Dynamics of historical and projected future drought and its impact on Robusta coffee productivity in central Uganda

Abstract

Drought monitoring and early warning are crucial elements that affect drought sensitive sectors such as crop production. The overall aim of the study was to characterize historical and future drought and establish its effect on Robusta coffee yield for two districts in Uganda’s drylands, that is Bukomansimbi and Mubende. The standardized precipitation index (SPI) was applied to both historical and model-projected future rainfall in order to characterize the drought events. For the historical period considered (1981 to 2018), the decade 2001 to 2010 had the highest percentage drought frequency of 16.7% in Bukomansimbi and 20% in Mubende. It also had the highest records of drought duration, magnitude and intensity. The historical drought trend showed an insignificant increasing trend (p > 0.05) for both districts. The future drought characterization showed that the decades 2021 to 2030 and 2041 to 2050 are anticipated to have the highest percentage drought frequencies, for which RCP 4.5 are 11.9% in Bukomansimbi and 15.6% in Mubende while under RCP 8.5 they are 9.2% in Bukomansimbi and 9.1% for Mubende. The results from ARIMAX model revealed that there could be an increasing trend in coffee yield from the year 2021 to 2030 though it will be more pronounced in Bukomansimbi than in Mubende. However, under both emission pathways, in Bukomansimbi, the yields could be significantly lowered by drought thus making coffee farmers in this district vulnerable to the detrimental effects of drought both now and potentially in the future. Therefore, sensitizing coffee farmers and implementing drought mitigation measures should be prioritized in this district in order to minimize the expected adverse effects on coffee yields.