Vulnerability of Bangladesh’s coastal region to climate change

Vulnerability of Bangladesh’s coastal region to climate change

1 September 2008

By Manir Hossain

The coastal region of Bangladesh is already perspiring with different types of natural disasters. Bangladesh is situated at the interface of two contrasting settings with the Bay of Bengal and the North Indian Ocean to the south and the Himalayas to the north. This gives the country the life giving monsoons, on one hand, and the catastrophic disasters like tropical cyclones, storm surges, floods, droughts and erosion, on the other. In the foreseeable future, the country is likely to be affected by the biggest ever, long lasting and global scale human-induced disaster- the climate change and sea level rise. The geographical location, low and almost flat topography, very high population density, etc.. have made country one of the most vulnerable countries of the world to be affected by the impact of climate change. About 10% of Bangladesh is hardly 1m above the mean sea level and one-third is under tidal because Bangladesh is not large in area, effects in the coastal area are likely to be felt by the whole country. The impacts of climate change on the coastal region of our country may observe to the following aspects- tropical cyclones, storm surges, back water effects, agriculture, forestry, fisheries, erosion, salinity intrusion, mangrove ecosystem and biodiversity.

Bangladesh is basically a deltaic plain of three mighty rivers, namely the Ganges, the Brahmaputra and the Meghna (GBM) which form one of the largest river systems in the world. These rivers have large number of distributaries, tributaries, sub-distributaries and sub-tributaries. The country has a total number of 230 rivers covering a length of about 24,140km. These rivers carry huge amount of water and sediments to the Bay of Bengal in the south where they are subjected to dynamic actions by the conditions in the Bay, leading to coastal erosions and accretions and other phenomena. The country has three distinct coastal regions, namely the western, central and eastern regions. The western zone is very flat and low and is crises-crossed by numerous rivers and channels. It houses the famous mangrove area called the Sundarbans. The central region is the most active one and continuous process of accretion and erosion is going on there. The eastern region is covered by hilly areas and it is more stable and has a long beach there. The coastal region is characterized by: (i) A vast network of rivers, (ii) An enormous discharge of river waters heavily laden with sediments, (iii) A large number of islands in between the channels and rivers, (iv) Northward converging Bay of Bengal towards Bangladesh, (vi) A very shallow area all along the coast, particularly in the central region, and (vii) A submarine canyon, named Swatch of No Ground, in the western region. The geographical location and geomorphological conditions of have made the country one of the most vulnerable ones to disasters in the world.

There are various estimates of temperature rise in Bangladesh. The average increase in temperature would be 1.30C and 2.60C by the year 2030 and 2075 respectively with respect to the base year 1990. The seasonal variation of temperature will be more in winter than in summer: 1.30C in winter and 0.70C in summer for 2030 and 2.10C for winter and 1.70C for summer for2075. The annual mean maximum temperature will increase by 0.400C and 0.730C by the years 2050 and 2100 respectively. But the mean annual temperature will increase by 0.220C and 0.410C respectively. Global warming will increase the intensity of south-west monsoon which will, in turn, bring about catastrophic ravages like erosion, land sides and floods and have far reaching consequences on agriculture, habitat, economy, etc.

The impact of climate change is the melting of polar glaciers and icecaps that will inflict its impacts on Bangladesh in the coastal area and through the coastal area, on the whole country by the increasing of sea level. About 2,500, 8,000 and 14,000 km2 of land will be lost due to sea level rise of 0.1m, 0.3m and 1.0m respectively. About one-fourth population of our country lives in the coastal area. Increase in sea level rise may cause migration of people inland, thus raising the population density there and causing socio-economic problems and other harmful impacts on their living. Sea level rise will bring more coastal area under inundation. Coastal waters will become more saline and soil salinity will increase. Not only that, even the ground water aquifers will bear the brunt of salinity intrusion. Agriculture, forestry and fisheries sectors will be severely affected by increased water and soil salinity.

About 90% of the river water discharges into the Bay of Bengal. It is particularly important during flood seasons. As a result of back water effect, flood water inside the country continues to accumulate, bringing more areas under inundation and increasing the length and depth of flooding. Bangladesh is already vulnerable to extreme climate events such as cyclones, storm surges and floods. A slight increase in the frequency and intensity of extreme events will make them even more destructive. The Bay of Bengal is a favorable breeding ground of tropical cyclones and Bangladesh is the worst suffer of all cyclonic casualties in the world. About 5.5% cyclonic storms (wind speed greater than or equal to 62 km/hr) form in the Bay of Bengal and about 1% cyclonic storm of the global total hit Bangladesh.

Change in climate will also have serious impacts on the mangrove forests. The rise in sea level and availability of less fresh water particularly during winter when rainfall will be less will cause inland intrusion of saline water. As a result, many mangrove species, can not tolerant of increased salinity, may be threatened and extinct. Increase in temperature and sea level rise will seriously affect the Sundarbans ecosystem and bio-diversity. A wide range of mammals, birds, amphibians, reptiles, crustaceans, and above all the Royal Bengal Tiger will face extinction. The ecosystem of the only coral island of the St. Martin’s island may also be affected. Shrimp farming in the coastal area is a lucrative business. Increase in salinity is likely to jeopardize the shrimp farming.

Building adaptive capacity to climate change and managing climate risks will be addressed through the mainstreaming of climate risk into sustainable development strategies. To do this successfully requires awareness and understanding of climate change issues. Specific adaptation actions take place at community or individual level. Communication between communities will allow coping strategies to be shared.. Some steps that should be taken to reduce the impacts of and adaptation to climate change in the coastal region of our country may includes- capacity building & promoting partnerships; mainstreaming climate change into development plans and processes; disaster risk reduction with climate change adaptation offers a win-win opportunity; promoting adaptation to coastal crop agriculture to combat salinity intrusion; adaptation to agriculture, fisheries in areas to prone enhanced flash flooding; climate change and adaptation information dissemination to vulnerable community to raise awareness; promotion of research on natural hazards to facilitate adaptation in future; and development of eco-specific adaptive knowledge on adaptation to climate variability to enhance adaptive capacity for future climate change. For better environment to coastal people we have to take all possible adaptive and other measures that will help to the whole country.

(Manir Hossain (1st Batch) President of Society for Environment and Nature Study (SENS) at Mawlana Bhashani Science and Technology University, Tangail.)

Source: The New Nation