that a salinity front of more than 500 micromhos intrudes nearly 160 km inland during the dry season. It is nonetheless significant that salt water intruding further up the river mouth is altering the entire estuarine ecosystem. The area affected, as reported, by more than 2000 micromhos level was found to be nearly 20,700 sq km. In particular the salinity-affected areas have been Satkhira, Khulna, Jessore, Narail, Bagerhat and Gopalganj.

While it is noted that the increase in salinity is totally attributed to the reduced flow of the Padma water, a large part of the southwestern part of the southwestern region is subject to the tides of the Bay of Bengal. The flora-fauna ecosystem of the southwestern region once used to be dominated by the mangrove forest of the Sundarbans. Before the withdrawal of water at Farakka, of the flow water from the Ganges downstream used to counteract the flow of salt-water inland. However a vast area has been adversely impacted by the increased salinity, especially in such activities as agriculture, fishery, forestry, power generation, industry and some other enterprises- not to mention the spread of diseases and increased mortality rates, causing thereby an environment of hazards.

The Sundarbans The area stretching over 0.57 million ha in the southern districts of Bangladesh, namely Khulna, Satkhira and Bagerhat, is the largest mangrove forest ecosystem of the world. Out of the total area, nearly 0.17 million ha is occupied by rivers, channels and other watercourses.

Some decades back mangrove forests were abundant all along the coastline, especially in Cox's Bazar, Chittagong, Patuakhali and Khulna districts. According to one estimate a little over 1.5 m acres of mangrove forest, mainly in the Sundarbans, are in existence. Although the size of the Sundarbans mangrove forest has been reduced greatly from their former extent owing largely to shrimp cultivation, salt production and subsistence agriculture, it still remains the largest single tract of mangrove ecosystem in the world. Though habitation is not permitted, the Sundarbans has been exploited since time immemorial. The principal economic activities include harvesting of timber, fishing, collection of honey, beeswax, and oysters and shells.

A significant ecological change is taking place in the Sundarbans because of the activities of man. Changes in land use has brought about changes in biodiversity and biogeochemical cycles leading to a change in the weather pattern as a whole. The top dying of sundari, the principal commercial tree species is a matter of grave concern. Oil spill, increasing salinity and reduced river discharge and illegal activities are greatly destroying the ecological balance. The climatic system of Bangladesh is interlinked with the weather system of the Sundarbans area. Any change in the Sundarbans weather system is bound to produce an adverse impact on the climate and life of the people of Bangladesh.

In the interest of mankind, and especially for preserving environmental quality, the Sundarbans has received recognition as a natural heritage of the world. A declaration by the UNESCO to this effect has been would be a step further to preserve and maintain the worldmost vulnerable areas.

Poldered projects The traditional poldered projects of the southwestern region in the saline zone and the Chalan Beel project in the sweet water zone represent the detrimental effects of present-day flood control and drainage (FCD) system. Since the land is not graded, most of the low-lying areas inside many poldered projects have been turned into waterlogged areas though there were numerous controlled structures for flood control and drainage. The channels outside and inside the compartments get silted up gradually. Moreover, the outfalls and inlets are also choked up due to rapid sedimentation and waterlogging creeping gradually to other elevated areas. As a result, an irreversible change in the hydrological regime of the channels is brought about due to human activities through numerous structures.

Shrimp cultivation It has posed a grave environmental problem in the coastal area. In some places, especially in the Satkhira-Khulna area, shrimp cultivation is practiced almost 80 km inland, inducing thereby the problem of salinity with concomitant dying of vegetation and destruction of fertile agricultural land.

The cultivation of shrimp requires the holding of at least 8-9 months of stagnant saline water every year. The deliberate inundation of coastal polders to facilitate the production of brackish-water shrimp has brought a new dimension in the land use pattern, a practice seen as having detrimental effects on the economy and environmental set-up. The areas with a potential for brackish-water shrimp cultivation are located in the coastal areas, including polders adjacent to tidal creeks and rivers.

The shrimp culture industry being a major source of overseas export earnings for Bangladesh, has resulted in the seasonal inundation of large areas of land, especially in the farm and grazing lands. It is asserted that dry season brackish-water shrimp cultivation is consistent with wet season rice production. This has resulted in deliberate cutting of the coastal embankment to allow the inflow of saline water. The agricultural land has thus been lost to shrimp ponds and wet season rice yields have declined progressively as salinity and soil changes have taken their toll on land fertility.

Chakaria Sundarbans Its mangrove forest ecosystem is unique in the coastal area and covers a vast coastal area of Bangladesh. Before the turn of the 20th century most of the northern part of the Sundarbans area was cleared for habitation and other economic uses. Today virtually all of the mangrove forests in the vicinity of the Chittagong Chakaria and the naf river have been cleared for shrimp farming, salt production and agriculture.

Shrimp cultivation in the Chakaria mangrove forest has affected adversely on the socio-economic and ecological system as the loss of mangrove forest has made the area vulnerable to cyclonic winds and associated tidal wave in addition to exacerbating soil erosion, environmental disruption and destruction of biodiversity. Shrimp culture is basically responsible for the destruction of mangrove resources of Chakaria Sundarbans.

The Naf River Estuary Like Chakaria Sundarbans, the Naf River Estuary which at one time had luxurious mangrove swamps and inter-tidal mudflats has been subject to negative environmental impacts in recent years owing to the cultivation of shrimps, salt production and seasonal paddy cultivation. The process of converting agricultural land and mangrove forest into shrimp ponds has adversely affected the soil and water system in the adjoining land, making the entire area sensitive to normal production process. The old mangrove forested areas along the Naf river near Teknaf are also being taken over for shrimp farming, a process whereby agricultural farms are being converted into shrimp farms with negative consequences to the lifestyle of the people.

Coastal pollution The pollution in the coastal area has several sources, one of them being the effluent from pulp mills and other industrial plants at upstream locations. Most of the industries, not having been planned with pollution treatment facilities, discharge their untreated wastes directly into the river Karnafuli or in to the Bay of Bengal, threatening thereby the aquatic life and the estuarine ecosystem. In a similar way untreated domestic wastes are also thrown into the river or the Bay affecting local fisheries adversely with fish catch diminishing gradually on account of oxygen depletion.

The fishing environment and aquatic life in the coastal zone is also seriously affected by water resources development activities, thereby seriously affecting the biodiversity and life support system.

Marine pollution One of the major environmental concerns relates to marine pollution in the Bay. The sources of marine pollution are urban industrial effluents and river run-off including oil spills in the vicinity of the two major ports of Bangladesh, namely Chittagong and Mongla. The problem has been with the discharge of waste oil, spillage and bilge washing in the river creating pollution in the marine environment. The average oil spill effect has caused such a severe water quality problem that it has affected the multiplication of phyto- and zooplankton, and breeding grounds of shrimp and prawn fishery. The Sunderbans mangrove forest is also affected as much by marine and industrial pollution as by salt water flooding.

Chalan Beel Once a flourishing wetland with rich flora and fauna, the area is now almost degraded and converted into an area of environmental concern. The problems of drainage congestion and flooding have been created by the very construction of polders. The extent of the beel has now been reduced to 26-40 sq km owing mostly to sedimentation and agricultural invasion, and serious drainage problems from stagnant monsoon water inside the polder. There are also a number of beels located between the Barind Tract and the Padma floodplain, which are in effect extensions of the chalan beel having similar geomorphic features. The beels are flooded to more than 4.5 m and are covered with water throughout the year.

The encroachment of sediments, mostly sandy in character, from the Padma basin to the Chalan Beel area has transformed the area into a morass, bringing in environmental change and the concomitant suffering of the people owing to agricultural decadence and the depletion of fish resources.

Beel Dakatia In this area, sedimentation and land formation within the polders have ceased- a process that has led to ecological catastrophe with disastrous socio-economic consequences.

Siltation

As observed, poldering has impeded drainage on both sides of the protected area that led to rapid siltation of drainage channels. Siltation outside the polders prevents outflow of water held within the polders, obstructing the natural drainage system and leading to the progressive and permanent flooding of large areas of once productive farmland. Permanent flooding of thousands of hectares of land owing to siltation of drainage channels has forced the displacement of a large proportion of the farmer population and led to environmental decadence. Access to clean drinking water is one of the major problems, especially for those who are still living in the beel area.

Flash flood While the usual river-borne monsoonal flood brings about a gradual rise of the river stages, flash floods on the other hand show characteristics of sharp rise and fall- up to about 4 m in a day in some cases. They are caused by rapid surface water run-off due to heavy monsoonal and pre-monsoonal rainfall in April and May in the hills of Meghalaya and Tripura. The area that suffers most owing to flash floods is the Sylhet basin in the northeastern region of the country, notably in the Habiganj area, regularly causing extensive damages to boro crops.

Massive deforestation, especially in the hilly areas, causes severe soil erosion and landslides, which contribute to river siltation. The process of deforestation reduces the water retention capacity of soils and increases the rate of surface run-off. The sediment load, carried by streams mostly consisting of coarse sand, is deposited on the land, just as the silts fill up river beds, inducing flash floods.

Elsewhere, increased pineapple cultivation and resultant soil loss threatens the Kaptai Multi-purpose Project and the Monu river irrigation scheme, accentuating siltation in the surrounding rivers and provoking flash floods. Similarly, in the Cox's Bazar area conversion of rich tropical forests with their unique bio-diversity into plantation and shrimp farms have had a negative impact on the environmental system. Improper land use and mode of farming, jhum cultivation for that matter, leading to massive erosion and flash floods in general have made the north and southeastern hill areas vulnerable to both physical and cultural interventions.

The Sylhet Basin 'It occupies roughly the depressions bordering eastern Mymensingh and western Sylhet, which is also the heart of the Meghna Basin. The lowest part of Bangladesh, the Sylhet Basin lies under water for more than six months of the year with the underlying sediments being clay. Further, large marshy areas cover the basin and are completely unsuitable for agriculture. The occurrence of early floods including flash floods is an environmental constraint. This is also the region of large water bodies locally known as haors.

The Barind Tract The area occupying the west central part of Bangladesh, in the districts of Rajshahi, Bogra and Dinajpur, is the largest of the Pleistocene areas of the country. Its surface has a domal appearance and rises 6 to 12 m above the floodplains. Pleistocene sediments are well oxidized and typically are reddish, brown or tan, and are mottled. They commonly contain ferruginous or calcareous nodules. Water content is lower, resulting in firmer, more compacted material. Organic material in Pleistocene sediments is commonly confined to the surface soil profile. Divided into several parts by the rivers, the Barind has been laboriously terraced for aman rice cultivation.

While the soils in the Barind Tract bake too hard during the summer season, drought is a major environmental problem during the winter season. Monsoon rainfall in the region suffers from extreme variability, often exceeding 60 percent. An important fact is that this variation occurs in both time and space. Not only the annual and monthly variation but also the micro-variation is of significance environmentally. Persistent drought for at least half of the year (November to March) and the intense rainfall variability together with an average of about 15 cm of soil moisture deficiency characterize this region.

The Moribund Delta This area, the western part of the deltaic plain, bounded on the east by the madhumati river, comprises the areas which extend from the northern boundary of the Khulna district to Jessore and parts of Kushtia district. The area lacks the important effect of the flooding from the Padma and is characterized by rivers that are now abandoned or drying up, having lost connections with their parent streams. The rivers having now no off-take from the main streams cannot bring down enough water and silt, even during the flood season, and being confined within high levees, are not in a position to inundate the entire area. As a result, land building has ceased and the delta has grown moribund up to this limit. The moribund delta area has for a long time been noted for its agricultural decadence and incidences of diseases, especially malaria. [M Aminul Islam]

River erosion and siltation Riverbank erosion is one of the major environmental hazards in Bangladesh. Vast areas come under this phenomenon during the season of floods (July-September) disrupting normal lifestyles of people. Agricultural land, human settlements, markets and towns are just as much vulnerable as the environment itself. According to the bangladesh water development board data (1984-85), among the major 16 rivers, river bank erosion has been observed in 254 places and in many places the process at work is dangerously threatening the existence of a number of old towns and cities. The very best example is the case of Chandpur, located along the Padma-Meghna interface.

Riverbank erosion [Courtesy : Amanul Haq]

Although river erosion is observed in almost all the areas of Bangladesh, their effect on bank erosion is most noticeable in the two most important rivers ie the Padma and the Jamuna. Every year it is because of the effect of river bank erosion caused by the Brahmaputra Jumuna and the Padma river system, that thousands of people living in the floodplains become homeless as well as landless - homesteads and agricultural land coming under damage syndrome. The losses and damages to properties are exacerbated when the process of riverbank erosion is synchronized with the widespread flooding. Riverbank erosion has been endemic in Bangladesh in recent years, with almost a million people being adversely affected by the process, directly or indirectly, leading to an economic loss of more than US $ 40 million annually.

Siltation The aspect of siltation is as critical as the changing courses of the major rivers of Bangladesh. Almost every year the two major rivers change their courses and in the process form sand bars or chars as they are called locally, which can be formed overnight while some coastlines are estimated to be receding at rates of up to about 270 m per year. The surface flows bring about 3 million m tons of sediments every year in the country. While it is seen that the process of siltation and erosion is a natural phenomenon in the rivers of Bangladesh, there is evidence of serious problems with many rivers becoming dead, dislocating many navigation routes. In recent years deforestation and landslides in the upland countries have caused siltation problem in Bangladesh rivers.

While the process of siltation is continuing unabated, it is to be noted that the rivers of Bangladesh, notably the Padma, Brahmaputra and Meghna carry a huge amount of annual sediment supply of up to 1.48 billion m tons during the wet season to one of the world’s largest deltas keeping the expansion of the delta in progress. Further, as an area of over 30% of land area in Bangladesh comes under normal flood regime, a large quantity of suspended sediments are deposited. Moreover, relatively rapid changes in landforms due to erosion and sedimentation have been occurring for long; the physical evidence of such changing conditions is apparent in eroding riverbanks, areas of new deposition and consequent changes in environment.  [M Aminul Islam] Siltation

Environmental protection agency The environmental programmes in Bangladesh hardly got off to a start until the mid 80s. Following the UN Stockholm Conference in 1972, environmental programmes were initiated for the first time by the Government of Bangladesh with the creation of the Pollution Control Board in 1974, and the Pollution Control Ordinance was enacted in 1977. In 1989 the Ministry of Environment and Forestry was set up along with the Department of Forests and a newly created Department of Environment under it. The former Pollution Control Board was eventually renamed as the Ministry of Environment and Forests. The year 1990 was declared as the Year of Environment and the years 1990-91 declared as the Decade of Environment.

Meanwhile, the Ministry of Disaster Management and Relief and the Disaster Management Bureau (DMB) brought out 'Standing Orders on Disaster' through updating and thorough review of the disaster situation. The 'Standing Orders on Disaster' distributed down to the union level is acting as a guide book for all concerned for coping with and recovering from disasters in effective ways.

There was another dimension in regard to disaster management. The environmental crisis was being felt most severely by the rural poor in Bangladesh where resource exploitation combined with a poor understanding of the environment has led to further environmental stresses, threatening not only economic development but also the survival of the most vulnerable people.

The effort for the formulation of an Environment Conservation Strategy began in 1984 and much progress has been made since then. Further, the National Environmental Management Plan: An Action Plan for Bangladesh (NEMAP, 1991) has been prepared with the objective of addressing vital environmental concerns, taking into consideration the activities that would arrest further degradation. NEMAP, as claimed, is the logical follow-up to the National Environmental Policy and the National Conservation Strategy (NCS), with the objective of providing guidelines for the preparation of various activities necessary for structuring socio-economic development of Bangladesh on a sustained basis. [M Aminul Islam]

Planning and management Bangladesh experiences an almost unique environmental situation, being located on two of the world's largest rivers (the Padma and the Brahmaputra), and in one of the great flood and cyclone hazard zones of the earth. While physical environmental problems merge imperceptibly into development problems, the socio-economic development of the country has been constrained owing to pressures exerted on the total environmental system bringing in disharmony between resource development and utilization. With a population of about 130 m and a limited resource base, the man-land ratio being the most critical, the importance of environmental planning and management can hardly be over-emphasized- a perspective necessitating a working knowledge of the environment which it is felt would have a seminal influence on the proper planning of development and environmental management.

Of late, much emphasis is being given on the aspect of environmental management. Mention must be made of the National Environment Policy (1992), National Environment Action Plan (1992), Forest Policy (1994), Forestry Master Plan (1993-2012), and Environment Conservation Act (1995). The National Conservation Strategy and especially the National Environment Management Action Plan (NEMAP) have been drawn up with assistance from people from all walks of life. Further, for executing management programmes and action plans in particular, various policy instruments such as government regulations and control, including social instruments have been enforced, though these have not always yielded fruits. Among other considerations, the policy objectives include in addition to enhancement of the environment, such items as urban beautification programmes, recreation, aesthetics, ecosystem and habitat conservation, landscape preservation, wildlife protection and heritage safeguard.

Environment and developmental planning Recognizing the importance of the environment as a crucial factor in development planning as well as taking steps to development policy more responsive to governmental concerns has been a step consistent with broad national objectives. Building environmental concerns into development is indeed a life and death situation in Bangladesh. By the same token, improving the quality of the physical environment without thinking of improving the status of man himself is an anomalous assertion. Population control, sustainable resource exploitation, environmental conservation and rural development are all best served not by starting with them in a normal professional way, but by starting with poor rural people and with what they want and need. It is precisely sustainable livelihoods, which can secure rights and ownerships, integrate the poor people's wants and needs, that those concerned with population resources, environment and rural development seek. [M Aminul Islam]

Greenhouse effects and global warming Increase of temperature of the lower atmosphere of the earth due to effects similar to that of a greenhouse, or a glass house used for growing delicate plants (flowers and vegetables) mostly in cold countries. The solar radiation comes through the glass and warms the materials, the structures and soils inside. Being heated up they, in turn, emit infrared radiation (heat radiation). This longer wavelength radiation cannot penetrate the glass shield of the green house and is trapped inside. Thus radiant energy can enter the greenhouse but the heat it produces cannot escape so easily and the greenhouse remains moderately warm allowing plants to grow.

In a roughly analogous manner the atmosphere acts like a greenhouse glass shield for the earth. Solar radiation penetrates the long columns of air and warms up the earth's surface. The earth then re-emits in the long wave infrared region which is then largely trapped in the lower atmosphere. This phenomenon is known as the greenhouse effect. The trace gases in the atmosphere which largely absorb the reradiated infrared radiation are known as greenhouse gases (GHGs). They are: water vapour, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3) and the chlorofluoro carbons (CFCs). The consequential production of heat throughout the world because of greenhouse effect is known as global warming.

If the atmosphere were absent the average global temperature would be about -18' C instead of the present value of 15' C. All the incoming energy in the from of sunlight is striking the earth's surface and causing the earth to emit infrared radiation like a giant radiator. Only a fraction of this heat could escape directly back to space; the rest of this radiation is trapped inside the atmosphere. As mentioned before, the greenhouse gases are heated up and some of this heat is radiated down to the surface of the earth making the earth warm.

The predominant greenhouse gas, water vapor causes a large part of the heating. As the heating is increased, more water evaporates from the oceans, rivers, lakes and the soil. The warmer atmosphere again can hold more water vapor. This creates a powerful feedback loop and thus the greenhouse warming is enhanced.

Greenhouse gas emissions in Bangladesh 'A publication of the Department of Environment, Bangladesh (Global Climate Change, Bangladesh Episode, June 1997) reports that the rich developed countries are emitting GHG's as a result of their wasteful consumption pattern and reckless lifestyle.

On the other hand, activities of the vast population living in poor developing countries also contribute to the GHG load, but to a much lesser extent. The per capita GHG emission by industrialized countries is about 6 times the world average emissions. The GHG emission from USA alone accounts for about 20% of the total global emission.

According to the report the total carbon dioxide released from all primary fossil fuel use in Bangladesh amounted to 13,443 Gg in 1990 (base year), the corresponding value of carbon (oxidized) amounted to 3,666 Gg. On a per capita basis (the 1990 population being 109 million) this amounts to just about 123.3 and 33.6 kg respectively. Biomass combustion caused an annual release of 61,283.7 Gg of CO2 in 1990. The emission from agricultural residues contributed about 59% of total emission from biomass energy combustion.

Emission from energy production and landfills In Bangladesh, natural gas is the only indigenous source of commercial energy, except for a little oil discovered in 1987 and coal which remains yet to be mined. Hence natural gas is the only source from which methane emission is to be estimated. It is estimated that annually 6.1 Gg of methane (by weight) gas is emitted due to energy production by natural gas.

Land fills (Municipal wastes used for land filling) Very little quantitative information exists in Bangladesh on municipal wastes. Methane emission from six major urban areas of Bangladesh (Dhaka, Chittagong, Khulna, Rajshahi, Sylhet, Mymensingh) from landfills has been estimated to be about 73.6 Gg per year.

Emission from agriculture, livestock and waste water Methane emissions have been reported from the flooded rice fields, enteric fermentation in livestock, manure management, and anaerobic wastewater treatment in the municipalities.

The methane flux in Bangladesh rice cultivation is expected to be lower than in other countries. Estimated values of CH4 from flooded rice fields vary between 257 and 622 Gg. Considering the median value it is estimated that rice cultivation emits about 468 Gg of methane gas per year. HYV Boro rice contributes about 42% followed by HYV transplanted aman (about 31%).

The low body weight of animals in Bangladesh results in low level CH4 (446.8 Gg) emission by enteric fermentation of livestock, 67.5% of which is contributed by non-diary cattle. About 73.07 Gg of methane is emitted from manure management, a large fraction of which comes from non-diary cattle. Emission from wastewater treatment is insignificant.

Usually when forestland is cleared for agricultural or other purposes by felling frees, a part of the carbon locked in them is released when parts of the trees are used as fuel. The land is cleared through slash and burning. In the process the soil is disturbed. This also releases the carbon locked therein. If on the other hand, the forest or tree cover area increases there is likely to be a net sink effect.

In the 1990 base year, 5,456 Gg of carbon was removed from the forests while 12315 Gg of carbon was absorbed during the same time by vegetation in the remaining forest areas of Bangladesh. Net annual carbon flux was about 6,859 Gg. This amount has the capacity to offset about 25,151 Gg of carbon dioxide from other sources.

Emission from biomass burning In the rural areas of Bangladesh a part of the biomass is left in the field after each harvest. Open air burning of these release gases such as CO2, CH4, N2O and NOx. It is estimated that 695.4 Gg Carbon, and 9.7 Gg Nitrogen are released annually from field burning of biomass. The major sources of rural energy in Bangladesh are biomass sources like rice straws, husks, dung, twigs, leaves, bagasse, jute sticks, fuel wood etc. It is estimated that normal biomass fuel combustion in open air releases about 189.5 Gg methane, 2339.9 Gg CO, 2.4 Gg N2O, and 85.9 Gg NOx gas. The Department of Environment, summarizes most of the results of GHG emissions in Bangladesh.

Table 2' Annual GHG emissions in Bangladesh

Source of GHG emissions Quantity of  GHG emitted (Gg)
Combustion of fossil fuel 13443 as CO2
Energy production 79.7 as CH4
Flooded rice fields 468 as CH4
Livestock (enteric fermentation & manure management) 520 as CH4
Burning of agricultural biomass 4.7 as CH4
97.3 as CO
0.11 as N2O
3.84 as NO
Forest No net emission
Biomass burning 189.5 as CH4
2340 as CO
2.4 as N2O
86 as NO

The estimates indicate that on the basis of global warming potentials more than one half is due to methane while about 30% are contributed by fossil fuel burning (due to CO2). [M Shamsul Islam and Quamrun Nessa Begum]

Educating environment Given the country's need to respond to an emergency situation and its longer term requirements to rehabilitate and reconstruct immediately after the advent of environmental disasters it was long been advocated that centres for environmental education be established and developed at various postgraduate institutions of Bangladesh, especially at the universities and various research bodies.

Environmental education programmes so far developed in the institutions have focused on multidisciplinary issues related (i) to monitoring existing disaster-active and disaster-prone areas, and where feasible, provide forecasts of potential disaster situations, consequent needs and management strategies that can mitigate the effects of such disasters; (ii) to provide an interdisciplinary forum for research into disaster forecasting, management and means of redressing the immediate and long-term impacts of disasters; (iii) to create a series of extension programmes and services through education and training programmes for private and government personnel engaged in environmental response and management in this area; and (iv) to develop a curriculum in environmental studies ranging from school level to the post-graduate level in the universities through existing departments and interdisciplinary programmes.

Among other things, the institutions have the potential to develop a body of specialists among its faculty able to provide information services, research capability and formal and informal training programmes in environmental management.

Developing educational materials or exhibits related to environmental system in Bangla have received priority consideration from many private and public organisations including the Disaster Management Bureau. Lessons in Bangla on disaster management in the schools at the primary and secondary levels have already been introduced. Other programmes include the development of specific university curricula and holding of seminars and workshops aimed at formulating action programmes, vis-E0-vis, actual practice of mitigation measures. Further, in addition to evolving educational communication and establishment of an education network, personnel training and practitioner exchange programmes have been developed. [M Aminul Islam]

Nemap denotes the National Environment Management Action Plan of the Government of Bangladesh. This plan has been prepared by the Ministry of Environment and Forest (MOEF) in consultation with people from all walks of life.

NEMAP has been prepared as the basis for programmes and interventions aimed at promoting better resource management, making people aware of environmental problems and reversing the present trend towards environmental degradation. NEMAP is also expected to identify key environmental issues, including conservation and improvement of environmental conditions, promoting sustainable development and raising the quality of human life. Since these may change over a period of time, it was anticipated that the NEMAP would evolve in response to the changes. [Mamunul Haque Khan]

Environment policy Course of action adopted and pursued by the government to preserve and maintain healthy environment relations. Global environmental degradation in recent years calls for serious environmental planning making and effective implementation of policies. The industrial countries have made good progress in the management of environmental concerns of their priorities. However, the art or science of environmental policy-making in a developing country is a new area, with not much of past experience. The process of governance and environmental priorities of developing countries also differ from those of the industrial world. There is an acute lack of data as well as inter/multi-disciplinary expertise needed for policy planning. This makes the task all the more difficult.

With its physical and socio-economic parameters, Bangladesh can be said to present a test case of sustainable environment management. The pressure of a huge population of about 130 million on a very limited resource base has, perhaps, surpassed the country's carrying capacity in terms of both the source and sink functions of the environment. Recurring natural disasters and huge casualties are to a large extent man-made. In such an all-pervasive predicament, the importance of environmental policy-making in Bangladesh cannot be overemphasized.

In recent years, environmental protection has become a priority agenda of the Government of Bangladesh. The government as well as the civil society are showing increasing concerns about the rapid degradation of both urban and rural environments. Implementation of the government's commitments to the environment and the mitigation of other environment-related problems are possible only through a well-defined national policy. The successive governments have initiated a series of policies and programmes aimed at putting development on a sustainable path, including the adoption of an Environment Policy in 1992.

The objectives of Environment Policy are: (a) to maintain ecological balance and overall development through protection and improvement of the environment; (b) to protect the country against natural disasters; (c) to identify and regulate activities which pollute and degrade the environment; (d) to ensure environmentally sound development in all sectors; (e) to ensure sustainable, long-term and environmentally sound use of all national resources; and (f) to actively remain associated with all international environmental initiatives to the maximum possible extent.

Environmental activities encompass all geographical regions and development sectors of the country. Policies towards realization of the overall objectives of the 1992 Environment Policy encompass fifteen sectors, such as, agriculture, industry, health and sanitation, energy and fuel, water development, flood control and irrigation; land, forest; wildlife and biodiversity; fisheries and livestock, food; coastal and marine environment; transport and communication; housing and urbanization; population; education and public awareness; and science, technology and research. [Mizan R Khan]