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1st August 2023

Traffic may be as important as industrial farming for destroying wildlife

UKHACC Chair, Richard Smith writes his thoughts on Traffication and the need for greater recognition of the impacts of traffic on nature, human and animal health

Health professionals have for years been campaigning on the climate crisis, but we have been slower to recognise that preserving nature, of which we are a part, is just as important. The current species extinction rate is between 1000 and 10000 times higher than natural extinction rates.

I thought of this as I read Paul F Donald’s book Traffication: How the Car Killed the Countryside. I thought too of the line from Joni Mitchell’s 1970 song Big Yellow Taxi: “They paved paradise and put up a parking lot.” That’s exactly what we’ve done.

The core argument of Donald, who was the principal scientist of the Royal Society for the Protection of Birds, is that the spread of traffic may have been just as important as industrial agriculture and climate change in destroying wildlife. Road ecology is a scientific discipline that is strong in the US and Scandinavia but weak in Britain that “permits only one conclusion: road traffic has wrought immense damage on the world’s wild plants and animals.” It has done this in many different ways.

Road ecology

Road ecology has its beginning in June 1924 with a 300-mile drive by Dayton Stoner, a zoologist, and his wife Lillian, an ornithologist, from Iowa City to a laboratory on West Okoboji Lake. The roads were mostly gravel or dirt, and the Stoners rarely went above 25 mph. As they drove, they noticed the many dead animals on the road that had clearly been killed by collisions with traffic. They decided to count the dead, and the results were published in Science in 1925. They counted 225 dead reptiles, birds, and mammals of almost 30 species. Collision is one of ways that traffic kills wildlife as well sometimes as the people in the vehicle.

The growth of traffic and the harm to humans

Everybody knows that traffic kills people—about 1.5 million a year, WHO estimates. Another 20-50 million are injured, some of them needing lifelong care. Traffic is also the main contributor to the air pollution that kills another seven million each year, and noise pollution from traffic kills hundreds of thousands. Donald sums up: “Road traffic brings a global pandemic of death and injury that no government seems willing to lock down.”

The first car journey in Britain took place in Hampshire in July 1895 at a speed of about 10 mph. Now there are estimated to be between 1.2 and 1.5 billion cars in the world together with about 400-500 million other types of vehicles. This is predicted to grow by 2024 to 2 billion cars and 800 million other types of vehicles.

Donald uses the word traffication rather than traffic because it has three components: the number of vehicles; their speed, and their reach. The top speed of cars has increased steadily from about 20 mph in 1900 to over 120 mph in 2021. Most countries have speed limits, but British government data suggest that “the average speed of vehicles on Britain’s roads exceeds the maximum legal limit for the respective type of road.” (Note that that is the average speed) And more speed means more exhaust gases, noise, and microparticles.

Britain has one of the highest road densities (length of road per square mile of land) in the world, twice as high as the US. Sixty thousand miles of road have been added in Britain to what was already a dense network in 1950. Some 80% of Britain and 90% of England are within 1 km of a road compared with a European average of under 60%. Virtually nowhere south of a line from the Severn to the Humber is more than 2km from a road (some of Dartmoor is an exception), and noise from traffic pollutes 80% of Britain and 90% of England.

The many ways in which traffic destroys wildlife

It’s impossible to know the full scale of roadkill, but one estimate is that 360 million birds, reptiles, amphibians, and mammals are killed on the roads in the US each year, while across Europe it may be 200 million birds and 30 million mammals. Extensive studies make clear that roadkill is not a random event; factors like time of the year, time of the day, and the volume and speed of traffic are all important. As evolution dictates, birds and animals also adapt, some more successfully than others. These studies point to ways of reducing roadkill.

Some animals will not cross any roads, and most animals will not cross the busiest roads. Roads, particularly busy roads, thus have the effect of creating “islands” of countryside, and we know that islands experience a progressive loss of biodiversity. We know this from the famous study of Barro Colorado, a 15 km square island that was created in 1924 during the construction of the Panama Canal. The island has been studied more intensively than almost anywhere else on the planet, and despite strenuous conservation efforts a quarter of forest bird species have been lost. Busy roads have divided the planet into 600,000 islands with quieter roads creating even smaller islands. The result is progressive loss of biodiversity.

Roads, which have been called “the Anthropocene’s battering ram,” are also conduits for pests. The cane toad, which is native to Central and South America, was introduced into Queensland in 1935 in the hope that it would control pests affecting sugar cane. The toads, which are extremely poisonous, failed to eliminate pests but were highly effective at destroying local wildlife. The toads have followed Australia’s roads to Sydney end beyond. Invasive plants also spread along roads: some 600 plants have had their seeds spread by cars, a hundred of which cause important environmental problems.

Noise is the next way that roads harm wildlife. Transport noise, most of it from road traffic, is, says WHO, the second largest cause of ill health in humans after air pollution, itself mostly caused by traffic. We subconsciously perceive noise even at low levels as a danger signal, prompting a fight or flight response. Noise like air pollution contributes to  a wide range of problems, including hypertension, heart disease, depression, premature birth, and dementia.

Animals and birds are also harmed by noise and harm begins at low levels of noise. There is growing evidence that noise also affects the genes of animals, and Donald points out the irony that we know more about the effect of noise on the genetics of birds than on humans.

The emissions of traffic—heavy metals, nitrous oxides, and particulates—are also harmful to wildlife as they are to humans. One study estimated that between 70-90% of Britain is polluted by motor vehicles. Traffic is the main source of particulates, accounting for a quarter of PM10 and 40% of the more dangerous PM2.5 (the smaller particles the deeper they can reach into the lungs) The particulates are produced from the wear and tear of tires, brake pads, and the surface of the road, and as cars get faster and heavier the emissions increase. These non-exhaust emissions as they are called exceed emissions of particulates in exhaust by a factor of well over a thousand, and the non-exhaust emissions from electric cars may be greater than from cars fueled by diesel and petrol because they are heavier.

Salt from roads and light from traffic are other causes of damage to wildlife, and the impact of light pollution is increased by a third of vertebrates and two-thirds of invertebrates being nocturnal. Only a third of the world’s people can see the Milky Way from where they live, and in Britain it’s only 10%.

Donald makes the case that traffication is as important—and possibly more important—in the destruction of wildlife than industrial farming, habitat loss, and hunting, the usual suspects. Whether it is as or more important matters less than the recognition than it is very important and that “almost nobody seems to have noticed it.” Donald’s important book seems not to have had the impact I think it deserves. I read the book before it was published in May and have been embarrassingly slow in writing about it, but as of July 2023 I can find no reviews of the book.

Lessening the damage to wildlife from traffic

The book is not all doom and gloom. After pointing out that electric vehicles will reduce greenhouse gas emissions but will not improve most of the ways that traffic harms wildlife, Donald sees five reasons for hope. Firstly, although we seem to have come to see cars as essential for life as water, air, food, and housing, we are all harmed by traffication. As a famous ad pointed out: “You are not stuck in traffic. You are traffic.” Secondly, traffic is regulated: exhaust emissions of particulates have fallen because of regulation, whereas non-exhaust emissions have risen because there is no regulation. Thirdly, there are many things that can be done that meet the holy trinity of being effective, affordable, and socially acceptable. Fourthly, there are technological responses, and, fifthly, there is already a trend towards detraffication, including, for example, more people working from home. Four fifths of journeys made in Britain are less than 10 miles.

Among possible responses to traffication, reducing speed is high on the list as most of the damage to wildlife increases exponentially with speed. Much of inner London has reduced the speed limit from 30mph to 20mph, and a computer model shows that if everybody stuck to the limit journey times would fall. Signs warning drivers of wildlife on the road limits harm to drivers and wildlife, and signs have increased, covering hedgehogs, ostriches, kangaroos, camels, snails, ducks, pheasants, otters, snakes, swans, coypu, and many more creatures. Underpasses and green bridges are another response. Many countries, including Britain, have more roads than they need, and closing roads is possible.

Donald ends with things that all drivers can do:

His list does include drive less, but Donald has been anxious—too anxious, I suggest—to avoid upsetting car drivers. When we remember that most cars are immobile for 95% of time, there is huge scope for having far fewer cars and much more sharing. Even more important is to improve public transport and encourage walking and cycling. The move towards 15-minute environments, where work, school, shops, and entertainment are all available within 15 minutes of walking and cycling could mean a dramatic reduction in the number of cars. I’m privileged to live in such an environment, and I haven’t driven our car for 18 months. 

Traffication: How cars destroy nature and what we can do about it.