Seite - 55 - in Biodiversity and Health in the Face of Climate Change

55 the main pollen season. Even though the exact relationship between symptoms (pul- monary, nasal or ocular) and pollen occurrence and abundance is not yet clear, there are some recent reports clarifying this interaction (e.g. Berger et  al. 2013; Bastl et  al. 2014; Karatzas et  al. 2014; Osborne et  al. 2017; Voukantsis et  al. 2015; Damialis et  al. 2019). Overall, there are indications that there is a positive correla- tion between allergic symptoms and pollen abundance. However, this relationship can differ significantly among different bioclimatic regions, among different atopic patients, and for each different pollen type, and of course the relationship itself is not linear and there is usually a variable time lag between the actual pollen exposure and the occurrence of the allergic symptoms. The above do make pollen season forecasting (and consequent symptom forecasting) rather complex, thus highlight- ing the need for additional research in order to achieve accurate and operational predictive models. Knowing the exact pollen season (in terms of occurrence, magnitude and shape) increases the capacity to accurately and in a timely way forecast the potential pollen exposure significantly and constitutes the first-line tool for allergy prevention. As an example, in Germany (Fig.  3.1), the main pollen season is confined to only a few months, usually commencing in March with the highly allergenic and cross-reactive pollen of hazel, alder and birch, and extending to the end of summer with the also very allergenic pollen from grasses and ragweed. A big allergy risk may exist even with shorter pollen seasons; even though a shorter duration of relevant allergic symptoms could then be hypothesised, such seasons tend to be highly peaked, thus potentially causing extreme exacerbations of symptoms even during these short intervals. Overall, in order to define the exposure to pollen beyond which respiratory Fig. 3.1 Typical pollen seasons in Germany according to the Polleninformationsdienst (averages from pollen data from 2007–2011; www.pollenstiftung.de). Ragweed pollen has been added to this diagram only recently 3 Climate Change and  Pollen Allergies