Due to recent changes in climate in The Netherlands, the start and duration of the growing season length in The Netherlands is changing. The changes in the growing season have several consequences for human health to which society needs to adapt. Examples are the timing and duration of the hay fever season, the presence of the Oak processionary caterpillar and the activity of ticks in relation to Lyme disease. The Dutch phenological network Nature’s Calendar (Natuurkalender) aims to monitor, analyze, forecast and communicate climate induced phenological changes. It furthermore aims to develop methodologies and techniques that allow society to adapt to the observed and expected future phenological changes. The Nature’s Calendar network currently involves over 7.000 volunteers, hundreds of school children and over 30 organizations with various backgrounds (including universities, NGO’s, media, ICT, commercial sector, hospitals). In our paper we will address the following questions: What is the contribution of citizens in

1. determining how plants and animals responded to the observed changes in climate?
2. quantifying the variability of health impacts and health risks of natural systems?
3. improving adaptation to the climate induced ecological changes?

Results/Conclusions

Based on the phenological observations of hundreds of thousands of volunteers via the Nature’s Calendar Network we conclude that the recent increase in temperature lengthened the growing season with one month. The volunteers significantly contributed to the quantification of the (variability in) amount of daily hay fever symptoms (via www.allergieradar.nl), the location and timing of tick bites, the amount of ticks and the percentage of ticks infected with the Borrelia bacteria causing Lyme disease in Natural area and the location and the presence of the Oak processionary caterpillar. With their contribution we were able to develop forecast models and informative websites with which we continuously inform the public and media on the developments in nature and the related health risks. The information allows the public and relevant organizations to adapt to the climate induced ecological changes.