The current warm and dry weather is perfect for swimming, eating ice cream and barbecue parties. For hay fever patients it may not be so much fun, as they are dealing with runny noses and itchy eyes. The weather conditions stimulate grasses, herbs and some tree species to release their pollen into the atmosphere. But did you know that temperatures during last year’s spring and summer influenced the amount of pollen that is in the atmosphere today?
To study pollen-climate relationships, I needed high resolution pollen data and detailed information on precipitation and temperature. A combination of such datasets is rarely available. Luckily, researchers at the Leiden University Medical Center (LUMC) have been counting and identifying pollen in the atmosphere since 1969 on a daily basis and were very willing to collaborate with me and my supervisors dr. Timme Donders and dr. Stefan Dekker. I statistically correlated their pollen data with climate data from the KNMI. It was hard work, but it paid off! I found strong relationships between temperatures in previous spring and early summer, and annual pollen production in the next year. We already knew that the pollen concentration in the atmosphere is higher on dry and warm days, but with this project I showed that the weather conditions of last year’s spring and summer are also important factors in pollen production. To check whether this effect was just a local phenomenon, I also investigated pollen records from the Elkerliek Hospital in Helmond and fossil pollen data from the Mariapeel. The annual variations in pollen counts were very similar, suggesting that the temperature effect on pollen production is similar throughout the Netherlands, and probably for much of north-western Europe.
The idea is that high temperatures during spring and summer will stimulate the production of pollen and the formation of flower buds. These pollen will be released into the atmosphere in the next year, after a dormancy period during the winter. So, when you’re sneezing and dealing with a runny nose and itchy eyes, remember, it is not just the warm, dry and sunny weather of today…
Want to know more about this research project? We published a nice article, you can find it at the website of PLoS ONE:
Donders, T.H., Hagemans, K., Dekker, S.C., de Weger, L.A., de Klerk, P., Wagner-Cremer, F. (2014). Region-Specific Sensitivity of Anemophilous Pollen Deposition to Temperature and Precipitation. PLoS ONE 9(8): e104774. doi:10.1371/journal.pone.0104774