Airborne ragweed pollen loads are likely to increase over large parts of Europe over the coming decades, which may heighten the prevalence of allergies, suggests a study published online this week in Nature Climate Change. The study estimates that a third of the predicted pollen increase is due to ongoing seed dispersal, and the remaining two-thirds is due to climate and land-use changes.
The common ragweed (Ambrosia artemisiifolia) is native to North America but the plant is rapidly spreading as an invasive alien species in Europe. When exposed to ragweed pollen, susceptible individuals can suffer allergic reactions, with symptoms including itchy eyes, sneezing and, in some severe cases, respiratory distress.
To assess the probable impact of land-use and climate change on the further spread of ragweed and annual pollen loads across Europe, Lynda Hamaoui-Laguel, Robert Vautard and colleagues used a modelling approach that takes into account changes in seed dispersal, pollen production, and wind-driven pollen dispersion. The computer simulations predict that by 2050, airborne ragweed pollen concentrations will be an average of four times higher (with a range of uncertainty from 2 to 12 times, depending on speed dispersal rate) than current levels, regardless of whether a high or moderate increase in average global warming is considered. Substantial increases in pollen load are projected for north-central Europe, northern France and southern UK, areas where pollen loads are virtually zero at present, while pollen concentrations will also increase in many areas already affected.