Impact of flash droughts on cereal crops under Mediterranean conditions

Aim of study: To identify and characterize flash droughts (FD) in areas with rainfed cereal crops under Mediterranean conditions, analyzing their effects on cereal gross primary productivity (GPP), yield, and phenology from 2000–2023. Area of study: The main Mediterranean cereal-producing regions of Spain, Portugal, France, and Italy. Material and methods: FD were identified using soil moisture from the ERA5-Land reanalysis database and characterized in terms of frequency, duration, and severity. GPP sensitivity to FD was analyzed using two response time indices. To evaluate the impact of FD on wheat and barley yield, the percent yield reduction during FD years was calculated, while the effect of FD on cereal health and phenology was assessed using the normalized difference vegetation index (NDVI). GPP and NDVI data were obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS). Main results: FD had a significant impact on cereal under Mediterranean conditions, with higher frequency and intensity during months critical for cereal development. Cereals responded rapidly to FD, experiencing peak stress during critical months. FD reduced wheat and barley yields by up to 33%, led to poorer cereal health compared with years without FD events, and caused a slight advancement in the phenological phases. Research highlights: These results warn about the effects of FD on cereal crops under Mediterranean conditions and in water-limited regions in general, highlighting the potential consequences that are already affecting these crops. This knowledge helps identify response patterns that determine crop resilience to FD, facilitating the development of strategies to cope with future adversities under climate change scenarios.