Global warming, local impact
Global warning is bearing a global warning for the low-lying sea-facing over populated countries like Bangladesh. This perhaps has made the world community more concerned about than other environmental issue. But it is man who has made it so alarming through his unbridled one-sided development activities without taking the environmental aspects into account over time.
The connotation of global warming first provided by a famous Swedish chemist named S.R. Helis in 1896 became a widely known global issue after 1920s experiencing a continuous increase in atmospheric temperature and consequently a bit of irony in behaviour of the nature. On February 2 in 2007 in Paris IPCC (Inter-governmental panel for climate change) disclosed that global warming was the increase in the average temperature of the earth's near-surface air and oceans in recent decades and projected its continuation (Daily Star, June 22, 2007).
Contribution of Bangladesh and developed world: The developed countries contribute to global warming the most. In contrast, the least contributing low lying poor and over populated tropical countries like Bangladesh are the most vulnerable to the impact. The United States of America is the largest contributor with about 25 per cent of greenhouse gas emissions, but it is a home of a population lesser than 5 per cent of the world's total. US government has done virtually nothing, even has not signed the Kyoto protocol till now. In terms of per capita greenhouse gas emission, the contribution of Bangladesh to global warming is negligible -- 0.13 percent.
Impact on Bangladesh
The poorest countries have always been predicted to be worst hit by this human-induced global warming. According to the Third Assessment Report of IPCC, Bangladesh ranks high in the list of most vulnerable countries. High vulnerability of the country to global warming is due to a number of hydro-geological and socio-economic factors that include geographical location, flat deltaic topography with sea-facing low elevation, extreme tropical climate variability, high population density and poverty incidence, dependency of majority of population on crop agriculture. However, two major impacts of global warming on Bangladesh may be categorized as that of sea level change and climate change.
Sea level change: Global warming will cause a thermal expansion of the sea water. A rise in atmospheric temperature will also melt the polar and Alpine ice sheets. Besides, the sea floor is also being raised by the deposition of the sediments brought down by the rivers. These three processes together are giving rise to sea level. World Bank reported in 2001 that sea level was rising by about 3mm per year in the Bay of Bengal. The impacts are stated below:-
A taskforce report predicts a one meter rise in the sea level will inundate a greater portion of southern region which is about 15.8 per cent of the total area of Bangladesh (Taskforce report, 1991). The predicted one meter sea level rise will lead to the loss of about 22,889 square kilometers of agriland which will cause a 30 per cent decline of rice crop. It will also cause decline in production of other crops. It will permanently inundate the Sundarbans, a world heritage site, with the loss of Bengal tigers (world Bank Report, 2001). Sea level rise will also increase the frequency of coastal flooding that will threaten animals, plants and fresh water supplies in the coastal plain of Bangladesh.
A rise in sea water level will enable saline water to intrude further inland during high tides, coastal flooding and storm surge. As a result, extended salinity will deteriorate soil quality and cause loss of sweet water fauna and flora. It will also destruct sweet water sources including ponds and lakes etc. Sea level rise will cause shoreline retreat, resulting in increase of basin area, which contributes to increasing the cyclone path length that will allow the cyclone to remain more time in the water, acquire and release more latent heat, intensity and wide speed. The projected sea level rise along the coastal areas of Bangladesh will be about 88cm by the year 2100 (Khan et al. 2007)
Climate change: Climate change is likely to heavily hit Bangladesh because global warming is causing increase in temperature affecting precipitation intensity, pattern and distribution. Bangladesh will receive a heavier rainfall during the monsoon because the rate of evaporation is expected to increase by up to 12 per cent. Mean monthly rainfall may significantly change over current variability. Monsoon rainfall may increase by 11 per cent by 2030 and 27per cent by 2070 (Khan et. Al. 2007). Due to global warming, over the past 100 years temperature has increased by 0.5?C but in the next 50 years that is, by 2050, the temperature in Bangladesh is projected to rise by 1.5 to 2.00C.
A number of studies found that high temperature would reduce the yields of HYVs of Aus, Aman and Boro rice during all the seasons throughout Bangladesh. An important study reveals that a 60 per cent moisture stress on top of other effects might cause as high as 32 per cent decline in Boro yield. A quarter of the country's landmass is currently flood prone in a normal hydrological year, which may increase to 39 per cent and prolonged flooding can effectively reduce overall potential for HYV Aman production. Global warning will make tropical cyclones and tornadoes in Bangladesh bigger and more frequent. The super cyclone Sidr on 15 November, 2007 has already drawn attention to the devastation that may yet be caused in future.
Water related impacts due to climate change and sea level rise are likely to be some of the most critical issues for Bangladesh, not only in relation to coastal and reverine flooding but also in relation to enhanced possibility of winter drought in certain areas. In the dry season, river flow will be reduced. Consequently, salinity will penetrate along the coastal rivers. It will cause increase in evapo-transpiration that is detrimental to crop growth. It will also result in more release of carbon from the topsoil. Increased water withdrawal by India will also lead to further decrease in lean season flow in the rivers.
Rise in temperature will favour pest and pathogen activities and human health will be at higher risk, i.e. increased risk of some infectious diseases like malaria, diarrhoea, dengue etc. Rising temperature may jeopardise the forest succession processes. It may result in low productivity and poor vegetative cover of the forest and affect its rich biodiversity. Quarter of a million hectare land will become affected by salinity, on top of the 3.05 million hectares already affected (Khan et.al.2007). Farmers will be forced to grow crops of economically lesser returns.
Concluding remarks
However, to sum up, we can say that global warming is a global issue; so, it should be treated globally. It will have its impact felt throughout the whole world; for geographical settings and some socio-economic conditions, Bangladesh will be affected the most. It is a matter of hope that world leaders at the UN climate conference in December, 2007 in Bali, Indonesia, agreed to reach a new deal on fighting global warming by 2009. It simply sets an agenda and schedule for negotiations to find ways to reduce pollution and help poor countries adapt to environmental changes by speeding up the transfer of technology and financial assistance.
A technology based, efficient system to deal with natural disasters and other global warming impacts to be put in place is an urgent need. Setting up of a strongly funded international adaptation centre, here in Bangladesh, for undertaking research on the effects of global warming as well as suggesting measures toward preparedness in the face of coming challenges will reflect a seriousness of approach to the issue on the part of the world community.
If the world dwellers do their duties accordingly following the rule "think globally, act locally", it will ensure both the conservation of the environment and sustainable development and will particularly save countries like Bangladesh from catastrophe induced by 'global warming'.
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