Climate change would alter crop water requirement in drought-prone Bangladesh. The highest
crop water needs (Fig.3.3) are in hot, dry, windy and sunny seasons (November-May). The lowest
needs occur when it is cool, humid and cloudy with little wind. It is clear that crops grown in
current and future climatic conditions will have different water needs. For example, rice grown
in the future will need more water per day.
Of the net cultivable area, 37 percent is single cropped, 50 percent is double cropped and
13 percent is triple cropped. The three cropping seasons coincide approximately with the three
meteorological seasons namely, kharif I (pre-monsoon), kharif II (monsoon) and rabi (dry season).
Aus, aman and boro are the three rice crops grown in these three cropping seasons respectively.
During the past two decades, the area under boro rice has increased – a trend that is likely to
continue in future. Because boro is an input intensive crop and requires use of water in the
winter season, such a trend would increase pressure on the limited water supply, leading to land
degradation, food insecurity.
Box 3.5: Climate Change and
rice production
Under a moderate climate change
scenario, aus production in Bangladesh
would decline by 27% while wheat
production would be reduced to 61%.
Under a severe climate change scenario,
yield of boro might decrease by 50%.
Moisture stress during the dry season
might force farmers to reduce the area
under boro cultivation.
J F M A MJ J A S O N D
Dry season Rainy season Dry season
Irrigation Rainfall Irrigation
22CLIMATE VARIABILITY AND CHANGE: ADAPTATION TO DROUGHT IN BANGLADESH
Drought normally affects about 2.3 million ha of cropland from April to September and
1.2 million ha in the dry season, from October to March. Drought during monsoon season
severely affects t.aman rice and can incur an annual 1.5 million tonne production loss. With
climate change, more area would be exposed to severe droughts because of projected change in
rainfall pattern and dry spell frequencies.
Incidence of pests and diseases may increase with climate
variability and climate change. With long dry spells and
more intense rainfall, the resulting decline in water quality
will lead to greater risk of water-born diseases. Changing
temperatures and rainfall in drought-prone areas are
likely to shift populations of insect pests and other vectors
and change the incidence of existing vector-borne diseases
in both humans and crops. The physical and social
disruptions caused by these diseases and extreme events
such as droughts may affect the community. Under high
temperature and humidity, there will be problems of
dehydration, especially affecting the elderly and children.
A temperature increase of 1-2°C would perhaps not cause
significant change, but high intensity of extremes might
intensify heat stress and associated health hazards.
Fresh water availability in drought-prone areas also would
be threatened under climate change which would affect
small-scale fishery activities. For example, the duration
of water availability in traditional ponds would be shortened due to longer dry periods and
increased frequency of dry years, and high temperatures would lead to increased salinity. As the
solubility of oxygen in water decreases with high temperature, fish growth would be affected.
Fresh water fish hatchlings cannot survive under high salinity levels. A temperature rise of about
2°C would have substantial impacts on distribution, growth and reproduction of fish.