Since about mid-May, the grass pollen load in Switzerland has been practically consistently high to very high, hay fever symptoms were and are thus very widespread. The drought was also partly responsible for this; precipitation was mostly infrequent and far too little, so that the pollen was hardly ever washed out. In the course of climate change, the future outlook regarding grass pollen is rather bleak, as more pollen as well as an extension of the flowering period can be expected in the next years to decades.
Long-suffering grass pollen allergy sufferers
After the grass pollen season got off to a slow start in April and the excessively wet weather in the north in April until around mid-May ensured that the grasses were repeatedly washed out of the air, giving allergy sufferers repeated breathers, the grass pollen load has been high to very high from around mid-May onwards. From then on, there was little precipitation and if any, then only for a short time, so that there was hardly any relief. No wonder that itchy and watery eyes, runny and blocked noses as well as coughs and sore throats are currently very common. Around 15% of the population suffers from hay fever, with grass pollen responsible for more than half. The grass pollen season lasts even longer and ends only around the end of September, so the suffering period for grass pollen allergy sufferers continues (see Fig. 1). The further frequency of symptoms this year will depend on how the weather develops and whether there are repeated phases when pollen is washed out of the air.
Fig. 1: Pollen calendar: grass pollen until about the end of September; Source: MeteoNews
Grass pollen and climate change: more and longer pollen
Since grasses are the main allergen for hay fever, it is crucial how grass pollen concentrations will continue to develop in the future as a result of climate change. Increasing warming, especially in combination with increased CO2 levels (natural fertilization effect), has been shown to change the intensity and timing of grass flowering, causing a shift and lengthening of the growing season and an increase in biomass. The beginning of the pollen season is earlier, and at the same time the pollen season lasts longer due to higher temperatures in autumn. Thus, on average, grass pollen is in the air longer and more. While other allergenic pollen-producing plants such as birch are partly displaced by higher temperatures (fewer birches at lower altitudes, more at higher altitudes), grass pollen is more abundant at lower altitudes.While other allergenic pollen-producing plants such as birch are partially displaced with higher temperatures (fewer birches at lower altitudes, more at higher altitudes), there will be little change in grasses; at most, cold-loving species will be displaced by warm-loving species. In contrast, the composition of the grasses will not change much in rich meadows, which are dependent on the nutrient content and will simply produce longer and more pollen in the future. Another unfavorable effect will be that although there will be more precipitation with higher temperatures, it will be distributed differently. Dry phases are likely to become longer, while heavier precipitation can be expected for short periods. This, in turn, means that pollen will be washed out less frequently and thus pollen concentrations will be reduced less frequently. However, with longer dry periods, the grasses wither and the grass pollen concentration decreases. However, this is unlikely to be the case in the current climate. All in all, the outlook for grass pollen allergy sufferers is not rosy...
Evasion more difficult
One possibility to avoid the grass pollen is to go to the heights where hardly any grasses are blooming, i.e. above the border of the alpine mats, which is currently at about 2500 meters in the foothills of the Alps and at almost 3000 meters in the central Alps. With the higher temperatures, however, the alpine grasses are now shifting higher and higher, so that one has to climb higher and higher in order to escape large grass pollen concentrations. Basically, however, only alpine huts, especially SAC huts, come into question as alternative locations in midsummer anyway. Until about the beginning of June, however, you can escape the grasses even at lower altitudes, but as the flowering of the grasses progresses higher and higher, the grass pollen-free zone shifts further and further up.
Fig. 2: At the Hörnli hut you hardly have to deal with grass pollen; Source: pixabay
