Pollution from roads affects virtually every part of Britain, with 94% of land having some pollution above background levels, according to research.
Roads, which occupy less than 1% of the country, “form vast, pervasive and growing networks, causing negative environmental impacts”, the scientists said.
The most widespread pollutants are tiny particles, mostly from fossil fuel burning, nitrogen dioxide from diesel vehicles, and noise and light. More than 70% of the country is affected by all of these, with the only land to escape road pollution being almost entirely at high altitudes.
The serious impact on human health from road pollution in urban areas is well known. But the researchers said even low levels of pollution may harm wildlife including birds, mammals and insects, although research to date is limited.
The findings are likely to apply to densely populated regions around the world, the scientists said, and roadless areas are expected to become increasingly scarce due to the predicted 65% expansion of the global road network by 2050. Today, there are an estimated 64m kilometres of road on Earth, a length equivalent to travelling 1,600 times around the equator.
Ben Phillips, of the University of Exeter, UK, who led the research, said: “In Great Britain, we basically live on an island completely covered by roads. We found half of land is no more than 216 metres from a road. That’s a really shocking and quite depressing statistic and it seems like that would have massive environmental consequences.”
“Pollution from roads impairs small animals by disguising the scent of flowers, fertilising habitats [with nitrogen] so they become unsuitable for specialist species, and spilling light pollution that disrupts their movements and life-cycles,” said Matt Shardlow, of the conservation group Buglife.
“This research exposes that the impact of roads has become omnipresent in the UK. In particular, microplastic pollution from car tyres is an emerging issue that must be addressed.”
The research, published in the journal Science of the Total Environment, concludes: “The ubiquity of road pollution should be seriously considered as a potential contributor to global and regional-scale environmental issues such as insect declines.”
The researchers started with maps of roads from motorways down to local access roads. “We found that 25% of land was less than 79 metres from a road, 50% of land was less than 216 metres away and 75% of land was less than 527 metres from a road,” they said.
They used available data on exhaust, metal, light, and noise pollution and how it disperses to estimate the total area affected. Background levels were deemed to be 0.1% of the level on the roads for particles and chemicals and 0.001% for light and noise, which are usually measured using exponential scales.
The study did not calculate the impact of other pollutants, such as de-icing salt and herbicides used on verges, or include the contamination of ponds and streams, vehicle-wildlife collisions and the habitat fragmentation caused by roads.
Previous studies of human health indicate that impacts from air pollution occur up to 500 metres from roads, and air pollution is known to harm birds, mammals and insects. Other research has shown roads can reduce populations of mammals up to 5km away. Across Europe, 98% of land is this close to a road.
The researchers said the extent of the influence of roads on the environment has been “somewhat overlooked and underestimated”.
Phillips said: “We’ve got global-scale environmental pressures and people always point at agriculture, because agriculture is absolutely everywhere across the country. The point we’re making is that road pollution is another thing that’s absolutely everywhere, even though it’s low level.”
Shardlow said: “While roads are contributing to insect declines and extinctions, much of the harm can be eased: lighting can be reduced, electric cars will reduce chemical pollution, wildlife bridges can be built to reconnect nature, and verges are increasingly managed to boost populations of wildflowers and pollinators.”
The UK government is planning a £27bn expansion of England’s road network, but the Guardian reported in February that transport secretary, Grant Shapps, had overridden official advice to review the policy on environmental grounds.
Phillips said: “The environment still isn’t prioritised enough in deciding whether or not these things go ahead.”