Along mile after mile of Britain’s rural highways, especially the closer you get to London, every spring you will see masses of cow parsley. Many people now think of as an attractive addition to the landscape. It’s a pity they do, for the point about the syndrome is this: there’s lots of cow parsley, sure. But what you often won’t find is the lovely variety of wildflowers that 30 to 40 years ago decorated these same roadside verges. The cow parsley is crowding out wild flowers largely because of nitrogen from vehicle exhaust, especially diesel ones, which enriches the soil; and richer soil means fewer different species of plant can grow (whereas poor soil allows a wide variety of wild plants to coexist). It’s a striking example of how air pollution from motor vehicles is impacting on the natural world.
We know only too well how it impacts on us. This same air pollution causes 40,000 premature deaths in Britain every year and is now right at the top of a list of environmental health concerns. Vehicle emissions are breaking EU air quality laws, and the government has had to be ordered by the supreme court to find an effective strategy.
But what is not nearly so well appreciated is the way in which air pollution is now playing havoc with the natural environment too, principally through the atmospheric deposition of nitrogen compounds and perhaps also through particulates, the microscopic soot particles that diesel engines emit. It is the nitrogen that is doing the most obvious damage, enriching the soil which means only certain grass species and others such as stinging nettles, brambles and cow parsley (Anthriscus sylvestris, it’s scientific name), will be able to out-compete everything else.
And there is growing evidence that particulate pollution is behind the sudden disappearance of house sparrows from central London; whether it was connected to the widespread uptake of diesel vehicles remains to be investigated.
[Source: The Guardian, 1 June 2017]