Introduction of high-yielding varieties In the initial stages of wheat growing in Bangladesh, several Mexican varieties, especially ‘Sonora 64’ and ‘Kalyansona’, were successfully introduced in collaboration with the International Maize and Wheat Improvement Center (CIMMYT). However, the release of ‘Sonalika’ in 1972 created a true breakthrough in wheat production. This fast maturing and high-yielding variety (yield = 2 tons ha-1 ) became very popular among wheat growers and adapted well to different production environments, and was adopted in 80 % of the wheat area by the early 1980s (WRC 2009). In 1983, the Wheat Research Centre (WRC), Bangladesh Agricultural Research Institute (BARI), released four more high-yielding (yield = 2–3 tons ha21 ) varieties (‘Ananda’, ‘Kanchan’, ‘Barkat’ and ‘Akbar’). Among these, ‘Kanchan’ proved particularly adaptable and gradually replaced ‘Sonalika’ to become the predominant variety in Bangladesh by the early 1990s. Two other high-yielding varieties, ‘Aghrani’ and ‘Protiva’, were recommended by the Bangladesh National Seed Board in 1987 and 1993, respectively. These varieties were more responsive to a wider range of weather conditions as well as crop management practices such as fertilizers, irrigation and intercultural operations. Therefore, by the mid-1990s, adoption of high-yielding varieties was almost 100 %, thereby increasing wheat productivity substantially. The year of release and average yield of the new wheat varieties developed in Bangladesh from 1974 to 2012, combined with the recent global financial problems, volatile energy prices, natural resource depletion and climate change have combined to undercut and threaten the livelihoods of millions of poor people worldwide. Wheat accounts for a fifth of humanity’s food and is second only to rice as a source of calories in the diets of consumers in developing countries and is first as a source of protein (Braun et al. 2010). Wheat is an especially critical foodstuff for 1.2 billion people classified as ‘wheat-dependent’; 2.5 billion are classified as ‘wheat-consuming’ and live on ,US$2 day21 . There are also 30 million poor wheat producers and their families for whom wheat is the staple crop (FAOSTAT 2012;). Demand for wheat in the developing world is projected to increase 60 % by 2050 (Rosegrant and Agcaoili 2010). The International Food Policy Research Institute projections indicate that world demand for wheat will rise from 552 million tons in 1993 to 775 million tons by 2020 (Rosegrant et al. 1997). At the same time, climate change-induced temperature increases are likely to reduce wheat production in developing countries (where around 66 % of all wheat is produced) by 20–30 % (Esterling et al. 2007; Lobell et al. 2008; Rosegrant and Agcaoili 2010). The Intergovernmental Panel on Climate Change (IPCC) (2007) noted that global climate change will have a major impact on crop production. CIMMYT and ICARDA (2011) estimated that 20–30 % wheat yield losses will occur by 2050 in developing countries as a result of a predicted temperature increase of 2–3 0C. On a global scale, these yield losses will not be fully compensated by yield gains in high-latitude regions (Canada, Russia, Kazakhstan and Northern USA), estimated at 10–15 % (OECD-FAO 2009), since major wheat producers such as France have already reported yield reductions due to increasing temperatures (Charmet 2009).
Global warming and its impact on wheat production in Bangladesh Change of temperature in Bangladesh due to global warming The Geophysical Fluid Dynamics Laboratory transient model (Manabe et al. 1991) projected that, in Bangladesh, temperatures would rise 1.3 0C by 2030 and 2.6 0C by 2070, compared with mid-20th-century levels. These values are slightly above those given in Table 3 and may reflect lower climate sensitivity in more recent climate models. The core findings, however, are consistent with the analysis presented above. The report estimated that winter warming would be greater than summer warming. The study also estimated little change in winter precipitation and an increase in precipitation during the monsoon season (Ahmed and Alam 1999). On the other hand, the annual mean temperature of Bangladesh is 25.75 0C and is expected to rise by 0.21 0C by 2050 (Karmakar and Shrestha 2000). Karttenberg et al. (1995) stated that crops may be exposed to more thermal stress in the near future since global warming is expected to increase temperatures by 2 0C by the middle of the 21st century. The Organization for Economic Co-operation and Development (OECD) estimated a rise in temperature of 1.4 0C by 2050 and 2.4 0C by 2100 in Bangladesh (OECD 2003;). The current assessment for Bangladesh by the IPCC (2007) predicts warming of 1.5–2.0 0C by 2050, with 10–15 % increased rainfall by 2030 and a 12 % increase in evaporation by 2030. Using data from 34 meteorological climate sites in Bangladesh, A. S. Islam (2009) and C. M. A. Islam (2009) estimated that maximum and minimum February temperatures had increased by 0.62 and 1.54 0C, respectively, over the past 100 years for all of Bangladesh. Poulton and Rawson (2011) reported that temperature in Bangladesh increased over the past two decades at 0.035 0C year21 . If this trend continues, by 2050, temperatures will have increased over 1990 levels by 2.13 0C. Yusuf et al. (2008) stated that between 1961 and 2007, mean south-west monsoon (June–October) as well as post monsoon (October–November) temperature increased by 0.8 0C. They also noticed that annual mean maximum temperature had risen by 0.6 0C while, more alarmingly, both the annual mean minimum and the winter (December–February) mean minimum temperature increased by 0.3 0C over the same period.