The effects of climate change on crop production are international concerns, but they are particularly significant for the sustainable agricultural development of Bangladesh [1
]. This is a country of variant climatic conditions year-round due to its geographic position and physiographic status. The biggest mountain Himalayas in the north and the funnel-shaped Bay of Bengal in the south have made Bangladesh a meeting point of the life-long monsoon precipitations and the catastrophic devastation of floods, droughts, cyclones, storm surges, etc.
]. Agriculture is always susceptible to unfavorable weather conditions and climate events. In spite of technological progress (such as improved crop varieties and irrigation potentialities), weather and climate are still key determinants for agricultural productivity and sustainability. Agriculture in Bangladesh is already under pressure, both from huge and increasing demands for food as well as from obstacles related to the degradation of agricultural land and water endowments [3
]. Any internal and external threat (social, political, natural and environmental) to agriculture directly affects food grain production as well as food security of the country [4
]. Sometimes the relation between these key factors and production losses are obvious, but often the relations are less direct. In spite of the recent strides regarding gaining sustainable development, Bangladesh’s ability to restore its development is experienced with significant challenges and confounded by climate change [5
Bangladesh has been facing higher temperatures over the last three decades [6
]. Moreover, it is forecasted to experience a rise in annual mean temperatures of 1.0 °C by 2030, 1.4 °C by 2050 and 2.4 °C by 2100. The prediction for the winter season (December, January and February) average temperature also showed a similar increasing pattern, 1.1 °C by 2030, 1.6 °C by 2050 and 2.7 °C by 2100. The projected value is 0.8 °C by 2030, 1.1 °C by 2050 and 1.9 °C by 2100 for the monsoon months [7
]. However, the Global Climate Model (GCM) data estimated more warming for winter than for the summer months [9
]. Based on the above projections, Bangladesh is likely to face more hot days and heat waves, longer dry spells and higher drought risk. In contrast, almost 80 percent of rainfalls in Bangladesh have been occurring during monsoon season (June-September). The remaining 20 percent covers eight months, including the winter months in which the high-yielding rice Boro is grown. Though monsoon season’s rainfall is projected to increase; the rainfall variability may increase significantly causing more intense rainfall and/or longer dry spells. Most of the climate models estimated that precipitation will increase during the summer monsoon [10
]. This erratic and unevenly distributed pattern produces extreme events, such as floods and droughts, which have remarkable harmful effects on major food crops’ yield, especially on Aman rice. As a result, rice production is likely to decline by 8%–17% by 2050 [6
]. It is noticed that Aman rice had dominated in Bangladesh from 1980–1981 and contributed to 57% of the total share. However, due to drought and flood events, the trend of share of Aman rice to the total rice production decreased to 40% by 2005–2006, even though the total cultivated area devoted to this crop is much higher than others to date [4
Food security is defined as access to enough and safe food by all people at all times for maintaining an active and healthy life. Bangladesh is predominantly an agrarian country with a high population density, where food security is a crucial issue. However, aggregate domestic production and per capita availability of food grains have increased in the country over the past decades. Nonetheless, the country still depends on import of food grains [4
]. In 2007–2008, it imported 11.5 percent of total availability and it is predicted that until 2021, the annual requirement for staple food will also exceed supply, indicating that demand is higher than production [15
]. Thus, it needs to increase the rice and wheat yield in order to fulfill the growing demand for food emanating from population growth. Climate change is a potential threat towards achieving the above mentioned objective. It is therefore necessary to realize the effects of climate change on the production of major food crops under sustainable environmental conditions [16
]. Examination of climatology at the national level is most important for the remedy of agricultural problems arising from climate change. Climatic information not only recommends the most suitable time for sowing and harvesting but also acts as a guide to the selection of the proper sites for a certain crop [17
]. Historically, most of the past studies regarding climate change impacts have concentrated on US outcomes [18
]. Interestingly, recent work has increasingly studied the impacts of climate change on agricultural production in the developing nations (such as Asia and Africa) [20
]. However, all of these studies have demonstrated that agricultural activities in developing countries are extremely vulnerable to climate change.
Despite the status of Bangladesh as a country that is greatly sensitive to climate change, factual studies of the significance of climate change on major food crops in this country have been scarce [26
]. The study of climate change impacts on Bangladesh agriculture has achieved recent attention, due to the share of Bangladeshʼs agricultural sector. Rimi et al.
] have conducted a study on the trend and prediction of future climate change scenarios with GCMs, most purposively investigating the impacts of climate change on rice production. They found that temperature variations had spectacular implications on crop yield. The summer crop Aus production has decreased significantly. The production of Boro rice, a winter crop, has increased significantly with the increase of minimum temperature. The inter-annual fluctuation in the amount of winter season rainfall was little. Boro production, therefore, was insignificantly affected by this variable. However, correlation between the climatic variables and crop production was not statistically significant. In most situations, they found that irrespective of crops and GCMs, climate change would have an adverse effect. However, their study simulated the future scenarios of a specific region and specific crop (confined to Satkhira district and rice crop only). Awal and Siddique [28
] estimated the trend of rice production by employing ARIMA model but did not consider climate influence. Hossain and Teixeira da Silva [1
] have undertaken an initiative to document the climate change impact on rice and wheat yield in Bangladesh. Their study has drawn a conclusion that global warming is expected to severely reduce the yield of various crops, including rice and wheat, directly affecting the food security of 165 million people in Bangladesh. However, this study only reviewed the past studies. Sarker [29
] carried out a study to examine the relationship between three climate variables (maximum temperature, minimum temperature and rainfall) and three rice crops. He considered 1971–1972 fiscal years’ yield as the yield of 1972. However, to ensure consistency between climate parameters and yield, he accounted 1972’s climate for 1972’s yield. Actually, the previous (1971) year’s climate data should be calculated for Aus and Aman rice as their growing season completely fell in this year. In case of calculating climate data for Boro rice, it should merge two calendar years into one (for example, from December of 1971 to May of 1972 for 1972’s yield), as he considered the growing months for Boro rice to be December-May. That is why his study might not represent the real relation between climate change and crops yield. In addition, he did not consider humidity and sunshine as climate variables although these variables have significant influence on crop production. Furthermore, to explain climate change impacts, he considered only rice in terms of the climate parameters, and did not pay attention to wheat.
Few studies have been done in Bangladesh to investigate the pattern and trend of rainfall, temperature, solar radiation, relative humidity, heat budget and energy balance on various ecosystem, and meteorological application on rice production, response of weather on wheat yield. However, previous records show that very few of them have intensively examined the relationship between climate change and crop production [2
]. Consequently, these studies might have generated deceptive findings owing to misinterpretation. Moreover, different crops might be affected non-uniformly [21
]. Accordingly, crop-oriented research (particularly on major staples) is pledged to formulate better policy suggestions for sustainable development. Therefore, the purpose of this study is to analyze the nexus between climate change and yield as well as cropping area of major food crops in Bangladesh using national level time series data over the span from 1972 to 2010.