Air pollution is not just harming human health, it is having a 'devastating impact' on UK wildflowers and landscapes, conservation experts have warned.

Nitrogen emissions from transport, power stations, farming and industry in the form of nitrogen oxides and ammonia are deposited back into the natural environment directly from the air, or in the rain, over-fertilising the soil.

The pollution creates nutrient-rich soils which allow 'thuggish' plants such as nettles, hogweed and hemlock, that thrive in the conditions, to overpower rare and endangered wildflowers, a report by nature charity Plantlife warned.

The charity says the problem, which is 'force-feeding the natural world a diet of nutrient-rich junk food', harms plants and the wider habitat, is in addition to the impact of nitrogen fertilisers being spread on the land.

Research shows 90pc of habitats across England and Wales that are sensitive to levels of nitrogen, such as heathlands, acid grasslands and sand dunes, are receiving pollution from the air and rain at higher levels than they can tolerate.

Across the UK, the figure is 63pc, according to the report backed by conservation organisations including the National Trust, the Woodland Trust, the RSPB, the Botanical Society of Britain and Ireland and Chester Zoo.

More than a third (37pc) of UK flowering plants prefer low-nutrient conditions and are under threat, declining while high nitrogen plants are on the rise.

Lichens, mosses and liverworts are particularly sensitive to nitrogen, while other plants at risk include harebell, which was recently classified as near-threatened in England, and bird's-foot trefoil, which supports 160 species of invertebrate.

Dr Trevor Dines, Plantlife's botanical specialist, said nitrogen being deposited from the air and rain could present a far more immediate threat to parts of the countryside than climate change.

'As the first flush of warm weather sees the countryside and waysides greening up, all may seem as it should, but look more closely and the truth is a little different.

'The negative impact of poor air quality on human health is, rightly, increasingly well-documented and it is now incumbent on us to ring the alarm bell for nitrogen deposition.

'We are force-feeding the natural world a diet of nutrient-rich junk food and it is having a devastating impact.

'Once diverse habitats are becoming monotonous green badlands where only the thugs survive and other more delicate plants are being bullied out of existence.'

With the problem spreading across borders, and nitrogen pollution coming to Britain from the continent, Dr Dines called for European and international action.

Locally, habitats could be managed to reduce nitrogen levels, with grazing, hay meadow management and tree coppicing to remove vegetation.

And farmers, who are already taking action on nitrogen, could take practical steps to reduce ammonia pollution such as covering up slurry tanks and planting buffers of trees around chicken sheds, a particular problem, but need proper incentives to do so, he said.

Efforts to reduce nitrogen oxide from traffic and power stations, which improves health, will also have a 'massive benefit' for the environment, he added.

FARMING INDUSTRY RESPONSE

National Farmers' Union (NFU) vice president Guy Smith said farmers are working hard to reduce nitrogen emissions.

He said: 'Farmers have made some real improvements to our wildlife, environment and our landscapes, particularly in the past 25-30 years. We see an improving picture, the indications are positive and we need to continue to build on this.

'Nitrogen emissions are down due in part to the fall in livestock numbers and in fertiliser use – application rates have been decreasing since the 1980s.

'Good practice and regulation have also been key. Support for innovation and new technologies that can help mitigate impacts but sustain growth in the agricultural sector is critical, but planning policy is also important, particularly if we would like more modern, efficient buildings and storage facilities for the food we produce.

'We are importing more and more of our food and if more constraints are placed on UK food production then the net effect is to increase a reliance on imports, which could lead to a net increase in nitrogen use globally. In England, we have high standards when it comes to mitigating environmental impact from food production.

'The agriculture sector has committed to further address emissions through industry-led initiatives such as the Greenhouse Gas Action Plan and Tried & Tested. In addition, the NFU, DairyUK and AHDB Dairy recently updated the 'Dairy Roadmap' to highlight the good environmental work that dairy farmers are undertaking.'