Fig. 3.

Effects of climate change on the Bangladesh outbreak of wheat blast in 2016. (A) Temperature anomalies of February from 2014 to 2017 in the India-Bangladesh region. The temperature anomaly indicates a departure of monthly mean temperature from long-term average, and therefore a positive anomaly means that the observed temperature was warmer than the long-term average value. Figures were generated based on the NOAA global surface temperature anomaly dataset, produced by the United States National Center of Environmental Information in 2018 (Smith et al., 2008). (B) Calculation of the modified DFI (day favouring infection) index for the wheat blast-infected regions in 2016. To estimate infection risk for the wheat blast disease, we adopted the DFI index by Fernandes et al. (2017) as an infection risk proxy, which was modified based on the availability of weather variables from the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) climate data (Gelaro et al., 2017). Daily maximum temperature and precipitation variables of the MERRA-2 for 2015–2018 were extracted from eight overlapping grids over the target districts of Bangladesh (latitudes 22° 49′ 43.5468″ N to 24° 21′ 48.258″ N and longitudes 88° 33′ 29.8224″ E to 89° 43′ 42.294″ E), where severe wheat blast epidemics were reported in 2016. The modified DFI index is the number of days with maximum temperature > 23°C and rainfall > 0.1 mm for the period of January to February.