Introduction

Saffron (Crocus sativus L.), renowned globally as "Red Gold," represents one of the most economically valuable spice crops in world agriculture. Iran maintains its position as the dominant global producer, accounting for approximately 90% of worldwide production. However, Iranian saffron cultivation faces substantial threats from accelerating climate change, particularly in its main production regions. This comprehensive study examines the impacts of extreme climatic indices on saffron yield dynamics in two principal production hubs—Kashmar and Torbat Heydarieh—located in Razavi Khorasan Province, northeastern Iran. Climate change manifestations, including escalating temperature extremes, altered precipitation regimes, and prolonged drought periods, pose critical challenges to saffron production systems, potentially compromising both quantitative yield and qualitative attributes. Understanding these complex climate-crop relationships is fundamental for developing robust adaptation strategies to safeguard saffron farming livelihoods in these vulnerable regions.

Materials and Methods

This research employed a multi-faceted methodological approach integrating historical data analysis with future climate projections. The investigation utilized the comprehensive climate records obtained from synoptic stations for 1991-2014 in both Kashmar and Torbat Heydarieh, encompassing daily minimum and maximum temperatures (°C) and daily precipitation measurements (mm). For future climate projections, the study incorporated CMIP6 (Coupled Model Intercomparison Project Phase 6) outputs, including both historical baseline data and future climate scenarios under two representative pathways: SSP2-4.5 (moderate emissions) and SSP5-8.5 (high emissions). These datasets were acquired from the Copernicus Climate Data Store (CDS), a reputable repository for climate model data.

The research employed the ACCESS-ESM1.5 global climate model for its projections, recognized for its reliability in regional climate simulations. To ensure data quality and applicability, the study implemented the CMhyd (Climate Model data for hydrologic modeling) tool for bias correction using the sophisticated delta change (DC) methodology. For analyzing extreme climate events, the study computed ETCCDI (Expert Team on Climate Change Detection and Indices) indices through RClimdex software, a specialized tool for climate extreme analysis.

Saffron yield data, spanning the same 30-year period, were systematically collected from the Agricultural Jihad Organization records for both regions. Statistical analyses incorporated Pearson correlation coefficients to quantify relationships between extreme climate indices and saffron yield fluctuations, while multiple regression models identified key predictive variables and their relative contributions to yield variability. The modeling framework also enabled simulation of future saffron yield patterns under the two climate scenarios across multiple time horizons: 2026-2050 and 2051-2075.

Results and Discussion

The analysis revealed compelling evidence of significant climate shifts in both regions over the study period. A marked decrease in annual precipitation combined with increased frequency and intensity of extreme temperature indices was consistently observed. Statistical analysis demonstrated strong correlations between saffron yield and specific extreme climate indices, particularly TMm (Mean Minimum Temperature), FD (Frost Days), ID (Ice Days), TXn (Min Tmax), R95p (Very Wet Days), and consecutive dry days (CDD). Regression analysis further substantiated that these extreme climate indices collectively explain a substantial proportion of observed yield variance, highlighting their critical role in saffron productivity.

Projections under climate change scenarios present concerning trends for future saffron production. Under the moderate SSP2-4.5 scenario, yield reductions for Torbat Heydarieh were projected at 10% and 14.5% for the periods 2025-2050 and 2051-2075 respectively. Corresponding reductions for Kashmar under the same scenario were 11.5% and 16% More alarmingly, under the high-emission SSP5-8.5 scenario, projected yield losses escalated substantially: 17% and 28% for Torbat Heydarieh and 19.5% and 31.3% for Kashmar across the same future periods.

The differential vulnerability between the two regions warrants attention, with Kashmar demonstrating greater sensitivity to extreme climate events, particularly under high-emission scenarios. This discrepancy may be attributed to microclimatic variations, soil characteristics, and agricultural management practices.

This study provides compelling evidence that climate change, particularly through alterations in extreme climate indices, poses a substantial threat to saffron production in northeastern Iran. The significant correlations established between specific climate extremes and yield reductions, coupled with concerning future projections, highlight the urgent need for strategic adaptation interventions. The research demonstrates that high-emission scenarios could lead to devastating yield losses exceeding 31% in particularly vulnerable regions like Kashmar by the middel of the century.

These findings have crucial implications for agricultural planning, policy development, and climate resilience strategies in saffron-producing regions. Recommended adaptive measures include developing drought-resistant saffron varieties, implementing efficient irrigation systems, optimizing microclimate management through protective structures, and diversifying agricultural systems to reduce economic vulnerability. Future research should focus on refining climate-crop modeling approaches, exploring genotype-environment interactions, and evaluating the economic viability of proposed adaptation strategies to ensure the long-term sustainability of saffron production in a changing climate.