Climate change extends North American allergy season

The warmer winters caused by climate change have also shifted the flowering seasons of plants, and scientists including Lewis Ziska, a plant physiologist with the US Department of Agriculture have found that this has impacted on the length of the pollen season. The flowering season of the ragweed plant (Ambrosia) has increased in recent decades.

At least two weeks, and up to a month has been added to the pollen season across North America, and the research shows that the more northern latitudes are warming up faster than the mid-latitudes. The longer pollen seasons correlate with the disproportionate warming around the planet, which is attributed to the increase in greenhouse gas emissions. The findings are consistent with recent Intergovernmental Panel on Climate Change projections viewing increased warming as a function of latitude.

Pollen allergy affects millions of people around the world, and an increase in intensity of pollen production can contribute to an increase in reactions which can include asthma attacks.

Source: Proceedings of the National Academy of Sciences

Carbon emissions linked to Europe’s hayfever rise

Researchers from 13 EU nations under Dr Annette Menzel from the Technical University of Munich analysed pollen levels from more than 20 species of tree and plant, and have found that a raise in pollen counts correlates with a rise in CO2 levels across Europe. Thier findings were presented at the European Geosciences Union (EGU) annual meeting.

It had been suggested that higher temperatures might be responsible for higher pollen counts, but this latest study has found that CO2 is the cause. Or rather, after all other possibilities (temperature, land use change and others) have been eliminated, CO2 levels are all that is left.

The scientists used data taken from 13 pollen monitoring stations across the EU, and also tree cover information from the UN Food and Agriculture Organisation, and weather data.Twenty five species were studied, and pollen counts from some have gone down. However there is an increase in pollen production in 60% of the species, nine of which are known to produce allergic pollen. They found differences between trends in different countries, as well as finding that pollen counts have mostly increased with CO2 inside cities, but not outside – which researchers suggest could be down to the longer life of ozone molecules (which disrupt plant growth) outside urban areas.

Planners are urged to consider the allergic problems that their choices of ‘pretty’ trees, such as silver birch, might be causing. The increasing length of the pollen season is linked to the introduction of trees and plants from outside Europe.

Source: BBC – April 9th.

More research on hay fever

First Published Febuary 2004 Update in April 2011

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