D3.467 - When urban green spaces meet human allergies – Evidence from an urban pine park in Thessaloniki, Greece

Airborne allergenic pollen is closely related to the actual flowering phenology timing and intensity of the respective plant species. While many researches have been focusing with increasing frequency on airborne pollen forecasting, the biological component is often missing. Thus, the modelling approaches, albeit promising, lack accuracy, particularly in extreme weather events and under the ongoing climate change. Since flowering phenology of anemophilous plant species is connected both with urban greenery and with manifestations of pollen allergy symptoms, its quantification has proven to be a valuable tool for the optimal prophylaxis of allergic individuals.  

Flowering phenology of Pinus pinea L. was studied in the urban green spaces along the seafront of Thessaloniki, Greece, for three full seasons (2023-2025). The entire area is surrounded by a high traffic street on one side and the sea on the other side. Reproductively-mature tree individuals (36) were selected along the urban park, based on proximity to the sea and street, position of traffic lights, distance from the city center. Frequent visits per week to each tree were performed throughout the three-year study period in order to record the phase of floral units, in both the north and south direction of the canopy.

It was found that warmer years and/or higher urbanization resulted in earlier onset of the pine flowering season, with air pollution not exhibiting as dramatic effect comparatively. Proximity to the city center advanced the onset of the flowering season. Interestingly, while there were variable differences in flowering season traits between years and among trees, there was a consistent earlier flowering start in those trees that were the closest to the sea, which was attributed to the higher salt content in the air.

To accurately quantify the produced and dispersed pollen in the atmosphere, which may be responsible for allergic symptoms, we need to take into account a variety of parameters: apart from urban greenery and flowering phenology information, also ecological traits and abiotic factors, in a Planetary Health approach. Here we suggest that the optimization of allergy risk forecasting lies in the complexity of the multi-exposome.