Commercial tourism puts St Martin's Island at risk

Shahidul Islam Chowdhury

The government agencies shut their eyes to unabated construction works on St Martin's Island to prop up the commercial tourism, which experts see as a threat to coral reefs.
   The government seemed to have finished its duty by declaring the country's lone coral island an ecologically critical area back in 1999, with no follow-up actions to preserve its unique biodiversity.
   The island is losing its scenic beauty fast amid invasion of commercial tourism that has led to a proliferation of hotels, resorts and shops, and has been stripping the island of its natural cover to satisfy the increasing human greed.
   The government must stop all unauthorised construction works, unabated extraction of marine resources and pollution of the natural habitat of wildlife on and around the island at the earliest, conservationists suggested.
   'The St Martin's Islands is about to lose its existence although there are laws and rules to protect it from human greed.' professor Ainun Nishat, country representative of the IUCN-The World Conservation Union, told New Age Sunday. 'There are government agencies and laws. But the laws are hardly enforced.'
   Thirty-six privately-owned hotels and resorts have already been built on the small quiet island and four others are under construction, according to sources at the island.
   None of the builders bothered to take environmental clearance from the department concerned.
   'Rich people of Dhaka have bought almost a half of the island. Their men are running the hotels and other businesses here,' said Ziaur Rahman, an islander who owns a tea stall near the makeshift jetty. He described how land price there soared only in few years.
   Another youth developed his career as a local 'tourist guide' as his ancestral land was sold and a resort, Jalpari, was built there. Like him, many people are employed as caretakers of the private resorts built on their land.
   Private companies are also advertising to sell dozens of duplex cottages and resorts on the islands.
   The number of travellers has been on the rise as three spacious private ships, each with the capacity of more than 500 persons, ferry people between the island and Teknaf during peak season, apart from scores of mechanised boats.
   The small town receives on an average 2,500 visitors everyday between November and February.
   Permanent migration of people including Rohingyas from Myanmar has raised the population of the island from about 5,700 in 2001 to nearly 9,000 in 2006.
   'Everything has a capacity to bear certain amount of load, be it physical and ecological,' professor Nishat said. 'A small ecologically vulnerable island like St. Martin's cannot cater for several thousand tourists everyday.'
   He warned the island is likely to become unliveable for human being by next five to seven years for shortage of sweet water.
   'The underground water table is continuously dropping in the island made of just sand and hard rock. The aquifer cannot meet the need of ever increasing tourists and permanent population. Increased salinity would intrude into the soil of the island if over-extraction of sweet water from the deep aquifer is continued,' Nishat said.
   He said the growth of coral has almost stopped as pollution went unabated affecting the reefs in many ways including the dumping of oil spills from several thousands engine boats, and sewage and wastes from houses and tourist resorts.
   Giving an example how biodiversity is under threat, he said, 'We are internationally pledged bound to conserve the sea turtles. But they face disturbance in nesting and laying eggs these days from outdoor lights of the hotels and noise and fire camping by the tourists.'
   Nishat said, 'I'm not against tourism, but I am against commercial tourism. We must go for ecotourism.'
   'We will have nothing to see and sell if the island is ruined,' he warned.
   Syeda Rezwana Hasan, executive director of Bangladesh Environmental Lawyers Association, called for recovery of land in the island from human interference and its proper maintenance.
   'The construction works must be stopped as fragile eco-system of the island cannot sustain commercial tourism,' she told New Age Sunday.
   Ecotourism can be promoted only keeping the carrying capacity of the island in consideration, she said.
   Considering its rich natural biodiversity, the government in a gazette notification declared the island an ecologically critical area on April 19, 1999.
   When asked if they got clearance to advertise for construction of duplex cottages on the island, Zafar Iqbal Chowdhury, chairman of Pubali Group and managing director of Tokyo Resort City, admitted that they did not seek clearance from the DOE before making the announcement.
   'We will obtain the certificate before staring construction of the project,' he said.
   The DOE recently served a notice to Pubali Group for violation of the Bangladesh Environment Conservation Act, 1995.
   According to the act, the court can impose maximum 10 years imprisonment or fine 10 lakh taka or both for non-compliance of a direction issued by the DOE.
   Both IUCN and BELA officials said the Department of Environment (DoE), the local authorities and the tourists are jointly responsible to protect the island.
   Asked whether the DoE had issued 'Environmental Clearance Certificates' for constructions of hotel, resorts and restaurants on the island, M Mahbubur Rahman, project manager of DOE, said they did not give permission for a single construction.
   He said local union council chairman allowed the people to carry construction materials to the island.
   The DoE official claimed that notices were served time and again to stop construction. 'But none complied with them.'
   To a question whether DOE sued anybody for unauthorised construction ignoring the law, he replied in the negative.
   'We are to go step by step,' he said.
   Moulana M Firoz, chairman of local union council, realised that he had committed mistake by giving permission to carry construction materials to the island.
   Zafar Ahmed Khan, who recently joined the DoE as its director general, told New Age that they would file cases, if necessary, to stop damage of the island. 'The issue was discussed at the conference of the deputy commissioners. The DCs will be given certain authorities, including filing of cases on behalf of the DOE, to enforce the law. We will also engage the upazila nirbahi officers too.'
   He stressed that sale of private lands on the St. Martin's Island need to be stopped.
   The dumbbell-shaped island, locally known as Narikel Jinjira, is located on the southern-most tip of Bangladesh, and separated by an 8 kilometre channel of Bay of Bengal from the mainland.
   It has about 153 varieties of fauna, 157 varieties of mangrove, 66 kinds of coral, 187 types of bivalves, 240 types of marine fish and other marine lives.

Source: newagebd

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Controlling river pollution

It is imperative that rather than having a reactive approach, we need to think of a proactive approach to provide a practical and a sustainable solution to river pollution, writes M Ashiqur Rahman


RIVER water is considered polluted when it is altered from the natural state in its physical, chemical and microbiological composition and when its suitability for any safe and beneficial use becomes questionable. The signs of physical water contamination may become obvious through bad taste, offensive odours, unchecked growth of aquatic weeds, decrease in the number of aquatic animals, floating of oil and grease, colouration of water and so on. However, more intensive laboratory testing is required to determine the chemical and microbiological water quality parameters such as pH (to measure the level of acidity or alkalinity), dissolved oxygen, biological and/or chemical oxygen demand, phosphorus and nitrogen ion concentration, dissolved solids, heavy metals, salinity, coliform bacteria count and so forth.
Generally, our rivers are being polluted by the discharge of untreated industrial effluent and urban wastewater, agrochemicals, sewage water, storm runoff, solid waste dumping, oil spillage, sedimentation and encroachment. The water quality also depends on effluent types and discharge quantity from different types of industries, types of agrochemicals used in agriculture, and seasonal water flow and dilution capability by the river system. The river Buriganga is a typical example of serious surface water pollution in our country. In the present scenario this river carries only wastewater during the months (November to April) of the dry season becoming toxic during this period. The level of pollution is so high that no aquatic species can survive in it and the situation is getting worse day by day. Test results during the dry season at eight points along the river found the level of dissolved oxygen within 0.6 to 1.8 mg/l at five points and zero at other points. The requisite level of oxygen is more than 5 mg/l for the survival of aquatic lives. In fact, the Buriganga has become a dumping ground of all kinds of solid, liquid and chemical wastes which are generated by the activities in and around the river. Studies show that up to 18,500 cubic metres of liquid wastes, 19,000 kilograms of solid wastes and 17,600 kilograms of biological oxygen demand load go into the Buriganga each day from these sources. The Bangladesh Inland Water Transport Authority sources confirmed that huge quantities of discarded polythene deposits are unearthed near Sadarghat area during dredging.
Like many other countries of the world, river pollution control in Bangladesh has been a burning issue for at least the past two decades. Moreover, abundant research has been undertaken and many recommendations have been forwarded to protect the rivers from further pollution. At the government level since the late 19th century several rules, regulations, policies and strategies have been formulated and a fairly comprehensive set of environmental laws exist to save our rivers from pollution. However, the implementation and enforcement of the policies and the regulations have so far been very ineffective, leading to poorer river water quality. In addition, in many cases the policies and strategies seem far from being practical in terms of their implementation. Though it may appear to be a nightmare to overcome this serious problem but the reality is that we need to get to the core of the problem and implement strategies to safeguard these precious natural resources for the sake of our own survival. It is imperative that rather than having a reactive approach, we need to think of a proactive approach to provide a practical and a sustainable solution to the problem.
The pollution problem of our rivers have become complex because of its multidimensional nature. There are social, economic, political and environmental dimensions to this issue which need to be addressed simultaneously while attempting a sustainable solution to the problem. It is a mammoth challenge for developing countries like Bangladesh where a speedy economic growth is requisite without compromising with the conservation of the natural environment or endangering the livelihood of a particular community such as the fishermen or the farmers.
Like many other developing countries, river pollution control in Bangladesh relies on expensive and somewhat outdated technological solutions transferred from the ‘west’. Moreover, these technologies from industrial countries are not always suitable or easily adaptable to the socio-economic and environmental conditions of developing countries. So far emphasis has been given either on treatment of pollutants through the set up of effluent treatment plants or augmentation of rivers to increase the flow through the construction of river water diversion structures. Even the relocation of the pollution causing agents may not capacitate a permanent solution to the problem unless the pollutants are controlled at their sources through adopting proactive approaches such as cleaner production, recycling and resource recovery mechanism.
Experiences in countries like the United States, Australia and China show that the proactive approaches are being implemented voluntarily by the polluters to reduce their pollutants once the ‘market-based’ mechanisms are introduced. In these systems polluters are not told how much they can pollute or what technology they must use, but their choices will have financial consequences and this will influence the choices they make. With these policies, emission constraints are not source-specific; rather they provide equal incentives to all polluters by increasing the marginal costs of pollution. Moreover, several stakeholders such as producers, consumers, users, government authorities and local community members get directly involved with this process. The importance of inclusion of all the stakeholders (both who generate and manage the pollution) to develop an effective approach for pollution control cannot be undermined.
It is obvious that to protect our rivers from further pollution we need to look beyond the ineffective conventional policies and strategies. We need alternate, innovative and integrated approaches to be implemented to overcome this problem. In this regard, provisions of monetary incentives, rewards and recognitions for the polluters who reduce their pollution may work effectively for reducing the amounts of pollutants which are being discharged into the rivers. The direct involvement of community and civil society can also play a great role for this purpose.
The rivers of Bangladesh suffer from the pollution problem mostly during the dry season (November to April) but the assimilation and the dilution capacity of most of our rivers increase dramatically during the wet season (May to October). This phenomenon of the rivers overrules the application of a uniform acceptable level of the pollutants throughout the year. This opens the possibility for using ‘non-uniform reduction’ measures for the polluters and thus offers flexibility to them in terms of reducing their harmful pollutants for the water bodies.
Another significant issue is that different polluters have different levels of capacity to reduce their pollutants. Some are better off than others to control their pollutants. This tendency opens the opportunity for the application of a tradable permit system for water pollution control. This system allows pollution to be reduced wherever it is least costly to do so and a ‘cap’ guarantees the total allowable emissions are not exceeded. For instance, the Hunter River Salinity Trading Scheme of Australia leads the world in using such economic instruments for the effective protection of waterways. This scheme involves a number of point sources of salinity in the Hunter River and the average river salinity has been halved since the scheme commenced in1996, while economic activity and employment have grown substantially. It has thus become a classic example of win-win situation for all the stakeholders who are involved with the use of the river.
Regular monitoring of river water quality (physical, chemical and biological composition) is an important aspect to control river pollution. However, this is an expensive and time consuming ongoing activity which might be difficult for any government agency like the Department of Environment alone to perform the task on a regular basis. Even the powerful agencies like the Environmental Protection Agency of the United States assign this task to the community with assistance from the local administration. In Bangladesh we may think of exploring this option to ease the monitoring activity of hundreds of rivers in our country.
We need to shift from the nightmare of river pollution management to the serenity of our beautiful rivers by any means. In summary, a suggestive list of prescription is given below to help make this issue a reality.
* An action plan with its processes has to be developed on the basis of the prospective market-based instruments.
* The method of permit allocation and lifespan of permits need to be addressed.
* An information system should be established to provide potential participants relevant information on river water pollution.
* Procedures for compliance monitoring must be identified for designing a new program.
* A package of incentives, appreciation and recognition of the industries and other polluters who do better work in reducing their pollutants should be developed.
* A system of assessing the environmental reputation of the industries should be developed to measure as criteria in financial lending process.
* A guideline has to be developed for introducing the community monitoring system.
* The concern of the local community regarding the pollution has to be formally recognised by the regulatory authority.
* A strong market pressure should be created on the polluters to shift to cleaner production technologies.
* Environmental education should become mandatory from all primary to tertiary level of educational institutes.
As we would all agree the time has come to take actions to protect our rivers from further degradation and before nature takes revenge on us. However, the prerequisite of taking any action is that we need environmentally aware and enlightened people for the purpose. Awareness about the negative consequences of our harmful activities which ultimately affect our precious natural resources including rivers can minimize the damage caused to them in many folds. That is why it is high time to stress on environmental education from the primary to the tertiary level of studies in our country because learners of today are the leaders of tomorrow.

M Ashiqur Rahman, a senior lecturer of the North South University, is currently on a study leave to pursue PhD in environmental management at the University of Sydney, Australia.

NewAgeBD

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Bangladesh PM makes river pledge

In pictures: Bangladesh flood misery

The Bangladeshi Prime Minister, Sheikh Hasina, has pledged to do her utmost to save the country's "severely degraded river systems".

She said that people must be prepared for climate change and engage in more "environmentally-friendly activities".

Bangladesh is criss-crossed by rivers and creeks which are vital for irrigation and transport purposes.

The prime minister also criticised the country's weather forecasters, ordering them to be more alert about cyclones.

Last month Cyclone Aila killed at least 200 people in Bangladesh and India and left 500,000 homeless.

'Imminent catastrophe'

In a speech to mark World Environment Day, the prime minister said it was necessary to protect the country's rivers "to save people from imminent catastrophe".

"All our rivers today have lost the free flows they had in the past due to heavy silt depositions," she said.

"But once the rivers are given back their original beds, frequent overflowing will cease, reducing the negative impact of global climate change in our region."

Sheikh Hasina said that Bangladesh's ample river systems had maintained the "environmental balance since time immemorial".

She said that rivers had been losing their water-retention capacity because of "heavy siltation and unbridled encroachment".

"We must save our rivers," she said, "even though it is going to be a huge, time consuming and challenging project. But we must do it.

"Whatever the costs be, we'll do the job."

She said that rivers could be preserved through dredging and other erosion-countering measures.

The prime minister also said that more must be done to improve the country's food security whenever there are natural disasters such as floods and cyclones.

She said that developing the capacity to store food for at least two to three years was an important first step.

BBC

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Bangladesh launches campaign to save rivers

Dhaka, June 2 (IANS) Bangladesh’s lawmakers, media and industry leaders have launched a campaign to ’save’ the rivers around the national capital by evicting encroachers and improving the environment.

Called “Save rivers, Save Dhaka” campaign, the programme was launched Monday by parliament Speaker Abdul Hamid with the participation of The Daily Star newspaper and ‘i’TV channel.

Agriculture Minister Motia Choudhury assured government support. He and Speaker Abdul Hamid resolved to come up with a law that would end encroachment.

The Daily Star has undertaken a mission to focus on the dying rivers Buriganga, Turag, Balu and Shitalakhya that encircle Dhaka, the 400-year-old capital.

The newspaper has been campaigning to end the encroachment. The banks have been encroached and even ’sold’.

Bangladesh is a riverine country with numerous river systems, the larger ones being Padma, Meghna and Brahmaputra.

Poor river management, silting, absence of dredging and the rising population have reduced the country’s riverbed from 5,000 km to 3,600 km, according to a recent report of the Bangladesh Inland Water Transport Authority (BIWTA).

The government is taking measures to carry out dredging of rivers since shipping activity at its river ports, among them Chittagong, Mangla and Khulna has been badly hit.

“We must save our rivers, which have been seriously polluted and partly grabbed. Influential people whoever they are cannot be any barrier to the justified demands of common people,” said Hamid.

Abdur Razzak, chairman of the standing committee on the Ministry of Water Resources, said it is not the absence of laws, but the negligence in their application that has almost killed the rivers surrounding the capital.

News Link
Campaign on Daily Star link

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Can river silt save Bangladesh?

By Katherine Harmon in 60-Second Science Blog

Bangladeshis are already feeling the effects of climate change, especially those living on the low-lying river delta near the mouths of the Ganges. Frequent floods and stronger storms have been inundating the area with more water than many local rice growers can cope with, driving thousands to seek work in overcrowded cities.

But some rice and shrimp farmers are holding out hope that the very waters that have oft plagued them might hold the solution – in suspension. River silt, carried down in suspension from the ancient Himalayan mountains hundreds of miles away, might be able to build up land elevation to save the area's livelihoods and homes, The New York Times reports today.

In Bangladesh, deposited sediment has been slowly filling the marshy delta outward into the Bay of Bengal for the past few decades, but engineers are examining ways that it might be used to build the land up rather than out, according to the Times. The goal is to allow water to flood some especially low areas and let it out – through dams and channels – slowly. As the murky water slows, sediment drops out and filters to the bottom, leaving a new bed of silt after the water recedes. Residents in Beel Bhaina discovered this phenomenon after releasing stagnant floodwaters through an embankment; to the surprise of many, the Times reports, three feet (or more) of silt had been deposited, boosting land higher above sea level.

"Usually people are trying to get rid of the sediment," says John Gray, a hydrologist at the U.S. Geological Survey. "But here, people are using it as a resource." But Gray is skeptical that it's a viable answer. One major obstacle, he tells ScientificAmerican.com, is that it would require yet more flooding to achieve decent amount of sediment buildup.

"If they're really talking about building land," he says, "the experimental patches are a good start, but they're really going to have to start working on a much large scale."

Gray praises the effort, noting that it's "laudable" to try to "take something that most consider a nuisance" and turn it into an asset. But he warns that if massive quantities of water are diverted, unexpected consequences, such changes in river behavior, are likely to occur. Gray isn't even sure that it's a surefire stopgap against rising sea levels, which are predicted to top three feet by the end of this century. "The timing of accretion [deposit of the sediment] and the timing of the climate change, he says, "might not be compatible."

Centuries of engineering have gone into clearing river channels and mouths of silt to make them more navigable and easier to control. But as rivers have been carved out and dammed for easier navigation, sediment rushes out to sea, rather than getting deposited in the delta. This means many deltas worldwide, including the Mississippi River Delta in Louisiana, the Nile Delta in Egypt, the Yangtze Delta in China and others, are disappearing, leaving costal towns and cities more vulnerable to increasingly strong storm surges. If Bangladesh succeeds in bracing its floodplains this way, it might be a new safeguard for costal areas across the globe. But the proof will be in the (rice) pudding.

Image of Bangladeshi farmers harvesting rice in flooded fields courtesty of the International Rice Research Institute via Flickr

Scientific American

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Laws there, loopholes too

That’s not strawberry ice cream but pure toxic dyes. Untreated wastes from a single dying factory along the river Shitalakkhya create this layer of deadly froth. Hundreds of such factories have turned the river into a lifeless water body. Photo: Amran Hossain

Pinaki Roy

Not a lack of laws, but a lack of proper implementation of the existing laws is the reason for the dire condition of the country's rivers, canals, and other water bodies.

Over the years, successive governments failed to implement relevant laws for conserving the rivers and other natural water resources, resulting in rampant encroachment on those, and in their wholesale pollution by industries, while the Environment Conservation Act 1995 stayed in books.

The definition of a river is also sketchy in the laws. Generally Bangladesh Inland Water Transport Authority (BIWTA) is in charge of the rivers and riverbanks where there are river routes, under the Bengal Port Act 1908.

But if there is no river route then it becomes hard to figure out who has the authority over the rivers, as many authorities including land offices, district administrations, local governments, the water resources ministry, and the Water Development Board -- all have some kind of role or control over the rivers and riverbanks according to relevant laws.

At the moment there is no unified law that clearly defines what is a river, a riverbank, or an off shore, and lawful use of river water is also not well delineated. To save the rivers from encroachment and pollution, a unified law and a dedicated authority that will implement the law as the regulatory body, are imperative.

The first law regarding water bodies was enacted during the British colonial age in 1864 to control and collect tolls from river routes.

The Bengal Canal Act 1864 is the mother of all laws about rivers, canals and other water bodies. Beginning from that act up to the recent Open Space and Water Body Conservation Act 2000, all laws restrict changing of the characteristics of water bodies including rivers and riverbanks.

The Bengal canal act says, "It shall be lawful for the government from time to time to authorise any person to make and open any navigable channel, or to clear and deepen any navigable channel, and to stop any watercourse, make any tracking path, or do any other act necessary for the making or improvement of any such channel."

Under that law the government is authorised to 'take possession for a public purpose of any land that may be necessary for the execution of any of the above mentioned works, under the provisions of the act'.

It goes on, "Any person who shall wilfully cause ........ any obstruction to any line of navigation or any damage to the banks or works of such line of navigation, or who shall wilfully omit to remove such obstruction after being lawfully required to do so, shall be punished on conviction before a magistrate with simple imprisonment which may be extended to one month or with fine which may extend to Tk 50, or with both."

The recent significant law to protect natural water resources is titled, 'Wetland and Open Space Conservation Act, 2000', which extended the fine up to Tk 50,000, and the imprisonment up to five years, or both. But successive governments have not been very sincere to implement the law.

On the other hand, the laws specify what punishments the judiciary may mete out to the violators, but it does not direct the government to recover the original characteristics of water bodies if someone fills them up.

So once someone changes the characteristics of a river, canal, or any other water body -- it does not get back its old shape.

Other relevant laws, rules, and regulations in Bangladesh are -- the Bengal Irrigation Act 1876, East Bengal Embankment and Drainage Act 1952, Inland Water Transport Authorities Ordinance 1958, East Pakistan Irrigation (Imposition of Water Rate) Ordinance 1963, Bangladesh Water and Power Development Boards Order 1972 (President order No 59 of 1972), Bangladesh Water Rate Ordinance 1983, Land Reforms Ordinance 1984, Ground Water Management Ordinance 1985, Water Resources Planning Act 1992, Water Supply and Sewerage Authority Act 1996, National Water policy 1999, and the Act No 27 of 2000.

Daily Star

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Death of rivers will lead to death of our cities

Slowly gobbling up the river. Sand traders of the booming construction sector fill up the river Turag, wiping out the river's foreshore, shore, and the channel. There is no authority to check these river killers. Photo: Anisur Rahman

By Mahfuz Anam

It would not be an exaggeration to state that encroachment and pollution of the five rivers surrounding the capital now threaten the very existence of Dhaka city, and with it jeopardise the future of our economy. We would like to draw a direct link between the country's growth prospect and livability of the capital city, which in its turn is directly linked with the existence of the rivers that surround it. Dhaka already has a population that makes its one of the most crowded metropolis in the world. In not to distant a future it will become one of the biggest mega-cities in the world. Fresh water supply will be a crucial issue for such a city and failing to provide it will lead to intense civic unrest and related social instability. No investment, both domestic and foreign, is likely to occur in cities or areas where fresh water supply cannot be guaranteed.

Not only of Dhaka city, but rivers around the country are being filled up or being encroached upon in a manner that is threatening the very existence of human habitation. Very soon, the land grabbers will have gobbled up most of the rivers leaving a barren country greatly increasing the impact of flooding in the wet season and increasing the possibility of desertification of specific areas during the dry season.

Hidden behind the issue of saving our rivers is the concern of supply of fresh water for drinking, cooking and normal livelihood needs that relate to public health issues. According to reports, 80 percent people suffer from jaundice, skin diseases or diarrhoea in the watershed areas.

As rivers around Dhaka got polluted we became more and more dependent on ground water as a source of drinking water. It is reported that presently 86 percent of WASA's drinking water comes from ground water. Due to widespread urbanisation the replenishment of the ground water is not occurring as before as a result of which the ground water level is falling between 1-3 metres every year.

It is our view that the destruction of rivers in Bangladesh, especially those surrounding Dhaka city, has reached a stage so as to pose a threat to our nation's future and as such should be treated a national security concern.

Now is the time for all of us, the public in general, the government, political parties, professional bodies and the civil society to work together to save our rivers, and thus save ourselves.

Daily Star

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What lies beneath

10 ft layer of polythene under Buriganga

Morshed Ali Khan

A ten-feet layer of discarded polythene bags, plastics, coconut shells, and heavy sludge created by millions of tons of biodegradable waste from kitchen markets now cover the bed of the river Buriganga.

The highest concentration of these deadly wastes have settled on the bed of the river near Sadarghat launch terminal in the capital, one of the busiest river ports in South-East Asia, according to Bangladesh Inland Water Transport Authority (BIWTA) sources.

One of the main sources of this huge amount of polythene on the riverbed is Dhaka City Corporation's (DCC) conservancy department.

Along Shaheed Nagar, Kamrangir Char, Showari Ghat, Waiz Ghat, and Shyam Bazar -- DCC conservancy workers empty their bins of household rubbish into the river everyday. Household rubbish contains a large number of polythene bags, which are too dirty for the tokais (street urchins) to sort out for sales for recycling.

DCC conservancy department's second-in-command, Dewan Shah Alam, admitted that such irregularities are taking place along the river Buriganga, but added that most of the dumping is done by private household garbage collectors, not the DCC trucks.

"We have strict instructions for all our staff involved in garbage disposal, not to dump waste anywhere other that the designated site at Amin Bazar," Shah Alam said.

BIWTA sources said the situation in the river is almost out of their hand with limited resources and also due to a lack of proper directions. They said they do not have adequate manpower to stop the dumping of rubbish into the river, which takes place all along the flood protection embankment. There are instances when DCC conservancy workers 'signed deals' with river grabbers, and dumped truck loads of household rubbish into the river. Such dumping usually takes place so early in the morning that officials, who should be monitoring, are hardly awake let alone being on the spot.

"I can show you, between Mohammadpur and Postagola more than 50 sites where DCC is dumping rubbish," said a BIWTA official requesting anonymity.

On the slope of the flood protection embankment at Kamrangir Char, dozens of female workers can be regularly found washing and drying huge polythene sheets. They said they buy those sheets from business establishments in Nawabpur and Mitford areas, from garment factories, and from the tokais.

"After buying these dirty sheets we wash and dry them on the embankment and carefully pack them for reselling by weight to buyers, who pay us good prices. Why should we discard them into the river, recycling is our livelihood," said Moina Begum, when asked how so many polythene bags found their way to the riverbed.

Moina's co-worker Hafiza Khatun pointed her finger at a dumping site on the slope of the embankment, and said most of the small polythene in household rubbish piles end up into the river because those cannot be sorted out easily.

On one Friday afternoon, Sadarghat Launch Terminal area was a chaotic crossroad with thousands of passengers, coolies, traders, squatters, and beggars milling around. On the shore between the concrete terminal and the jetty -- human excreta, piles of coconut shells, polythene bags, and an array of rubbish were lying around.

A dozen launches were anchored at the jetty. Vendors selling coconuts, lychees, bombay-mix, puffed rice, bread, and fruits were using the river as a dumping ground.

"The accumulation of polythene and other wastes is so deep and solid that it might not be possible to remove the wastes with a dredger, we might have to do it manually," said an official of BIWTA.

The government banned production, marketing, and use of polythene bags in 2002. An offender under the law may be sentenced to ten years of imprisonment and fined Tk 10 lakh.

Daily Star

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Death of a lifeline

Thus die the rivers. Trimohoni, off the river Balu, on the eastern fringe of the capital bears the unbearable testimony of pollution originating mainly from Dhaka Wasa's sewerage system that dumps untreated wastes in the network of canals connected to the river. PHOTO: SK Enamul Haq Inam Ahmed and Morshed Ali Khan

The kingfisher was sitting lonely in the gathering dusk on a dead branch sticking out of tar black water. Our handkerchiefs were proving too inadequate to keep the stench out of our nostrils. With each stroke of the oar, a thick liquid similar to burnt lube oil splashed up. The sound of the oar was blunt and heavy, like hitting mud with a stick.

We were surprised at the kingfisher -- the first sighting of any bird that depends on water for survival. It means there must be fish too in this muck that we still call a river -- Buriganga. Our hope evaporated soon as the kingfisher dived and picked up an insect, looking like the ones you find in your septic tank. When fish is gone, sewage insects are the only feed.

For the last three hours we have been sailing through a river that resembles nothing but pure muck. From Bosila Ghat near the under-construction Third Buriganga Bridge up to as far as you may go towards Munshiganj, the river is just a flowing black sheet of sewage. The stench only increased when the propeller of passing barges whipped up the 'water'. The Buriganga river today is the most stunning monument to an environmental disaster where no vertebrate life form survives. It is a river without fish and water.

One of the main sources of this highly toxic sludge is just on the other side of the river at Hazaribagh of the capital. From there, nearly 250 large leather industries and several hundred small ones have been dumping untreated chemical-mixed water into the river. Every day they pump a staggering 22,000 cubic metres of poison into the Buriganga. According to a World Health Organization (WHO) bulletin, every day these units also dump ten tons of solid waste into the river. Efforts to relocate them to a modern zone in Savar, equipped with effluent treatment plants (ETP), has not worked out in years, as neither the industry owners nor the government want to pay for the relocation cost. Nobody has ever calculated how much these industries contribute to the economy, and how much they destroy.

Polluters vs fishermen
Experts believe Hazaribagh tanneries alone inflict the most severe blow to the air, land, and water in the city. The air within a ten-kilometre radius of the Hazaribagh tanneries is so foul and toxic that thousands of people suffer from various respiratory and skin diseases. Residents in Hazaribagh, Lalbagh, Azimpur, Rayer Bazar, Dhanmondi, and Beri Bandh areas complain of 'corrosion' in their tin roofs and other metal household objects. Housewives even complain of having their ornaments corroded due to the toxicity in the air.

While our industries proudly boast of foreign exchange earnings, no matter how much pollution they are causing by refusing to install ETPs, thousands of traditional fishermen who have been tossed out of the rivers and canals, think if the rivers and canals around the city were clean, they could also bring in a huge amount of foreign currencies, producing and exporting good quality fishes.

Lakhan Rajbangshi from Zaillapara, Basila where a fishermen community of 50 families have lived for over 100 years, said the Buriganga alone could produce enough fish to feed the city population.

"We are spending crores of taka in foreign currencies to import fish from Myanmar, India, and Thailand, but I can assure you, if you return us our river with flow of good quality water we would start exporting river produce within a year," Lakhan, who is now unemployed and miserable, said.

Three days before, we had gone to the Shitalakkhya river near Kanchpur Bridge and saw the unbelievable sight of a swath of 'strawberry shake' tone of purple dye pouring into the river through a drain pipe, frothing and spreading across the river, poisoning everything as it worked through.

At Demra, we again oared through a filthy liquid that is the Shitalakkhya. A small channel that comes parallel to the main river was disgorging effluent at full speed from nearby industries. The refuse then mix with the Shitalakkhya water and ripple down in bubbles poisoning fishes to death, and seeping into the underground aquifer, polluting that as well.

A more horrifying story emerges about the possible contamination of the city's groundwater, as a study jointly done by the World Bank and the Institute of Water Modelling (IWM) warns that the groundwater, on which over 80 percent of the city's population depend, is fast getting contaminated. The contamination mainly occurs at river beds, and at industrial effluent dumping points from where aquifers get recharged. While the Hazaribagh groundwater is classified as the most affected, with time the groundwater pollution is creeping towards other parts of the city too.

Sorry tale of Trimohoni
Residents of Nandigram near the eastern fringe of the city should have been the luckiest people on earth because three rivers -- the Narai, Devdholai, and the Balu -- meet there to form the Trimohoni and pass through the village. Instead local residents consider themselves cursed and doomed. Millions of cubic metres of sewage, and industrial and household wastes generated in the capital's Tejgaon, Dhanmondi, Gulshan, Rajabazar, Maghbazar, Motijheel, Bashabo, and many other densely populated areas fall into the Trimohoni. We, living in plush apartments in the capital, are the source of their misery, as each time we flush our toilets the Trimohoni residents receive it in their rivers through Dhaka Water and Sewerage Authority's (Wasa) outlets at Rampura and Motijheel through Begunbari canal. The Nandigram people are now surrounded by rivers of excreta, where the rivers flow with everything but water.

In Trimohoni area we stood at the doorway of a hut in the smelly village watching a sick child curled up in a bed. Her breaths were shallow. For two days, she had been having a bout of diarrhoea. Her mother had repeatedly warned her not to go near the poisoned river. Still she had taken a dip in the river in a forgetful moment. And now she was in a terrible state.

Pitch black effluents from Tejgaon Industrial Area containing heavy metals such as lead, cadmium, and magnesium are causing serious pollution in Begunbari and Narai canals, leading to pollution of the Balu river. Interestingly, the same river is one of the major sources of water for Saidabad Water Treatment Plant for Dhaka city in the downstream, where it joins the Shitalakkhya. Experts already warned that the river water around the metropolis is so contaminated that it is 'beyond treatment'. Our lack of foresight in planning is well established in the setting up of the water treatment plant at Saidabad before thinking about installing ETPs in our highly polluting industrial units. There is no data to indicate contamination of the supplied water, but frequent outbreaks of waterborne diseases surely suggest an alarming level of contamination in our tap water.

Turag, Buriganga, Shitalakkhya
The Turag river is another bead in the string of the dying rivers that surround the capital. Only a trickle of black liquid represents the river that serves as the lifeline of the southern fringe of the capital. Not only pollution, currently there are more earth filling projects in the Turag than in any other river of the city.

The existence of all these rivers has been pushed to a further edge by a free-for-all encroachment galore. We sailed for miles up and down the four rivers and saw the chilling evidence of how criminals and renowned business enterprises are taking their claims in the rivers at will. And there is no one to stop them; no vigil to identify them.

As we sailed through the Buriganga, we spotted a vast swath of the river fenced off with bamboo poles near Kholamora. Dredgers were moored there that roared sand-filled water inside the fenced area. The river was being filled up, slowly. Already about 500 feet of the river has been turned into land where stands a concrete structure. Another 500 feet or so are in the process of being filled. We stood there and searched for the original river boundary, and finally located the embankment about half a kilometre away that once marked the beginning of the river. That half a kilometre is already gone to meet the appetite of the encroachers. Another half a mile will be gone, in who knows how many months, or days.

A few hundred yards down, we found a few hundred acres of land jutting out into the river in the name of 'Titanic Housing', the same crook is filling up more sections of the river with earth and nobody to stop it. A building is standing right in the middle of the river. Fresh signs of earth-filling of the river are everywhere. It is an awe-striking sight. How effortlessly they are gobbling up the river, making it slimmer and slimmer until nothing will be left.

The same is the case along the Turag and Shitalakkhya. Universities and housing projects have sprung up in the rivers. Sand traders have expanded into the waters, fencing off their own stakes. Industries have found land. It is an unfettered bonanza of river grabbing. You grab it and cook up some documents. Pay tax for the land, which once was part of a river, by some strange manipulation of the system. And it is all yours on the cheap.

Dry canals
The story does not stop here. Just when you think things cannot get any worse, they do. We found canal after canal that either fed into the river systems of Dhaka or fed from them, are choked and dead now. It is mayhem of an unprecedented scale. Even whole river systems have been rendered dry.

Standing on 'a private road' to a brick kiln at Waaspur we witnessed what havoc could be wreaked by a single person. The brick kiln owner built the road chocking the passage for one of the most widely used canals, Atir Khal. As far as the eyes can see, the canal is just a dry gulch. For over 50 years, Atir Khal that winds its way through dozens of important trading centres in Keraniganj and Savar areas, has served millions of farmers and commuters. Today, it could at best be a grazing ground for cattle.

Dhaka by any measure is supposed to be an ideal location for human settlement -- a very few cities have four rivers encircling them. It is supposed to have constant sources of clean surface water supply, a fantastic navigability around the city, which is a source of tourism, and of entertainment for its residents -- all centring the rivers. Because of all these features, the Mughals had chosen it as their capital in Bengal.

But today, the residents of the city have almost forgotten the rivers. In their daily life bound to the traffic packed streets, they do not feel the existence of the Buriganga, Shitalakkhya, Turag, and the Balu. We have let them flow towards extinction.

But the Dhaka residents are already paying for that indifference. Groundwater extraction for supplying household water is dragging down the groundwater table by about 9 feet every year. A big underground void poses the risk that the city might collapse into the pit. It is high time we wake up.

Daily Star

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Bay of Bengal 03

South patches located at 91.30ºE to 92.10ºE and 20.55ºS to 21.52ºS, having a total area of 3,662 sq km. Depth ranging from 10m to 100m, but 90% of the total area is less than 40m deep. Bottom sediment is sandy or slightly muddy sand. Nearest distance of the ground from Chittagong and Cox's Bazar is 40 km and 10 km respectively. Salinity in surface water ranges from 26% to 32% and 30% to 35% in bottom water. Water temperature varies between 20 and 28ºC.

South of south patches located at 91.30ºE to 92.20ºE and 20.15ºS 20.50ºS, having an area of 2,538 sq km. The nearest boundary of this area is 5 km from Teknaf. Depth ranges from 10m to 100m. Within this ground 75% of the area is more than 40m deep. Bottom is sandy or muddy sand. Surface salinity ranges from 18% to 34% and bottom water salinity from 28% to 38%. Water temperature ranges between 22ºC and 30ºC.

Middle ground located at 90.20ºE to 91.30ºE and 20.25ºS to 21.20ºS, having a total area of about 4,600 sq km. The nearest distance from Cox's Bazar is about 65 km. The depth of 70% of the total area is more than 40m. Bottom sediment is soft mud or muddy sand. Surface salinity ranges from 22% to 34% and bottom salinity 28% to 35%. Water temperature is between 26ºC and 28ºC.

Swatch of no Ground located at 89.35ºE to 90.10ºE and 20.55ºS to 21.55ºS, about 30 km away from Dublarchar and 40 km from Sunarchar. Total area is about 3,800 sq km, of which 70% is more than 40m deep. Overall depth of the area ranges from 10m to 100m. Bottom sediment consists of muddy sand. Surface salinity is 28% to 34%, while the bottom salinity is 30% to 35%. Water temperature falls within 24ºC to 30ºC.

All these fishing grounds are potential reserves for fish and shrimp. Most of the known commercial species of shrimps and fishes are harvested from these areas by trawlers or mechanized fishing boats. Commercially important shrimp and fish species include tiger shrimp, karuma shrimp, cat fish, Bombay duck, snapper, flounder, Indian salmon, crocker, seabream, jawfish, mullet, pomfret, ribbon fish, anchovy, hilsa, oil sardine, tuna, mackerel and skipjack. [Hossain Zamal]

Pollution marine environment of Bangladesh is directly or indirectly becoming polluted due to addition of so many polluting agents. To protect water pollution and control of mine drainage, large scale drilling and production of natural gas from the Sangu offshore gasfield, discovery of Kutubdia offshore gasfield and exploration of beach sand placer deposits from the offshore islands of Chittagong and Cox's Bazar districts must follow standard regulations both from mine safety and environmental protection point of view. Sangu gasfield is located about 50 km southwest of Chittagong City and stands at a depth of 10m water in the Bay of Bengal. Kutubdia gasfield is about 92 km southwest of chittagong port.

The coastal environment of Bangladesh is contaminated by oil tanker traffic, harbour operations and effluents discharged from petroleum processing. sewage disposal by the karnafuli and pasur rivers into the Bay of Bengal contains higher concentration of Biochemical Oxygen Demand (BOD) and foecal coliform. Moreover, the coastal environment of Bangladesh has also been affected by industrial effluents, agricultural residues, some other human activities like deforestation and irrational expansion of coastal shrimp farming, etc resulting in ecological degradation. Overfishing and dumping of discarded fishes in these areas are becoming a threat to the resourcefulness of the fishing grounds. Only proper management of the existing grounds and finding of new fishing grounds can ensure the continuous harvest of fisheries resources. [Sifatul Quader Chowdhury]
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Bay of Bengal 02

Geographical characteristics Hydrological conditions surface hydrology of the Bay of Bengal is basically determined by the monsoon winds and to some extent by the hydrological characteristics of the open part of the Indian Ocean. Fresh water from the rivers largely influences the coastal northern part of the Bay. The rivers of Bangladesh discharge the vast amount of 1,222 million cubic metres of fresh water (excluding evaporation, deep percolation losses and evapotranspiration) into the Bay. The temperature, salinity and density of the water of the southern part of the Bay of Bengal is, almost the same as in the open part of the ocean. In the coastal region of the Bay and in the northeastern part of the Andaman Sea where a significant influence of river water is present, the temperature and salinity are seen to be different from the open part of the Bay. The waves and ripples entering from the southern part of the Bay provide the energy for mixing the water and consequently bring uniformity in its chemical and physical properties. Tidal action is also very great in the shallow coastal zones.

Temperature the mean annual temperature of the surface water is about 28°C. The maximum temperature is observed in May (30°C) and the minimum (25°C) in January-February. But the annual variation in temperature is not great, about 2°C in the south and 5°C in the north.

Salinity the surface salinity in the open part of the Bay oscillates from 32% to 34.5% (parts per thousand, ie grams per kilogram of sea water) and in the coastal region varies from 10% to 25%. But at the river mouths, the surface salinity decreases to 5% or even less. The coastal water is significantly diluted throughout the year, although the river water is greatly reduced during winter. Along the coast of the Ganges-Brahmaputra Delta, salinity decreases to 1% during summer and increases up to 15% to 20% in winter. Salinity gradually increases from the coast towards the open part of the Bay. The surface salinity at the mouths of some large rivers like the ganges, brahmaputra, Irrawaddy and some Indian rivers like the Krishna, Godavari, Cauvery and Mahanadi varies widely from one day to another, especially in summer. Salinity of water also changes vertically. The influence of the fresh water is experienced up to depths of 200-300m. From the surface, the salinity gradually increases downward and at about 200-300m it reaches 35% and at about 500m the salinity is more than 35.10%, but at 1,000m it decreases slightly and attains 34.95%. With further increase of depth salinity decreases and at 4,500m it is close to 34.7%.

Tides the semi-diurnal type of tides, ie two high and two low tides during the period of 24 hours and 52 minutes. The highest tide is seen where the influence of bottom relief and the configuration of the coast are prominent, ie in shallow water and in the Bay and estuary. The average height of tidal waves at the coast of Sri Lanka is 0.7m and in the deltaic coast of the Ganges it is 4.71m. In the Bay of Bengal tidal currents specially develop in the mouths of the rivers, like the Hooghly and the meghna.

Colour and water transparency the colour of the water in the open part of the Bay is dark blue which gradually changes to light blue to greenish towards the coast. Transparency is great, 40-50m in some places. In the central part of the Bay of Bengal, the anticyclone circulation is generated and in the centre of this lies the zone of convergence. This region is characterised as a rule by high transparency of water. Regions of low transparency and turbid water are available in the limited area of the pre-deltaic part of the rivers Ganges and Brahmaputra.

Sea Level due to the influence of water density and wind the seasonal changes of the sea level in the Bay are remarkable and one of the highest in the world. The range at Khidirpur is 166 cm, at Kolkata 130 cm and at Chittagong 118 cm. But towards the southwestern coast at Madras and Vishakhapatnam [Vishakhapatnam] the range is small compared to the northern and northeastern coasts of the Bay. The lowest variation of sea level at the southeastern coast of India is due to its geographical location at the edge of a comparatively deep sea.

Ocean Current surface circulation is found to be generally clockwise from January to July and counter-clockwise from August to December, in accordance with the reversible monsoon wind systems. The flow is not constant and depends on the strength and duration of the winds. The effects of a strong wind blowing for a few consecutive days are reflected in the rate of flow. Currents to the northeast generally persist longer and flow at greater speed because of the stronger southwest monsoons. An important vertical circulation in the Bay of Bengal is up-welling. In this process, sub-surface water is brought toward the surface, and conversely a downward displacement is called down-welling or sinking.

Up-welling and down-welling are seasonal, being created by monsoon winds that blow from the southwest during the summer, then reverse direction and come from the northeast during the winter. The persistence of the monsoon, especially from the southwest and the orientation of the coasts cause up-welling to occur along most of the east coast of India. That is why in the east coast of India the up-welling takes place in summer and down welling in winter, and in the eastern part of the Bay of Bengal and in the Myanmar coast, up-welling occurs in winter and the down-welling in summer. However, the duration and intensity of vertical movement of water on both sides of the Bay of Bengal is not as great as on the Somali or North and South American coasts. But it does have a profound effect on the food economy of the sea through its influence on chemical properties and biological populations. [Subash Chandra Das]

Biological characteristics the occurrence of marine species - both plants and animals - has largely been controlled by the physico-chemical properties of ocean water. Water discharges from the surrounding river catchments carry huge influx of sediments full of nutrients to the Bay, particularly along the near shore region. This has turned the Bay into a fertile marine fishing ground of the region. The near-shore up-welling zone not only has a high yield of nutrients, but also is a high primary production area for the phytoplankton and related zooplankton zones.

Fishing the hydrological conditions of the Bay of Bengal is favourable for a variety of shrimps and fishes. Although fishes remain scattered in the Bay in some places they get concentrated and constitute important fishing grounds. Four fishing grounds have been identified so far. They are south patches, south of south patches, middle ground and Swatch of no Ground.

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Bay of Bengal 01

Bay of Bengal a northern extended arm of the indian ocean, is located between latitudes 5°N and 22°N and longitudes 80°E and 100°E. It is bounded in the west by the east coasts of Sri Lanka and India, on the north by the deltaic region of the Ganges-Brahmaputra-Meghna river system, and on the east by the Myanmar peninsula extended up to the Andaman-Nicobar ridges. The southern boundary of the Bay is approximately along the line drawn from Dondra Head in the south of Sri Lanka to the north tip of Sumatra. The Bay occupies an area of about 2.2 million sq km and the average depth is 2,600m with a maximum depth of 5,258m. Bangladesh is situated at the head of the Bay of Bengal.

Bottom topography characterised by a broad U-shaped basin with its south opening to the Indian Ocean. A thick uniform abyssal plain occupies almost the entire Bay of Bengal gently sloping southward at an angle of 8°-10°. In many places underwater valleys dissect this plain mass.

Continental Shelf the width of the continental shelf off the coast of Bangladesh varies considerably. It is less than 100 km off the south coast between Hiron Point and the swatch of no ground and more than 250 km off the coast of cox's bazar. sediments are fine seaward and westward with the thickest accumulation of mud near the submarine canyon, the Swatch of no Ground. The shallow part (less than 20m) of the continental shelf off the coast of chittagong and teknaf is covered by sand and the intertidal areas show well-developed sandy beaches. The shallower part of southern continental shelf off the coast of the sundarbans, patuakhali and noakhali is covered by silt and clay; and extensive muddy tidal flats are developed along the shoreline. Some of the shoals and sand ridges present on this part of the continental shelf show an elongation pattern pointed towards the Swatch of no Ground.

Swatch of no Ground also known as Ganga Trough. Swatch of no Ground has a comparatively flat floor 5 to 7 km wide and walls of about 12° inclination. At the edge of the shelf, depths in the trough are about 1,200m. The Swatch of no Ground has a seaward continuation for almost 2,000 km down the Bay of Bengal in the form of fan valleys with levees. The sandbars and ridges near the mouth of the ganges-brahmaputra delta pointing toward the Swatch of no Ground showing sediments are tunnelled through this trough into the deeper part of the Bay of Bengal. The Swatch of no Ground is feeding the Bengal Deep Sea Fan by turbidity currents.

Sunda Trench also known as Java Trench. Running parallel along the west side of the arc of the Nicobar and Andaman islands it is extended northward up to 10°N into the Bay and joins the eastern limit of the Himalayan range. It originated tectonically at the junction of the Indian and Myanmar plates.

Ninety East Ridge major feature of the Indian Ocean which runs in a north-south direction approximately along the longitude 90°E. It lies at the immediate outboard of the Sunda Trench between the Bengal Fan and the Nicobar Fan. The Ninety East Ridge has existed since early in the formation of the Bay of Bengal. The ridge represents the trace of a hot spot formed during the northward flight of India and its associated oceanic lithosphere of the Bay of Bengal.

Eighty-five Ridge a ridge along 85°E longitude. More than 5 km thick sediments have been deposited on either sides of the ridge. The main turbidity current channel of the subaerial drainage pattern lies immediately east of the buried ridge.

Bengal Deep Sea Fan the world's largest submarine fan, also known as Bengal Fan. Together with its eastern lobe, the Nicobar fan, it covers an area of 3106 sq km. It is 2,800 to 3,000 km long, 830 to 1,430 km wide and more than 16 km thick beneath the northern Bay of Bengal. Sediments are tunnelled to the fan via a delta-front trough, the Swatch of no Ground. It can be divided into three parts: upper fan, middle fan and lower fan. Rapid terrigenous sedimentation on an incipient Bengal fan began in the Eocene age (58 to 37 million years ago) as a response to the first intraplate collision and continued to the present, building the world's largest submarine fan. [Mahmood Alam]

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Swatch of no Ground

Swatch of no Ground a trough-shaped marine valley or canyon that cross the continental shelf diagonally and situated on the south of the Ganges-Brahmaputra delta. It is also known as Ganga Trough. Similar delta-front troughs are found off the mouth of the Indus River known as Indus Trough and off the West Side of the Mississipi delta, the Mississipi Trough. Swatch of no Ground has a comparatively flat floor 5 to 7 km wide and walls of about 12° inclination. At the edge of the shelf, depths in the trough are about 1,200m. It has been suggested that the Swatch of no Ground has a seaward continuation for almost 2,000 km down the bay of bengal in the form of fan valleys with levees. The sandbars and ridges near the mouth of the Ganga-Brahmaputra delta pointing toward the Swatch of no Ground indicate that sediments are tunnelled through this trough into the deeper part of the Bay of Bengal. Slumps, growth faults and evidence of mass movement coupled with high sedimentation rates near the Swatch of no Ground provide dramatic evidence that modern sediment is being channelled off-shelf through the submarine canyon to the Bengal Fan. Studies on the bengal deep sea fan suggest that Swatch of no Ground is feeding the Bengal Fan by turbidity currents. Most of the sediment of the Bengal Deep Sea Fan has been derived from the confluent of ganges and brahmaputra rivers, which drain the south and north slopes of the Himalayan, respectively. Under the present condition perhaps low-density turbidity currents and sand cascading are perhaps dominating process of sediment transport from the shelf to the deep sea through the Swatch of no Ground.

There is some controversy regarding the origin of Swatch of no Ground. However, it is generally believed that during the Pleistocene (2-0.1million years ago) lower sea level, Ganga-Brahmaputra River was discharging its sediment load directly on the shelf edge. Combination effect of river flow and turbidity currents generated at the shelf break and upper slope was responsible for the formation of the Swatch of no Ground. Evidence from the Bengal Deep-Sea Fan also tends to support this view. It has been observed that turbidity currents during the Pleistocene lower sea level dominated sedimentation on the Bengal Deep-Sea Fan and the sediments were distributed on the fan by a system submarine channel originating from the Swatch of no Ground. [Mahmood Alam]

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Global Warming: The Fate of Bangladesh- 02

4. Bangladesh's Noah

In the middle of Bangladesh, in the middle of my road trip, I tracked down Abul Hasanat Mohammed Rezwan. He was sitting under a parasol by the banks of a river, scribbling frenetically into his notebook.

"The catastrophe in Bangladesh has begun," he said. "The warnings [by the IPCC] are unfolding much faster than anyone anticipated." Until a few years ago, Rezwan was an architect, designing buildings for rich people – "but I thought, is this what I want to do while my country drowns? Create buildings that will be under water soon anyway?"

He considered dedicating his life to building schools and hospitals, "but then I realised they would be under water soon as well. I was hopeless. But then I thought of boats!"

He has turned himself into Bangladesh's Noah, urging his people to move on to boats as the Great Flood comes. Rezwan built a charity – Shidhulai Swanirvar Sangstha, which means self-reliance – that is building the only schools and hospitals and homes that can last now: ones that float.

We clambered on to his first school-boat, which is moored in Singra. In this area there is no electricity, no sewage system, and no state. The residents live the short lives of pre-modern people. But now, suddenly, they have a fleet of these boats, stocked with medicines and lined with books on everything from Shakespeare to accountancy to climatology. Nestling between them, there are six internet terminals with broadband access.

The boat began to float down the Curnai River, gathering scores of beaming kids as it went. Fatima Jahan, an unveiled 18-year-old girl dressed in bright red, arrived to go online. She was desperate to know the cricket scores. At every muddy village-stop, the boat inhaled more children, and I talked to the mothers who were beating their washing dry by the river. "I never went to school, and I never saw a doctor in my life. Now my children can do both!" a thin woman with a shimmering heart-shaped nose stud called Nurjahan Rupbhan told me. But when I asked about the changes in the climate, her forehead crumpled into long frown-lines.

I thought back to what the scientists told me in Dhaka. Bangladesh is a country with 230 rivers running through it like veins. They irrigate the land and give it its incredible fertility – but now the rivers are becoming supercharged. More water is coming down from the melting Himalayan glaciers, and more salt water is pushing up from the rising oceans. These two forces meet here in the heart of Bangladesh and make the rivers churn up – eroding the river banks with amazing speed. The water is getting wider, leaving the people to survive on ever-more narrow strips of land.

Nurjahan took me up to a crumbling river edge, where tree roots jutted out naked. "My house was here," she said. "It fell into the water. So now my house is here –" she motioned to a small clay hut behind us – "but now we realise this is going to fall in too. The river gets wider day by day."

But even this, Nurjahan said, is not the worst problem. The annual floods have become far more extreme, too. "Until about 10 years ago, the floods came every year and the water would stay for 15 days, and it helped to wet the land. Now the water stays for four months. Four months! It is too long. That doesn't wet the fields, it destroys them. We cannot plan for anything."

When the floods came last year, Nurjahan had no choice but to stay here. She lived with her children waist-deep in the cold brown water – for four months. "It was really hard to cook, or go to the toilet. We all got dysentery. It was miserable." Then she seemed to chastise herself. "But we survived! We are tough, don't you think?"

We sat by the river-bank, our feet dangling down towards the river. I asked if she agrees with Rezwan that her only option soon will be to move on to a boat. He is launching the first models this summer: floating homes with trays of earth where families can grow food. "Yes," she said, "We will be boat-people."

I clambered back on to one of the 42 school-boats in this area. Young children were in the front chanting the alphabet, and teenagers at the back were browsing through the books. I asked a 16-year-old boy called Mohammed Palosh Ali what he was reading about, and he said, "Global warming." I felt a small jolt. He was the first person to spontaneously raise global warming with me. Can you tell me what that is? "The climate is being changed by carbon dioxide," he said. "This is a gas that traps heat. So if there is more of it, then the ice in the north of the world melts and our seas rise here."

I asked if he had seen this warming in his own life. "Of course! The floods in 1998 and 2002 were worse than anything in my grandfather's life. We couldn't get any drinking water, so the dirty water I drank made me very sick. The shit from the toilet pits had risen up and was floating in the water, but we still had to drink it. We put tablets in it but it was still disgusting. What else could we do?"

Mohammed, do you know who is responsible for this global warming? He shakes his head. That answer lies a few pages further into the book. Soon he, and everybody else on this boat, will know it is me – and you.

5. The warming jihad

What happens to a country's mind as it drowns? Professor Philip Jenkins of Pennsylvania State University believes he can glimpse the answer: "The connection between climate change and religious violence is not tenuous," he says. "In fact, there's a historical indicator of how it could unfold: the Little Ice Age."

Between the ninth and 13th centuries, the northern hemisphere went through a natural phase of global warming. The harvests lasted longer – so there were more crops, and more leisure. Universities and the arts began to flower. But then in the late 13th century, the Little Ice Age struck. Crop production fell, and pack ice formed in the oceans, wrecking trade routes. People began to starve.

"In this climate of death and horror, people cast about for scapegoats, even before the Black Death struck," he says. Tolerance withered with the climate shocks: the Church declared witchcraft a heresy; the Jews began to be expelled from Britain. There was, he says, "a very close correlation between the cooling and a region-wide heightening of violent intolerance."

This time, there will be no need for imaginary scapegoats. The people responsible are on every TV screen, revving up their engines. Will jihadism swell with the rising seas? Bangladesh's religion seems to be low-key and local. In the countryside, Muslims – who make up 95 per cent of the nation – still worship Hindu saints and mix in a few Buddhist ideas, too. In the Arab world, people bring up God in almost every sentence. In Bangladesh, nobody does.

But then, as we returned to Dhaka, I was having a casual conversation with Shambrat. He had been driving all night – at his insistence – and by this point he was wired after chewing fistfuls of pan, and singing along at the top of his voice to the Eighties power ballads. I mentioned Osama bin Laden in passing, and he said, "Bin Laden – great man! He fight for Islam!" Then, without looking at me, he went back to singing: "It must have been love, but it's over now...."

I wondered how many Bangladeshis felt this way. The Chandni Chowk Bazaar – one of the city's main markets – was overcast the afternoon I decided to canvass opinions on Bin Laden. I approached a 24-year-old flower-seller called Mohammed Ashid, and as I inhaled the rich sweet scent of roses, he said: "I like him because he is a Muslim and I am a Muslim." Would you like Bin Laden to be in charge of Bangladesh? "Yes, of course," he said. And what would President Bin Laden do? "I have no idea," he shrugged. What would you want him to do? He furrowed his brow. "If Osama came to power he would make women cover up. Women are too free here." But what if women don't want to cover up? "They are Muslims. It's not up to them."

A very smartly dressed man called Shadul Ahmed was strolling down the street to his office, where he is in charge of advertising. "I like him," he said. "Bin Laden works for the Muslims." He conceded 9/11 "was bad because many innocents died," but added: "Osama didn't do it. The Americans did it. They are guilty."

As dozens of people paused from their shopping to talk, a pattern emerged: the men tend to like him, and the women don't. "I hate Bin Laden," one smartly dressed woman said, declining to give her name. "He is a fanatic. Bangladeshis do not like this." As the praise for Bin Laden was offered, I saw a boy go past on a rickshaw, stroking a girl's uncovered hair gently, sensuously. This is not the Arab world.

The only unpleasant moment came when I approached three women selling cigarettes by the side of the road. They were in their early thirties, wearing white hijabs and puffing away. Akli Mouna said, "I like him. He is a faithful Muslim." She said "it would be very nice" if he was president of Bangladesh. Really? Would you be happy if you were forced to wear a burqa, and only rarely allowed out of your house? She jabbed a finger at my chest. "Yes! It would be fine if Osama was president and told us to wear the burqa." But Akli – you aren't wearing a burqa now. "It's good to wear the burqa!" she yelled. Her teeth, I saw, were brown and rotting. "We are only here because we are poor! We should be kept in the house!"

I wanted to track down some Bangladeshi jihadis for myself, so I called the journalist Abu Sufian. He is a news reporter for BanglaVision, one of the main news channels, who made his name penetrating the thickets of the Islamist underground. He told me to meet him at the top of the BanglaVision skyscraper. As the city shrieked below us, he explained: "In the late 1980s, a group of mujahideen [holy warriors] who had been fighting the Soviets in Afghanistan came back to launch an Islamic revolution here in Bangladesh. They tried to mount an armed revolt in the north and kill the former Prime Minister. But it didn't come to much."

Islamic fundamentalism is hobbled in Bangladesh, because it is still associated for most people with Paki-stan – the country Bangladesh fought a bloody war of independence to escape from.

But Sufian says a new generation of Islamists is emerging with no memory of that war. "For example, I met a 21-year-old who had fought in Kashmir, whose father was a rickshaw driver. He said it was his holy duty to establish an Islamic state here through violence. Most were teenagers. All the jihadis I met hated democracy. They said it was the rule of man. According to them, only the rule of God is acceptable."

He said it would be almost impossible to track them down – they are in prison or hiding – but my best bet was to head for the Al-Amin Jami mosque in the north-west of Dhaka. "They are fundamentalist Wahhabis, and very dangerous," he said. Yet when I arrived, just before 6pm prayers, it was a bright building in one of the nicer parts of town. Men in white caps and white robes were streaming in. An ice-cream stall sat outside. I approached a fiftysomething man in flowing robes and designer shoes. He glared at me. I explained I was a journalist, and ask if it would it be possible to look inside the mosque? "No. Under no circumstances. At all."

OK. I asked a few polite questions about Islam, and then asked what he thought of Osama bin Laden. "Osama bin Laden?" he said. Yes. He scowled. "I have never heard of him." Never? "Never." I turned to the man standing, expectantly, next to him. "He has not heard of Osama bin Laden, either," he said. What about September 11 – you know, when the towers in New York fell? "I have never heard of this event, either." Some teenage boys were about to go in, so I approached them. Behind my back, I can sense the Gucci-man making gestures. "Uh... sorry... I don't think anything about Bin Laden," one of them said, awkwardly.

I lingered as prayers took place inside, until a flow of men poured out so thick and fast that they couldn't be instructed not to speak. "Yes, we would like Osama to run Bangladesh, he is a good man," the first person told me. There were nods. "He fights for Islam!" shouted another.

The crowd says this mosque – like most fundamentalist mosques on earth – is funded by Saudi Arabia, with the money you and I pay at the petrol pump. As I looked up at its green minaret jutting into the sky, it occurs to me that our oil purchases are simultaneously drowning Bangladesh, and paying for the victims to be fundamentalised.

After half-an-hour of watching this conversation and fuming, the initially recalcitrant man strode forward. "Why do you want to know about Bin Laden? We are Muslims. You are Christian. We all believe in the same God!" he announced.

Actually, I said, I am not a Christian. There was a hushed pause. "You are... a Jew?" he said. The crowd looked horrified; but then the man forced a rictus smile and announced: "We all believe in one God! We are all children of Abraham! We are cousins!" No, I said. I am an atheist. Everyone looked genuinely puzzled; they do not have a bromide for this occasion. "Well... then..." he paused, scrambling for a statement... "You must convert to Islam! Read the Koran! It is beautiful!" Ah – so can I come into the mosque after all? "No. Never."

6. The obituarist?

In a small café in Dhaka, a cool breeze was blowing in through the window along with the endless traffic-screams. The 32-year-old novelist Tahmima Anam was inhaling the aroma of coffee and close to despair.

She made her name by writing a tender novel – A Golden Age – about the birth of her country, Bangladesh. When the British finally withdrew from this subcontinent in 1948, the land they left behind was partitioned. Two chunks were carved out of India and declared to be a Muslim republic – East Pakistan and West Pakistan. But apart from their religion, they had very little in common. The gentle people of East Pakistan chafed under the dictatorial fundamentalism imposed from distant Islamabad. When they were ordered to start speaking Urdu, it was enough. Her novel tells how in 1971, they decided to declare independence and become Bangladesh. The Pakistanis fought back with staggering violence, but in the end Bangladesh was freed.

Now Anam is realising that unless we change, fast, this fight will have been for the freedom of a drowning land – and her next novel may have to be its obituary.

Anam came to Bangladesh late. Her Dhaka-born parents travelled the world, so she grew up in a slew of international schools, but she always dreamed of coming home. Her passion for this land, this place, this delta, aches through her work. About one of her characters, she wrote: "He had a love for all things Bengali: the swimming mud of the delta; the translucent, bony river fish; the shocking green palette of the paddy and the open, aching blue of the sky over flat land."

"You can see what has started to happen," she says. The vision of the country drowning is becoming more real every day. Where could all these 150 million people go? India is already building a border fence to keep them out; I can't imagine the country's other neighbour – Burma – will offer much refuge. "We are the first to be affected, not the last," Anam says. "Everyone should take a good look at Bangladesh. This story will become your story. We are your future."

It is, she says, our responsibility to stop this slow-mo drowning – and there is still time to save most of the country. "What could any Bangladeshi government do? We have virtually no carbon emissions to cut." They currently stand at 0.3 per cent of the world's – less than the island of Manhattan. "It's up to you."

Anam is defiantly optimistic that this change can happen if enough of us work for it – but, like every scientist I spoke to, she knows that dealing with it simply by adaptation by Bangladeshis is impossible. The country has a military-approved dictatorship incapable of taking long-term decisions, and Dutch-style dams won't work anyway. "Any large-scale construction is very hard in this country, because it's all made of shifting silt. There's nothing to build on."

So if we carry on as we are, Bangladesh will enter its endgame. "All the people who strain at this country's seams will drown with it," Anam says, "or be blown away to distant shores – casualties and refugees by the millions." The headstone would read, Bangladesh, 1971-2071: born in blood, died in water.

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Global Warming: The Fate of Bangladesh

Bangladesh is set to disappear under the waves by the end of the century - A special report by Johann Hari

Bangladesh, the most crowded nation on earth, is set to disappear under the waves by the end of this century – and we will be to blame. Johann Hari took a journey to see for himself how western profligacy and indifference have sealed the fate of 150 million people went to see for himself the spreading misery and destruction as the ocean reclaims the land on which so many millions depend

Alamy

Battling the waves: many Bangladeshis depend on the ocean

This spring, I took a month-long road trip across a country that we – you, me and everyone we know – are killing. One day, not long into my journey, I travelled over tiny ridges and groaning bridges on the back of a motorbike to reach the remote village of Munshigonj. The surviving villagers – gaunt, creased people – were sitting by a stagnant pond. They told me, slowly, what we have done to them.

Ten years ago, the village began to die. First, many of the trees turned a strange brownish-yellow colour and rotted. Then the rice paddies stopped growing and festered in the water. Then the fish floated to the surface of the rivers, gasping. Then many of the animals began to die. Then many of the children began to die.

The waters flowing through Munshigonj – which had once been sweet and clear and teeming with life – had turned salty and dead.

Arita Rani, a 25-year-old, sat looking at the salt water, swaddled in a blue sari and her grief. "We couldn't drink the water from the river, because it was suddenly full of salt and made us sick," she said. "So I had to give my children water from this pond. I knew it was a bad idea. People wash in this pond. It's dirty. So we all got dysentery." She keeps staring at its surface. "I have had it for 10 years now. You feel weak all the time, and you have terrible stomach pains. You need to run to the toilet 10 times a day. My boy Shupria was seven and he had this for his whole life. He was so weak, and kept getting coughs and fevers. And then one morning..."

Her mother interrupted the trailing silence. "He died," she said. Now Arita's surviving three-year-old, Ashik, is sick, too. He is sprawled on his back on the floor. He keeps collapsing; his eyes are watery and distant. His distended stomach feels like a balloon pumped full of water. "Why did this happen?" Arita asked.

It is happening because of us. Every flight, every hamburger, every coal power plant, ends here, with this. Bangladesh is a flat, low-lying land made of silt, squeezed in between the melting mountains of the Himalayas and the rising seas of the Bay of Bengal. As the world warms, the sea is swelling – and wiping Bangladesh off the map.

Deep below the ground of Munshigonj and thousands of villages like it, salt water is swelling up. It is this process – called "saline inundation" – that killed their trees and their fields and contaminated their drinking water. Some farmers have shifted from growing rice to farming shrimp – but that employs less than a quarter of the people, and it makes them dependent on a fickle export market. The scientific evidence shows that unless we change now, this salt water will keep rising and rising, until everything here is ocean.

I decided to embark on this trip when, sitting in my air-conditioned flat in London, I noticed a strange and seemingly impossible detail in a scientific report. The International Panel on Climate Change (IPCC) – whose predictions have consistently turned out to be underestimates – said that Bangladesh is on course to lose 17 per cent of its land and 30 per cent of its food production by 2050. For America, this would be equivalent to California and New York State drowning, and the entire mid-West turning salty and barren.

Surely this couldn't be right? How could more than 20 million Bangladeshis be turned into refugees so suddenly and so silently? I dug deeper, hoping it would be disproved – and found that many climatologists think the IPCC is way too optimistic about Bangladesh. I turned to Professor James Hansen, the director of Nasa's Goddard Institute for Space Studies, whose climate calculations have proved to be more accurate than anybody else's. He believes the melting of the Greenland ice cap being picked up by his satellites today, now, suggests we are facing a 25-metre rise in sea levels this century – which would drown Bangladesh entirely. When I heard this, I knew I had to go, and see.

1. The edge of a cliff

The first thing that happens when you arrive in Dhaka is that you stop. And wait. And wait. And all you see around you are cars, and all you hear is screaming. Bangladesh's capital is in permanent shrieking gridlock, with miles of rickshaws and mobile heaps of rust. The traffic advances by inches and by howling. Each driver screams himself hoarse announc-ing – that was my lane! Stay there! Stop moving! Go back! Go forward! It is a good-natured shrieking: everybody knows that this is what you do in Dhaka. If you are lucky, you enter a slipstream of traffic that moves for a minute – until the jams back up and the screaming begins once more.

Around you, this megalopolis of 20 million people seems to be screaming itself conscious. People burn rubbish by the roadside, or loll in the rivers. Children with skin deformities that look like infected burns try to thrust maps or sweets into your hand. Rickshaw drivers with thighs of steel pedal furious-ly as whole families cling on and offer their own high-volume traffic commentary to the groaning driver, and the groaning city.

I wanted to wade through all this chaos to find Bangladesh's climate scientists, who are toiling in the crannies of the city to figure out what – if anything – can be saved.

Dr Atiq Rahman's office in downtown Dhaka is a nest of scientific reports and books that, at every question, he dives into to reel off figures. He is a tidy, grey-moustached man who speaks English very fast, as if he is running out of time.

"It is clear from all the data we are gathering here in Bangladesh that the IPCC predictions were much too conservative," he said. He should know: he is one of the IPCC's leading members, and the UN has given him an award for his unusually prescient predictions. His work is used as one of the standard textbooks across the world, including at Oxford and Harvard. "We are facing a catastrophe in this country. We are talking about an absolutely massive displacement of human beings."

He handed me shafts of scientific studies as he explained: "This is the ground zero of global warming." He listed the effects. The seas are rising, so land is being claimed from the outside. (The largest island in the country, Bhola, has lost half its land in the past decade.) The rivers are super-charged, becoming wider and wider, so land is being claimed from within. (Erosion is up by 40 per cent). Cyclones are becoming more intense and more violent (2007 was the worst year on record for intense hurricanes here). And salt water is rendering the land barren. (The rate of saline inundation has trebled in the past 20 years.) "There is no question," Dr Rahman said, "that this is being caused primarily by human action. This is way outside natural variation. If you really want people in the West to understand the effect they are having here, it's simple. From now on, we need to have a system where for every 10,000 tons of carbon you emit, you have to take a Bangladeshi family to live with you. It is your responsibility." In the past, he has called it "climatic genocide".

The worst-case scenario, Dr Rahman said, is if one of the world's land-based ice-sheets breaks up. "Then we lose 70 to 80 per cent of our land, including Dhaka. It's a different world, and we're not on it. The evidence from Jim Hansen shows this is becoming more likely – and it can happen quickly and irreversibly. My best understanding of the evidence is that this will probably happen towards the end of the lifetime of babies born today."

I walked out in the ceaseless churning noise of Dhaka. Everywhere I looked, people were building and making and living: my eyes skimmed up higher and higher and find more and more activity. A team of workers were building a house; behind and above them, children were sewing mattresses on a roof; behind and above them, more men were building taller buildings. This is the most cramped country on earth: 150 million people living in an area the size of Iowa. Could all this life really be continuing on the crumbling edge of a cliff?

2. 'It is like the Bay is angry'

I was hurtling through the darkness at 120mph with my new driver, Shambrat. He was red-eyed from chewing pan, a leaf-stimulant that makes you buzz, and I could see nothing except the tiny pools of light cast by the car. They showed we were on narrow roads, darting between rice paddies and emptied shack-towns, in the midnight silence. I kept trying to put on my seatbelt, but every time Shambrat would cry, "You no need seatbelt! I good driver!" and burst into hysterical giggles.

To see if the seas were really rising, I had circled a random low-lying island on the map called Moheshkhali and asked Shambrat to get me there. It turned out the only route was to go to Coxs Bazar – Bangladesh's Blackpool – and then take a small wooden rowing boat that has a huge chugging engine attached to the front. I clambered in alongside three old men, a small herd of goats, and some chickens. The boat was operated by a 10-year-old child, whose job is to point the boat in the right direction, start the engine, and then begin using a small jug to frantically scoop out the water that starts to leak in. After an hour of the deafening ack-ack of the engine, we arrived at the muddy coast of Moheshkhali.

There was a makeshift wooden pier, where men were waiting with large sacks of salt. As we climbed up on to the fragile boards, people helped the old men lift up the animals. There were men mooching around the pier, waiting for a delivery. They looked bemused by my arrival. I asked them if the sea levels were rising here. Rezaul Karim Chowdry, a 34-year-old who looked like he is in his fifties, said plainly: "Of course. In the past 30 years, two-thirds of this island has gone under the water. I had to abandon my house. The land has gone into the sea." Immediately all the other men start to recount their stories. They have lost their houses, their land, and family members to the advance.

They agreed to show me their vanishing island. We clambered into a tuc-tuc – a motorbike with a carriage on the back – and set off across the island, riding along narrow ridges between cordoned-off areas of sand and salt. The men explained that this is salt-farming: the salt left behind by the tide is gathered and sold. "It is one of the last forms of farming that we can still do here," Rezaul said. As we passed through the forest, he told me to be careful: "Since we started to lose all our land, gangs are fighting for the territory that is left. They are very violent. A woman was shot in the crossfire yesterday. They will not like an outsider appearing from nowhere."

We pulled up outside a vast concrete structure on stilts. This, the men explained, is the cyclone shelter built by the Japanese years ago. We climbed to the top, and looked out towards the ocean. "Do you see the top of a tree, sticking out there?" Rezaul said, pointing into the far distance. I couldn't see anything, but then, eventually, I spotted a tiny jutting brown-green tip. "That is where my house was." When did you leave it? "In 2002. The ocean is coming very fast now. We think all this" – he waved his hand back over the island – "will be gone in 15 years."

Outside the rusty house next door, an ancient-looking man with a long grey beard was sitting cross-legged. I approached him, and he rose slowly. His name was Abdul Zabar; he didn't know his age, but guessed he is 80. "I was born here," he said. "There" – and he points out to the sea. "The island began to be swallowed in the 1960s, and it started going really quickly in 1991. I have lost my land, so I can't grow anything... I only live because one of my sons got a job in Saudi Arabia and sends money back to us. I am very frightened, but what can I do? I can only trust in God." The sea stops just in front of his home. What will you do, I asked, if it comes closer? "We will have nowhere to go to."

I was taken to the island's dam. It is a long stretch of hardened clay and concrete and mud. "This used to be enough," a man called Abul Kashin said, "but then the sea got so high that it came over the dam." They have tried to pile lumps of concrete on top, but they are simply washed away. "My family have left the island," he continued, "They were so sad to go. This is my homeland. If we had to leave here to go to some other place, it would be the worst day of my life."

Twenty years ago, there were 30,000 people on this island. There are 18,000 now – and most think they will be the last inhabitants.

On the beach, there were large wooden fishing boats lying unused. Abu Bashir, a lined, thin 28-year-old, pointed to his boat and said, "Fishing is almost impossible now. The waves are much bigger than they used to be. It used to be fine to go out in a normal [hand-rowed] boat. That is how my father and my grandfather and my ancestors lived.

"Now that is impossible. You need a [motor-driven] boat, and even that is thrown about by the waves so much. It's like the bay is angry."

The other fishermen burst in. "When there is a cyclone warning, we cannot go out fishing for 10 days. That is a lot of business lost. There used to be two or three warnings a year. Last year, there were 12. The sea is so violent. We are going hungry."

Yet the islanders insisted on offering me a feast of rice and fish and eggs. I was ushered into the council leader's house – a rusty shack near the sea – and the men sat around, urging me to tell the world what is happening. "If people know what is happening to us, they will help," they said. The women remained in the back room; when I glimpsed them and tried to thank them for the food, they giggled and vanished. I asked if the men had heard of global warming, and they looked puzzled. "No," they said. We stared out at the ocean and ate, as the sun slowly set on the island.

3. No hiding place

Through the morning mist, I peered out of the car window at the cratered landscape. Trees jutted out at surreal angles from the ground. One lay upside down with its roots sticking upwards towards the sky, looking like a sketch for a Dali painting. Shambrat had spat out his pan and was driving slowly now. "There are holes in the ground," he said, squinting with concentration. "From the cyclone. You fall in..." He made a splattering sound.

It was here, in the south of Bangladesh, that on 15 November last year, Cyclone Sidr arrived. It formed in the warmed Bay of Bengal and ripped across the land, taking more than 3,000 people with it. Like Americans talking about 9/11, everybody in Bangladesh knows where they were when Sidr struck. For miles, the upturned and smashed-out houses are intermixed with tents made from blue plastic sheeting. These stretches of plastic were handed out by the charities in the weeks after Sidr, and many families are still living in them now.

There have always been cyclones in Bangladesh, and there always will be – but global warming is making them much more violent. Back in Dhaka, the climatologist Ahsan Uddin Ahmed explained that cyclones use heat as a fuel: "The sea surface temperatures in the Bay of Bengal have been rising steadily for the past 40 years – and so, exactly as you would expect, the intensity of cyclones has risen too. They're up by 39 per cent on average." Again I circled a cyclone-struck island at random and headed for the dot.

The hour-long journey on a wooden rowing boat from the mainland to Charkashem Island passed in a dense mist that made it feel like crossing the River Styx. The spectral outline of other boats could sometimes be glimpsed, before they disappeared suddenly. One moment an old woman and a goat appeared and stared at me, then they were gone.

The island was a tiny dot of mud and lush, upturned greenery. It had no pier, so when the rowing boat bumped up against the sand I had to wade through the water.

I looked out over the silent island, and saw some familiar blue sheeting in the distance. As I trudged towards it, I saw some gaunt teenagers half-heartedly kicking a deflated football. From the sheeting, a man and woman stared, astonished.

"I was in my fields over there," Hanif Mridha said. "I saw the wind start, it was about eight at night, and I saw everything being blown around. I went and hid under an iron sheet, but that was blown away by the wind. The water came swelling up all of a sudden and was crashing all around me. I grabbed one of my children and ran to the forest" – he pointed to the cluster of trees at the heart of the island – "and climbed the tallest one I could reach. I went as high as I could but still the water kept rising and I thought – this is it, I'm going to drown. I'm dying, my children are dying, my wife is dying. I could see everything was under water and people were screaming everywhere. I held there for four hours with my son."

When the water washed away and he came down, everything was gone: his house, his crops, his animals, his possessions. A few days later, an aid agency arrived with some rice and some plastic sheeting to sleep under. Nobody has come since.

His wife, Begum Mridha, took over the story. Their children are terrified of the sea now, and have nightmares every night. They eat once a day, if they're lucky. "We are so hungry," she said. The new home they have built is made from twigs and the plastic sheet. Underneath it, they sleep with their eight children and Begum Mridha's mother. The children lay lethargically there, staring blankly into space over their distended bellies.

Begum Mridha cooks on a lantern. They eat once a day – if that. "It's so cold at night we can't sleep," she said. "The children all have diarrhoea and they are losing weight. It will take us more than two years to save up and get back what we had."

If cyclones hit this area more often, what would happen to you? Hanif looked down. He opened his mouth, but no words came.

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