On May 8, 2021, at dawn, shreds of mist crept from the cold fields onto Ziendeweg, a country road south of Amsterdam. Rush-hour traffic caused by commuters using the road to bypass traffic jams on the freeway had yet to pick up. But another activity was taking place. Along the four-kilometre-long road, small groups of people carried bundles of white crosses and quietly began to erect them on the side of the road. When the sun rose, the first motorists were greeted by an eerie sight: 642 crosses marked the exact spots where dozens of animals had been killed by vehicles in recent years. Each cross displayed the common name of each animal, a drawing of the animal and a QR code linked to the road incident recorded on the citizen science platform Observation International.
This guerrilla campaign was the brainchild of biologist Bram Koese, who was frustrated by the large number of otter and waterfowl deaths due to speeding and a lack of response from local authorities. Koese decided to take matters into his own hands, and by mid-morning his cross parade was featured on local and national news, embarrassing the municipality.
While not all share this intensity of activism, community-based road fatality surveillance programs such as Koese’s are underway around the world. In fact, because road authorities themselves do not routinely monitor animals killed by traffic – and if they do, it is only because such collisions pose a risk to road users – most data comes from citizen scientists. These amateur investigators have found evidence that some species are being driven to extinction by trafficking.
A first effort in this direction was launched in 1992 by Brewster Bartlett, alias “Dr. Splatt,” then a science teacher at Pinkerton Academy, a high school in New Hampshire. He used the school’s first-ever mail server to exchange students’ observations and post them on a bulletin board. Since then, technology has improved and road fatality monitoring is now carried out through the use of dedicated apps or online citizen science platforms.
In Belgium, which has the densest road network in Europe, drivers can use voice recognition on the ObsMapp app to report and log road accidents. In Israel, a traffic accident mapping project relies on a feature of the Waze navigation app. Motorists can tap an icon of a porcupine’s face that has crosses for its eyes and tongue sticking out when they spot a dead animal.
In 2020, Clara Grilo from the University of Aveiro in Portugal and her colleagues brought together data from 90 European road fatality surveys and concluded that on European roads 194 million birds and 29 million mammals die every year. Similar calculations suggest that more than 350 million vertebrate animals are killed by trafficking in the United States each year.
As astronomical as these numbers are for larger animals, they pale in comparison to the amounts of insects and other smaller creatures that perish on the road. To figure this out, Arnold van Vliet of Wageningen University and Research in the Netherlands and his colleagues designed a citizen science project specifically focused on insect mortality. Drivers were asked to take a daily photo of all the squashed bugs on their license plates, record their car’s mileage, then scrub the license plate to start with a clean slate the next day. By extrapolating from the approximately 18,000 dead insects thus counted, the group arrived at estimates which, if extended to a global scale, would mean that 228 trillion insects are killed each year over the 36 million kilometers of roads in the world.
Community scientists don’t just map road crashes; they also map the roads themselves. They do this because that 36 million kilometer figure is little more than a rough estimate and is quickly becoming outdated. Global road networks are actually expected to increase by 25 million kilometers by the middle of the century. The OpenStreetMap open license project aims to create a map of the world made by the general public for the general public. In 2016, a team of researchers used it to calculate that roads slice the world’s land into as many as 600,000 roadless patches. Half of them are less than one square kilometer and only about 7% are larger than 100 square kilometres. In other words, we live in a world completely broken up into tiny fragments surrounded by roads.
And that, Grilo says, is bad news for the world’s species. She and her team combined information from the International Union for Conservation of Nature’s Red List of Threatened Species and existing roadkill data and determined the risk that roadkill posed to specific species. While some, like the common blackbird (Turdus merula), suffer huge losses – 35 million people are killed on the road each year – populations are able to absorb the losses without a noticeable traffic-induced drop in numbers. Other species are not so lucky. Hazel grouse (Bonasia Black Grouse) in Eurasia, the maned wolf (Chrysocyon brachyurus) in South America and the brown hyena (brown hyena) in southern Africa are likely to be literally driven to extinction by road traffic in the coming decades.
So road accidents are not just the inevitable but inconsequential collateral damage that inspires the crude humor of books such as The Fake Field Guide. Flattened Fauna, The Roadkill USA Coloring and Activity Book or the lyrics to the song “Dead Skunk” by Loudon Wainwright III, “You got your dead skunk in the middle of the road stinkin’ to high paradise.” Vehicles continue to be overlooked by environmental forces that are likely to decimate more and more animal populations. Although mitigation measures such as “ecoducts”, underpasses and fences are helpful, they usually only protect one or a few species.
Community outreach projects like the one launched by Koese are perhaps more powerful. The scientific data that researchers have collected are only statistics, but hundreds of shrines erected for slain stoats, weasels, swallows, owls, frogs and geese produce a visual impact that makes people understand the road and builders that road fatalities are no laughing matter. . Sadly, some members of a local community through which Ziendeweg passes were unimpressed with the white crosses last year, Koese says ruefully. “Two days after we erected them, they had rolled down each of the crosses,” he says.