Ambrosia artemisiifolia (common ragweed) is a highly allergenic weed that causes a variety of symptoms ranging from rhinitis, conjunctivitis, to asthma. It is currently spreading in Europe and a number of studies suggest that the pace at which it is happening is on the rise, climate change being one of the main factors influencing its spread.
But what is climate change’s role in the pollen allergy scenario? Atopica scientists focused on this particularly allergenic pollen in order to produce quantitative estimates of the potential impacts of climate change upon pollen allergy in humans. Two different projection models were used to estimate the change in ragweed’s range under climate change and future ragweed pollen levels. The data obtained from these projections were then translated into health burdens.
The numbers emerging from this study are by no means promising. According to the obtained data, sensitisation to ragweed will more than double in Europe, from 33 to 77 million people, by 2041 to 2060.
Naturally, the influence of climate change is complex and a certain degree of uncertainty is inevitable. However, in order to produce the most accurate estimates, a great number of variables were taken into account and projections were made considering two different suites of regional climate/pollen models, two green gas emission scenarios (RCP 4.5 and RCP 8.5), and three different plant invasion scenarios.
Based on these scenarios, fourteen estimates of current and future ragweed pollen were made and then combined with health and population data to quantify their public health significance using ragweed sensitisation rates as a health consequence. Sensitisation to ragweed (the initial process by which an individual becomes sensitive to a substance/allergen, i.e. ragweed pollen) is a health problem due to long-term pollen exposure.
The overall impact will be an increase in the range of ragweed, a change in timing and length of the pollen season as well as an increased plant productivity (and consequently pollen production), resulting in a rise in the number of sensitised people. Moreover, individuals that are already sensitised to ragweed may experience more severe symptoms due to higher pollen concentrations and a longer pollen season.
The most affected areas will be countries such as Romania and Italy, where ragweed is already established and therefore an already existing problem. However, the greatest proportional increases will be seen in Germany, France, and Poland, where ragweed sensitisation is currently relatively uncommon. By 2041-2060, sensitisation to ragweed will be widespread across the whole of Europe except for Scandinavia, the Baltic States, most of Spain, Portugal, and Ireland.
The choice of RCP scenario and model suites make a very little difference to the results by 2041-2060, with the exception of the plant invasion scenario. Under the reference plant invasion scenario, the population sensitised to ragweed at the European level is estimated to increase from 33 million to 77 million. In comparison, a slow plant invasion scenario reduces the projected future value to about 52 million, while a rapid plant invasion scenario increases the projected value to about 107 million.
In conclusion, the projected health consequences depend greatly on the rate at which ragweed spreads, therefore control measures against the invasion of this plant species will be an important adaptation strategy in response to climate change.