Roadkill literally “drives” certain species to extinction News and research
On May 8, 2021, at dawn, strips of fog crept from the cool fields onto Ziendeweg, a country road south of Amsterdam. The rush hour traffic caused by commuters using the road to bypass traffic jams had not yet picked up speed. But another activity was going on. Along the four-kilometer-long road, small groups of people carried bundles of white crosses and began to travel quietly along the roadside. When the sun rose, the first motorists were greeted by an eerie spectacle: 642 crosses marked exactly the places where dozens of animals had been killed by vehicles in recent years. Each cross showed the common name of each animal, a drawing of the animal and a QR code that linked to the traffic fatal incident logged on the civil science platform Observation International.
This guerrilla campaign was the idea of biologist Bram Koese, who was frustrated by the large number of otter and seabird deaths due to rapid traffic and the lack of response from local authorities. Koese decided to take matters into his own hands, and by mid-morning his parade of crosses was shown on local and national news, which appropriately embarrassed the municipality.
Although they do not all share this intensity of activism, surveillance programs for community roadkills such as Koeses are ongoing worldwide. In fact, because road authorities themselves do not routinely keep track of animals killed by traffic – and if they do, it is only because such collisions pose a risk to human road users – most of the data comes from citizen researchers. These amateur investigators have found evidence that reveals that some species are being driven towards extinction due to traffic.
An early effort along these lines was started in 1992 by Brewster Bartlett, aka “Dr. Splatt,” then a science teacher at Pinkerton Academy, a high school in New Hampshire, who used the school’s very first e-mail server to exchange students’ observations and post them on Since then, technology has improved, and road death monitoring is now being implemented through the use of dedicated apps or online civic science platforms.
In Belgium, which has Europe’s densest road network, drivers can use speech recognition on the ObsMapp app to report and log roadkill. In Israel, a roadkill mapping project relies on a feature in the Waze navigation app. Motorists can tap an icon that shows the face of a porcupine that has a cross in front of its eyes and a tongue that protrudes when they see a dead animal.
In 2020, Clara Grilo at the University of Aveiro in Portugal and her colleagues compiled data from 90 European road death surveys and concluded that 194 million birds and 29 million mammals die annually on European roads. Similar estimates suggest that more than 350 million vertebrate animals are killed each year by traffic in the United States
However astronomical the numbers may be for larger animals, they pale in comparison to the amount of insects and other smaller creatures that perish along the way. To grasp this, Arnold van Vliet from Wageningen University & Research in the Netherlands and his colleagues designed a civic science project specifically focused on insect mortality. Drivers were asked to take a daily photo of all insects pinched on their license plates, record the car’s mileage and then scrub the license plate to start with a clean sheet the next day. By extrapolating from the nearly 18,000 dead insects thus listed, the group arrived at estimates that, if expanded globally, would mean that 228 trillion insects are killed each year on the world’s 36 million kilometers of roads.
Social scientists are not just mapping roadkill; they also map the roads themselves. They do so because that figure of 36 million kilometers is little more than a rough estimate – and it is fast becoming obsolete. The world’s road network is actually expected to increase by 25 million kilometers by the middle of the century. The open licensing project OpenStreetMap aims to create a world map made by the public for the public. In 2016, a team of researchers used it to calculate that roads divide the world’s land into no less than 600,000 roadless packages. Half of them are less than a square kilometer, and only 7 percent or so are more than 100 square kilometers. In other words, we live in a world that is completely fragmented into small road-surrounded fragments.
And that, says Grilo, is bad news for the world’s species. She and her team combined information from the International Union for the Conservation of Nature’s Red List of Threatened Species and existing roadkill data and calculated the risk that roadkill poses to specific species. While some, such as the Eurasian blackbird (Turdus merula), suffer huge losses – as many as 35 million deaths per year – populations can absorb the losses without noticeable traffic-induced reductions in numbers. Other species are not so happy. Hassel ripa (Tetrastes bonasia) in Eurasia, the man-made wolf (Chrysocyon brachyurus) in South America and the brown hyena (Hyaena brunnea) in southern Africa is likely to be literally driven to the extinction of road traffic in the coming decades.
So roadkill is not only the inevitable but insignificant side effect that inspires the crude humor in books like faux field guide Flattened Fauna, The Roadkill USA coloring book and activity book or the lyrics to Loudon Wainwright III’s song “Dead Skunk”, “You got your dead skunk in the middle of the road stinkin ‘to high heaven.” Vehicles continue to be overlooked by environmental forces that are likely to decimate more and more animal populations. Although restrictive measures such as “ecoducts”, tunnels and fences are useful, they usually protect only one or a few species.
Perhaps more powerful are projects for social awareness such as the one Koese started. The scientific data collected by the researchers is just statistics, but hundreds of shrines erected for the killed wetlands, weasels, swallows, owls, frogs and geese produce a visual effect that drives home the message to road users and builders that roadkill is no laughing matter. . Unfortunately, some members of a community that Ziendeweg is going through were not impressed by the white crosses last year, Koese says with regret. “Two days after we raised them, they had run down each of the crosses,” he says.