'Junk food' diet helps invasive plants to take over road verges

'Junk food' diet helps invasive plants to take over road verges


Posted 14th May 2018 by Peter Byrne


A gang of invasive native plants are thriving on a 'junk food' diet and taking over our once flower-rich road verges, Plantlife has revealed

Nearly 90 per cent of Britain's wild flowers prefer lower-nutrient soil but with air pollution creating unnaturally rich conditions, they are being crowded out of the countryside, especially on our road verges.

Plantlife has analysed our road verges since 1990, and has identified a dramatic change, as plants that enjoy nitrogen-rich soil have started to spread, including stinging nettles, brambles and cow parsley.

This is mainly being deposited from vehicle exhausts.

These 'nitrogen guzzlers' are crowding out wild flowers that had found a haven on our road verges, including some of our rarest and most threatened species, such as fen ragwort and wood calamint which are now clinging on at only a handful of verges - their last remaining habitat. Victims of the changing verge include wild flowers such as tufted vetch, bugle, tormentil, red clover, lady's bedstraw, white campion and greater knapweed.

A combination of air pollution and decades of poor management has led to the floral richness of our verges declining by nearly 20 per cent.

Dr Trevor Dines, Plantlife Botanical Specialist, said: "Our once colourful and botanically diverse road verges are becoming mean, green thickets where only thuggish species can thrive and more delicate flowers are being driven to the brink of extinction. After the froth of cow parsley in May, many verges no longer enjoy a bountiful summer; for the 23 million people who commute to work by road, the verge can be their only daily contact with nature – a floral parade of pink orchids, sapphire-blue tufted vetch, white oxeye daisies and billowing yellow lady’s-bedstraw - that we know can boost health and wellbeing."

Dines added: "The destructive impact of air pollution on human health is well documented but how pollution affects plantlife remains under-appreciated: vehicle exhausts can result in up to 2.5 kg of nitrogen per mile per year being dumped on our road verges – a rate that only a fraction of our wild flowers can cope with. Poor management has combined with pollution to create a perfect storm. Not only have councils adopted an over-eager regime that sees flowers cut down before they can set seed, but the mowings left on the verge simply add to the soil richness. Under this management, summer-flowering plants such as eyebright and harebell are disappearing and only the toughest of characters - like nettle and bramble – are prospering."

Despite being easy to overlook, road verges are home to over 700 species of wild flower (nearly 45 per cent of our total flora), which include 29 of 52 species of wild orchid.

As our other grassland habitats disappear (97 per cent of meadows have vanished since the 1930s), verges are one of our last remaining refuges for many of our bees, butterflies, birds, bats and bugs as our wider countryside becomes increasingly hostile. Red clover and lady's bedstraw (two of the top six verge species that support the highest number of invertebrates) are amongst the plants undergoing the most rapid decline.

Plantlife are suggesting road verges remain safe for motorists but are managed for wildlife. Some simple changes - cutting less often and later in the year, along with harnessing the power of semi-parasitic yellow rattle to act as nature's own lawnmower - could all significantly improve the biodiversity on our verges, benefitting wildlife and us alike.

The charity estimated that if our road verges were managed for nature, there would be an additional 418.88 billion flowers in the UK.

Images courtesy of Bob Gibbons / Plantlife





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