2.1 Coastal boundary Bangladesh, a flood plain delta, is a land of rivers and canals. The country is sloping gently from the north to the south, meeting the Bay of Bengal at the southern end. The whole coast runs parallel to the Bay of Bengal, forming 710 km long coastline. According to the coastal zone policy of the Government of Bangladesh, 19 districts out of 64 are in the coastal zone covering a total of 147 upazillas1 of the country. Out of these 19 districts, only 12 districts meet the sea or lower estuary directly.
The zone is divided into exposed and interior coast according to the position of land. The Upazila's that face the coast or river estuary are treated as exposed coastal zone. Total number of upazillas that fall on exposed coastal zone is 48 in 12 districts. A total of 99 upazillas that are located behind the exposed coast are treated as interior coast. The exposed coast embraces the sea directly and is subject to be affected highly by the anticipated sea level rise.
The southern part of Bangladesh falls under coastal zone that receives discharge of numerous rivers, including Ganges-Brahmputra-Meghna (GBM) river system, creating one of the most productive ecosystems of the world. Except Chittagong-Cox’s Bazar, all parts of the coastal zone are plain land with extensive river networks and accreted land, which is known in Bangladesh as char land. India is at the west of the zone whereas Myanmar is at the east of the coast. Pramanik has divided the Bangladesh coastal zone into three regions namely eastern, central and western coastal regions. However, the shape of the coastal zone is quite unstable and changing time to time due to erosion and accretion.
2.7 People and livelihoods Total population living in the coastal zone is 35.1 million that represent 28 percent of total population of the country (BBS, 2003). Population density in exposed coast is 482 persons per square kilometer whereas the value is 1,012 for the interior coast. Average population density of the zone is 743 per sq. km., and the same value for Bangladesh average is 839. Population density in interior coast is much higher than that of exterior coast and the country’s average. There are about 6.8 million households in the zone of which 52 percent are absolute poor according to Islam.
Fishing, agriculture, shrimp farming, salt farming and tourism are the main economic activities in the coastal area. The Sundarbans is a major source of subsistence for almost 10 million people. Main activities in the Sundarbans area are fisheries, wood collection and honey collection. Almost ten thousand households in the area have neither homestead land nor cultivable land. On the other hand, more than a million households in the area have only homestead but no cultivable land. Per capita gross domestic product (GDP) for the coastal zone was US$277, a little bit lower than that of national average (US$278), during the fiscal year 1999-2000.
3.1 Causes of sea level rise Due to various human activities, carbon dioxide (CO2) and other greenhouse gases are accumulated in the earth’s atmosphere, resulting in climate change. Rising temperature expand the ocean volume in two ways. Firstly, it melts mass volume of ice of the polar region and secondly, it causes thermal expansion of water of the ocean. Wigley and Raper (1987) comment that the relative contributions of thermal expansion and ice melting to this sea level rise are uncertain and estimates vary widely, from a small expansion effect through roughly equal roles for expansion and ice melting to a dominant expansion effect. These two factors increase volume of ocean water of the earth and rise in the sea level. The human factor that is mainly responsible for global warming and sea level rise is burning of fossil fuels. Deforestation is another human activity, responsible for decreasing the CO2 sink. Miller (2004) states that, 75% of the human caused emissions of CO2 since 1980 are due to fossil fuel burning and the remainder is the result of deforestation, agriculture, and other human changes in the land use. The two largest contributors to current CO2 emissions are the world’s thousands of coalburning power and industrial plants and more than 700 million gasoline-burning motor vehicles (555 million of them cars). Emissions of CO2 from U.S. coal burning power and industrial plants alone exceeded the combined CO2 emissions of 146 nations, which contain 75% of the world’s people. As a small nation, Bangladesh plays an ignorable role for greenhouse gas emission.
3.3 Sea level rise in Bangladesh Bangladesh is highly vulnerable to sea level rise, as it is a densely populated coastal country of smooth relief comprising broad and narrow ridges and depressions (Brammer et al., 1993). World Bank (2000) showed 10 cm, 25cm and 1 m rise in sea level by 2020, 2050 and 2100; affecting 2%, 4% and 17.5% of total land mass respectively. Milliman et al. reported 1.0 cm per year sea level rise in Bangladesh.