Carbon dioxide emissions may be raising pollen counts in European cities, according to a continent-wide study.
By Michael Smith (Veshengro)
Researchers from 13 EU nations analysed pollen levels for more than 20 species of tree and plant and found that many, including several that cause allergies such as hay fever, correlated with rising CO2 levels.
Presenting their study at the European Geosciences Union (EGU) annual meeting, scientists said city planners might need to review which trees they plant as hay fever and other allergies appear to be rising across Europe.
In the UK, GP diagnoses of allergic rhinitis, which includes hay fever, rose by a third between 2001 and 2005 and it has been suggested that higher temperatures might be causing plants to produce more pollen.
Being in the open environment as part of my day job day in day out and being a hay fever sufferer I must also concur with the suggestion that trees are producing more pollen. One of the earliest plants that we have whose pollen is like clouds of yellow-orange dust are the Yew trees and from what I have seen over the last ten or so years alone I must say that the pollen clouds seem to be getting thicker annually.
But by comparing pollen counts during relatively hotter and relatively cooler years, this latest study found temperature was not the cause and Annette Menzel from the Technical University of Munich said that other possible factors were eliminated as well.
They had thought that the increase in the amount of pollen could be related to land use changes, but did not observe this and and trying to link it to temperature also proved not possible.
Thus, the only effect that's left, the scientists say, would be a CO2 effect from experiments in the real world and in climate chambers it is known that CO2 does promote the amount of pollen that trees produce and this is serious for people with hay fever and also asthma.
The fact that hay fever and asthma, in children and adults, is on the increase in the UK could be as a result of this. It is, however, a proven fact too that allergic rhinitis – to which hay fever belongs – can show up in later life. I personally never had hay fever until I was in my mid twenties or thereabouts.
The data in the study came from pollen monitoring stations in 13 countries, supplemented by tree cover information from the UN Food and Agriculture Organization and weather data.
Not all the 25 species studied show the same trend - pollen counts from some have actually gone down, but 60% of species have seen an increase in pollen production across the decades of the study period, including nine species known to produce allergenic pollen.
There were also differences between trends in different countries, with pollen counts falling in a few and perhaps the most intriguing finding was that pollen counts have generally increased with CO2 inside cities, but not outside.
The researchers suggest this could be down to the longer lifetime of ozone molecules outside urban areas and this gas is known to disrupt plant growth.
Although more research remains to be done, Professor Menzel's team suggests further rises in pollen counts probably lie ahead, given that CO2 concentrations are rising.
The increasing length of pollen seasons in Europe is linked to the introduction of plants and trees from other continents, in addition to any impact of CO2 and we therefore, seriously, should look at those alien species and, maybe, eradicate them.
In Germany, it is now only in November that no allergenic pollen is seen and therefore
the season of suffering for people with hay fever is getting more serious, as there is virtually no longer any respite for them either.
On a local scale, planners must become more aware of what sort of problems may arise from the urban trees that they're planting and should carefully consider what pollen they produce and whether they are known allergic reactors.
They often use birch trees, for example, because of their nice silver colour, not aware that they leave a serious allergenic problems behind and while birch is great in the proper setting and accumulation – and it is also a brownfield colonizer; one of the first in fact – and therefore care must be taken as to their extra introduction into towns and cites.
Hazel pollen is another well know hay fever agent as is the pollen of the Hawthorn and the Cherry Laurel.
We must, therefore, rethink, in light of CO2 emissions, which trees we plant, especially in an urban environment, and also, and equally important. Of reducing our CO2 emissions.
© 2011
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