Dryland wheat yield and yield variability responses to climate change across climatic zones in Iran

Predicting the future impact of climate change on wheat losses is essential for strategic decision making and adaptive strategy formulation in Iran and elsewhere. This study evaluates the impacts of climate change on dryland wheat yield and variations over phenological stages across six climatic zones in Iran using moment-based regression models, mixture probability distribution functions, and simulation models applied to data from 1991-2018. The findings reveal that, by the 2030s, climate change significantly reduces yield and increases variability in warm and warm-and-dry zones. The reductions in yield are predicted to reach 12.91% in warm zones and 20.20% in warm-and-dry zones under the combined climate scenarios by the end of the analysis horizon, corresponding to an overall decline of 6.74% in national dryland wheat yield. The results indicate that yield levels and their variability in response to climate variables are strongly dependent on both climatic zone and crop growth stage. A 1 °C increase in daily temperature leads to yield reductions of 82.25 kg/ha in warm zones, 62.15 kg/ha in warm-and-dry zones, and 9.32 kg/ha in the Caspian coastal zone. From a phenological perspective, a 1 mm reduction in precipitation during the flowering stage results in a yield loss of 4.84 kg/ha in the Caspian coastal region, whereas the same reduction during the stem elongation stage causes a larger loss of 16.98 kg/ha in the same zone. These findings underscore the importance of spatiotemporal analysis in developing climate smart adaptation strategies tailored to both regional conditions and specific crop growth stages. Strategies such as relocating wheat cultivation to less vulnerable zones and adjusting planting dates may help mitigate adverse climate impacts and support future agricultural resilience.