Millions of wildlife die on the roads every year -
© Shutterstock via The Conversation
194 million birds and 29 million mammals die each year on European roads, according to a study published by our partner The Conversation.
This number could be drastically reduced by rethinking the fencing system and its geographic deployment.
The analysis of this phenomenon was carried out by Jochen AG Jaeger, associate professor of environment (Canada), Ariel Spanowicz, student in Master of environmental sciences (Switzerland) and Fernanda Zimmermann Teixeira, researcher (Brazil).
Wild animals travel for miles in search of water, food, a mate or a breeding ground.
But they come up against the dangerous obstacles of roads and traffic.
Road development, which is growing in several countries, particularly in the tropics, poses an increasing risk for the survival of many mammals, birds, reptiles and amphibians.
However, roads are already killing a massive amount of wild animals, leading to the decline of some local populations, especially species that live in low density or reproduce slowly, such as lynx, badgers, porcupines, turtles and owls.
This can set off a chain reaction by disrupting mutually beneficial relationships or breaking food webs, leading to the extinction of other species.
Hundreds of thousands, if not millions of animals, depending on the country, collide with vehicles every year.
Indeed, a recent study allows us to estimate that 194 million birds and 29 million mammals die each year on European roads.
Although several regions have taken action against road wildlife mortality, including the Netherlands and Switzerland with fences and eco-pipelines, the issue remains of concern globally.
Animal mortality has consequences for animal populations, our communities and our ecosystems © Shutterstock (via The Conversation)
Wildlife fences installed along a road reduce accidents, but are not without controversy.
They are in fact far from having the good reputation of eco-pipelines, because they amplify the barrier effect of roads.
We have developed a plan to identify the most urgent road sections to close based on our observations of the most dangerous road sections.
Essential, but controversial
Installing and maintaining fences along roads is very expensive.
Except where driver safety is at stake, transportation agencies have largely overlooked measures to reduce traffic accidents involving wildlife.
Ecoduct in Dwingelderveld National Park, the Netherlands, with fences to guide animals to the crossing and prevent them from going on the road © Shutterstock (via The Conversation)
Many transportation agencies and wildlife managers interviewed about roadside fencing are skeptical and often view them as unpleasant measures.
Conversely, eco-pipelines have a reputation for being “awesome”.
However, in reality, these “great crossings” alone do not reduce wildlife mortality on the roads.
Recent data show that road mortality is more damaging to most wildlife populations than fences.
In the majority of cases, it is more urgent to install fences than eco-pipelines.
But how long should they be and where should we focus our efforts?
The deadliest areas
It is unrealistic to fence off an entire road network.
We determined how transport agencies can identify the most urgent sections of road for closure using mortality surveys, identifying the most dangerous roads at multiple scales and putting in place mitigation measures for methodical way using an adaptive management approach.
Are your fences too short? Transport organizations can decide to enclose the three dangerous zones identified at the scale of 200 meters (on the left) or the one identified at the scale of 1,000 meters (on the right), but the longest fence in the analysis to 1,000 meters clearly gives better results in this example / diagram © J. AG Jaeger, A. Spanowicz & F. Zimmermann Teixeira
Hazardous areas can be identified at different scales, which can affect the positioning of fences.
A hazardous area on one scale could be less lethal on another scale.
We used wildlife mortality data obtained on three roads: one road in southern Quebec and two roads in Rio Grande do Sul, Brazil.
The first route passes through the Laurentides wildlife reserve and runs alongside the Jacques-Cartier national park in Quebec.
One of Brazil's roads crosses two protected areas and runs along the Atlantic Forest Biosphere Reserve, while the other runs along the slopes of the Serra Geral and the coastal lagoons.
Our "Animals" file
Our hypothesis was that several sections of short fencing could be built near the identified hazardous areas on a small scale to reduce accidents.
We believed that this approach would further reduce the total length of fencing relative to protecting a few large-scale identified hazardous areas, without worsening the wildlife death toll.
Animals can easily get around short fences, however.
They are even at risk of getting hit at the end of fences, a problem known as the “end of fence effect”.
This is because fences must be long enough to reduce the risk of end-of-fence effect.
A few long fences or many short fences?
The trade-off between using a few long fences or many short fences has important consequences for biodiversity conservation.
Finding the right balance depends on the distance the animals travel, their behavior towards the fence, the mortality reduction targets for each species, and the structure of the surrounding landscape.
For example, turtles travel much shorter distances than a lynx, and their danger areas are very localized.
As a result, while an abundance of short fences are fine for turtles, lynx fences need to be much longer.
The length of a fence influences the predicted reduction in wildlife mortality. In this sense, the installation of fencing in the hazardous areas identified on a smaller scale, i.e. 200 meters (line displayed in purple), would further reduce wildlife mortality on the roads if there was no end effect. fence / diagram © J. AG Jaeger, A. Spanowicz & F. Zimmermann Teixeira
Once the fences are installed, the danger zones can disappear or shift and new ones can appear, so we must be able to adapt the mitigation measures.
Our step-by-step plan helps transportation managers decide on the location and length of fences.
Fences have been shown to be an effective and realistic way to reduce wildlife mortality on roads.
Wildlife protection and transportation agencies should rely on fencing rather than eco-pipelines to reduce the impact of roads and traffic on wildlife populations.
Motorists also benefit from the beneficial effects of fences on road safety.
Finally, the boom in road construction around the world represents a growing threat to biodiversity, highlighting the urgent need to reduce road deaths globally and to put up fences to protect wildlife.
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This analysis was written by Jochen AG Jaeger, Associate Professor of Geography, Planning and Environment at Concordia University in Montreal (Canada), Ariel Spanowicz, Master student in Environmental Sciences at the Federal Polytechnic of Zurich (Switzerland) and Fernanda Zimmermann Teixeira, post-doctoral researcher at the Federal University of Rio Grande do Sul (Brazil). The original article was published on The Conversation website.
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Animal protection
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