Impacts of climate change on airborne Quercus pollen trends in Andalusia region (southern Spain)

Quercus species are the most frequent autochthonous arboreal taxa in the natural areas of Andalusia region (southern Spain). Due to their abundance and anemophilous character, high airborne pollen concentrations are detected in natural and urban areas of the region. Variations in its reproductive phenology can be considered an important bio-indicator regarding the impacts of climate change on vegetation in the Mediterranean region. This study aims to analyze trends in flowering patterns using airborne pollen concentrations from the capital cities of the 8 provinces of Andalusia region and to study its relationships with meteorological parameters and climate change over decades. Variations in time and intensity of flowering have been studied using different methods for defining the pollen season. This study demonstrates that for comparing results, it is relevant to choose the right definition to calculate the pollen season. The analysis of historical databases of Quercus airborne pollen in Andalusia showed variations in the floral phenology with an increase in the intensity of the pollen season throughout the studied period and an advance in the start trends due to the increase of temperature. Nevertheless, this increase might have been smoothed by the decrease of precipitations in some sampler locations, a limiting factor in the area. It has been also observed a delay in the end dates that caused a lengthening of the season. Climate change could be provoking longer and more intense pollen seasons that will lead to more intense and persistent symptoms in sensitive patients.