Ragweed – long the bane of hay-fever sufferers in the United States – will spread its sneeze-provoking pollen over much of Europe by mid-century, according to researchers.
Common ragweed, or Ambrosia artemisiifolia, is not native to Europe. The invasive plant arrived from the U.S. sometime in the late 19th century. Climate change and its ensuing warmer temperatures will make much more of Europe suitable for the plants to grow and spread, according to a recent study, and rising carbon dioxide levels will help them flourish even further.
That's the conclusion provided by computer models looking 35 years into the future — based on ragweed's pollen production and seed dispersal, combined with prevailing winds normal for Europe and the most likely projections for global warming, reported in the journal Nature Communications.
Already firmly established in northern Italy and the southeast of France, ragweed is likely to move farther north into continental Europe and even onward to southern Britain under expected climate change scenarios.
Other experts, although not directly involved in the study, agreed that it could be problematic for people sensitive to pollen.
"As warmer temperatures and higher carbon dioxide concentrations allow ragweed to become more vigorous and invade further north, we can expect to see many more allergy sufferers," said Daniel Chapman, an invasive species expert at the Centre for Ecology and Hydrology in Edinburgh, Scotland.
Unless the world can successfully reduce carbon dioxide emission from fossil fuels, the annual pollen count in various parts of the ragweed's territories could increase between 100 and 1,100 percent, with an average rise of 300 percent, said study co-author Robert Vautard of the Climate and Environment Sciences Laboratory in Yvette, France.
Previous studies have already confirmed the ragweed pollen season in North America has become as much as 3 weeks longer in some northern regions — partly because of climate change.
Ragweed – also known as blackweed, bitterweed or America wormwood – is a global problem, with the invasive species already moving into South American, Japan and Australia.
The scientists suggest that Northern France, Germany and the United Kingdom could be beset by ragweed and its allergens by 2050.