Possible role of climate change in the pollen scatter of Japanese cedar Cryptomeria japonica in Japan

We conducted an atmospheric pollen survey using a Durham sampler from 1983 through 1998 in Toyama City, Japan. We investigated yearly changes in the pollen season of Japanese cedar Cryptomeria japonica and analyzed the relationships between climatic factors and changes in the pollen counts. The results were as follows: (1) The first day of the Japanese cedar pollen season advanced from mid-March to late February. The yearly change in the first day was significantly associated with the mean temperature in February. (2) An increase in total pollen count was significantly associated with the mean temperature in the previous July. (3) The duration of the pollen season was suggested to be associated with the total pollen count. These results indicate that climate change, especially increasing global warming, influences the early pollen scatter and increase in pollen count as well as elongation of pollen season of Japanese cedar. Further study will be needed to clarify its effect on the health of pollen-allergy patients.