Ragweed pollen concentrations predicted to rise by 2050

26th May 2015

Ragweed is an invasive plant from North America with highly allergenic pollen that is spreading northwards from Central Europe. Currently, instances when ragweed pollen loads across the UK are high enough to result in hayfever symptoms are rare. But can we expect these events to become more frequent and severe in the future in response to climate change? Rothamsted Research scientists worked with a large team across Europe as part of project funded by the European Union, ATOPICA, to predict how the extent and magnitude of the ragweed pollen cloud may change by the middle of the century. Even without climate change, a small increased risk from higher pollen loads in Northern Europe was predicted as the plant continues to fill available habitats. The study is published in the journal Nature Climate Change.

Hayfever sufferers currently have to contend with large amounts of pollen released into the air by trees in the spring and grasses in the early summer. However, there is another source of highly allergenic pollen on its way to the UK from continental Europe - Common ragweed (Ambrosia artemisiifolia). In August to September, large populations of ragweed in Hungary, Italy and France produce an allergenic pollen cloud that moves with the wind, resulting in people suffering with hayfever across a much wider area than the current distribution of the plant. Because ragweed flowers late in the year, this has the effect of extending the hayfever season into a time when people would normally expect to be free from symptoms.

When the research team factored in the combined effect of climate change on the future distribution of the plant, the length of the flowering season and pollen production per plant, the potential problem was predicted to be much worse. Airborne ragweed pollen concentrations were estimated to reach levels 4 times higher than under current conditions by 2050. We would expect this to lead to increased sensitisation of the UK population to ragweed pollen and more people suffering hayfever symptoms later into the summer in the future. These results highlight the need for increased surveillance of the incidence both of ragweed pollen in pollen traps and possible colonising plants of ragweed in the UK.

Dr Jonathan Storkey, a plant ecologist at Rothamsted Research said: “Once established, ragweed is difficult to eradicate because of its long-lived seed, its capacity to re-sprout after cutting and its propensity to evolve resistance to herbicides. Our results indicate that controlling the current European ragweed invasion will become more difficult in the future as the environment will be more favourable for ragweed growth and spread, highlighting the need for the development of regionally co-ordinated eradication programmes.”

Dr Mikhail Semenov, who is strategically funded by the BBSRC and whose team at Rothamsted Research contributed to this project, commented: “Atopica is a multi-disciplinary project that gives an excellent example of collaborative research between ecologists, climate scientists and medics which provides the knowledge base needed to develop robust strategies to tackle a complex problem that spans national boundaries”.

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