Crop yield variability driven more by cultivated area changes than climate extremes in Iran

Climate change has intensified the frequency and severity of droughts in arid and semi-arid regions, posing increasing challenges to agricultural sustainability. Iran, located within the global arid belt, is particularly vulnerable due to its strong dependence on both rainfed and irrigated cereal production. This study examines the relative impacts of drought severity and changes in total cultivated area on long-term wheat and barley yield dynamics in Iran from 1995 to 2022. We used crop yield data (from Iran’s Agricultural Ministry), the Standardized Precipitation Evapotranspiration Index (SPEI), non-parametric trend tests, and boosted regression tree (BRT) modeling. Our results indicate that wheat and barley yields increased during the study period, with average rates of 0.26 t ha⁻¹ year⁻¹ and 0.075 t ha⁻¹ year⁻¹, respectively, despite recurrent drought conditions. These increases were primarily driven by the expansion of cultivated area rather than by climatic improvement. Changes in cultivated area emerged as the dominant driver of yield variability, explaining approximately 71–87% of observed yield changes across crop types and production systems, whereas drought severity accounted for 12–29%. Rainfed agriculture exhibited greater sensitivity to drought severity than irrigated agriculture, particularly for wheat, highlighting the limited buffering capacity of rainfed systems against climatic stress.