Agneta Ekebom

Common ragweed (Ambrosia artemisiifolia) is one of the most harmful alien invasive species in Europe. Ragweed pollen is a potent aeroallergen, and can travel long distances in the atmosphere. In this research we studied pollen samples collected in Turku, Finland, during 1990–2022, to identify when ragweed pollen was first transported to the country and how frequently it has happened since, how much pollen has been transported to the country yearly, and whether it is possible to observe trends in airborne ragweed pollen occurrence in Finland during the past decades. We show that (1) ragweed pollen has been transported to Finland since the 1990’s, significantly earlier than previously thought, and (2) the long-distance transport episodes have often been more intense in the recent years. Ragweed pollen transports occur in the late summer or in the autumn, thus lengthening the pollen season in Finland. We also describe a case study where we show that ragweed is able to produce mature viable seeds in Finland. Our conclusion is that the significance of ragweed as an aeroallergen in Finland is increasing, and thus the situation needs to be regularly monitored.

Bird species in boreal forests that utilise seed crops from masting trees face large temporal and spatial variation in food availability. Seed crop size is therefore expected to influence breeding population size, migration, and wintering. We analyse ≤36-year time series of Eurasian Siskin Spinus spinus numbers in Sweden in relation to seed crop sizes of Norway spruce Picea abies, Scots pine Pinus sylvestris, birch Betula spp. and alder Alnus spp. Breeding numbers were somewhat positively associated with spruce, birch, and alder seed crop sizes, but peak breeding numbers sometimes also coincided with small crop sizes. Migration was not strongly related to seed crop sizes, but positively associated with breeding population size. Wintering numbers were strongly positively associated with spruce, birch, and alder seed crop sizes. Pine did not affect any Siskin numbers. This suggests that at large spatial and temporal scales, spruce seeds are less important for Siskin breeding than previously thought. Nevertheless, spruce, birch and alder may all have some influence on breeding and were positively associated with wintering numbers, while migration appears to be a density-dependent process rather than a response to lack of food. The results provide a unique insight into how multiple seed crops affect a seed-eating bird.

The dataset presents a 43 year-long reanalysis of pollen seasons for three major allergenic genera of trees in Europe: alder (Alnus), birch (Betula), and olive (Olea). Driven by the meteorological reanalysis ERA5, the atmospheric composition model SILAM predicted the flowering period and calculated the Europe-wide dispersion pattern of pollen for the years 1980–2022. The model applied an extended 4-dimensional variational data assimilation of in-situ observations of aerobiological networks in 34 European countries to reproduce the inter-annual variability and trends of pollen production and distribution. The control variable of the assimilation procedure was the total pollen release during each flowering season, implemented as an annual correction factor to the mean pollen production. The dataset was designed as an input to studies on climate-induced and anthropogenically driven changes in the European vegetation, biodiversity monitoring, bioaerosol modelling and assessment, as well as, in combination with intra-seasonal observations, for health-related applications.

Background: Allergic rhinitis (AR) is one of the most common chronic diseases worldwide. There are limited prospective long‐term data regarding persistency and remission of AR. The objective of this study was to investigate the natural course of pollen‐induced AR (pollen‐AR) over 20 years, from childhood into early adulthood.Methods: Data from 1137 subjects in the Barn/Children Allergi/Allergy Milieu Stockholm Epidemiologic birth cohort (BAMSE) with a completed questionnaire regarding symptoms, asthma, treatment with allergen immunotherapy (AIT) and results of allergen‐specific IgE for inhalant allergens at 4, 8, 16 and 24 years were analyzed. Pollen‐AR was defined as sneezing, runny, itchy or blocked nose; and itchy or watery eyes when exposed to birch and/or grass pollen in combination with allergen‐specific IgE ≥0.35kU_A/L to birch and/or grass.Results: Approximately 75% of children with pollen‐AR at 4 or 8 years had persistent disease up to 24 years, and 30% developed asthma. The probability of persistency was high already at low levels of pollen‐specific IgE. The highest rate of remission from pollen‐AR was seen between 16 and 24 years (21.5%); however, the majority remained sensitized. This period was also when pollen‐specific IgE‐levels stopped increasing and the average estimated annual incidence of pollen‐AR decreased from 1.5% to 0.8% per year.Conclusion: Children with pollen‐AR are at high risk of persistent disease for at least 20 years. Childhood up to adolescence seems to be the most dynamic period of AR progression. Our findings underline the close cross‐sectional and longitudinal relationship between sensitization, AR and asthma.