Effects of climate change on Platanus flowering in Western Mediterranean cities: Current trends and future projections

Current and Future Effects of Climate Change on Airborne Allergens

PURPOSE OF REVIEW

Delineation of the impact of elevated carbon dioxide and concomitant global warming on airborne allergens is performed.

RECENT FINDINGS

European tree pollen trends in general showed earlier start and end dates and increased total pollen release, with some differences both in locale and among species. Earlier flowering was also seen with grasses and weeds. In the case of some boreal trees, flowering was delayed due to a pre-seasonal requirement for necessary accumulated chilling temperature to achieve bud-set. Anthropogenic climate change induced rise in temperature and CO2 levels has resulted in demonstrable increases in aeroallergens. This has been most dramatic in tree pollen annual load, but also seen with grasses and weeds. Collected data is greatest for the Northern Hemisphere, especially the European continent, with supporting data from North America and Australia.

Projections of the start of the airborne pollen season in Barcelona (NE Iberian Peninsula) over the 21st century

The effects of global warming are numerous and recent studies reveal that they can affect the timing of pollination. Temperature is the meteorological variable that presents a clearer relationship with the start of the pollination season of most of the observed airborne pollen taxa. In Catalonia, in the last fifty years, the average annual air temperature has increased by +0.23 °C/decade, and the local warming has been slightly higher than the one on a global scale. Projections point to an increase in temperature in the coming decades, which would be more marked towards the middle of the century. To analyse the effect of the increase in temperature due to global warming on the starting date of pollen season in Barcelona, a forecasting model has been applied to a set of projected future temperatures estimated by the European RESCCUE project. This model, largely used in the literature, is based on determining the thermal needs of the plant for the pollen season to begin. The model calibration to obtain the initial parameters has been made by using 20 years of pollen data (2000-2019), and the model effectiveness has subsequently been tested through an internal evaluation over the period of the calibration and an external evaluation on 4 years not included in the calibration (2020-2023). The mean bias error in the internal calibration ranged between -0.4 and - 0.6 days, and between +0.5 and - 8.3 in the external one, depending on the taxon. The results of the application of the model to the temperature projections over the 21st century point to a progressive advancement in the pollination dates of several pollen types abundant in the city, allergenic most of them. These advances ranged, at the end of the century, between 15 and 27 days, depending on the climate model, for the scenario of the highest concentrations (RCP8.5) and between 7 and 12 days for the emissions stabilization scenario (RCP4.5).

Predicting the main pollen season of Broussonetia Papyrifera (paper mulberry) tree

Paper mulberry pollen, declared a pest in several countries including Pakistan, can trigger severe allergies and cause asthma attacks. We aimed to develop an algorithm that could accurately predict high pollen days to underpin an alert system that would allow patients to take timely precautionary measures. We developed and validated two prediction models that take historical pollen and weather data as their input to predict the start date and peak date of the pollen season in Islamabad, the capital city of Pakistan. The first model is based on linear regression and the second one is based on phenological modelling. We tested our models on an original and comprehensive dataset from Islamabad. The mean absolute errors (MAEs) for the start day are 2.3 and 3.7 days for the linear and phenological models, respectively, while for the peak day, the MAEs are 3.3 and 4.0 days, respectively. These encouraging results could be used in a website or app to notify patients and healthcare providers to start preparing for the paper mulberry pollen season. Timely action could reduce the burden of symptoms, mitigate the risk of acute attacks and potentially prevent deaths due to acute pollen-induced allergy.