Assessment of the effects of climate change on future wheat cultivation in Bangladesh

Abstract

Being an agro-based country that is very much vulnerable to the impacts of possible climate change and its variability, climate change issues can have significant impact on agriculture of Bangladesh. A simulation study was conducted in this context to assess the vulnerability of wheat production in Bangladesh to potential climate change. Simulation runs were made for high yielding wheat variety KANCHAN, which is grown from November through March using the CERES-Wheat model of DSSAT (v4) modeling system. The yield of KANCHAN variety for the years 2008, 2030, 2050 and 2070 were simulated for 6 locations (districts), which were selected from among the major wheat growing areas in different regions of Bangladesh. The DSSAT model uses a set of crop specific genetic coefficients for predicting yield. The wheat variety KANCHAN was selected in the present study for which the genetic coefficients were determined by local researchers. Available data on soil and hydrologic characteristics of these locations, and typical crop management practice for wheat variety KANCHAN were used in the simulations. The weather data required for the model (daily maximum and minimum temperatures, daily solar radiation and daily precipitation) were generated for the selected years and for the selected locations using the regional climate model PRECIS. The DSSAT model predicted both increase and decrease in yield of KANCHAN due to climate change; the increase was predicted in most of the selected stations in the years of 2030 and 2050 whereas the yield decrease was predicted during the year 2070 in all selected locations. Compared to baseline year 2008, for fixed CO2 concentration, average yield increases of around 9.4% and 5.8% were predicted for the years 2030 and 2050, respectively and average yield decrease of around 22.1% was predicted for the year 2070 in the 6 selected regions. Increases in daily maximum and minimum temperatures have been found to be primarily responsible for reduction in wheat yield. On the other hand, rainfall had some positive impact on the wheat yield in some locations. Increases in incoming solar radiation had significant contribution for the increase in wheat yield in all selected years and locations. The increase in the level of CO2 also had some positive effect in the increase of wheat yield. For increased CO2 concentration, average yield increases of around 12.8% and 12.7% were predicted for the years 2030 and 2050, respectively and average yield decrease of around 10.3% was predicted for the year 2070 in the 6 selected regions with respect to the baseline scenario. Comparing to fixed CO2 concentration yields, the increase in wheat yield was observed in all selected locations and years in this context. Increasing temperatures were found to reduce the duration of physiological maturity of the wheat variety. Model results also suggested that in addition to reducing wheat yield, climate change may also make wheat yield more vulnerable to planting date. Since, wheat plant growth is very susceptible to temperature change, significant reduction in yield was predicted as planting date was delayed, especially beyond 7 December. Heat stress was also found to have significant effect on yield of wheat. Wheat exposed to high temperature especially during anthesis and grain filling phase can result in substantial yield loss. Crop models such as DSSAT are highly useful for scientists who want to better understand processes that contribute to the growth and yield of crops, and who also want to apply the models to improve crop management. DSSAT modeling system could be a useful tool for assessing possible impacts of climate change and management practices on different local varieties of wheat and other crops.