Assessing trends and variability of rainfall and temperature in the Kafa biosphere reserve, southwest Ethiopia

Climate change poses one of the greatest threats to the livelihoods of smallholder coffee farmers in the Kafa Biosphere Reserve (KBR), a region renowned for its Coffea arabica L. production in southwestern Ethiopia. This study analyzes the spatio-temporal variability of rainfall and temperature in the KBR using gridded and historical recorded data obtained from the Ethiopian Meteorological Institute (EMI) for the period between 1985 and 2023. The Mann-Kendall non-parametric test, Sen’s slope estimator, and standardized rainfall anomaly were employed to assess climate variability and change. All statistical analyses were conducted using Python version 3.13.1. Results revealed that the dry months (December to February) exhibit the highest variability in rainfall. Rainfall shows positive trends at both annual and seasonal scales. At annual level, rainfall increased at a rate of 5.38 mm year⁻1, a statistically significant trend, while summer, spring, and autumn rainfall increased by 1.101, 2.048, and 2.229-mm year⁻1, respectively, though these changes were not statistically significant. Conversely, mean, minimum, and maximum temperatures all displayed statistically significant increasing trends. Specifically, minimum and maximum temperatures rose at rates of 0.006 -0.015 °C year⁻1 and 0.004-0.028 °C year⁻1, respectively. The rapid increase in temperature, combined with notable fluctuations in rainfall anomalies is likely to adversely affect smallholder coffee producers. Therefore, to sustain and improve coffee yields in the future, policymakers should consider the potential impacts of climate change on coffee production.