The growing season and with it the pollen season is slowly coming to an end. The pollen year was characterized by a very early start to the season and by very high grass pollen concentrations in some areas, which led to an above-average number of complaints. A brief review.
Early start to the pollen season
Normally, there is little pollen in the air from October to January, giving allergy sufferers time to breathe deeply. However, as was the case last year, the first allergenic pollens(hazels and alders) got off to a veritable early start and, as a result of the exceptionally high temperatures at the turn of the year, began to bloom more heavily as early as the first half of January (cf. Fig. 1).
Fig. 1: The hazels were already in bloom in the first half of January (picture from Sarganserland); Source: Roger Perret
In some areas, the first hazel and alder pollen could even be registered already at the end of the year, which has happened only very rarely so far. Usually, the beginning of the stronger blooming of hazels and alders is around the end of January to the beginning of February.
Many hazel and alder pollen especially in the second half of February
After already partly high concentrations of especially hazel pollen in the first half of January, the hazel and alder pollen count in the north was mostly small until around mid-February due to cool and repeatedly wet weather. From mid-February, a second phase of strong hazel and this time also alder pollen counts occurred, which lasted until the end of February. In March, hazel and alder pollen concentrations were mostly low to moderate.
Tree pollen season with constant ups and downs in concentrations
The pollen season of the most important allergenic tree pollens ash and birch (beginning of flowering in the second half of March) was characterized by a constant up and down of concentr ations due to the very changeable and repeatedly wet weather during the main flowering period in April (cf. fig. 2).
Fig. 2: Birch pollen concentrations were very variable this spring; Source: pixabay
The pollen was washed out again and again during the frequent wet phases, so that there were only briefly high concentrations and allergy sufferers were relieved again and again. Overall, the birch and ash pollen seasons were somewhat weaker than normal. This was also expected for birch after the very strong bloom last year.
Partly very high grass pollen concentrations
In the south, the pollen count of the main allergen, the grasses, began much earlier than normal at the end of March, and in some cases high concentrations were already reached from mid-April. In the north, on the other hand, grasses did not begin to bloom until the end of April, and the timing was pretty much within the norm. In the first two May decades, there were repeated rains, so that the pollen was repeatedly washed out and at most medium concentrations were reached. This then changed in the last May decade, the grass pollen concentrations rose rapidly to high to very high values and then remained mostly at this level in the too dry, much too warm and sunny June (cf. Fig. 3).
Fig. 3: Grass pollen was often in the air in large to very large concentrations from late May to early July; Source: pixabay
Only in July were the concentrations lower again, but in some cases still reached high levels. Overall, the grass pollen count was clearly above average, which also led to allergic reactions in more people than usual.
Ragweed pollen mainly in the Lake Geneva region and in Ticino
From August onwards, there were sometimes quite a lot of ragweed poll en in the air, especially in Ticino and in the Lake Geneva area, with a large part of this pollen being transported by the wind from France or Italy (cf. Fig. 4).
Fig. 4: Der invasive Neophyt Ambrosia macht stark allergene Pollen; Source: pixabay
Ragweed, which originates from North America, is spreading more and more as an agricultural weed, especially in Italy and France. Even in small quantities, its pollen can trigger severe health effects in humans. While ragweed has so far been quite successfully prevented from spreading in Switzerland, this is not the case in neighboring countries. Thus, ragweed pollen is likely to become more and more of a problem in our country, too, especially in the western and southern border regions.
Climate change: Earlier start of pollen season, higher pollen concentrations and more aggressive pollen
Climate change, with increasingly mild winters, is not only causing the pollen season to start earlier on average, but concentrations are generally increasing, according to several studies. The reason for the increasing number of pollen produced is that higher temperatures and more frequent dry spells put plants under stress, causing them to get into an emergency situation and react by producing more pollen. In addition, the stressed plants produce not only more pollen, but also more aggressive pollen. This changes the nature of the pollen by producing certain proteins to which allergy sufferers react more strongly. To make matters worse, not only does the allergic reaction intensify in sufferers, but more people overall can develop a pollen allergy. Truly not a good outlook for allergy sufferers in the future...