Climate change influences on the phenology of aeroallergens

Background/Question/Methods    Pollen contains proteins to which humans can readily become allergic. Therefore, release of pollen from wind-pollinated plants has important implications for human allergic diseases. Hence, it is important to understand the factors that govern the timing and magnitude of flowering for the effective management of these diseases. In addition, the phenology of fungal spores, which also contain allergens, is tied both to climate and plant host dynamics. An important question then is, how is global climate change affecting aeroallergen seasons now, and what is projected for the future? Airborne pollen and spore concentrations are regularly monitored using volumetric sampling devices such as the Burkard, Lanzoni, or Rotorod. Pollen is collected on optically clear media and microscopically identified and quantified from daily samples typically collected from building rooftops, 1-4 stories above ground. There are several networks of stations worldwide, including the Aeroallergen Monitoring Network in the US, and data from these stations have been used to examine changes in phenology of allergenic plants.  

Results/Conclusions    There is a seasonal progression of flowering, particularly in wind-pollinated tree taxa, and the degree of overlap of pollen seasons of individual taxa is dependent on the course of springtime warming. Warm and early springs, as anticipated to occur more frequently with global warming, lengthen the spring pollen season and potentially the length of suffering for individuals allergic to multiple tree pollen types. The onset of flowering is highly responsive to changes in climate, and long-term datasets indicate that onset of pollen seasons are advancing by almost 1 day/year. Plants that flower later in the growing season, such as ragweed, also respond to changes in springtime warming. Warm and early springs allow them to acquire greater biomass and resources that can be channeled into pollen production. This means more severe pollen seasons for allergic individuals. Hence it is anticipated that global climate change, by affecting the phenology of allergenic plants, could increase human suffering from allergic disease.