Impact of Rainfall Variability on Crop Intensification and Diversification in the Coastal Region of Bangladesh

The coastal regions of Bangladesh are highly vulnerable to climate change. Crop intensification and diversification in these areas are lower than in other parts of the country due to climate change and multiple stress environments. With other factors, high rainfall variability is one of the regions that impact agricultural production and productivity. The current study investigates the impact of rainfall variability on crop intensification and diversification in the coastal region of Bangladesh. Based on the historical climate data (1980-2020) of six weather stations, this study examines the onset (ON) and withdrawal (WD) of monsoon precipitation by forward and backward accumulation technique and the probability of dry and wet spells utilizing the Markov Chain (MC) probability model. The average ON and WD of monsoon precipitation were found at the 21st‒22nd and 43rd‒44th standard meteorological weeks (SMWs), respectively for all the stations. Extreme rainfall events have increased in recent periods (2001–2020) compared to earlier periods (1981–2000) in the rainfall months (Jun-Oct), potentially contributing to the recurrent flash floods and waterlogging in coastal Bangladesh in that time. The probabilities of dry spells are elevated in the early (1st‒17th SMWs) and late (43rd‒52nd SMWs) of the year. The region's higher likelihood of wet weeks (18th–42nd SMWs) experiencing precipitation ranges from 40‒100%. We also analyzed the effect of rainfall variability on aus (pre-monsoon rice) production, which has great potential in this area. Additionally, the frequency and return periods of extreme rainfall events of different thresholds during the dry months (Nov-Apr) were analyzed to assess the risks of cultivating rabi/non-rice crops due to increased precipitation and waterlogging and to evaluate the potentiality of rabi crops. We found that higher return periods of extreme events might delay the sowing of rabi crops and have adverse effects, particularly during their maturity phases. This study emphasizes the optimizing sowing windows of rice and non-rice crops, and cropping systems innovations based on variable rainfall patterns that will foster sustainable agricultural intensification and diversification in the coastal regions of Bangladesh.