Date Published: June 1, 2018
Publisher: Elsevier Applied Science [etc.]
Author(s): J. Timsina, J. Wolf, N. Guilpart, L.G.J. van Bussel, P. Grassini, J. van Wart, A. Hossain, H. Rashid, S. Islam, M.K. van Ittersum.
Bangladesh faces huge challenges in achieving food security due to its high population, diet changes, and limited room for expanding cropland and cropping intensity. The objective of this study is to assess the degree to which Bangladesh can be self-sufficient in terms of domestic maize, rice and wheat production by the years 2030 and 2050 by closing the existing gap (Yg) between yield potential (Yp) and actual farm yield (Ya), accounting for possible changes in cropland area. Yield potential and yield gaps were calculated for the three crops using well-validated crop models and site-specific weather, management and soil data, and upscaled to the whole country. We assessed potential grain production in the years 2030 and 2050 for six land use change scenarios (general decrease in arable land; declining ground water tables in the north; cropping of fallow areas in the south; effect of sea level rise; increased cropping intensity; and larger share of cash crops) and three levels of Yg closure (1: no yield increase; 2: Yg closure at a level equivalent to 50% (50% Yg closure); 3: Yg closure to a level of 85% of Yp (irrigated crops) and 80% of water-limited yield potential or Yw (rainfed crops) (full Yg closure)). In addition, changes in demand with low and high population growth rates, and substitution of rice by maize in future diets were also examined. Total aggregated demand of the three cereals (in milled rice equivalents) in 2030 and 2050, based on the UN median population variant, is projected to be 21 and 24% higher than in 2010. Current Yg represent 50% (irrigated rice), 48–63% (rainfed rice), 49% (irrigated wheat), 40% (rainfed wheat), 46% (irrigated maize), and 44% (rainfed maize) of their Yp or Yw. With 50% Yg closure and for various land use changes, self-sufficiency ratio will be > 1 for rice in 2030 and about one in 2050 but well below one for maize and wheat in both 2030 and 2050. With full Yg closure, self-sufficiency ratios will be well above one for rice and all three cereals jointly but below one for maize and wheat for all scenarios, except for the scenario with drastic decrease in boro rice area to allow for area expansion for cash crops. Full Yg closure of all cereals is needed to compensate for area decreases and demand increases, and then even some maize and large amounts of wheat imports will be required to satisfy demand in future. The results of this analysis have important implications for Bangladesh and other countries with high population growth rate, shrinking arable land due to rapid urbanization, and highly vulnerable to climate change.
Bangladesh is a deltaic country located in South Asia, with a relatively small land area (147,570 km2) but with the 8th largest world population (ca. 161 million) and the 13th highest world population density. According to the medium variant UN projection (UN, 2015), Bangladesh’ population will further increase to 186 and 202 million by the years 2030 and 2050, respectively. Increasing income level and urbanization may lead to diet changes such as switching from traditional rice to wheat and to livestock, poultry, and fish products, which in turn require large amounts of maize for their production (Alkanda, 2010, Mukherjee et al., 2011). Most land suitable for cropping in the country is already under cultivation. Arable land area is even decreasing over time due to increasing demand for residential and industrial use (Hasan et al., 2013). Bangladesh also suffers from periodic natural calamities such as drought, flooding, and cyclones. Due to its location in a delta, climate change and associated sea level rise is expected to increase risk for flooding and salinization of agricultural lands, especially near the southern coast (Hossain and Silva, 2013, MOA-FAO, 2012).
Future domestic supply of cereals depends mainly on possible changes in land use and yield gap closure. Our simulation results reveal that the Yp of maize and boro rice in Bangladesh can be > 11 t ha− 1 and that of wheat can be > 5 t ha− 1, while Yw can range between 6.5 and 7.8 t ha− 1 for aman and aus rice (Table 3; Figure SI1 and Figure SI2). The simulated maize Yp in this study is lower than those reported by Timsina et al., 2010, Timsina et al., 2011, the simulated Yp of rice is similar. Likewise, the simulated Yp for wheat across the country is slightly lower than that recorded from well-managed trials from large numbers of fields (Rawson et al., 2011) as well as also lower than those reported by Timsina and Humphreys (2006). The discrepancies in simulated and observed yields for rice are expected as the Yp for boro rice in this study was averaged for eight locations of Bangladesh using observed weather data while the Yp from Timsina et al., 2010, Timsina et al., 2011 was based on only three locations and simulated using the NASA weather data. Difference in Yp for wheat between the current study and Timsina and Humphreys (2006) is probably due to difference in weather years and models used for simulations. We used the WOFOST model while Timsina and Humphreys (2006) used CERES-Wheat and these two studies used different years of weather data for simulations.