Rainfed crop yield response to climate change in Iran

Despite many concerns about climate change impacts on rainfed crops, few studies have been conducted on the yield variations of different crops arising from climate changes in Iran. This study aims to quantify uncertainties of yield anomalies (as predictands) in the future for fifteen rainfed crops through an index depicting water balance known as the standardized precipitation evapotranspiration index, SPEI (as predictors). For this purpose, we used multiple linear regression models (MLRs). We considered three types of uncertainty, coming from: (1) the regional climate models' output; to address it, we analyzed the output of three models (CN-REGC, EC-REGC, and GF-REGC), under three scenarios (RCP2.6, RCP4.5, and RCP8.5), for three time periods (imminent future: 2011-2040, near future: 2041-2070, and far future: 2071-2100); (2) the MLRs; to address it, six MLR models were applied on various validating sets; and (3) the stochastic nature of statistically downscaled output; to address it, 100 realizations of monthly air temperature and precipitation were stochastically generated by a weather generator based on the K-nearest neighbor (KNN). Averaging on all crops and calibration sets, about 82.6% and 86% of the observed values fell within the 95% prediction intervals at validating and evaluating stages, respectively. The crop-specific regions for a given crop overlap the major provinces providing that crop. This overlapping ranges from 70 to 90% for the various crops. In addition, the crop-specific temporal features cover the growing season of that crop entirely or partially. Overall, except for few crops like potato and clover, the most strategic crops providing food and forage will experience a yield decrease by up to 80% due to climate change. Management options should be adopted by decision-makers for mitigating climate change impacts and securing sustainable food security.

Automated summary

This study analyzes the yield variations of rainfed crops in Iran using multiple linear regression models. The results show that, except for a few crops like potato and clover, the strategic crops providing food and forage will experience a decrease in yield by up to 80% due to climate change. It is important for decision-makers to adopt management options to mitigate the impacts of climate change and ensure sustainable food security.