The PRIME Index: Prioritization of cultivated Regions IMpacted by drought in agriculturE

Introduction Drought is one of the major challenges for Italian agriculture, with significant repercussions on food production, the economy, and water security (Liu et al., 2025). As part of the Mediterranean Basin, Italy is particularly vulnerable to climate change, experiencing rising average temperatures and decreasing precipitation levels (Leijnse et al., 2024). Within the framework of the CASTLE project, aimed at identifying areas where small reservoirs for irrigation are essential for sustaining the agricultural sector, this research focuses on targeting Italy’s most drought-affected agricultural regions to mitigate economic losses and crop failures. The key innovation of this study lies in the development of the “PRIME index,” an integrated assessment tool combining climatic and agricultural data. This index classifies the Italian territory into ten priority intervention classes, providing policymakers with a scientifically robust yet operationally simple instrument to guide mitigation actions both in the present and the future. Unlike conventional drought assessments that primarily focus on analysing drought events and their impacts, the “PRIME index” serves as a practical decision-making tool designed for ease of use and direct application, thereby enabling strategic water storage solutions to support agriculture under prolonged drought conditions. Materials and methods This research integrates the Standardized Precipitation Evapotranspiration Index (SPEI) at multiple time scales, computed between 1951 and 2024, with crop sowing and harvest dates to identify Italy’s agricultural drought-exposed areas. The analysis of the 6-month SPEI, commonly used to assess agricultural drought, reveals a significant increase in the frequency, duration, and intensity of drought events, indicating progressively worsening drought-prone conditions. To evaluate the impact of drought on the Italian agricultural sector, the study considers the sowing and harvesting months for each crop. Specifically, the SPEI magnitude at the time of harvest is assessed using a water deficit accumulation period (D), where D = precipitation – evapotranspiration, corresponding to the months between sowing and harvesting. This methodology, allows the identification of water shortages during critical growth stages, thereby determining the potential risk of yield loss (Liu et al., 2025). For each crop, we initially determine the severe drought threshold exceedance frequency during the 74 year observation period. This analysis, combined with the percentage of cultivated area per grid cell and the economic value of the selected crops, leads to the development of the “PRIME Index,” an innovative tool capable of ranking intervention priorities by considering both spatial extent and economic impact. Once these results are obtained, the procedure is repeated using future climate projections up to 2100, considering both the most severe Shared Socioeconomic Pathway (SSP5-8.5) and the sustainability scenario (SSP1-2.6) (Riahi et al., 2017). This analysis provides insights into how climate change will affect Italian agriculture, contributing to an early warning system framework for risk assessment and mitigation planning. 1 Results and concluding remarks The evaluation of the SPEI index highlights a rise in agricultural drought occurrence, while dually revealing a marked expansion of drought-affected regions over the past two decades, highlighting not only the intensification and increased frequency of drought events but also a broader geographic impact. By accounting for both the agricultural area extent and crop economic value, the “PRIME index” allows the identification of the areas at the highest risk, underscoring the urgent need for tailored mitigation strategies to enhance the resilience of agriculture to climate change. Given the ease of computation of the “PRIME Index” and the availability of climatic and agricultural datasets at the European level, future research will extend this analysis beyond national borders. Additionally, we aim to enhance the reliability of the index by incorporating annual crop-specific irrigation volumes, yearly crop yields, crop resilience to drought-induced shocks, drought event magnitude, and the strategic value of crops in terms of production importance. By refining and expanding this framework, we strive to provide a more comprehensive tool for policymakers and stakeholders, fostering proactive and data-driven adaptation strategies for a more sustainable agricultural future.