Road safety for wildlife: the importance of an appropriate type of crossing

Published on: 27 May 2024, 16:29 hrs

In the Netherlands, you don't have to travel far before you come across a motorway, river, canal or waterway. They criss-cross urban and rural environment. And that applies to our nature reserves, too. The term we use for this phenomenon is 'fragmentation'.

Marieke Severijns, nature consultant at Rijkswaterstaat, explains how fragmentation of nature reserves can have an impact on wildlife.

'Many animals like to roam around in a large area. Fragmentation means that this is not possible: there might be a road or waterway running through the area. We want to create ways for animals to move safely from one natural area to the next. This gives animals more options for suitable partners in the mating season, which is good for genetic diversity.'

'They then have a more varied habitat type which offers them more food and shelter. So, in a nutshell, defragmentation is the process of making this possible,' explains Severijns.

Preventing dangerous situations

‘For example: in the breeding season, geese often nest in the unpaved areas of cloverleaf interchanges. They offer access to water and protection, with few predators or none at all. The perfect breeding site, on paper. But right after their young hatch, the geese are unable to fly. They start moulting after the breeding season.'

'When sources of food dry up in their immediate vicinity, they will cross the roadway to find other food. Which is, of course, highly dangerous.' To prevent these dangerous situations, Rijkswaterstaat thinks up ways of allowing animals to cross safely.

'We generally build bridges over roads or tunnels under them', says Severijns. 'But we also have gully escape ladders for toads. Those are sunken sections below the road that look like drains, but with a 'ladder' to help toads to cross under the road. The best available crossing always depends on the type of animal that we are trying to help.'

Picky passers-by

Severijns: 'We try to go the extra mile to get the crossing right; many animals are quite picky about how they use wildlife crossings. A badger, for instance, has different needs to a red deer and red deer in turn can't always get through a roe deer tunnel. So there is a guideline for each species.'

'Together with international networks and research institutes, we study which under- and overpasses work for which species', says Severijns. 'And how we stop specific species from using specific areas. We use this knowledge in the process of refining our wildlife crossings. The results of new research from Wageningen, for instance, led us to look at new principles dedicated to pine martens and stone martens.'

Safe crossings

Severijns: 'When making a crossing, we also take the context of the road into account. If the road is in a dip, we make a bridge. If the road is on an embankment, then it is more logical to dig a tunnel. Another important factor is that wildlife crossings must not be too far away from each other. How far is that? Again, that differs for each species. All things considered, it's quite a conundrum.'

'There's more to it than just the crossing. The animals also have to be able to locate the wildlife corridor. We use grids that they can follow to guide them to the passage, where they can cross safely.'

Issues and improvements

'More to the point, nature still has the ability to surprise us. Imagine our surprise when a small wolf recently crawled through a badger tunnel on the Veluwe. It was unexpected! It's important that we remain alert to what happens with our wildlife crossings, and whether we need to adapt them. We keep a close eye on that.'

'If there's one place where there are a lot of accidents involving animals, we look at whether there's a crossing available and whether there are any specific issues or improvements that can be made to prevent these accidents. One thing we can do to assess this is to look into the number of reports of accidents from road users and contractors.'

Reporting is crucial

'Data is crucial to us. We often see that reports focus on 'cute' animals; there are fewer reports about seagulls, for example. But we want to protect them, too. Our data helps us both to protect animals and to safeguard road safety', says Severijns.

'Road users need to be vigilant in spring in particular. That is when there are a lot of young animals that have no idea what traffic is, or how dangerous it can be. The result is more collisions.' Is there anything else Severijns would like to remind people about?

'Look after the wildlife crossings: our wildlife really needs them. For instance, if you see a damaged crossing or passage, report it to Rijkswaterstaat. Lastly, remember that wildlife crossings are for animals. Increasingly, we see people enjoying a pick-nick on a wildlife crossing.'

'That's not just illegal; people who do this are blocking the crossing for the animals for hours on end, because animals can pick up the scent long after the people have left. If we're aware of things like this, then people and animals alike can live alongside each other in safety.'