Air pollution doesnt just harm humans it is destroying nature too | Michael McCarthy

Sharing is caring!

The poisonous residue from car exhausts is causing a public health crisis and could be the death of sparrows too

You may never have heard of cow parsley syndrome, yet its been visible over much of Britain for the past month the spectacle of country roads fringed with a dense throng of tall white feathery flowers, three- to four-feet high, which many people now think of as an attractive addition to the landscape. Its a pity they do, for the point about the syndrome is this: theres lots of cow parsley, sure. But there isnt anything else.

Along mile after mile of our rural highways, especially the closer you get to London, every spring you will see masses of this frothy foam. But what you often wont find is the lovely variety of wildflowers that 30 to 40 years ago decorated these same roadside verges: comfrey, ladys smock, white dead-nettle, garlic mustard, birds-foot trefoil, ox-eye daisy, early purple orchid and many more. The cow parsley has largely crowded them out because it has been fertilised into excessive growth. Much of the fertiliser has come in the form of nitrogen compounds from car exhausts, especially diesel ones 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. Causing up to 40,000 premature deaths a year, air pollution in Britain is now right at the top of our list of environmental health concerns. It is seen in human terms as a crisis and a public health emergency. 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.

People get that. Absolutely. 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.

To flourish, most of our wildflowers need poor soil. A bumble bee on a spear thistle. Photograph: Tony Phelp/Alamy Stock Photo
It is the nitrogen that is doing the most obvious damage. To understand it, you need to grasp the key fact about our wildflowers, which is strongly counterintuitive: that to flourish, most of them need poor soil. Poor soil allows a wide variety of wild plants to coexist; but a rich soil full of nutrients such as nitrogen means that a small number of robust and resilient plants, especially certain grass species and others such as stinging nettles, brambles and indeed Anthriscus sylvestris, as cow parsley is scientifically named, will be able to outcompete everything else.

This is not just an impression: the supporting data is there, in the Countryside Survey, the enormous census of the habitats and vegetation of rural Britain that the government carries out every 10 years, and it shows that there is more than half as much again of cow parsley along our roadsides as there was 40 years ago. More importantly, work by scientists such as Dr Carly Stevens of the University of Lancaster has shown that there is a direct mathematical link between the amount of nitrogen a habitat receives and its plant species-richness: the more nitrogen it gets, the fewer species it supports, which is why many lovely wildflowers are disappearing.

Two months ago the wildflower charity Plantlife produced a vivid report sounding the alarm about this situation it said that nitrogen pollution was now a greater danger to our wildflowers than climate change but although the report was well reviewed, it seems clear that the scale of the threat has still not generally sunk in.

This is unfortunate, because we are also beginning to understand that more organisms than plants are being affected by air pollution. It is highly likely that there is a substantial knock-on effect for insects and other invertebrates, and this may be one of the causes of the catastrophic crash of insect populations in parts of Europe highlighted in a recent issue of the journal Science.

Most remarkable of all, air pollution may be behind the greatest environmental mystery in Britain of the past 25 years: the sudden disappearance of house sparrows from central London in the early 1990s. The world expert on the sparrow, Dr Denis Summers-Smith, believes particulate pollution is to blame (although he does not have proof).

Certainly, something catastrophic happened in the house sparrow ecosystem in the capital; whether it was connected to the widespread uptake of diesel vehicles remains to be investigated. It is a reasonable assumption that a phenomenon that is thought to trigger nearly 10,000 premature deaths a year in London alone may well have had just as drastic an effect on the capitals smaller inhabitants. Yes, air pollution kills. It kills us, but it kills off the natural world just as effectively.

Read more:

Sharing is caring!



Powered by Facebook Comments