Trends in climate extreme indices and implications for coffee farming in The Kafa Biosphere Reserve, southwest Ethiopia

Smallholder coffee farming in tropical highlands is increasingly threatened by climate change. This study examines the trends and potential effects of climate extreme indices on coffee farming households in the Kafa Biosphere Reserve using daily rainfall and temperature data (1985–2023). Twelve extreme climate indices (six temperature and six rainfall indices) were computed from Ethiopian Meteorological Institute (EMI) records following the Expert Team on Climate Change Detection and Indices (ETCCDI) standards. Trend analyses were performed using the Mann-Kendall test and Sen’s slope estimator. Results indicate significant warming with annual maximum temperatures (TXx) rising at rates of 0.02–0.04°C yr −1 across stations. The number of hot days (TX90p) increased significantly at all stations except Wushwush. Rainfall extremes show significant upward trends with annual rainfall increment up to 11.43 mm yr −1 in Genji. Heavy rainfall days (RX1day) and rainfall intensity (SDII) increased notably across multiple stations, while consecutive wet days (CWD) decreased slightly in some stations. In general, many climates extreme indices trends seem to exceed the tolerance range of Coffea arabica , reducing yield and quality and raising pest and disease risks. These trends threaten both farmer livelihoods and Ethiopia’s position in the global specialty coffee market. Therefore, adaptation strategies such as shade management, heat-tolerant varieties, and soil and water conservation are essential to sustain smallholder livelihoods. Moreover, integrating local climate adaptation into agricultural and environmental policies is critical for strengthening the resilience of both coffee systems and biodiversity in the Kafa Biosphere Reserve.